GM slip yoke clunk

[Tradarcher]

I've been dealing with it for years and I think I finally fixed it. The clunk was quite persistant and predictable and annoying. If you remember my other thread about stripping the drain and fill plugs, you know I was trying to replace the fluid in the t-case. Had the dealer extract the plugs and replace them with some nice brass plugs with allen heads. Then had them fill it with Auto Trak II blue ATF fluid. I drove it off the lot and after it warmed up sufficiently the clunk was gone. Hopefully it will not return. I have an electronically switched t-case with auto 4wd and apperently this is the appropriate fluid for this case. Not sure why it had red fluid in it since I've owned it from 77k to 127k. I had it changed once when I had tranny adjusted a while back but they put red back in it. I did some research on the net and found the fix. Even posted on Pirate once and never got this info. This may sound trivial to some of you but I have been battling this clunk for a long time and I thought it was going to be something I had to live with. I'm very pleased to say the least.

 

[Blkvoodoo]

The "clunk" you describe may have had nothing to do with the fluid in the Tcase, but with the slip spline in the tail shaft, the fix is to pack it with about 2oz of thick grease.

I forget the actual name, that shit is expensive and when we need it we have to get it from the dispatch office in measured quantities.

Is a typical GM fix for a typical GM problem, throw a band-aid on it, make noise go away for awhile, maybe they'll buy a new one next year.

Oh, and if you have the Auto 4x4, you have the NP246 tcase.

K

 

[Tradarcher]

I greased it myself and the other day and it was quiet for a few hours. Had to remove the driveshaft and finger some grease into the slip yoke. I have a 98 so I don't have the greased version with the boot. Mine is lubed with the fluid in the case with a seal on the slip yoke.
All I know is that it clunked before I took it in and it doesn't clunk now and all I had them do was replace the fluid and the plugs. I found many places on the net that said the blue fluid was the proper fluid for my case anyway, Part No. 12378508. This is the stuff that they originally said to fill and drain and fill again. Lotsa first hand experiences on the net about it fixing the clunk. Maybe coincidental though.
Thanks for correcting me on the 246.