Hey folks, Im in need of some guidance on my turbo 350 and the rear seal leak that for the life of me, I cant get to seal correctly. I have a leak from the actual seal itself, and a larger leak from the U joint area as well. I have removed the entire tail section, installed a new bushing, and at this point, I am on my 3rd new seal. The trans starts out with a s l o w leak, like a nickle sized spot over the course of 3 or 4 days in both spots without driving it, but as soon as I put ANY miles on it, the leak turns to a softball sized leak from each spot over the period of one night. The facts: The trans is behind a bone stock 350, and installed in my 53 Chevy 150 on air. I had a custom driveshaft built for my application, and one of my concerns is that maybe the shaft is too long and ruining the seal, or two short when aired to a certain height, and ruining the seal. Neither of these ideas can I prove, or even know if they are possible but with roughly 8" of height adjustment from the bags, im concerned that maybe the shaft is bottoming out on the back of the trans itself. I also know that while driving the leak seems to be substantial, due to the odor of trans fluid on my exhaust, and the nearly complete coating on the underside of my car. The tail section has a small "ding" on the bottom of the seal edge maybe 1/8th of an inch, as if the trans was dropped on the bottom of the tail section at some point in its life, and Im thinking this is possibly the culprit. This is my first build, and everything has been smooth except for this silly leak. I am at a complete loss on the solution, and really dont want to pay a trans shop to diagnose the issue. Can someone please shed some light on a possible fix? Thanks! Jaison
If that's the problem, then replace the housing and see if it fixes the leak. If you post some pictures we might be able to help you figure out what's wrong.
i am going to respond w/ this , possibly your tourqe converter is leaking back into trans. i have no posts to give any backup. even if its possible. just a theroy.
seems I remember some earlier gm trans had a hole in the yoke and if you use it on an output shaft with a blind spline the oil exits out the yoke and you have your self a leak, the remedy was to braze the hole shut. One idea was to run a blind spline and the oil could get to the back and around the splines to help keep the splines wet so they would not wear prematurely, the other idea [ not real common ] was to have a hole in the yoke and a full set of splines and a small amount of oil would find it's way out but at least it wouldn't hydraulic when the splines need to work back and forth, if you have this setup and its worn you could lose extra oil, if you have the output with an open spline and an open yoke your problem will be worse. I don't remember ever seeing this on a th350 but it definately exists on th400s.Maybe some other hamber has more insight or could explain this better.
It doesnt hurt to check the cap in the center of the slip yoke, you can do it by removing the shaft and cleaning it inside and out with some brake cleaner and then fill the center with water. I have seen them leak a time or two. they can be welded up to seal them.
and then i read your original post. you answered your own question....... replace the 1/8 inch of a ding.
If the tail section has a "ding" in the seal area the seal will probably never be perfect. Find a new tailhousing without any "dings" and see if that cures the problem. If your not sure of thedriveshaft length raise your bags to full height and check the measurement of the yoke out of the tailshaft housing, then put the system at full drop and check to see if the yoke is indeed shoved up against the seal, if it isn't measure this distance from tailhousing to yoke, also when you take the measurements mark the yoke at the seal both in the up and down positions. Now disconnect the driveline pull the yoke (plug the tailshaft) and see how much of the yoke is inside the housing based on the marks you put on it, there should always be at least 1 1/2 to 2'' inside the housing, if there isn't it will wobble and ruin the seal.
in stead of me giving uneducated guesses, how is the yolk shaft on your d-shaft.? are there pits from rust over the years b-tween the trans seal and yolk where it slips , it could be wearing out your seal prematurely. mabe some emory cloth to smothe things out . do you install your seal dry?
I checked the yoke this week when I installed the 3rd seal, no hole in the yoke at all, only what appeared to be a extra wide spline on one of the sections, if that makes sense. I also cleaned the yoke and poured enough fluid down it to fill it half way and left it over night, and it never leaked. The yoke is clean and smooth, no pitting or rust at all. And when I measured things for the shaft, I ran the yoke in the trans until it bottomed out, then pulled it out roughly 1 1/2 inches and took my measurements. The latest seal was installed on my bench, as to get it in as perfectly as possible and lined with fluid before the shaft when in.
can you grab the drive shaft, and wiggle it inthe trans (in other words play btween the yolk and trans shaft) rear trany bearing? or is it tight. theres nothing sexual here..
one thing to consider about the transmission is that the seal maybe okay, but your driveshaft has worn where the seal touches it. It happened all the time with diesel engines and front main seals (happens on regular engines too that is why they sell a repair kit). This maybe something to check with a set of calipers. And dumb question but there is a reason why I am asking.... do you lube up your seal before installing your driveshaft?
I honestly haven't tested the play in the shaft itself, but the output shaft had roughly 1/8 of play, so I put a new bushing in it this weekend when I installed the latest seal. The yoke is very smooth, and has no visible wear, so I dont think it's that. I guess I'll located a new tail section, and if that doesn't fix it, I'll have a new yoke put on it. Jeff, I don't know that the yoke run out is, so I can't comment :-/
Check the vent on top of the trans. If the vent is clogged fluid usually comes out the dipstick tube but check it anyway. peace
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