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Noticed the small drops of oil on garage floor.  Traced it to a rub hole in T case.  ordered and installed the adapt-a-case retro part to address the issue, but now when go into drive and apply gas, very distinct and noticeable 'clunk' from drivetrain.  Never did that before.    At speed cannot detect anything odd--no vibration, etc.  Come to a stop and ease up on brake and the same clunk happens, as if its unloading.


any ideas from the group?


2001 2500HD  Ali with 8.1





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Im not sure I posted in the correct area? So here again check the steering column "known problem with shaft losing the grease" and GM also noted a replacement moly chromed output yoke shaft! Hope this helps! I found it on the Internet over a year ago when i was considering buying an Avalanche 2500! Hope this helps I never bought the truck so I dropped the search!

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Thanks for the info. I too found several threads on a dry rear slip yoke. Will investigate further. Question is why would simply dropping the rear shaft suddenly create this situation? There are several TSBs on the topic but not covering a 2001, although I have the near exact symptom. GM suggested a special grease then promptly recalled that since it might migrate into and mix with the t-case lube. Thanks again and will keep on the problem.

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Interesting...Is this a splined coupler or a slip yoke?  If a splined coupler, even if you did not separate the spline section, you might have an issue with spreading or thinning the OE grease by extending the coupler and returning it to the normal/operating position.  Please clarify whether this is a splined coupler or slip yoke.  If migrating grease was an issue, it sounds like a slip yoke...


On aftermarket shafts with splined couplers, a special "coating" on the splines often acts as a friction barrier.  This is typically blue in color, and you've seen it on custom drivelines with splined couplers.  As for slip yokes, a spline matchup with the original position is seldom considered, and unless you carefully mark the slip yoke and transfer case output splines, there's very little likelihood that the shaft will end up at the original spline alignment.  Repositioning the slip yoke on the transfer case output splines would seldom create an issue unless there is abnormal spline wear on either the coupler or the output.


Of course, with a splined slip coupler, you must have the driveline's U-joints aligned or "in phase".  When a splined slip coupler is taken apart and reassembled, the U-joint and flange position at each end of the driveline must match and be in alignment.  Additionally, with a balanced driveline, these matched positions must also be consistent with the position of each U-joint flange when the shaft was built and balanced.



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