Transmission Clunk

ls steve · November 20, 2007

Hi I'm new to this forum. I have a 2000 1/2 ton silverado ext cab LS w/5.3 . with around 106,000. miles This weekend I took a trip about a 45 min ride on highway at 65 to 80 mph. when I left the highway,stopped at a red light. went to take off and the truck made a loud clunk noise. It kept making this noise every time I slowed down then accelarated.(took off slowly) I stopped for something to eat,the truck sat for about 1 hour. sarted up drove away with no problems,until the return trip. I had the same problem . stopped for gas and went away. might not be related but now my check engine lights on. Any help would be appreciated.

thanks Steve

ls steve · November 21, 2007

since nobody has replied,I'll try to explain the problem better. It's not the same clank noise from the sloppy drive line (that every GM truck seems to have), It was a loud thud almost like if there was something sliding around in the bed of truck (there isn't) I didn't have to come to a complete stop for the noise to recur just slow down 10 ,15 mph then just gradually increase speed. there didn't appear to be any slippage in the transmission. while I'm not a mechanic, i have been doing body work for 25 years. I cant diagnose some problems but i can fix most when i know where to look.

crazydog · November 21, 2007

Well, I'm not tech and not a mechanic either but I have a 2000 GMC Sierra 4X4. My truck did what you are describing, but only a few times, last summer when I used it to tow a gooseneck horse trailer. Being new to trailering, I thought it was the goose because it sounded like it was in the bed . . . It never did it again until this summer. And, yes, I used it a few times with the trailer again. However, it wasn't with the trailer that it started doing it. It was during a 12 hour drive, toward the end and this time it kept on clunking and jerking every time I accelerated from a stop. Took it to Mister Transmission and he said it was the truck's computer telling it to do that so that the owner brings it in to be looked at??? Seems kinda hard on the truck?? Anyway, my tranny had to be overhauled. Mister Trans claims that GM uses substandard parts with the trannies. He actually swears by Ford's transmissions but I wouldn't touch a FORD with a ten foot pole !

Anyway, still wonder if the trailering had anything to do with it--hope not as I have ordered a new HD to trailer with now---but Mister Trans seems to think I was lucky it lasted as long as it did and it wasn't the trailering.

ls steve · November 22, 2007

Well, I'm not tech and not a mechanic either but I have a 2000 GMC Sierra 4X4. My truck did what you are describing, but only a few times, last summer when I used it to tow a gooseneck horse trailer. Being new to trailering, I thought it was the goose because it sounded like it was in the bed . . . It never did it again until this summer. And, yes, I used it a few times with the trailer again. However, it wasn't with the trailer that it started doing it. It was during a 12 hour drive, toward the end and this time it kept on clunking and jerking every time I accelerated from a stop. Took it to Mister Transmission and he said it was the truck's computer telling it to do that so that the owner brings it in to be looked at??? Seems kinda hard on the truck?? Anyway, my tranny had to be overhauled. Mister Trans claims that GM uses substandard parts with the trannies. He actually swears by Ford's transmissions but I wouldn't touch a FORD with a ten foot pole !
Anyway, still wonder if the trailering had anything to do with it--hope not as I have ordered a new HD to trailer with now---but Mister Trans seems to think I was lucky it lasted as long as it did and it wasn't the trailering.

thanks for the reply,i guess I'm going to have to have it checked out. have happy thanksgiving.

billy65 · November 30, 2007

my 2000 z71 was clunking just as yours was and i discovered that every time i hauled something that amounted to a couple hundred pounds in the bed it dident clunk,i dropped the drive shaft and greased the yoke that slips up in the transmission and that fixed the clunking for awhile,i have discovered that one can buy a yoke thats made out of different metal thats self lubricating and cures the problem,the real problem is the drive shaft angle when the truck is empty,we can lower the back end and that will cure the problem also,if thats your problem when you accelerate it puts the yoke in a bind and it bangs when it turns loose,im thinking about just drilling a small hole in the tail shaft housing and screwing in a grease fitting,then every time i service the truck just hit it with a couple shots of grease,hope the helps some one,mine drove me crazy till i found it....