HELP! '97 Z-71 Transmission Clunk

[Pekoe]

I recently purchased a 1997 GMC Sierra Z-71 X-Cab with 76K miles. It has run fine but recently developed a slight "clunk" when shifting from 2nd to 3rd. Does anyone have a clue what this may be?

Thanks,

Barry

[Riche]

My 97 Z71 has a clunk. I bought it with 123K so I am sure it has been doing it for some time…. I think that I have read that it is normal. I imagine that means if it isn’t extremely loud. I noticed riding in a friends 2004 Z71 that his was doing the same between 2&3. It was quieter than mine but I could still hear it.
Did some one post that there is a special transfer case fluid that helps with this?

[broughy84]

welcome to the wonderful world of the mid-90's early-00's model 4L60E!!! Most all of em do it.

[Silverado Brethern]

Yep mine has the good ol clunk too. on mine its not so much the sound, the sound is coming from the driveshaft and U-joints which can develop slack over time, when you accelerate and the slack is picked up CLUNK. but i can definatly feel a heavy shift, maybe more of a thump since i dont really hear much noise from the tranny. i dont see it as a problem or something im gonna bother tryin to fix, the truck isnt even close to new so what can you expect.

[MyTOY]

If this only happens after you go about 45 and if you
can turn the truck off for a sec. and the prob. goes
away, then it is probably a common valve guide prob.
in the tranny which can be fixed with a kit if it's not
too late or you can wait and replace your transmission
and torque converter as I did in my 97 GMC.
Good Luck

[Pekoe]

Thanks for the info. I sold my '94 Z-71 with 194K and no tranny problems. Was that a 700R4?
My clunk isn't big enough to be felt much - it sounds like more of a higher-pitched rattle, as if some piece of metal is loose and rattles a bit when the shift occurs.
I have been careful to test it under steady, moderate accleration (it clunks), rather than pushing on, and letting off, the gas.

Having ditched a high mileage truck with potentially expensive engine and tranny problems soon to occur, I spent at the top of my limit to get a low mileage truck. I don't want to have to do tranny work!!!

Barry