700R4 won't stop leaking!

[Elpresidente]

I've got a 700R4 in my '82 C10, and for some reason it will not stop leaking out the tailshaft. It will stop for a few days, then one morning i'll wake up to see a small puddle of trans fluid.
Initially I changed the rear seal and that stopped it, but now its leaking out of the yoke (through that small pin hole in the center, behind the U-joint)
Is there supposed to be ANY tranny fluid in the tail shaft? I'm beginning to think one of the seals on the output shaft is leaking and the tailshaft is filling with fluid. It's a rebuilt transmission, so it's possible something went wrong.


Also, I noticed it happens more often if the truck is parked facing up hill.

[bd]

The tailshaft housing contains no fluid under pressure, but does rely on splash to lubricate the tailshaft bushing, yoke and speedo gear.  There's a drainback hole to allow fluid to escape back into the pan. 

As to your leak:
There's a stamped steel cup roughly 4" long by 2" in diameter that slips over and presses snug around the output shaft, shrouding the driveshaft yoke.  The cup cages an o-ring that presses against and encircles the yoke and allows the yoke to freely slip fore-and-aft.  The purpose of the cup and o-ring is to limit fluid pumping past the yoke splines and eventually leaking out the weep hole - like yours is doing.

1)  Make sure you don't have a worn-out tailshaft bushing, allowing excessive radial play and side-to-side movement of the yoke in the tailshaft housing.
2)  Either the cup has slipped forward on the output shaft, so it no longer cages the yoke, or the o-ring has lost its elasticity, or the cup and/or o-ring are missing.

[Elpresidente]

Sounds good. How would I do this, take the tailshaft right off and reseat this o-ring?

[bake74]

     Make sure when you do this that you check the area the o-ring is housed in for any damage, if the area where the o-ring is housed is warped or damaged at all, a new o-ring will not solve your problem.

[bd]

How would I do this, take the tailshaft right off and reseat this o-ring?

Remove the speedometer gear sleeve with the plastic driven gear, then remove the tailshaft housing.  The 'cup' I referred to is actually called the output shaft sleeve.  It fits tight around the output shaft about 3/8" rearward of the speedo drive gear.  The o-ring fits into the free end of the sleeve.  Slip the driveline yoke onto the splined output shaft to check sleeve position and fit, following Bake74's advice.  Replace the o-ring in the sleeve.  You may have to tap/slide the sleeve off of the output shaft to replace the o-ring.  Lube the new o-ring with a little Vaseline or ATF.  Reinstall the sleeve and secure it to the output shaft using red Loctite.  Be sure it's in the correct position on the shaft - and use the yoke to align it concentrically with the shaft.  Reinstall the tailshaft housing with a new o-ring, no sealer.  Reinstall the speedo gear and finish assembling.

[Captkaos]

Sounds like your O-ring is bad, see here:
http://73-87.com/7387garage/drivetrain/yokeleak.htm

[oldredtruck]

The 700 in old red did the same thing exactly... replaced O-ring, rear seal and slip yoke.... ( old slip yokes can get a "groove" worn in them - which will reduce the life of the new seal...and you will have a repeat issue later on)
Great thread!

[KerryBoehm]

The 700r4 in my 92 suburban is doing the same thing. I was wondering where to source the o ring.

[bd]

The 700r4 in my 92 suburban is doing the same thing. I was wondering where to source the o ring.

For GM P/N 3764601 (propeller shaft O-Ring)...
try your local AC Delco retailer; or any GM dealer; or any automatic transmission parts retailer.

[Elpresidente]

I removed the tailshaft, checked everything out to find no issues. put it all back together and have had no problems since, its a mystery but it's working great so i'll leave it alone haha