User Comments on Lockers for the Hummer H1

Install Article
Auburn Locker Article

If this site has helped you consider a Donation. Donation Info

Does a Detroit Locker work with a TT4/ ABS truck?

I have a Detroit in my 2000 TT4 truck. My girlfriend has a Detroit in her TT4 truck. ABS works fine, and there is no error code generated.

The part number for a Hummer (Soft Locker) according to TracTech's website is 187SL-163A

Note: The 2.56 ring and pinions aren't commercially available except through AMG (this is after calls to such places like Superior Gear, Randy's Ring and Pinion, Precision Gear, etc.). The 2.73's are hard to get, but still available.

The Lock Right would require a stock open differential carrier case from an early 80s Jeep with the model 20 axle. It will NOT fit in the Torsen carrier case.

Different tire diameters will contribute to rear end twitch. Given enough difference, it can cause the locker to lock and unlock frequently and can wear it out prematurely. 1/4" doesn't sound like much, but it is pretty close to the borderline of 3/8" which most locker manufacturers consider acceptable.

I have recently converted my rear diff to a Detroit Locker, specifically the 187SL-163A model of the Detroit Soft Locker. As a background, my truck (97.5 HMC4) originally came with what is normally called the Torsen T1 equipped Differential. While great in an all around capacity, some owners wanted to get away from stressing out components further, while enhancing the off roadability of the vehicle. My wife also finds it difficult to coordinate things while doing BTM, so an upgrade was also wanted to correct this issue as well. Taking a cue from the Land Rover and Land Cruiser world, many trucks have successfully run some wicked trails with a front High Bias Torsen equipped diff, and a rear diff equipped with a Detroit. I figured that I would try it out on my H1 with that exact combination. I did keep my original Torsen equipped diff as a backup. I'll spare the details on building up the diff and getting the parts for it. It did take over 5 months for me to get the parts together before the build up, including a complete spare diff (so that my truck could remain drivable while still building up the Detroit).

So, I wanted to give my own observations on how the Detroit works, both on and off road. Since I've been able to run the Detroit off road (finally!) on a trail that I've done many, many times in the past with only Torsen's in the truck, I'm now able to write this mini-article.

On Road: Since many of us drive our trucks on pavement to get to and from trails, on pavement handling is important. It's crucial to note that the truck will twitch slightly to the right when coming off the gas, and twitch slightly to the left when putting on the gas. The faster the speed, the more pronounced it is. When making turns, the Detroit Locker will differentiate by allowing one wheel to spin faster than the other. There is a catch - it will do so when you're coasting in a turn. I've kept the Detroit locked up in left hand turns (large intersections with two left hand turn lanes) while accelerating past 20mph. When that happens, you'll get a slight chirping from the tires. Under 20mph, I've yet to get any chirping at all. When navigating slight turns and bends in the road, I have noticed that the truck does have a tendency to stay going straight. There is a slight bit more effort to turn on curvy roads. Nothing major, but it is noticeable.

On slick roads, the driver does need to be a bit more cautious and judicious with the accelerator. Gradual build ups to speed is the key here, with smoother operation of the accelerator when speeding up and slowing down. I do have to note that the quirkiness of the Detroit is minimal compared to my last truck that had one (a Dodge Ramcharger). Since the vehicle is far heavier than my other Detroit equipped vehicle from my driving past, the handling characteristics mentioned are present, but very muted compared to a lighter vehicle.

After running with the Detroit for 2 weeks now, I don't notice the handling differences at all unless I look for them. Oh - and the clicking inherent in prior versions of the Detroit? Gone. I can't hear it. Must be the new design.

Off Road: I can sum it up in one word - WOW! Other verbal exclamations (some starting off with the word "Holy" comes to mind) are just as applicable, if slightly more vulgar. No more BTM (unless I'm really stuck and I have to have it for the front). I get less stress on my Transfer Case. I don't eat up my brakes. And I get point and go off roading. Point the truck in the direction you want to head, and hit the gas. Keep the engine in the max torque curve, and you'll go up hills like crazy. One of the dealer reps today told me to charge up this one hill (knowing that I just did the locker install last week), and I did so with no fuss, and a lot faster and surer than before (with stunned onlookers snapping away with their digital cameras, mainly since I took it twice as fast as any other truck).

As with any improvement, you can take the harder line and get in trouble further in. I did that today, taking the hardest line possible on this one embankment, and ended up backing up and taking one with a slightly less degree of difficulty. So adding the locker doesn't necessarily mean you'll get past more obstacles, it can mean that you get stuck a lot more further into things, with a higher degree of extraction/recovery difficulty. Off Road handling is the same as a Torsen equipped truck. There's no learning curve here. It's also as Murphy-proof as you can get. Despite the reliability of the ARB's, (the Detroit Locker's main competitor) the Detroit has some advantages in that it requires no external influences to operate in a locked mode.

Is it worth it? If you off road at least 6 times a year - yes, providing your trails require you to do a lot of BTM (98-back with 4.5:1 Torsen's or 2002/2003 with 2.5:1 Torsen's). If you don't do a lot of BTM, or you have been satisfied with TT4 (no jokes here!), then it might not be worth it. There is a lot of time that is taken to either build one up and swap the diff out (like I did, with some assistance), or buy a ready built one and swap it. If you're more of a hardcore wheeler, than a Detroit is a very viable option to put into your truck. I find it's been a more than worthy upgrade to my truck. So much so that when I'm able to upgrade, if the next truck doesn't have an E-Locker in it, I'm pulling my Detroit out and putting it in the other one.


1) I'm actually now starting to hear the locker "lock" and "unlock". It is still far quieter than the locker that I had back in 1990 in my Dodge Ramcharger, but I'm able to hear the ratcheting now when I have some sort of large object (like a wall or dumpster) next to my truck.

You are not actually hearing it lock and unlock, but rather its normal operation when unlocked. Much like a ratchet wrench. In one mode, it is locked and not making noise. In the other mode it is unlocked and ratchets. It is quite normal for them to make this noise, although in a Hummer it usually goes unnoticed except for very specific circumstances (such as you describe.)

2) I'm exhibiting some noticeable (well, to me at least) clunks, especially when I'm backing up (and turning), put the truck in forward gear, and within the first 2 feet, get a clunk when the rear end relocks.

I've never really noticed a "relocking" type of clunk as you describe in my truck. It is important to note that our trucks have considerable backlash in most of the driveline components and the inherent backlash in the Detroit may exacerbate this some, particularly when in Low range.

Regarding backlash within the differential, there are two type of backlash that you are dealing with. One is the backlash between the ring gear and pinion gear which, if properly set up, is very slight and wouldn't be noticeable in day-to-day operation. Then there is backlash in the locker itself which is relatively large compared to the ring and pinion backlash. When in the "in between" (as in no torque being applied from the engine) portion of the backlash, the locker is able to be unlocked by wheel torque (as in when turning) fairly easily. As engine torque is applied and the backlash is taken up, the gear sets in the locker are forced together and it becomes increasingly more difficult to unlock.

3) The right and left twitches (while letting off the gas or accelerating heavy) are even more noticeable now that I've changed out my rear lower ball joints.

I had a severely worn lower ball joint in my truck replaced a while back, and after doing so my alignment was off quite a bit. It actually moved my steering wheel off center a bit. I would suggest checking the rear alignment of your truck. A change in alignment could easily make the highway twitchiness more pronounced.

Assuming that alignment is normal, the twitchiness is caused by the tires being of slightly different circumference than each other. This can be due to differing amounts of wear, variations in production, or unequal air pressure (which is seldom true for a Hummer.)

4) I'm able to keep the rear locked even easier now while in turns. In left hand turns going over 20mph, I can now get the tires to chirp, no matter which left hand turn lane (in the case of multiple left hand turn lanes) I use. I have not been able to get the tires to chirp in a right hand turn, but I'm very speed limited in this case.

This is a matter of wheel torque vs. engine torque. If the torque going into the differential from the engine is greater than the amount of torque the outside wheel in a turn is required to produce to unlock the locker, then the locker will remain locked and your inside tire will chirp. Just being in a turn will not in and of itself cause the locker to unlock. Earlier versions of the Detroit also had higher spring rates in them which made them harder to unlock and were very "chirpy", particularly in light weight vehicles. The modern SofLocker has rather light spring rates and should unlock fairly easily under most circumstances, but given enough throttle input it may still remain locked. I should point out that in my NA truck, the only time I have been able to do this is when in 2WD.

5) When I had only the Torsen's, I used to get every once in a while the "rocking" back and forth when stopped. I get this rocking far more frequently now after stopped.

This really shouldn't have anything to do with what type of differential you have since the rocking takes place between the brakes and the wheel.

Does the right rear halfshaft Tend to Break?

On the detroit trucks. Usually when the wheel leaves the ground under revs. You actually don't have to jack both wheels up, you just have to get the release. It takes awhile, and is usually more difficult under any load on the grounded wheel. If you are doing a peddle to the metal hill climb and one rear wheel looses traction the Detroit will lock up and break a half shaft for the same reason that jamming on the brakes with a spinning tire will?

While doing trail repairs on said halfshaft (see #2), it was discovered that you have to jack up both rear wheels to allow the whole assembly to rotate to reach the bolts to remove and replace the halfshaft. That was a bit fun (sarcasm intended), and it ended up taking two Hi-Lifts and a bottle jack to perform the replacement. This is crucial to know, especially when out on the trail.

You should still be able to replace a halfshaft with only one wheel in the air. I use a long screwdriver inserted in the vent slots of the brake rotor to turn it. It can be a little difficult to rotate at times, but is doable. (I've done several on my truck with the lockers installed.)

How To Tell If My Unit Is Functioning Properly?

Step 1 - With the engine turned off, raise NoSPIN equipped driving axle(s) until all wheels are out of contact with any surface. Place the transmission in gear or park so that the drive-shaft is locked and does not rotate. Test for forward disengagement:
Step 2 - With two people, rotate both wheels rearward, as far as possible to lock both wheels.
Step 3 - With the left wheel securely held in the rearward direction, rotate the right wheel slowly forward. A faint indexing or clicking sound should be heard as the NoSPIN disengages on the right side.
Step 4 - With the right wheel slowly rotating forward, the left wheel should be rotated slightly forward. This will lock both wheels.
Step 5 - Again, rotate both wheels rearward, as far as possible to lock both wheels.
Step 6 - With the right wheel securely held in the rearward direction, rotate the left wheel slowly forward. A faint indexing or clicking sound should be heard as the NoSPIN is disengaged on the left side.
Step 7 - With the left wheel slowly rotating forward, the right wheel should be rotated slightly forward. This will lock both wheels.

Repeat steps 2-7 except, test for reverse disengagement.

If the above steps are completed successfully and rotating wheels disengage easily by hand, rotate freely and evenly, lock both wheels when required, and produce a faint indexing or clicking sound, then the NoSPIN is properly installed and is functioning correctly.

both wheels as required, re-check the installation of the NoSPIN in the axle. Also, check hand and foot brakes for possible drag caused by improper adjustment. Be sure that all thrust washers have been removed from the standard differential support case.

To check normal NoSPIN operation, drive the vehicle on a flat surface with good traction, in a right or left circle in forward and reverse to be sure that the outside wheel is free to overrun (i.e. that the outside tire does not scuff). A clicking or indexing sound may be heard. The sound of gear
re-engagement may also be heard upon completion of the turn. This is normal.

Operation Test:
Check to see that both wheels of each NoSPIN differential equipped axle are driving. Make this test under load, so that engine torque is applied through the NoSPIN differential with the wheels on the ground. One way to achieve this load is to drive up against a solid obstruction (on loose dirt or
gravel, if possible) and attempt to spin both wheels together. Perform this test in forward and reverse. (Exercise caution when performing this test to avoid damage to vehicle of obstruction.)

Backlash - How Much?

At the tire tread, 1" to 2" (at the driveshaft, 30 degrees to 90 degrees) depending on tire diameter and ring gear ratio.

Tire Pressure? Mismatched pressures mean different tire diameters and different wheel speeds. Recommendation: Keep tire rolling radius (by air pressure) matched within 1/4" for highway vehicles and 1/2" for off-road vehicles.

And from a conversation with Tractech's technical support earlier today (when I needed to order a replacement warning sticker for my door):

- The amount of torque and force needed to lock and unlock the unit is very small. The Soft Locker variants don't need a lot of force to unlock versus older variants (like the one I had in my '88 Dodge).

- It roughly takes about 25 degrees of rotational movement for the Detroit to re-engage.

- The Detroit will definitely exaggerate tire sizes that are different. Case in point is my current situation (to be corrected tomorrow - my new tires arrive tomorrow morning!) in which I have about 4/32nds difference between the left rear (larger) and right rear (smaller).

Since the left rear is larger, and the right rear is smaller, this situation will happen:

1) Coming from a standstill, both wheels are "locked"
2) Going up to speed, there is a minor variant in wheel speed that starts the truck to drift to the right when the right unlocks (due to it having a higher wheel speed) and the left rear drives the truck.
3) The driver corrects the right hand drift by turning the truck slightly leftward. This introduces the left wheel to scrub off speed slightly, then the diff relocks when both tires hit the same wheel speed. Hence, the spooky steering that my wife has been complaining about.

I think the sheer mass of the truck is what's helping cause this. The tech at Tractech said that 4/32nds difference is not enough to cause it, but in this case, I think it is.

Therefore, any tires on a Detroit should be as close to exactly the same diameter as possible. I'll know this better when I mount my tires tomorrow afternoon.


Clarke Ferber

Can be used in the front, in the back or both.
Selectable which lockers are active and when: rear locker, front locker, both lockers.
Open diff. when off, no effect on turning radius or drive ability.
Compressor can be plumbed for other uses (backup to CTIS, inflating other things).
Flexible. When locked, It's locked up tight and can be activated and de-activated on/off/on/off as required by terrain.
TT4 still works somewhat with the open diff.
From personal experience, ARB stands behind their product and warranty.

More complexity than a Detroit - more parts to fail (compressor. solenoids, electrics, lines, o-rings).
Internal o-ring and u-seal will require replacement after 30K+ miles on the older style carriers because gear oil will start to leak past.
Need to be used regularly to stay reliable and lubricated.
Slightly more expensive than Detroit's: the additional cost is in the wiring, compressor and lines. ($300-$400)

Simple. No additional stuff needed to make it work - under power it's locked, coasting it isn't.
Less cost because you don't need the compressor, lines, switches....
Diff. Carrier might be slightly stronger than an ARB carrier - but I've never heard of anyone breaking an ARB carrier.....
Was a factory option in the rear on some commercial Hummers in the '90's.

Adverse handling, especially in turns or snow/ice as the locker locks and unlocks - causes the truck to sway or the rear-end to twitch.
Wider turning radius under power as the rear tires are locked together and cannot turn at different speeds.
Need to "coast" through turns because of the above on the street.
Shouldn't be used in the front.

I have an ARB up front and a detroit in back. I decided on the detroit to eliminate a single point of failure after hearing about the problems ARB's can have. I will skip the talk on the obvious advantages of having lockers.

I read plenty about the effects of a detroit on the road (especially in light vehicles, like jeeps) but I also heard that it was not an issue in the heavier, all wheel drive hummer. Well, when I first drove my hummer after the installation, I was surprised to find that that I didn't notice anything different immediately. It took a while for me to notice that the truck would sway in turns if I suddenly let off the gas, and it is usually subtle. You can make it more dramatic if you hit the gas, then let off, if you like that sort of thing. Also, I can see where you would prefer an open diff in snow/ice so that if one wheel spins, the other keeps you on the road.

Overall, it works great. It is not perfect, but nothing is.

For fun, I thought I would try to describe how the detroit works, not internally, but the net effect. (note that my description below will make it seem much more dramatic than it really is in a hummer)

First of all, it is not a "spool" diff. It is not a locked axle, all the time. It does differentiate when turning. What is unique is how the detroit allows this to happen. The detroit will not allow one wheel to slow or stop as long as the drive line is turning, but, it WILL allow 1 of the wheels to go FASTER than the drive line would normally make it turn. This occurs when you are turning, the ground will push the outer wheel faster than the drivetrain. This is why only the inside tire is pushing while in any turn (the outside tire is being pushed by the ground faster). If you are on a twisty road, the wheel pushing will keep switching to the one on the inside of the turn. If you suddenly let off the gas while in a turn, you cause the push from the inside driving tire to stop abruptly, and the truck will sway into the turn.

This sway is only momentary and is offset by the following. All the rules I just mentioned above is for when the engine is applying power to the diff. Everything reverses when the diff is pushing the engine (when you let off the gas, engine braking). In the same turn where the inside tire was pushing, you let off the gas, the inside tire stops pushing (vehicle sways INTO the turn), ground starts pushing the engine, and now the OUTSIDE tire is what slows the vehicle (vehicle sways AWAY from the turn). For Example, If you were driving on a curve to the right and you let off the gas, the vehicle sways momentarily to the right, then pulls back. If you know it will pull back, and you don't react with your steering wheel, it pretty much balances out. Of course if you are hitting the gas and letting off allot you can really exaggerate this if you want.

Off roading with a detroit... I have no complaints. Neither wheel will stop turning, even if the other is in the air, period. Nothing to turn on. Also, if you let someone else drive your truck off road, they can get through just about anything without knowing how to operate the ARB's or doing BTM.. The Detroit will get you through most obstacles.

One time, my ARB compressor died, (leaving me with an open diff up front), and I was able to finish the trail with the detroit pushing me through. If I had 2 open diff's, (with dual ARB's) this would have been a problem. So if you go with dual ARB's, you will want the parts and know-how to fix the air supply system on the trail.

The detroit in a '98 is a good idea. keeps you from having to do BTM on every uneven surface (when 2 corners get light). There is always weight on at least one rear wheel at anytime. You can still lock up the front with BTM when you need it, no ARB complexity. I like it.

Clarke.... while you are almost always correct, I must chime in here on this one. The detroit does not act like a limited slip diff which will lock when enough power is applied. It will differentiate, even under power. see my detailed description below to understand how it works:

(rerun: I wrote the following a while ago, but some of you may find it interesting)
First of all a Detroit is not a "spool" diff. It is not a locked axle, all the time. It does differentiate when turning. What is unique is how the detroit allows this to happen. The detroit will not allow one wheel to slow or stop as long as the drive line is turning, but, it WILL allow 1 of the wheels to go FASTER than the drive line would normally make it turn. This occurs when you are turning, the ground will push the outer wheel faster than the drivetrain. This is why only the inside tire is pushing while in any turn (the outside tire is being pushed by the ground faster).

If you are on a twisty road, the wheel pushing will keep switching to the one on the inside of the turn. This is where the "twitching" comes from. This is also why you may think the axle is locking under power...(especially on ice) since all the power is going to the inside tire when turning, it is easy for it to break loose and match the speed of the outside tire (not good on ice). It won't spin faster than the outside tire though like on an open diff. You can give all the power you want, and the detroit will differentiate until the inside tire speed matches the outside tire speed.

Off roading with a detroit... I have no complaints. Neither wheel will stop turning, even if the other is in the air, period. Nothing to turn on. Also, if you let someone else drive your truck offroad, they can get through just about anything without knowing how to operate the ARB's or doing BTM.. The Detroit will push you through most obstacles.

My rear locker is an Aussie Locker, which is similar to a Detroit Locker. These are not selectable lockers. They are full time lockers that will unlock in a turn to allow the wheels to differentiate. I have been testing it for several months now in my truck before offering it for sale in our reman diff's. I have been very happy with it's on road characteristics. No noise, no driveline slack. Can't really tell much difference from the stock Torsen's Offroad... well, let me just say BTM is cool and it works, but lockers make things MUCH easier. I have not yet been able to test it on snowy roads, due to lack of.. well.. snow. I am planning to install one in the front to see how a full time locker like this handles in the front and how much it affects the steering. I wouldn't try this on road with a Detroit, but this locker seems to differentiate in turns rather easily as long as you don't get grossly stupid with the throttle.

I do not have any specific information on how much torque that Aussie can hold. I can say that from cruising other offroad forums, I haven't been able to find mention of a failure yet. The manufacturer states that the main gears are made from a strong alloy, but they do not state specifically what it is. My personal belief is that you are still much
more likely to break a halfshaft or other driveline component first. I do think that either the Detroit or Aussie will last longer than the stock Torsen's

As far as backlash goes, there is noticeable backlash in the unit as assembled. It is necessary for proper function. The only time I am able to notice it is when I abruptly let of the throttle, then abruptly get back on it. Even then it is not very bad, and I don't normally drive that way anyway nor would most people. Other than that situation, it doesn't seem to be any different on the street than the Torsen.

ARB Air Locker: I have ridden in Hummers that have had these installed and they performed very well. I think some list members in the past may have had some trouble with leaky air lines. Check the archives. Disadvantages: When unlocked they are completely open. It would be nice to retain some limited slip type functionality when unlocked. They are more expensive than the auto-lockers, but that is to be expected with any selectable locker. Complicated design, more stuff to break.

Detroit Locker: The standard by which all other lockers are measured. Beefy and reliable. The older style Detroit's tend to be a little noisy in turns and have some clunking from backlash, which is normal. The newer SofLocker's address this issue, but all auto lockers will exhibit some degree of backlash. That's inherent to the design. I have not yet had the opportunity to drive a Hummer with the newer one installed, but I have driven other vehicles with it. Basically, they are always locked until you turn the vehicle. The torque input from the outside wheel in a turn will cause it to unlock. Disadvantages: Non rebuildable, must be replaced as a unit. Street handling is a little different, but manageable as long as you are aware of the differences. You must use caution on wet or icy pavement and don't get stupid with the throttle (which you shouldn't anyway even without a locker). Not recommended for on road use as a front diff.

Aussie Locker: This is the one that I have been using in the rear of my truck for the past 6 months or so. It is an auto-locker similar to the Detroit in function. I have found it to be pretty much unnoticeable on the street. No noise, very little backlash. In fact, it has been tame enough that I am willing and about to test one out in the front as well. I have not yet had opportunity to drive it on icy streets, but I feel like it will do OK with some adjustments to driving technique. It is simple in design with only a few parts and is easily rebuildable by the average mechanically inclined user. Disadvantages: Same as Detroit, except as noted above. These require additional hard-to-find components to make them work in the Hummer, so availability is pretty limited.

Eaton E-Locker: Kinda the best of all worlds, locked when you want it to be locked, limited slip when you don't. Detroit is supposedly working on the Electrac for the Hummer, but who knows if it will ever happen. Disadvantages: Cost, I'm sure will be one. Added complexity is another. I would be concerned about the potential for it to stick in locked mode.

How do I know if I have a Locker installed?

Take it off road with a bunch of other Hummers owners , if you leave them all stuck beind you (it is not beginers luck) you've got a locker, If it's unlocked you'll find the more experienced drivers waiting for you with recovery straps (which is normal when your first learing the rig.) Or Put the rig in park, (so the drive line will not spin) jack up the rear end, have one guy hold one tire while you hold the other, then rotate both wheels rearward as far as posible to lock both wheels. With the the left wheel held securly in the rearward direction rotate the right wheel slowly forward, a faint indexing or clicking sound should be heard as the detroit disengages on the right side, with the right wheel slowly rotating forward the left wheel should be roating slightly forward (this will lock both wheels). Or the other clasic test from the owners manual is to drive up against a solid obstruction (on loose dirt or gravel if posible) and atempt to spin both wheels togther.{ have!someone else tell you if both or just one wheel is spinning (excercise caustion when performign this test to avoid damage to vehicle or obstruction) The way I like to do it is to strap your rig to a good size tree on wet grass and watch to see if one or two wheels spins

Now that I've had the chance to drive with a full-time mechanical locker (Detroit or Aussie) in the front diff for a few days, I thought I would take the opportunity to make some comments about it. First of all, let me state that putting a full-time locker in the front goes against conventional wisdom for a street driven vehicle that has no 2WD mode. But then again, I tend to like to find things out for myself.

You may have heard from people who drive smaller 4WD vehicles that a locked front end caused them steering and handling issues. Well, it doesn't work that way in the Hummer apparently. The Aussie has been virtually undetectable in the front as well as the rear, even on very wet roads. The noises I heard initially turned out to be a bad ball joint and other suspension wear. There is some backlash that presents itself from time to time, but it is minor and very normal. I would expect the Detroit to act similarly. Overall, I am very pleased with this setup and would recommend it to anyone that doesn't drive on icy roads all of the time (I think that occasional ice would be OK when driven with care.) Personally, I would choose mechanical lockers over the selectable types, even the Eaton (except for the reason just given), because of there strength and rock-solid reliability.

Detroit soft lockers front and rear work very well. NO problems with turning radius in two wheel or four wheel drive. In the past month I have driven on ice, snow, sand, and 3K miles of interstate.

I live in Ohio and installed a rear detroit last fall. It makes all the difference off road and is awesome in deep snow. As mentioned, on slick packed icy roads you need to pay attention if you drive over 45 or so. While under load, you quickly get off the gas pedal, the back end shimmies a bit. As mentioned, on the slick stuff you do drive differently and pay close attention while driving 65-70 on anything that is slippery.

The absolute best thing to do after installation is to find dry pavement, accelerate to 70, and let off the gas so you "get the feel".

I recently installed front ARB and rear Detroit lockers. I would have loved to buy them from AMG, but their price is just too much ($125,000, but it includes a spare truck). I wish that I installed the Detroit about 5 years ago. Off road it is just plain insane! I can crawl up things in 4HI that I wouldn't have even tried before. The only off road downside is that when you finally stop moving there are two huge holes in the ground at the back. I have yet to get so stuck that 4LOCK and backing up won't get me out.

The ARB is ok, but a bit finicky. It took 3 trips to the shop before it was working right. The first one they sent wasn't machined correctly and one axle shaft wouldn't fit in. The next time started a fire under the hood and dash when their wiring harness lit up. The third time required an o-ring to be replaced because the axle wouldn't lock due to air leakage. Now the ARB functions pretty well and adds even more to the capability of the Detroit. It is still a bit finicky about not wanting to unlock right away. I often have to put it in neutral and then backup.

While I read the Detroit was awesome off road I was hesitant to put it in because it was supposedly so bad on road. I don't agree with that at all. Under 45-50 mph I can't hardly tell it is even in the truck. Every once and a while I get a random click-click-click-click-click-clunk. I drove around for two hours in pouring rain quickly flooring it and then letting completely off trying to get the truck to spin or something. There was absolutely no reaction that I could find. Above 45-50 mph I can detect a slight sway, but nothing much. The sway only happens when the throttle is changed greatly. In the next month I am going to try flipping the axles and putting the Detroit in front. Supposedly it is real bad there, but if it isn't too bad I am going to replace the ARB with a Detroit.

A side note . . . I completely disabled the ABS a couple years ago so I have no clue how it interacts with lockers.

In terms of difficulty to install, not so bad. On mine we needed to remove the rear diff undercarriage. A lift is nice. Remove wheels, halfshafts, and calipers, Drain the diff and use a stand to support the diff to remove it. The job takes about 1.5 hours on the bench. remove the wheel flanges with a slide hammer or just use 2 bolts and nuts to evenly push them off, remove the diff cover. two bolts on each side hold the bearings in place. Remove them and the torsen carrier pops out. Our's came out without any special tools. Press on new bearings (easy) on the new detroit, install with the old shims (washers), and reinstall. Use a torque wrench to spec. Very easy - you do need a press and a lift. A helper is nice. You might as well replace the rear rotors and pads (or brake lines) since it's all apart. You will then bleed the rear brakes. Two guys - about 5-6 hours and we replaced minor stuff as it went. Nothing difficult.

Of all the work I have done on my truck, this probably had the best price/performance payback.

On the road (highway) you can notice the Detroit if you very suddenly let off the gas, the rear end sort of shimmies. For the most part you wouldn't know it was there. Snow may be a different issue.

Do you have to measure and setup the rear end? I don't believe that measuring is required since this part needs to be seated. If you were to replace the pinion, you would be measuring. light tapping on the shims did the seating. It's always easier the second time. We measured the play before and after and it was similar. A spreader would have made it easier, you need to be careful though since it's aluminum. Tapping it in with a dead blow hammer was fine.