automatic oil leak

[marvxyz1]

I have a 1980 gmc Sierra classic with automatic 6 cylinder, and have a oil leak in the area of where the speedometer goes into the transmission. the speedometer cable goes into a small box which is attached to the transmission. The oil seems to be leaking there. What is the box called?? I would like to look up the repair for it, and see if I can do it. I also have a leak coming from the plate, which covers the torque converter, what is this leak liklely coming from??? Thanks in advance for whatever information you can give me..

[magnethead]

not sure on the box. and probably a rear main seal.

[Slonaker]

My TH350 has a metal thing called a bullet that the speedo attaches to. It is held in the transmission with a bolt. The bullet has an o-ring on the outside that seals it to the transmission case. It has a rubber seal inside the bullet that keeps trasmission fluid from leaking around the speedo gear that turns the cable.

If this is the setup you have, you can buy the o-ring and seal at NAPA. I tried it, but it still leaked. It turned out that my bullet was worn, so a new seal still leaked. Then I bought a new bullet with the o-ring and seal already installed. That leaked too. Then I replaced the speedo gear and the bulet, and it has not leaked since.

As you can see, it was inexpensive:





The first time mine leaked from the cover over the converter, it turned out to be the pump leaking on the transmission. The next time it leaked it was coming from the seal on the front of the transmission. The bushing the converter rides on was loose, allowing the converter to wobbble and destroy the seal. That was how it was explained by the guy who rebuilt it for me.

Like magnethead said, it could also be the rear main on the engine.

Slonaker

[marvxyz1]

I have the th700r4 transmission, I guess I may have a similar setup for speedo gear on the transmission.You are probably right on the rear seal leaking. I just had a Jasper short block installed on this truck a couple of years ago.

[marvxyz1]

I believe I found my leak slonaker, Where the nut attaches to the bullet is a washer which looks like clear plastic. The washer is definitely leaking. I guess I'll go down to the chevy dealer for a new part.

[piecesparts]

If you are getting a lot of oil here, then there is an O-ring in the fornt of the tailshaft housing that is due for replacement, also.

[marvxyz1]

Picked up a o-ring which could replace the clear plastic gasket, There was a part on a stem sticking out of the transmission, I went to reinstall the bullet into the tyransmission and over the part sticking out of the transmission, and it went down into the transmission. I tried to remove the part with a telescoping magnet,no luck. I guess I have to remove the tail section of the transmission to retrieve the lost part.

[marvxyz1]

Can the tailshaft be removed without major problems???

[Slonaker]

On mine the housing is just held on by four bolts, but I don't know about your 700R4. Good luck.

Slonaker

[piecesparts]

Four bolts is the way they are mounted. The 700 R4 is basically a 350 with another gear inside. Do all of the seals if you take it apart.

[marvxyz1]

"Thanks Guys"!!