I'm about done...

[Rocket Man]

The 6L series transmissions and 4L80e have a rear case seal however the 4L60e/700r4s don’t, interestingly enough. The 4l60e and 700r4 rear output is mostly sealed off via the rear case bushing (a sealing bushing as opposed to a lubrication bushing) and rear planetary ring gear hub’s journal but excessive fluid can leak past and into the extension housing/trans-tcase adapter if that bushing is excessively worn. The extension housing/adapter takes a square cut rubber seal on the perimeter and there is a seal on the t-case side that prevents fluid transfer but if it’s also worn, transfer can occur. That bushing, along with all the others should have been replaced when the transmission was rebuilt (not saying it was or wasn’t, have no idea in this particular case)

6l80e
View attachment 399173
4l80e
View attachment 399177
4L60e (bushing removed, new bushing not yet installed)
View attachment 399178

Interesting. I have never rebuilt a trans but assumed there was a rear seal on a 4l60. I do know there have been members here who kept losing trans fluid and gaining transfer case fluid. Never have heard of it coming out the tc vent tube but I have heard of it coming out the trans vent tube due to overfilling.

 

[Mudsport96]

Interesting. I have never rebuilt a trans but assumed there was a rear seal on a 4l60. I do know there have been members here who kept losing trans fluid and gaining transfer case fluid. Never have heard of it coming out the tc vent tube but I have heard of it coming out the trans vent tube due to overfilling.

It gets worse on the older models. The front diffs on the S series was vacuum actuated. So after your trans went low and got mushy shifts and tcase over filled there was a possibility that the detent valve would suck fluid by the seal and into your vacuum hose to the ball underhood. Then into your dash vent actuators.... cant tell you how many of those i did at the dealership.

 

[davidbeaver1]

Well, @NickTransmissions and @Rocket Man called it! Checked the transfer case fluid and about 1 quart of oil came out. Mechanic ordered the seal and is going to install it next Tuesday. Wonder why the transmission guy didn't replace it when he performed the rebuild?