What is this? Thin spring inside where slip yoke enters transmission
 

I'm trying to fix a leaking rear seal out on the TH350. This spring was behind it, just hanging there loose not attached to anything:

https://c2.staticflickr.com/2/1634/2...8fe001db_b.jpg

Re: What is this? Thin spring inside where slip yoke enters transmission
 

That spring is part of the lip seal you removed from the tail shaft. It holds the lip seal against the drive shaft yoke. Your new seal will have one in it.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

I agree, it's part of the old seal

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Thank God! I was afraid I'd broken something inside the trans, while fighting to get that stupid seal out! It took some real doing. I basically had to tear the seal into pieces to remove it.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Well I replaced the seal, hopefully that will stop the massive leaking I've been getting from the rear of the transmission.

Thanks for the info on that spring.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Darn thing is still leaking. There is already a small puddle under the rear of the transmission.

The leak originally started when I removed the drive shaft to have a new u-joint put on at the back of the drive shaft. Now I've replaced the transmission's rear seal and it still leaks.

I read that some transmissions have an o-ring inside that can be replaced which requires removing the extension housing. Could that be it? Wouldn't the rear seal stop any fluid leaking past that o-ring? (The slip yoke does NOT have a 'weep hole')

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Does the seal fit snuggly on the yoke? I think I read somewhere there were two different diameter yokes. won't hurt to check..

Re: What is this? Thin spring inside where slip yoke enters transmission
 

It seemed to as I inserted the yoke, but I wasn't actually looking for a problem there so I could have missed it. Any idea what the two possible diameter sizes are?

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Is there a grove worn into the yoke ?

Re: What is this? Thin spring inside where slip yoke enters transmission
 

I actually did look for that - all looks smooth, no scrapes, scratches or gouges.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Where is the leak exactly?

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Dripping from the end of the tailpiece (?) right under the bottom of the rear seal I just installed.

The exact spot the picture shows, with the yoke plugged into it all the way and the DS fully reinstalled.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Did you lubricate the seal before you installed the driveshaft?

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Yes - took some trans fluid on my finger and ran it around the seal a few times.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Get under the truck and spray the tail shaft/seal area with brake cleaner. Then watch closely to see where the leak is coming from. Is the tail shaft possibly cracked where the seal presses in? I always put a skim of RTV around the outside of the seal before I press it in the tail shaft. Good luck.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

I had this same problem a while back. Turns out it was not the seal leaking but the speedo gear housing. It was running down and dripping off the bottom of the grand below the output seal. Might check that out to make sure it's not leaking there.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Alot of good suggestions so far. It does look like a lot of gouges/dings where the seal presses in. did you use any RTV or anything before pressing it in as suggested above?

Re: What is this? Thin spring inside where slip yoke enters transmission
 

I agree on the nicks/gouges. That would open up a pathway for a leak for sure.
RTV would surely close the gaps, but you want to make sure that area is dry and free of trans fluid, at least until the rtv cures.
Ben
:metal:

Re: What is this? Thin spring inside where slip yoke enters transmission
 

I would agree with the gouging being the culprit since it started leaking after the stubborn removal of the seal :lol: Been there done that, I agree with others.. clean and flatten out any rough spots, install new seal with light coat of sealant where gouged. I would double check slip yoke for rough spots, small nicks. I also recommend this seal puller . It is a pilot bearing remover, but It is a must have for seals in tight spots :chevy: Good luck :chevy:

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Thanks for the leads and good info everybody.

Two more:

1) is there more than one spline size a seal might need to fit, and if so what are the sizes?

2) if the spedometer cable connection could be leaking (as one person above said), how would you resolve that? Mine is a little loose feeling, I can wiggle it by hand. Is there a seal or gasket under that connector that needs to be replaced?

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Don't know about question 1; but here are photos re the speedo question - (wait; this was a TH350 right?) .. oh well, I'll assume so - here are the photos - it is an o-ring.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

I'll throw in my $.02 . When I put a lip seal in I put some grease on the "spring" on the back side of the seal and rtv around the metal to metal seal. Installing the seal can also knock the tension spring off the back of the seal.Should be able to check that out by pulling the driveshaft back out and looking in around the tailshaft.
The speedo adapters also have a small seal between the gear and adapter also don't they? I think to keep the tranny fluid away from the speedometer

Re: What is this? Thin spring inside where slip yoke enters transmission
 

On a TH400 there is s small lip type seal (some guys put in two) that seals the housing to the plastic speedo gear shaft, and there is also an o-ring that goes on the aluminum housing that the cable threads onto. You have to remove the one bolt that retains this housing to the transmission case in order to remove it and replace the seal and o-ring. Sorry I don't have any pics of this, but if you do a google search you will find pics.

Re: What is this? Thin spring inside where slip yoke enters transmission
 

Found a photo for you of at least one for sure spline size for the TH350 with a V8..

The caliper is just a cheapie and so the measurement shown is plus or minus probably about 1/16th lol

But still don't know if there were other sizes - might try typing in your truck on an auto parts website & see if it asks you to choose..

Re: What is this? Thin spring inside where slip yoke enters transmission
 

a TH350 slip yoke is a TH350 slip yoke, so if it's the proper slip yoke, you should be fine as far as outer diameter of the yoke vs seal lip dia. Did you look before installing to see if it was a slight interference fit on the yoke? or could you look now by inserting the yoke a bit? Should be fine. Speedo leaks are maddening, but, if you clean and wait to see where it leaks as mentioned above (as in literally stare at it and don't drive it - or at least don't drive it before you check it again, because the wind from driving will trickle the leak back toward the tip of the tailshaft and it will be hard to tell again) you should be able to decide which it is. If it's definitely the rear seal, the only advice would be as already mentioned - thoroughly clean inside tailshaft lip, tap it in, then rtv it a bit around the outer dia of the seal/tailshaft mating circumference. Don't put a big glob of rtv inside the tailshaft then whack the seal in - it will dry, detach, and end up back in your trans somewhere you don't want it to be.