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Transfer case Cooler Article

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This install was done by Rene Milas:

I just finished installing an auxiliary external cooler for my Tcase. I'm in Europe and it cost me around 1,200.00 US to do the job. The cooling kit is composed of a Weldon 9200 pump , a Mocal cooler (16x22cm), an oil canister with dipstick and some hoses. The system circulates Dexron III through the tcase internal cooling loop and an external oil cooler. Tcase oil remains separate from the transfer case lubricating oil.

Here are some results of the operation external cooling of the tcase tested over 10000 km of which 7000 km in the dunes of Libya. The cooling pump was wired to remain on all the time during this test.

Transmission: oil temp rose about 1 degree C. per km/ hr speed. Driving at 120 km per hour (60 mph) equals 120 celsius or 248f. The oil quality after the trip was good as new.

The transfer case oil temp did not go up on highway; it remained lukewarm. Severe off road use in low lock saw a raise of Tcase oil temp to somewhere around 50 C degree 122f.

After my evaluation I installed a thermostatic switch to control the pump and increase its life expectancy. The switch is set to turn on at 83 Celsius 181F.

If you want a temp gauge on the tcase and transmission see this article.

If I ever drop the case for maintenance, I will get rid of the cooling loop and re circulate the tcase oil direct.


Oil filter canister I found it at a surplus shop with a nice cap and measuring stick. 60.00.
Since I'm not circulating the actual lubricant in the transfer case I don't need to use the filter.

MOCAL / Aeroquip oil 172-55 cooler 16cm (6.25") x 22 cm (8.75") Europe 70.00. You can get a Permacool 1310 3.5" x 14" with 3/8 npt female fittings for 50.00

Weldon, 9200 pump (A sliding vane pump). 14 volt motor. Ports are -6 JIC (9/16 x 18) female. The pump body is machined from billet aluminum, rotating parts are heat treated high speed steel in precision bearings. Adjustable cam ring for varying pressure/flow. Suitable for all fuels and oils will pump 90 wt oil at 70oC 158f)
Weldon 9200: 700.00

16 feet of Gates GT8H hoses 1/2 diameter. GATES hoses which are good to 130°C 266f connecting direct on the Tcase cooling loop. 150.00

Push-fittings about 100.00

Thermostatic switch: Marelli p/n 116580729903 , or FIAT p/n 313320172 and 6313320172 working in the range 75°-85° Celsius. 167 to 185f

The system requires about 2 1/2 quarts of Dexron III.

The oil lines and oil/air cooler and a remote oil bottle (as on power steering) are not shown.  An oil filter is not used since the oil flows thru the transfer case cooler loop.

The pump is setup so that it only will come on when the engine is running. That's why we take the control feed from the ignition source. Most of the trucks have an ignition hot down on or near the fuse box.

Under dash grounds are taken from the master ground point which is on the drivers side left pillar.

System includes a Weldon 9200 pump which draws about 9 amps at full output. The pump is controlled through a relay which is activated by a FIAT/ Marelli radiator fan thermostatic which threads into the Tcase oil level plug. I have a few warning lights so I know that the system is operational.