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Topic: Leaking rear trans seal

Posted By: kcny on 03/07/14 08:30am

I have a P-30 with a 454 and Turbo 400 (with overdrive). 50k on the odometer and trans has 1/2 that.

I noticed a small drip underneath (only with the engine running) and when cold the motorhome "didn't want to go into gear" (put it in drive and it didn't move at first). Went to reverse and back to drive and then everything ran fine while I got back home.

Local shop quoted me $500 and said the rear trans seal was leaking, which would obviously eventually damage the trans and affect the auto-park.

My questions are:

1) Is $500 a fair price? What would I expect for the price, a full trans fluid flush/fill? I am mechanically inclined, is this something I could change myself?

2) Did I cause permanent damage? I assume it is way low on fluid which is why it had an issue finding gears when cold. My rig is parked at home and the shop is 10 miles away. Is it safe to just throw a couple quarts of fluid in and drive over or should I just call roadside, have them drop the driveshaft and tow it over?

.....thanks for any insight.

32' 1992 Holiday Rambler 1000

Posted By: Iraqvet05 on 03/07/14 08:55am

The output seal is leaking? That probably a $20 part. I can't see that much in labor if they are talking about an output seal and a flush/fill. Get a quote from another shop or do it yourself. You can probably get the filter, fluid and seal for about $100. The most expensive part of the process is the tran fluid with Dextron at $5 a quart. You can rent an seal puller from most large auto parts chains and do the job in half a day. Unless you ran the fluid so low the transmission wouldn't shift, you shouldn't have any damage. You can add fluid to get it moved if you need to drive it somewhere.

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Posted By: kcny on 03/07/14 09:03am

Iraqvet05 - thanks for the reply and more importantly, thank you for your service in the military

Yes, unless I am missing something on the service write-up it is the output seal. Does the auto-park mechanism complicate a layman changing the seal somehow (they definitely said it would be around $500, so trying to figure out why it would be so high).

And yes, once things warmed up a little the motorhome drove/shifted fine - the only reason why I noticed the drip is because it was landing on the hot exhaust and I could smell it [emoticon]

Posted By: Nutinelse2do on 03/07/14 09:26am


Spent 7 years in the transmission business and your question is more complicated than you think. You say you have a TH 400 with OD. Are you sure? Not a 700R4? You happen to have a picture of the pan of the trans? What year is it?

Let me answer the repair in short, the rear housing has a seal yes, but inside the housing is a bushing the rides the rear yoke. Usually when the seal leaks its due to wear on the bushing or yoke.

Back in the day, that repair was, remove driveshaft, inspect yoke, remove rear housing inspect bushing, and repair accordingly. If you can double check your trans type that would be the first place to start. Maybe it is a 400 but maybe it has a gear vendors OD unit on?

Other things you mentioned, was that when its cold it would not go into gear. This is a issue. If you low on fluid yes, it will hesitate going into gear because there is not enough fluid to build pressure to engage the clutch units. But if it is full, then that means the internal seals in the clutch units are hard and need to heat up to expand to allow pressure to build..

So in short, without seeing a picture of the trans and driveshaft it's hard to answer some of your questions about rear seal.

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Posted By: kcny on 03/07/14 09:36am

Richard, thanks for the reply.

When I get home today I will grab the manuals/service history and post the model info.

As for the "cold not going into gear" -- being that it is definitely leaking I would say it is low on fluid/not enough to engage clutch. In your opinion would I be fine with throwing a couple quarts in and driving to the shop?

Posted By: Nutinelse2do on 03/07/14 09:49am

If you count the bolts on the transmission pan that would tell me what kind you have. Or the shape. The 400 has 13 bolts and the 4l80 had 17 if I remember.

Guessing its 4L80E. As far as putting a few quarts in and driving, that depends on the amount it leaks. If there is any doubt in your mind, put it on the hook especially if you have no cost towing.

And personally I would be there for the whole repair, I would ask to check wear on driveshaft yoke and bushing in the housing and show you. You can tell if its bad by running you finger across it, it will have a noticeable ridge.

If they just pull the driveshaft off take old seal out with screwdriver, then 500 is way way too high, and only putting bandaid on problem that will come back.

Just did a quick internet search, found a tail housing kit for 30 bucks on Ebay including bushing and seal and gasket... :-)

* This post was edited 03/07/14 09:56am by Nutinelse2do *

Posted By: Nutinelse2do on 03/07/14 10:10am

As the old mind starts to come to life, started thinking of why it would be 500 bucks.

The rear housing is what has the trans mount on it, so possibly the crossmember would have to be removed, to get the housing out to do the job properly.

2.5 hours labor ( shop ours not real time )
Rear seal, bushing, gasket, pan gasket, filter, trans mount, fluid and flush.

500 is the high end but your in NY so have to take that into consideration.

Hope all this helps.

Posted By: kcny on 03/07/14 04:25pm

I'll have to wait till daylight tomorrow to crawl under and count the bolts on the pan. The service write-up just states "Found that the rear transmission seal is leaking"

In 2003 the transmission was replaced due to internal damage (i have the receipt from the previous owner). It lists the new one as a GM serta with overdrive, part number 000 008690965. A quick google search didn't turn up a match on that part.

Posted By: kcny on 05/09/14 06:54pm

Sorry about the delay, just providing a follow-up. I opted to let a shop perform the repairs while getting the inspection done.

Turns out they did need to remove the cross member and the leak ended up being the bolts for the rear housing: one was missing and one was loose! I also had them do a routine transmission service (new filter, fluid, pan gasket).

$300 and their work has a 12 month warranty - no leaks, so I'm happy with it.

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