Clunking on deceleration?

[Jason_Staggs]

Not sure if this is the right sub, but I have a 95 k1500 350 nv4500 and I recently noticed a very dramatic “CLUNK” and it kind of rocks back and forth when letting off the accelerator or clutching under a load. It never happens, that I’ve noticed, on acceleration only decel. I got under it last night to check my u joints and thought I saw some play in the front driveshaft u joint, so I removed it and test drove and it’s still there. My rear u joints appear fine with no slop as do my motor/trans mounts. Anyone ran into anything similar?

 

[PlayingWithTBI]

My rear u joints appear fine with no slop as do my motor/trans mounts. Anyone ran into anything similar?

If they look good, try putting it in neutral and, with emergency brake on (or rear tires on the ground) rotate the drive shaft. back and forth, to see how much slop, if any, you have in the rear. Then, with rear wheels off the ground and trans in gear, try rotating the drive shaft (back and forth) to see if there's any slop in the yoke or internally in the trans.

 

[movietvet]

I know you said there was no slop in the mounts. How did you inspect? May also have too much play in rear gears. There was also a time, years ago, when a customer had a similar situation and found the transmission attaching bolts at bell housing loose from previous work and we checked the transfer case and found a bolt loose there as well.

 

[Jason_Staggs]

If they look good, try putting it in neutral and, with emergency brake on (or rear tires on the ground) rotate the drive shaft. back and forth, to see how much slop, if any, you have in the rear. Then, with rear wheels off the ground and trans in gear, try rotating the drive shaft (back and forth) to see if there's any slop in the yoke or internally in the trans.

Currently under my truck, I tried it in gear and out of gear and neither time was there any slop in the u joints. I put a small pry bar in between and put pressure and they were solid. Same thing the the trans mount and for the motor mount I tried some quick snaps of the throttle and saw no excessive movement. Hard to brake torque a manual when you have no one to help you look. Also dropped my rear shaft and there was no play in the bearings but it had some while spinning the yoke

 

[Jason_Staggs]

I know you said there was no slop in the mounts. How did you inspect? May also have too much play in rear gears. There was also a time, years ago, when a customer had a similar situation and found the transmission attaching bolts at bell housing loose from previous work and we checked the transfer case and found a bolt loose there as well.

I’ll double check the mounting bolts for the transfer case I had some help putting it in and didn’t double check it afterwards

 

[Hipster]

Not sure if this is the right sub, but I have a 95 k1500 350 nv4500 and I recently noticed a very dramatic “CLUNK” and it kind of rocks back and forth when letting off the accelerator or clutching under a load. It never happens, that I’ve noticed, on acceleration only decel. I got under it last night to check my u joints and thought I saw some play in the front driveshaft u joint, so I removed it and test drove and it’s still there. My rear u joints appear fine with no slop as do my motor/trans mounts. Anyone ran into anything similar?

Under the truck or back by the differential? loose mounts, rusted u-bolt on diff allowing diff to slip-n-slide, u joints need to be tight smooth operating not dry and bound up, some report clunking for lack of grease at transfer case end yoke.

 

[Jason_Staggs]

Under the truck or back by the differential? loose mounts, rusted u-bolt ondiff allowing diff to slip-n-slide, u joints need to be smooth operating not dry and bound up, some report clunking for lack of grease at transfer case end yoke.

U bolts are solid and all mounts appear to be as well. Tried jacking up the transfer case to check the trans mount and it was pushing the truck up as well so I’m assuming it’s a good sign. Checked my motor mounts again by rocking the truck in gear while looking at them and they seem super solid but the passenger was moving a tiny bit. I don’t think my transfer case side ujoint has a grease fitting I didn’t see one so probably factory but I know my rearmost is fine I replaced it maybe a year or two ago. I planned on while I had it out to replace all 4 u joints anyways because I’m sure all but rear one are factory it has about 180k on it

 

[Jason_Staggs]

Trans mount very oil saturated might replace it just because

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Passenger side u bolts tight and no play

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Driver side second verse same as the first

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It’s really bugging me, not just from not being able to drive my truck but also from not being able to figure it out

 

[Caman96]

Driveline Clunk has long been part these trucks illustrious careers. I remember when my 98 Sierra was doing this with really low mileage back in 2000. I took it into dealership and they basically said nothing they could do, it was very common. Just Google GM Driveline Clunk. My current 96 K1500 will occasionally do it, but I’ve learned how to mostly avoid it. They did come out with a Nickel Plated Yoke that some had success with while others re-greased their yokes occasionally.

 

[Jason_Staggs]

Driveline Clunk has long been part these trucks illustrious careers. I remember when my 98 Sierra was doing this with really low mileage back in 2000. I took it into dealership and they basically said nothing they could do, it was very common. Just Google GM Driveline Clunk. My current 96 K1500 will occasionally do it, but I’ve learned how to mostly avoid it.

Occasionally I could put up with, but this is every single time I let off the gas it just lurches slightly and goes CLUNK CLUNK so loud that you can hear it over my exhaust which isn’t very quiet to begin with. I might just drive it until it breaks breaks and deal with it then