Transfer Case to Transmission Seal

[tbenedict]

Hello,

I have a 98 K1500 Z71 with a 350 and auto transmission (4L60E I think), that has been losing transmission fluid. A transmission shop said it was probably a bad seal between the transmission and transfer case, because there were no external signs of leaking.

How hard of a job is this? I have worked on clutchs, but don't have any experience with transfer cases. It looks fairly easy to remove once the driveshafts are disconnected. The shop wanted $400 plus the (fancy fluid?) and I as much interested in learning as saving a few bucks.

Any help would be much appreciated.

[Blue Bowtie]

Removing the transfer case is not a difficult task, just time consuming. Replacing the rear seal in the 4L60-E in an AWD/4WD installation is a bit more of a challenge, however. I found that mine was installed from the front side of the reverse/OD housing, as part of the reverse clutch hub seal:



You may find that your's is different, but if it isn't, you'll be removing the transmisison and disassembling it to replace the seal.

[alblogg]

Originally Posted by tbenedict

Hello,

I have a 98 K1500 Z71 with a 350 and auto transmission (4L60E I think), that has been losing transmission fluid. A transmission shop said it was probably a bad seal between the transmission and transfer case, because there were no external signs of leaking.

How hard of a job is this? I have worked on clutchs, but don't have any experience with transfer cases. It looks fairly easy to remove once the driveshafts are disconnected. The shop wanted $400 plus the (fancy fluid?) and I as much interested in learning as saving a few bucks.

Any help would be much appreciated.

If you can read shop manuals and have some mechanical knowledge and you have done clutches I guess you know some about the workings of a car and truck and know a little about tools it might be a job to try.

[JaVeRo]

Check the fluid level in the transfer case to see if it's too full.

James

[rdptrans]

don't know why they showed you a transmission, but just pull the t-case and replace the front input seal, problem solved, remove the four bolts that retain the housing and seal together. remove seal, reinstall new seal, reapply rtv to housing and reinstall in reverse order.

[tbenedict]

I'm confused, is there anyway the transmission would have to be removed? Are there two seals instead of just one between the two?

[Blue Bowtie]

Originally Posted by rdptrans

don't know why they showed you a transmission, but just pull the t-case and replace the front input seal, problem solved, remove the four bolts that retain the housing and seal together. remove seal, reinstall new seal, reapply rtv to housing and reinstall in reverse order.

I posted a photo of the rear of the transmision because the original poster stated he/she was losing transmission oil, not AutoTrak transfer case oil;

Originally Posted by tbenedict

Hello,

I have a 98 K1500 Z71 with a 350 and auto transmission (4L60E I think), that has been losing transmission fluid. A transmission shop said it was probably a bad seal between the transmission and transfer case, because there were no external signs of leaking.

Unless I misunderstood the problem, or the transfer case and transmission are somehow sharing the same oil, the seal on the transfer case input shaft may not completely solve the issue, If the transfer case were leaking out, your advice would be most prudent.

[tbenedict]

It is the transmission fluid leaking into the transfer case. I am trying to determine if the seal(s) can be replaced without pulling the transmission.

[winsett]

Originally Posted by tbenedict

It is the transmission fluid leaking into the transfer case. I am trying to determine if the seal(s) can be replaced without pulling the transmission.

I'm having the same issues. No effect on driveability (is that a word?), but concerned about lack of fluid in Tranny and too much in Transfer Case.

I'm looking for same info. Also, is there any special tools i will need to complete such a seal replacement?

[Blue Bowtie]

After reading back through the thread, it seems I wasn't completely clear on the seal issue. rdptrans had the correct response for your situation.

There is a seal for the input shaft of the transfer case. That is intended to keep the transfer case oil INSIDE the transfer case and the transmission oil OUT of the transfer case.

There is also a square cross-section ring seal/gasket which seals the connection between the two to keep anything from leaking out. Transmission oil will normally enter the area from the output shaft and reverse clutch hub, but there are two drain holes to allow transmisison oil to drain back into the transmission pan/valve body area.

That said, if the leak is at the transfer case input shaft seal, and the transfer case oil level is increasing, only the transfer case needs to be removed to replace its input shaft seal.

If the leak is external (leaking out and puddling on the floor) the transfer case needs to be unbolted and split from the transmission just enough to uncouple the splined shaft to replace the ring seal/gasket. This may be able to be done without completely removing the transfer case from the vehicle.

By my understanding of your symptoms, you would need to remove the transfer case completely and replace the seal. AFAIK, your '94 uses the NPG transfer case, so if there is appreciable mileage on the transfer case in 4WD mode, you may want to open the case, check the chain, and especially check the sprag clutch(es) for wear.

[tbenedict]

Do you know if there are any real tricks/snags in doing this on a 1998? I lost transmission fluid one time, so I filled it up. It hasn't leaked since, so I presume the transfer case is full.

I'll have to look in my manual, but do you know if the transfer case uses a special fluid?

Thanks!

Travis