Trans slips a bit at start of 1st gear ONLY in 4x4 LOW

[ala.frosty]

I have a fairly recently rebuilt 4L60E transmission in my '97 K1500 with 4.3L v6 (4x4 floor shift). It works perfectly in 2WD and 4WD high. In 4x4 Low, from a start, 1st gear seems to slip quite a lot to about 2mph before engaging fully. Given that the trans works perfectly when the transfer case is not in 4x4 low, I suspect the xfer case is slipping, somehow but I can't think of anything in the xfer case that might slip.

Given the slippage at light throttle and my desire to get home, I decided to not go full-throttle in 4x4 low from a standing start. With very light throttle in 4x4 low, from a start on flat ground, the engine spins up a bit before it feels like first gear fully engages. Once the truck is moving at a couple of mph, it behaves normally and shifts properly, both manually and when left in (D). I did not try 4x4 low on a steep hill.

Does this sound like a factory behavior? I don't use 4x4 low very often, so maybe this is normal and I just haven't noticed it before? AFAIK, there's nothing in the transmission that works differently when the xfer case is in 4x4 Low, but maybe there is and I just need a bit of education about it.

Any thoughts on whether this is normal or what potential problem might be occurring in the trans or xfer case? Thanks.

 

[Yukon98]

i have the same issue since my transmission 4L60E was replaced. i started a thread "np246 banging" to try and get some ideas.