65 transmission rear seal / bushing replacement

[JJ62]

 Hope everyone is doing well.

 My '65 sat for many years. Got it running last fall and finally took it for a drive for the first time the other day. I had to add 5 quarts of non-synthetic Mercon ATF to bring the level up on the dipstick. The rear seal is leaking. Wondering if anyone can tell me what's involved with replacing it. I'm not seeing any information on the internet about it.

 I understand that the bushing should be replaced also. I'm wondering if I need to remove the extension housing to replace the bushing or if I can get by with just replacing the seal and bushing. This "Turbo 400 3L80 Transmission Extension Housing Reseal Kit with bushing" is on eBay right now.

 

https://www.ebay.com/itm/GM-TH-THM-Turbo-400-3L80-Transmission-Extension-Housing-Reseal-Kit-with-Bushing/141635900617?hash=item20fa2854c9:g:-7AAAOSwPhdVKxYq

 

Also there's a note at the bottom of the kit that says: 

These are the larger components. If your vehicle is a 1964 to 1973 model year, be certain you don't have the smaller 2.5" diameter

rear seal and the smaller 1.800"  diameter bushing. 

 

Would mine have the larger or smaller components?

 

I do have a Riviera Service manual.

 

Any help is appreciated!

 

Jim

[1965rivgs]

  If you are replacing the bushing probably best to remove the extension housing and do so on the bench. The correct parts for the application should be available at any auto parts store or on line at Rockauto.

Tom Mooney

[telriv]

More than likely the manual will not give you the size, although '64-'67 are the smaller diameter. You could go to a salvage yard & get the newer, '68 & up, tail housing. It's the larger one & also a new yoke is available. 

It's all a bolt-on.

The older stuff is becoming harder & harder to procure as time goes on.

[RockinRiviDad]

While chasing down a vibration I found my 65 tailshaft bushing was worn badly. Lots of slop in the dshaft. I bought the parts, I took my tailshaft off & the parts were wrong 😞

 

So I took tailshaft to a trans shop that only deals with old transmissions. He claimed very few people have the right bushing 🤷🏻‍♂️. He sold me the right stuff, he removed the old seal & bushing, pressed in the new & sent me home…all for $35…I was happy…but my vibration is still there 😩

[JJ62]

8 hours ago, RockinRiviDad said:

While chasing down a vibration I found my 65 tailshaft bushing was worn badly. Lots of slop in the dshaft. I bought the parts, I took my tailshaft off & the parts were wrong 😞

 

So I took tailshaft to a trans shop that only deals with old transmissions. He claimed very few people have the right bushing 🤷🏻‍♂️. He sold me the right stuff, he removed the old seal & bushing, pressed in the new & sent me home…all for $35…I was happy…but my vibration is still there 😩

 

I know these driveshafts have a lot of parts, like the center support bearing that can wear out. I will probably take the housing off and measure the tail shaft so I get the right parts.

Thanks for your input.

[JJ62]

 

So I've pulled the driveshaft out, dropped the rear tranny mount and gotten the extension housing out. My housing has an o-ring instead of a paper gasket to seal the housing to the transmission. Problem is I'm seeing a lot of paper gaskets listed, but few O-rings. Diameter is 4.875" I.D. Pioneer seal 762007 is listed on Rock Auto, appears to be correct, no measurements given. Could I use a paper gasket instead of the seal? Should I use both?

 

I will drive out the extension housing bushing at work and measure it, but the O.D. appears to be about 1.790" and the length is 1.25". A lot of the bushings seem to be 1" or 1.5" long. Pioneer 755063 appears to be the right bushing, is listed as 1.795 O.D. But it's only .875" long.

 

The rear seal is easy enough to find, 2.5" O.D.

This has been a frustrating exercise as dimensions are not given in a lot of cases, just part numbers. I have spent many hours looking for the correct parts, comparing information on websites.

I will document my finds so someone else may find it easier.

 

Jim

[RockinRiviDad]

My tailshaft housing had a paper gasket. So I replaced it with a new paper gasket. No leaks. 
 

Call this guy. This is where I got my bushing. Sounds like he was right, not many people/sources have the right part.  

I don’t know where u live. If u are not in SoCal maybe he’ll ship it 🤷🏻‍♂️
 

Good luck

 

 

Edited May 19, 2020 by RockinRiviDad (see edit history)

[telriv]

ANY TH400's I've worked on had an O-Rind as do MANY others. Seldom is a paper gasket used on tail shafts.

[1965rivgs]

On 5/17/2020 at 7:55 PM, JJ62 said:

 

So I've pulled the driveshaft out, dropped the rear tranny mount and gotten the extension housing out. My housing has an o-ring instead of a paper gasket to seal the housing to the transmission. Problem is I'm seeing a lot of paper gaskets listed, but few O-rings. Diameter is 4.875" I.D. Pioneer seal 762007 is listed on Rock Auto, appears to be correct, no measurements given. Could I use a paper gasket instead of the seal? Should I use both?

 

I will drive out the extension housing bushing at work and measure it, but the O.D. appears to be about 1.790" and the length is 1.25". A lot of the bushings seem to be 1" or 1.5" long. Pioneer 755063 appears to be the right bushing, is listed as 1.795 O.D. But it's only .875" long.

 

The rear seal is easy enough to find, 2.5" O.D.

This has been a frustrating exercise as dimensions are not given in a lot of cases, just part numbers. I have spent many hours looking for the correct parts, comparing information on websites.

I will document my finds so someone else may find it easier.

 

Jim

Hi Jim,

  Did you try Rockauto.com for the parts? They list all the parts needed and you should be able to click on an info tab to get specs for each part.

  I`ve used the paper gaskets MANY times with no issues.

  You need a trans mount!! I have new ones for $20 if you havnt already found one.

Tom Mooney

[JJ62]

On 5/19/2020 at 9:01 AM, 1965rivgs said:

Hi Jim,

  Did you try Rockauto.com for the parts? They list all the parts needed and you should be able to click on an info tab to get specs for each part.

  I`ve used the paper gaskets MANY times with no issues.

  You need a trans mount!! I have new ones for $20 if you havnt already found one.

Tom Mooney

 

Tom,

 

 After looking all over the internet, I ended up calling Cyclone Transmission in Ohio. I figured I would need to call a family owned place that had been in business a while to find the correct parts. I was right. They found a place in California that had 3 of the 1 1/4 inch long bushings that I need sitting on a shelf since 2003.

It came with an o-ring, so that's what I'm going to replace it with. Don't want to take it apart again because of a leak. Should get the parts next week.

 I will take a trans mount. Let me know how much with shipping. Not sure why those washers are on there, that's not my quality of work.

 

Jim

[RockinRiviDad]

15 minutes ago, JJ62 said:

They found a place in California that had 3 of the 1 1/4 inch long bushings that I need sitting on a shelf since 2003

Interesting. I wonder if this place in Cali is the same place that I suggested u call. 

[JJ62]

On 5/19/2020 at 12:44 AM, RockinRiviDad said:

My tailshaft housing had a paper gasket. So I replaced it with a new paper gasket. No leaks. 
 

Call this guy. This is where I got my bushing. Sounds like he was right, not many people/sources have the right part.  

I don’t know where u live. If u are not in SoCal maybe he’ll ship it 🤷🏻‍♂️
 

Good luck

 

 

 

I'm in Wisconsin. I did not see this post before I ordered the parts. I will find out if they came from this business. Thanks!

[1965rivgs]

2 hours ago, JJ62 said:

 

Tom,

 

 After looking all over the internet, I ended up calling Cyclone Transmission in Ohio. I figured I would need to call a family owned place that had been in business a while to find the correct parts. I was right. They found a place in California that had 3 of the 1 1/4 inch long bushings that I need sitting on a shelf since 2003.

It came with an o-ring, so that's what I'm going to replace it with. Don't want to take it apart again because of a leak. Should get the parts next week.

 I will take a trans mount. Let me know how much with shipping. Not sure why those washers are on there, that's not my quality of work.

 

Jim

  Just an FYI regarding the extension housing gasket...Buick switched to a paper gasket to replace the O-ring with a pilot run of 24K ST400`s in `66...the `67-`68 parts books show a "gasket" for the application in those years.

Tom

[JJ62]

Update:

 

 I got my parts today from Cyclone Transmission. Unfortunately, there were no part numbers included with the paperwork. I'm thinking the hard-to-find 1 1/4 inch long bushing cost $15 because it was shipped from a distributor in California to Ohio. And thanks to Tom Mooney, I have a transmission mount that actually has rubber in it. What a concept!

I'll put it together this weekend and see how it goes...

 

Thanks to all who gave advice.

 

Jim

[RivNut]

56 minutes ago, JJ62 said:

Boy oh boy.  Someone's got vision and I'm stuck wearing bifocals.  What innovation.🤓