4L80E cracked extension housing and output seals replacement 

I just finished the job! I replaced my rear output shaft seal, front output shaft seal and the paper gasket between the transfer case and the transmission adapter plate. I used a floor jack to raise the transfer case up into place and then slid the transfer case onto the tranny output shaft. Then I tied a ratchet strap to the 2 pipes that run along the inside of the frame and used that to support the front of the transfer case, while I put the big paper gasket on. Took it for a long test drive in 4x4 and have no leaks. Thank you so much! I used a "campbells chunky soup" can to drive the outer race of the seal in and a big socket to drive the inner race of the seal in.

Nice vid S. A , i've just done one these on an '03 envoy , i have re-check my rebuild kit for the paper-hex-gasket , i must have some how missed it. When i originally removed the transfer case, i noted the large rubber O-ring stayed on the front of the transfer case. And the whole time that i was working on the trans, the extension housing stayed on the main trans case. So the seal in front of the extension housing never got replaced. But it's obvious now that my leak is because of a missing paper gasket. If i don't locate one in the rebuild kit, i will just apply Permatex Ultra black RTV silicone sealant. And naturally re-check to make sure the extension housing is not cracked like yours. Thanks so much S.A. , this is only my third automatic trans and this stuff ain't easy.

Great video and explanation we need more people like you on here

I was able to maneuver a swivel extension to the bolts made life alot less bloody and a little faster. Great video thanks!!

Good video great info thank you

Thanks a lot!

I've been searching far and wide for this procedure. Not even listed in prodemand

Great video, thanks!

How aggresive/bad was the leak with this crack. I would think thats a low pressure area (within the extension). I ask as mine is pouring fluid in and around my extension. I haven't crack checked it yet but confused and wondering if my pressure is too high due to some other issue. I also had a roar and then it went away right before it dumped fluid

When installing the paper gasket between the transfer case and the extension housing, is it placed dry or is the use of an adhesive recommended? '03 GMC 2500 6.0, 4L80E, 261 HD. Thanks!

I thought there was a seal around the shaft on the transmission side to keep the fluid from getting into this extension housing?? Everything I have read up until this video has suggested that the space between the transmission and the transfer case should be dry... Can you elaborate?

I have fluid drip at weep hole in bottom 4L60E 2007 if extention housion is not cracked iyo would the paper gasket or oring be bad? The leak is inbetween the transmission and transfer case already checked transfer case to see if it filled with ATF in case front seal on transfer case is bad and having problems finding right parts and part numbers

Should have checked the T-case housing for oil pump wear also while off, after going through all that work. Good video for sure!

Is it any differnt to do on the allison trans in 05 chevy 3500

I just have a question wouldn’t that mean the seal is leaking on the transmission? Bc mine is doing that or just change the housing that is cracked?

i just bought my 2005 silverado 2500 like 2 months ago and been driving with i think a seized u joint not knowing why my truck would vibrate hard at 35-45 mph recently noticed my tranny leaking out thought it was just the filter spot but most after further looking i noticed its this part right here thats leaking bad

Nice job man. This is just what i needed. I have the same exact issue on a Sierra. Going to tackle this job in a couple hours from now. How many quarts of ATF did you need to refill?

Thanks for posting this video, it looks similar to what I imagine is in my 4L60 trans on the NP246. I guess I expected to see you change a transmission output seal shown in the video at

I've changed about 8 of these on various trucks and would love to know why it happens

You point out a rear transmission case seal (