Allison 1000 Cracked / Leaking Tail housing
(be patient there is several large pictures)
Chevy & GMC HD 2500 & 3500 4x4 Pickups with the Duramax Diesel or 8.1L Gas engines are known for cracking the extension housing causing a hard to find leak. This webpage is devoted to the technician on where to look & how to stop the problem the 1st time. This page also shows how to tell the difference between the updated part & the problem housing.
As pictured in the above & below photo, you can see the bottom of the transmission adapter housing is wet. It's not a bad leak but a low seeping/annoying leak. Under close inspection you are un-able to find any reason for the leak. The GM updated housing sells for aprox $750 so you better be sure that it's needed or not. These housings are well known for cracking across the top of the housing which is easy to find. It's the lower portion that cracks in such a manner that makes it's so difficult to find.
The above photo is the early model that is known to crack & leak. The X casted in the side of the housing denotes the early / problem housing .
The above photo is the updated housing with the biggest/easiest difference pointed out.
still under construction