Diesel Gods,
How do you change your rear differential fluid? ??? Where is the diff drain plug for my truck? My truck is at 30,000 miles, should I use synthetic??? :-[ Also, I hear of guys that have said not to fill it to the top? Need as much info as possible. Does Geno's have a thread on changing the rear diff fluid? Obviously I've never done this before on this truck. Thanks for the information. Love my Cummins. 8)

 

There is no drain plug. There are 2 ways of doing it. One, you pry the cover off and let the gear oil drain, or two, suck it out with a pumping device. BTW, the no drain plug thing is normal. You didn't get taken or anything like that. ;D Synthetic?.....I would. I think the stock cover holds 4 quarts, but don't hold me to that. Don't forget to have some LS modifier on hand if you have a LS rear. Most swear by Mopar, but I've used Kendall with acceptable results. If you do you do a lot of pulling the Mag-Hytec differential cover holds 2 additional quarts and really looks nice under a 4x4. 8)

 

Some differential info here:
http://www.dodgeram.org/tech/specs/a...RBI_specs.html

Mag-Hytec Info:
http://www.mag-hytec.com/differential%20covers.htm

With the oil level in the diferential below the lower edge of the fill plug hole, less oil is available to reach the axle tube seals out by the wheels. Then these are basically running dry, with an occasional splash of lubricant when you zip around a corner.

You need to fill the differential to the lower edge of the fill plug hole. Sme people have been known to have one of the rear wheels on a curb or a block of wood to enable them to add a little more lube oil for the benefit of the seals.

The Mag-Hytec does this by having the full mark on the dipstick high enough to keep some oil in the axle tubes.

Usually, at about 85k miles on the truck, with the stock oil level in the differential, the axle tube seals get tired, and start leaking oil onto the brake shoes. After that, the best way to repair the sealing areas on the axle shafts is with a Speedi-Sleeve.

I decided to put a Mag-Hytec cover on when I had about 25k miles on my 98.5. I figured I could spend the money back then on the cover, or later on new seals and the sleeves. So far with 86k on the truck, everything looks good on the seals back there.

 

Mag-Hytec really makes a difference. Noticably cooler when pulling, use dipstick and clean any materials off. Oil seems to stay cleaner longer. Easy to drain, fill, check oil level etc. Comes with the Allen wrenches for it.