Trans Transmission and transfer case

[Frank1978]

I have 1978 CJ5 V8 with the T-150 transmission and a Model 20 transfer case. I was checking the fluid levels and noticed the trans was low on fluid and the transfer case was overfilled. I have been around cars long enough to know how to fill both and what level they should be at. Is there a way that the fluid from the trans can run into the transfer case. Is there a seal that can permit it. I don’t think they share reservoirs but I’m at a loss on why this happened.

 

[TSB8C]

There was a factory recall for the T-150 seal problem. It was called: "tranlube".... or something simliar. There was a factory condition with the seal where, if installed backwards, it allowed fluid to pass between the two, causing the t/case to overflow and the T-150 to run low.

In mid 1978, they redesigned the Dana 20 case to raise the fill plug height; mid '78 and earlier used the lower fill plug whereas mid '78 and later used the raised fill plug.

I believe they eliminated the seal altogether with the introduction of the raised fill plug Dana 20 case. I don't recall and I don't want to lead you astray, but that is the best I can remember.
Check the case of your Dana 20 for the location of the fill plug to know which you have. But of course over the years, previous owners could have swapped D20s.

Personally, I believe the T-150 should have the rear output seal either way. The p/n for the seal was: J5358980. Here's a shot of the seal installed correctly.