speedo sending unit
 

Does any one know where to find a replacement for the speedo sending unit (rectangular piece of aluminum with gears between the transfer case and speedo cable) mine leaks gear oil and its making a mess. I have tried to clean it and seal, it but no use

Re: speedo sending unit
 

The speedo adapter itself isn't meant to be leakproof. If it's leaking oil, you potentially have a couple of issues.

First, and the easier fix is, the speedo adapter "sleeve" on the tcase is probably worn out. It should run you about $25 from any GM dealer. Below is a pic with the part# (courtesy of Greg72)

http://www.norcalbigdawgs.net/Galler...Magic_Part.jpg

Second, check the tcase fill plug to make sure the case isn't full of tranny fluid. If it is, you need to replace the rear seal on the tranny. That said, tranny fluid isn't gonna hurt the transfer case...but if it's in the transfer case, your fluid level in the tranny will be low.

In my case, both problems were an issue. Hope that helps.

Re: speedo sending unit
 

AJ - Thanks for posting that part number. I have been trying to locate this part by describing it to the parts house jockeys and various transmission shops. Nobody had any clue what I was talking about. I located it on the AC Delco web site and ordered it. Do you happen to recall if there is some sort of rubber o-ring inside this part or on the speedo gear drive shaft, or is the oil seal created by the close tolerances between the two? If this thing stops the oil leak at my speedo housing I owe you my first born!

Re: speedo sending unit
 

Glad I read this post, I also have the mess under t-case, can I replace seal in tranny if I just remove t-case?

Re: speedo sending unit
 

There's a rubber "gasket" inside the sleeve. It's permanently attached. Only way to fix it a worn out gasket is to replace the sleeve.


I can't answer this one. My tranny ended up letting go and I replaced the whole thing with a 700r4 before I could get to the seal on the TH350. Maybe someone else can chime in.

Re: speedo sending unit
 

mine went out and filled the tcase with tranny fluid. if my memory still works, the seal is on the tcase side of the union. I resealed my entire tcase while i had it out, believe it or not the gears and bearings still looked new.