possible tranny prob.......

[cobra10494]

 

97 sierra 1500 z-71 5.0 auto.under reg load tranny shifts fine right up into o.d.If I nail it hard,it downshifts but hesitates and acceleration is sluggish.Also,on grades when the tranny dowshifts under acceleration I get a clunk.Clunk seems to come from rigt behind the cab.Afraid to take it to a tranny shop because most will just sayit needs a trans,$3000 please.What can thie be.Like I said shifts smooth and fine under light throttle and heavy(until it downshifts).Any guesses???

[Mr. Smith]

97 sierra 1500 z-71 5.0 auto.under reg load tranny shifts fine right up into o.d.If I nail it hard,it downshifts but hesitates and acceleration is sluggish.Also,on grades when the tranny dowshifts under acceleration I get a clunk.Clunk seems to come from rigt behind the cab.Afraid to take it to a tranny shop because most will just sayit needs a trans,$3000 please.What can thie be.Like I said shifts smooth and fine under light throttle and heavy(until it downshifts).Any guesses???

 

<{POST_SNAPBACK}>

 

 

 

I doubt that is the trans. Check the slip yoke in the trans, may need lube.

[MSUChevyMan]

Not sure if this is the same problem you have, but I drove for a year or so with a similar issue and didn't want to go to a tranny guy because I didn't have the money for it anyways. Well, I finally took the truck in for some other work, and they found out it was some sort of computer chip on the 5th cylinder, causing it to misfire big time. They were able to replace it with a used part, and the problem is solved. Much nicer because now I can accelerate without the chattering. Anyways, not sure if it's the same, but it might be worth a shot. Goodluck.

[fossil]

service it, add conditioner. sounds like a valve body or adjustment problem.

[02 Silverado Z71]

97 sierra 1500 z-71 5.0 auto.under reg load tranny shifts fine right up into o.d.If I nail it hard,it downshifts but hesitates and acceleration is sluggish.Also,on grades when the tranny dowshifts under acceleration I get a clunk.Clunk seems to come from rigt behind the cab.Afraid to take it to a tranny shop because most will just sayit needs a trans,$3000 please.What can thie be.Like I said shifts smooth and fine under light throttle and heavy(until it downshifts).Any guesses???

 

<{POST_SNAPBACK}>

 

 

 

I worked in GM stores pretty much all of my career.  I read thru your concern, and I have 2 questions here...

How old is your fuel filter?  What is your fuel pressure?

 

Years ago, I bought a used 1998 Sierra with a 5.7 and Z71.

Real super truck, but when I took it out on the highway and really stomped on it, the truck just bogged down.  Normal driving was ok; no check engine lights.

I took a few minutes and replaced the fuel filter.  With that $10 fuel filter; it felt like a NEW truck again...especially with performance.

Sometimes the simplest things...