Transfercase Oil from Yokes

W_A_Watson_II · Post by **W_A_Watson_II** » Tue Apr 14, 2009 6:26 pm

when I went through the M this winter I replaced the Transfer case seals as they were leaking bad. After this past weekends fun, I noticed a little oil leak from the T-case. When i crawled under the truck tonight for a quick inspection I noticed that the t-Case leak seemed to be not coming from the yoke seals, but the yoke to drive shaft joint, as if it was seeking through the yoke splines.

I'm running John Deere GL5 85-90 wt oil, is it seeping through the spline joints? Is this possible? Should I be re-checking the yoke torque? thoughts?

Post by **Cal_Gary** » Wed Apr 15, 2009 5:51 am

Hi Will,
The only way oil will creep out the splines is if there is too much clearance between the shaft and yoke splines. These normally do not wear much as ther shouldn't be any back and forth movement between the two-that's the job of the prop shaft. You could probably run a bead of silicone around the inner end of the yoke then slide it on-that would likely eliminate any seepage from the splines (would also make the yoke harder to pull off the next time).
Gary

Lifer · Post by **Lifer** » Wed Apr 15, 2009 7:57 am

I've never torn into a transfer case, but my experience with numerous engines, transmissions, differentials, and axles has shown me that oil seepage is always due to it getting past the seals. I know you "recently" replaced your seals, but several possibilities come to mind.

(1) If you used NOS seals, they could have become cracked/dried out from years of sitting on the shelf, in which case they may leak a little.

(2) You might not have gotten the seal seated correcly or possibly damaged it a little during the installation procedure.

(3) The shaft of the yoke that goes through the seal could be pitted/scarred, which could cause it to "eat up" the new seal.

(4) It could just be "the nature of the beast." We all know that M37s are like Harleys...they like to mark their territory. As it is now, you'll know when your t-case is low on oil when it stops dripping.

MSeriesRebuild · Post by **MSeriesRebuild** » Wed Apr 15, 2009 2:58 pm

What you describe is very typical, oil will leak down the splines & come out around the nut. Tightening the nut will not stop it, but this will; remove the nut & the flat washer from the shaft. Wash off all oil residue with aerosol brake cleaner & dry with compressed air. Run a nice bead of high quality silicone RTV around 1 side of the washer, install it onto the shaft carefully, siliconed side first along with the nut, blue lock-tite on the threads is a good idea. Torque the nut to spec. The silicone will compress into the end of the splined shaft under the washer, you won't have this problem again once you do this. This is standard procedure for us on all cases we build.

W_A_Watson_II · Post by **W_A_Watson_II** » Wed Apr 15, 2009 3:24 pm

Thanks Guys. Here are a couple of pictures. There is a little past the housing seal seapage, but in the first (year) you can see some oil on the cross member. On the second (front) you can see some oil trails on the yoke face.

Lifer · Post by **Lifer** » Thu Apr 16, 2009 6:43 am

Charles' fix sounds like it ought to work. He's done enough of 'em to know what he's talking about, so give it a try. I know I will if I ever get that far with my truck.

HingsingM37 · Post by **HingsingM37** » Fri Apr 17, 2009 8:30 am

So Will after reading your post I go out and check mine and sure enough I have a flim of oil on my frame crossmember under the same yoke. I had installed new CR seals and speedi sleeves so figured I was good to go. Now that I think about it that of course would not keep seepage from the shaft splines. Guess I will add another item to this weekends list and use Charles's fix as well:)

Lifer · Post by **Lifer** » Sat Apr 18, 2009 5:07 am

"Oil film" = "rust protection," does it not?

skinnedknuckles · Post by **skinnedknuckles** » Sat Apr 18, 2009 11:50 am

I use locktite 515 gasket eliminator on all of the spline to yoke connections that I do for semis, loaders, scrapers, and trucks. Just clean both internal and external splines and smear some all the way around, about a 1/4" bead, on the internal splines on the yoke seal end (not seal surface) and slide it on. As it slides on it will fill in voids as it goes on and it leaves a small amount out where the nut seats. tighten the nut and by the time you are ready to put in gear lube it has set up, lack of oxygen makes this product cure. When I open a new tube of this stuff I through away the lid and toss the tube in a drawer it lasts for a long time as long as oxygen can get to it.
Paul in Janesville, Wi
1945 CJ-2a
1952 m37
1955 CJ-5
1961 m37
1971 m35a2 4x4 w/w
1971 m35a2 6x6 wo/w
mvpa#31337
turnin' the big wrench for almost 30 years ....skinnedknuckles