Which Is The Correct Or Better Rear Seal For The Dana 18 Transfer Case?

I did, however I think the splines were worn out in the inside. Just comparing it to how difficult it was to install a new one. Put it this way, my old one, I can damn near push it all the way in by hand when I tried to fix his leak two times before. The outside of the shaft looks clean and smooth. No gouges or roughness. Although I didn’t take a mic to it, it could be out of spec. When I fill it up by the end of this weekend, if this thing still leaks I might just throw in the towel on this damn thing. And say it is what it is. These things leak, gotta live with it.

 

I finally spent some time this past weekend diving into both front and rear output seals. Here's the short version: The rear output seal is still dripping (more now than before) before I even moved the Jeep.

I followed all of the recommendations here. Front looks better so far but the rear is way worse. I used double Timken seals, grease packed into the seal, RTV on the splines, waited 24 hours to fill it up with oil so the RTV could set, and it was nearly immediately leaking. Major bummer. That's what drip pans are for I guess.

 

Are you certain you torqued the yoke all the way down.
I learned this the hard way.

 

I'm not necessarily 100% positive but I used a 4 foot cheater bar on my breaker bar so I would like to 'think' so.

I haven't seen any mention of rear bearing cap shims. I put what appeared to be a paper gasket back in place but I wouldn't say I did anything to seal it necessarily. What needs to be done there?

 

I see what you are referring to there. I didn't remove that section of the output housing so nothing changed there that I would have thought would lead to 'more' oil leaking right off the bat. From my recollection of rebuilding this 25 years ago there are definitely shims there.

 

Is it possible to replace the seals without rebuilding the case?

 

Yes, can even do it under the Jeep.
The OP looks like that’s what he may have done.
@KarlWithaK I hope you get it figured out and tell us about it.

 

I did this job ( for the third time)back in May and I’ve been driving the jeep almost every day here in Southern California enjoying the weather. Anyways, third time was the charm. I replaced the output shaft flange with a brand new one that I purchased from Kaiser Willies, ONE, double lip seal and RTV on the splines and it hasn’t leaked a drop since. Like I mentioned previously,when I installed my old output shaft flange I could almost slide it all the way down the shaft by hand before I tighten the nut down. With the new output shaft flange, I can barely get it started on the shaft. I had to use a rubber mallet to get it started half way down and then screw the nut down to get it to slide down the rest of the output shaft into position. That tells me that the splines on the old output shaft flange were worn out enough to not seal even with the RTV and that’s where the oil leak was coming from. Oil was running down the inside of the backing plate and out between the backing plate and the E-brake drum.,

 

I don’t have the fsm so it might be called out, but is there a different end play clearance if you’re using used bearings? I’m going to remove this housing to seal the shims.

 

I will keep you posted

I’m thinking that maybe the shaft is worn down at one spot and maybe the seals fell right on that spot. I suppose the splines is still possible too but it wasn’t that bad of a leak before and it didn’t have RTV on the splines before.

TBD.

 

I know many contribute leaking due to the outer bearing surface of the flange to be worn down, and in some cases that can be very true. For me, it was the splines on the inside of the flange that were out of tolerance. I don't know how one would determine that other than the ease or difficulty of installing the flange itself. like I said, replacing the flange was the ticket for me. Some say stay away from Omix-ada parts, but thats what Kaiser Willys sold me, and it it seems to be working, leak free. And id guess, that it's possible that the output shaft flanges could be worn down too, but thats a whole other project. Full rebuild. I got lucky I guess.

 

Everyone that is replacing a seal needs to check the shaft for play. Every one iv ever done had way too much. The seal isnt going to seal for long if your shaft is flopping around! The book calls for .003 I think. I set them at zero or as near as i can get with the available shims. Its easy to do. Pull the housing off and tap the bearing race in as far as itll go. Hold up the housing with no shims and measure the clearance. Use that many shims. All will be right with the world. I use one double lip seal set on the best part of the flange. Remove the flange that holds the felt seal but try not to scratch the shaft. You can sand out damage just dont go crazy with it.

 

Well I haven’t had time to pull the rear output yoke back off but I plan to do it this week.

It seems like everyone here is saying to avoid the Kaiser-Willys and Omix replacement yokes but I haven’t seen anyone recommend where to get replacements? Is this a replacement part that no one else is making with the expected level of quality?

 

I used it, fit like a charm. Not single drip sense from there anyway. I’m
Sure there are other tolerances and situations at play for all Dana 18’s as to why they leak. I just might have gotten lucky. Keep in mind, the Dana 18 likes to leave its mark. It just leaks. It’s the nature of the beast. I’ve got some slight oil leaking from the shifter rails. My therapist made me come to terms with it.

 

There's a Timken double-lipped seal that's recommended over the omix replacements - Timken National 473229

 

To clarify, I was asking specifically about the yokes, not the seals. Im already using the Timken 473229 seals.

 

Gotcha, apologies.

 

Went round two with the rear output last night. Unfortunately no real smoking gun. I'm not going to mess with it again for now even if its dripping (spoiler: it always has anyway as everyone would expect).

Based on the suggestions here, it's 'possible' it wasn't tight enough. I was able to get it off with just my breaker bar alone without a cheater bar. I can't say for sure it was at the specified 250 ft-lbs. It's back on a bit tighter but still can't really guarantee it.

The splines didn't seem to have any oil so the RTV seemed to be doing it's job on the splines.

I'm not sure what the specs are for the outside diameter of the yoke. Mine had .0035" difference from the shiny spots to the spot in the middle that you can see wear. That worn spot was 1.5465 with the main shiny diameter at 1.550.

Can anyone chime in with what this should be? I assume it's 1.550 nominal? I'm using the Timken 473229 seal which is spec'ed for a shaft diameter of 1.562. Being a double lip seal and the narrow band that is a smaller diameter, while using 2 seals, it seems like this wouldn't be the main driver of the leak BUT, it's also the part that changed so it must be.

I did check the output shaft plan and the most I could get it to move was about .001". It took a lot of force to get it to move.

I think that's that for now. I did get all the dimensions to CAD up the yoke. I'm considering making my own with a slightly larger diameter. Pretty easy part for the mill-turn machines we have at work that are already setup for cutting 4340.

UPDATE:
After I wrote this and was thinking about how silly it would be to make a new yoke to fit the seal I went to the Timken website and used the search tool.
Timken 473229: Shaft diameter = 1.562 (LINK)
Timken 473228: Shaft diameter = 1.500 (LINK)
All the rest of the dimensions for that seal are exactly the same.

I'll probably do this one more time with the 473228 seal to see what happens.

Some pics: