Technical question...please help

pallison74 · May 13, 2003

Hey Everyone. I just bought a 1999 silverado 1500 4X4 with auto with 80k miles. I didn't notice this when I test drove it, but I know notice a problem. When I come to a complete stop, and then hit the gas there seems to be a thump from underneath me or towards the front of the truck right when I hit the gas. Sometimes the thump occurs as soon as I let off the brake, before I even hit the gas. This does not happen if I only slow down and then hit the gas without stopping. I have never owned a car with this many miles, so I have very little experience with problems. I was thinking it might be the tranny, but it shifts very smooth while I am driving.

Has anyone experienced this before?

Thanks

Paul

BlueDevil · May 13, 2003

Could it be a U-Joint?? Or possibly the torque converter??

pallison74 · May 13, 2003

OK

I just checked it out under the vehicle and this is what I noticed. Off of the engine is a shaft that runs from the engine to the Transmission. I assume this is called a drive shaft. There is the interlocking connection between the shaft and engine, is this called a U-joint? There is also one at the other end that conects the drive shaft to the Transmission. What i noticed it that the front conection (U-Joint) to the engine is solid, there is no play whatsoever. However for the connection of the shaft to the front of the trnasmission there is a little bit of play, in that I can wiggle the two parts of the joint a little. Would this be causing the above problem?

Thanks All

toddgotfish · May 14, 2003

sounds like you may have just found your problem

to be sure get in and hold the brake down and shift between reverse and drive several times

if its bad you'll here you r mystery thump :thumb:

dru98 · May 14, 2003

Hello..I am new to the forum.. Just a little humor..Are you sure you have nothing in your bed that is rolling around?????

AHAHAHAHHA. I am having a similar noise..and I have pin pointed the proble to be a u joint in the rear.

GeoHawk · May 14, 2003

Could this be it? My '99 made this noise. It was more annoying than anything else. I never did anything about it before I traded it in.

Technical Service Bulletin No.: 01-04-17-004

Date: October, 2001

TECHNICAL

Subject:

Clunk, Bump or Squawk when Vehicle Comes to Complete Stop or Accelerating from Complete Stop (Replace Rear Drive Shaft Nickel-Plated Slip Yoke)

Models:

1999-2002 Chevrolet and GMC Extended Cab Short Box Pickup Models (Silverado and Sierra)

with 4L60-E (RPO M30) or 4L80-E (RPO MT1) Automatic Transmission and Automatic 4WD (RPO NP8)

Condition

Some customers may comment on a clunk, bump or squawk noise when the vehicle comes to a stop or when accelerating from a complete stop.

Cause

A slip/stick condition between the transfer case output shaft and the drive shaft slip yoke may cause this condition.

pallison74 · May 14, 2003

Geohawk

Thanks for the reply. That is what I now think it is. I didn't find too much about it here but over on the fordf150 forum there are lots of guys talking about it. Many that tried replacing the slip yoke actually ended up with a worse one. Therefore I will learn to live with it. Maybe I will learn to like it

RoadrunnerRod · May 15, 2003

I bought my 99 Z71 last year, and after driving it awhile noticed that same noise. The warranty was still good so I got the replacement slip yoke. It was quiet for another 3-4000 miles, but then it started clunking again. All you have to do is remove the driveshaft and lube the outside of the yoke. This should quiet things for 3-4,000 miles, give or take. Good luck with your clunking!

Dihappy · May 15, 2003

I bought my 99 Z71 last year, and after driving it awhile noticed that same noise. The warranty was still good so I got the replacement slip yoke. It was quiet for another 3-4000 miles, but then it started clunking again. All you have to do is remove the driveshaft and lube the outside of the yoke. This should quiet things for 3-4,000 miles, give or take. Good luck with your clunking!

Right on RoadRunner,

I was suppose to go and get the new nickel plated slip yoke, but havnt

Anyway, some good grease will work great for a few thousand miles.

duck slayer · May 15, 2003

DiHappy,

I had the same thing on my '02 Z71 the shop fixed it under warranty and about 3 months later the clunk was back

chvythndr · May 16, 2003

Geohawk

Thanks for the reply. That is what I now think it is. I didn't find too much about it here but over on the fordf150 forum there are lots of guys talking about it. Many that tried replacing the slip yoke actually ended up with a worse one. Therefore I will learn to live with it. Maybe I will learn to like it

pallison - what are you reading the f*rd f150 forum for? hehe I had my slip yoke replaced a while back and haven't had a prob. since. I have heard that it comes back, even w/ the new nickel plated slip yoke.