Yet Another Clunk When Shifting Question! Please Help Me :)

vlasveld · March 4, 2009

Hi everyone, i have a 1991 sierra 1500.

I know this question has been asked a million times but mine is a little different than the others i have searched in the forums.

It sounds like my tranny is shifting really hard it is a firm clunk shift, it always shifts and the right time and never misses its just a really loud JERK or CLUnk like its catching really hard.

Its an automatic trans and if i put it in "2" the shift from first to second is terrible CLUNK. IF i put it in drive and go its not as bad but still happens.

Another weird thing is it will happen not only when im accelerating but also say im pulling up to a red light and slowing down. When it shifts down from 2 to first i can hear the clunk again as im slowing.

Maybe its just me but it seems to be getting worse and im starting to worry about it. Any suggestions???

Thank you so much!

vlasveld · March 4, 2009

i also should add that the tranny was rebuilt 2 years ago and the tranny fluid level is up to par

DofD · March 4, 2009

Something is amiss with the shift to and from 2nd. If you got a warranty with the rebuild and it's still good I'd go back and complain. Otherwise I'd look for a new tranny shop. You could pop the 1-2 servo out to see if there's any damage to it.

vlasveld · March 5, 2009

Ok i took the truck out again tonight. It actually happens shifting from 1-2-3 and back down and it happens speeding up or slowing down.

What im really wondering is this for sure a tranny problem or can a sensor or something else cause this? can vaccum leaks cause this? I dont want to take it to a tranny shop unless im sure that is what it is.

Like i said its way worse when i have it in "2" rather than "D"

Also it seems worse once its warmed up. Also my oild pressure gauge doesnt work once my vehicle is warmed up. It has been like this for a year. I must have oil pressure though because my vehicle wouldnt have ran for a year with no oil pressure.

Also i wanted to thank you guys so much for helping me out with this. I really cant afford to get ripped off so i usually like to try and learn as much as i can from you guys before i go into a shop.

Thanks again