Should I do my own Work on My Diff - Detroit Locker?
Updated June 5, 2012
How to identify your diff:
Hummers came with 3 types of diffs and 2 ratios depending on the year. The T2 has a much lower torque bias than the older T1. That means that you pretty much can't use BTM (brake throttle Modulation) on a T2. For that reason a T2 is not as good as a T1 off the road.
All the trucks up to and including 1998 have T1 diffs. All the trucks up to and including 1997 have 2.73 gear ratios. The 1998's which have T1's are the only truck with the same rear end ratio; 2.56:1 as all the newer trucks with the T2's. This means that you can't mix diffs from trucks built before and after 1998. The 12k rated trucks and armored hmmwv's have 3.08 gears, but those are pretty rare.
Diffs will normally have a tag on the cover stating the ratio and type. Below is a 2.56:1 T1 diff. Otherwise, open the cover and look on the outside edge of the ring gear. The tooth count will be stamped there. 41 15 for 2.73 and 41 16 for 2.56. As mentioned, T2s almost always come in a 2.56 ratio.
2.56 can also be found in almost all pre 94 Humvees.
In response to customer dissatisfaction with TT4 and a desire to make the Hummer even better, AMG offered The Eaton Electrical Locker in the rear of the 2003 and newer Hummers and in the front and rear of the 2004's and 2006's equipped with the adventure package. The locker has many of the benefits of the Torsen without the drive line stress and leaves the TT4 active to boot. The Eaton diff is a full electrical locker with an integral limited slip (posi traction) clutch pack. It's the best of both worlds.
Should I rebuild my diff?
by Scot Smith:
Here is a quick run-down for you. This is not a complete step-by-step, but it will give you an idea about what you're getting into, if you have never done anything like this before. This is not a job for a novice or the under-equipped. First of all, since your ring gear is shot, you will have to do a major overhaul, which means you will need all of the bearings (actually two sets, more on that later), all of the seals, a ring & pinion set, dial indicator, assorted hand tools, a press, bearing puller, torque wrenches, and a case spreader. You can't just replace the ring gear itself. Ring and pinions are matched sets. You also need to inspect the gears on the Torsen unit very closely and make sure that the pieces from your ring gear didn't screw it up as well. If it did, it will not be worth it to rebuild it yourself. Also, if you don't have most of the tools listed above already, then you are about to spend a great deal of money on this.
First, remove the cover, pinion yoke, output flanges and stub shafts/output bearings. Next remove the two large bearing caps that are located on either side of the carrier case. There is a notation on them for the direction they should face and for which side they should be installed on. Make a note of this; they will need to go back on the same way they came out. Now you will need to remove the carrier/ring gear. Here is where a case spreader comes in real handy. The carrier is fit rather tightly in the housing. Under the bearing caps, next to the carrier bearings, there will be one or more shims on each side. Note which side you remove each shim set from. This will be a starting point for reassembly. Next, remove the pinion seal and drive the pinion out of the housing and save the old crush sleeve on it. Remove the races from the housing. Under the large pinion race there is another shim. Save this one for the starting point of your pinion depth. Now remove the bearings from the carrier with the bearing puller and unbolt the ring gear. The ring gear can the be tapped of the carrier with light hammer strokes. So everything is apart now.
Now you are ready for assembly. Here is why you should have two bearing sets (at least pinion bearings, depending on the shims you will be using). The bearings are all a press fit and you will need to do several test fits to get everything set up properly. One set is for test fits and one set is for final assembly. Take one set of bearings and polish out the inside races until they slide on and off the component they will be used on. Also polish the outside of the large pinion race until it fits in the housing easily. This will be your test set. Having fun, yet? :) Place the large pinion race and the shim you removed earlier in the housing and tap in the the small pinion race in the housing. This one will stay in place. Put the large pinion bearing on the pinion and insert the pinion in the housing. Put your old crush sleeve on the pinion, the small pinion bearing, pinion yoke and your old nut. Snug up the nut just until there is no play in the pinion. Check your preload by turning the pinion yoke with an in-lb torque wrench. Keep tightening in small increments until you get a reading of 6-8 in-lb. Install the ring gear on the carrier and using red Locktite, torque to spec. (I don't have all of the specs in front of me right now, the ones that are given are coming from memory.) Place the polished out carrier bearings on the carrier. If you are using factory style large shims, you can go ahead and press your real bearings on the carrier at this time. Usually if I need to re shim the carrier, I put shims between the carrier bearing and the carrier case which is why I use test carrier bearings. Put the old shims back in the housing in the location you originally removed them from. (You did mark them, right?) Put the carrier/ring gear in the housing and install the bearing caps. Using your dial indicator, check the backlash between the ring and pinion gears. It should be .006"-.010". Brush some gear marking compound on the ring gear in several places and rotate the assembly several times. Observe the pattern on the ring. Patterns will tell you where you need to add/remove shims to get the correct pattern. Repeat the above steps until you get the pattern right.
Now you get to take it all back apart, press on the real bearings and reassemble with a new crush sleeve and new pinion seal. The new crush sleeve must be torqued to something like 250 ft-lb, then the pinion bearing preload set to like 12-16(?) in-lb. Usually depending on the fit, when I put the carrier in the housing for the last time I add a few thousandths shim to each side to tighten up the carrier bearing preload. Torque everything to spec, install your stub shafts, output bearings and output seals, and add the cover.
I'm sure I've left out a few details, but that you give you a general idea of how this job is done. Like I said before, it is not an easy job; it requires a good selection of special tools, above average mechanical skills, and a LOT of patience. I'm not saying a do-it-yourselfer can't do it, but it is usually better to leave this one to the pros.
Having gone through an install myself from ground zero, here's what it took
me and a friend to install one Detroit into my truck. Note: I was willing
to go through the torture because I wanted to learn what it takes. I've
done lunchbox lockers before, but I've never done a complete carrier and
diff rebuild like this.
Saturday - 3 hours to tear apart the old diff, remove the Torsen, mark the shims, remove and reinstall the ring gear, remove/reinstall the new output bearings on the shaft stubs, test fit the new carrier/ring gear, install bearings on the carrier. One man job.
Sunday - 4 hours to shim and test backlash, install the diff seals, seal up pumpkin. Two man job (because I was learning how to set backlash and shims).
1 Week later, Saturday - 4.5 hours to remove tires, pull rear drive train apart, pull old diff, pull calipers, put in new diff, do rear brake job, bleed brakes, fill diff, reinstall tires, and test drive unit. Two man job.
Specialty tools are definitely needed! Specifically, a diff case spreader will make life a lot easier. So will air tools, large sockets in both standard and impact, gear wrenches or impact wobble adapters, two jack stands, two floor jacks, Locktite hi temp red, Locktite standard red, Locktite
blue, new nordlocks, DOT 5 brake fluid, flare wrenches (for the brakes), rear brake tools (including the specialty tools), large wrenches to 1 1/8", etc, etc.
So, if they want to do the above for $245, that's worth it. They should have all the skills necessary to do the job right. The job that George and I pulled totaled 11.5 hours to do the job, across two weekends, working continuously across the time spans mentioned (no breaks).
Oh - you'll need the bearings and seals. Get them now and give them to your friend. I had to put in new carrier (cone and race) and output bearings, and I had to use two new outer diff output seals (you destroy the existing ones when you take the diff apart) as well as the output star seal (these get destroyed by looking at them wrong!). I also used new ring gear bolts and new diff cover bolts.
As Scot mentioned in a prior message, it's not an easy job. To quote him in the past, it "...requires a good selection of special tools, above average mechanical skills, and a lot of patience.."
Another Self Install:
Got the Detroit in (along with a rear half shaft ,the rear rotors, pads and all rear brake lines) took about 8 hours (with a few minor delays , needing specialized tools and not planning to do brake lines and having to go to the parts store 3 times too many.
Some notes . after a few miles (that I have abandoned work for ) have not noticed any abnormal handling . Did get one minor "click" when forcing the rig from a hard right circle to a hard left circle (full lock 360s). Letting off the accelerator at speeds up to 50 (so far ) has not revealed the "lane changing" my old 93" wheel base Defender used to do.
If you don't have a "slide hammer" to remove the stub axle, seal and bearings from the dif and you don't want to go rent or buy one , simply pierce the steel and rubber seal with a flat head screw driver and use a pair of needle nose vice grips to pull the seal out, put the nut back on the end of the sub axle and pull it out (mine slid out without much if any force (the seal is all that really holds them in) using the "slide free the other side up.
If you don't have a dif housing spreader don't fret, I don't recommend prying the stock dif out with our soft aluminum cases, but you can put a steel pipe through the axle holes and tap either side of it up and out with a hammer, no stress on the case and very little force is needed.
I found it very strange that the stock Torsen dif had almost 0 play (the ring and pin gears looked perfect, no wear at all so it must have been correct setting for the torsen , once the Detroit was put in (same shims, same gears ) the Detroit came up with a good .005 what we expected and were looking for... very lucky.
All in all the jobs were very straight forward especially if you refer to the other articles on this site. I just wish the breaks were as easy as the Detroit swap. A word of caution; if you have never done a dif swap you will probably get better results bringing the entire pumpkin to an axle shop and have them do the swap for you. All you have to do is put one bearing cap in on the wrong side or backwards, or not know the signs of a bad bearing or race and your in for a very short dif life. Cant wait to get it off the pavement to play.