Clunk/thud while accelerating/slowing down

nadrojcote · May 11, 2015

My 2014 is clunking when I let off the gas after accelerating. I can shift from 1-2 nice and smooth during acceleration, but when I start to let off the throttle and it shifts to 3rd it lags a bit and thuds like the transmission is slipping. I have done some googling and believe it may be axle wrap. Has anyone else had this issue? My leafs are fairly worn out and I'm contemplating tying a some rear leaf clamps like people have been doing on previous generation trucks.

nadrojcote · May 12, 2015

Well if anyone is interested to know I installed some clamps on my leafs and it helped a lot, the clunking is still there but its very minor compared to before. It shifts nice, fast and smooth now with my diablosport.. I think I will still replace my old leafs to improve the ride. I couldnt find leaf clamps anywhere at this time of night so I bought shackle straps and bolts. They seem to hold in really well.

Jordan18 · May 12, 2015

Well if anyone is interested to know I installed some clamps on my leaf and it helped a lot, the clunking is still there but its very minor compared to before. It shifts nice, fast and smooth now with my diablosport.. I think will still replace my old leafs to improve the ride. I couldnt find leaf clamps anywhere at this time of night so I bought shackle straps and bolts. They seem to hold in really well.

In regards to the leafs my 08 sierra did this. I ended up putting a rubber stopper/gromet in between one of the leafs to reduce the noise.

fondupot · May 12, 2015

Hmm. Those are interesting. What do they cost?

Stevens03 · May 12, 2015

I wonder if some of the clunk is coming from your slip yoke. This was common on the GMT-900 and is an easy fix. Drop the drive shaft, pull it out of the transmission and pack the spline with some grease, Re-install. It should go in tighter since grease doesn't compact. See if the noise goes away.

nadrojcote · May 12, 2015

I wonder if some of the clunk is coming from your slip yoke. This was common on the GMT-900 and is an easy fix. Drop the drive shaft, pull it out of the transmission and pack the spline with some grease, Re-install. It should go in tighter since grease doesn't compact. See if the noise goes away.

I thought this wasn't recommended on the newer trucks? Something about there not being a proper seal and the grease was getting somewhere that it shouldn't be. You're right though, the noise is coming from the yoke, but the axle wrap is what is causing it. Eliminating the axle wrap seems to have fixed the problem for me.

Hmm. Those are interesting. What do they cost?

It was about $20 for all 4 bolts and shackle straps.

nadrojcote · May 12, 2015

I just looked into it some more, using grease on previous generation 4x4 would cause leaking into the transfer case, so they said you would need to use atf instead.

fondupot · May 12, 2015

I just looked into it some more, using grease on previous generation 4x4 would cause leaking into the transfer case, so they said you would need to use atf instead.

I feel like ATF is too viscous. It would just all come out right away.

Lol, I remember back on my 2002 GMT800 silverado I dropped the drive shaft to pack the splines with grease. But I forgot to put the parking brake on the truck. As soon as I got the drive shaft out of the truck, it started to slowly roll out of my garage. Luckily my garage is not too sloped and it moved slow enough for me to crawl out and hop into the truck and stop it from rolling.

nadrojcote · May 12, 2015

I feel like ATF is too viscous. It would just all come out right away.

Lol, I remember back on my 2002 GMT800 silverado I dropped the drive shaft to pack the splines with grease. But I forgot to put the parking brake on the truck. As soon as I got the drive shaft out of the truck, it started to slowly roll out of my garage. Luckily my garage is not too sloped and it moved slow enough for me to crawl out and hop into the truck and stop it from rolling.

I think the old tsb said to take the drive shaft out and grease it with atf, not to actually pack it like they recommended on the 2 wheel drive trucks.

CounterMeasure · May 12, 2015

I think the old tsb said to take the drive shaft out and grease it with atf, not to actually pack it like they recommended on the 2 wheel drive trucks.

I was told there's a TSB that says you can grease the slip yoke on 2WD, but not 4WD models because the grease will get into the transfer case. II came across this info because I was chasing a very similar clunk/pop which turned out to be leaf springs as well. GM Rep and dealership found leafspring/axle bolts not tightened to spec. They cranked them down and the noise was greatly reduced. Still does it occasionally, especially when wet. I've been meaning to get some clamps to see if that solves it.

nadrojcote · May 12, 2015

I was told there's a TSB that says you can grease the slip yoke on 2WD, but not 4WD models because the grease will get into the transfer case. II came across this info because I was chasing a very similar clunk/pop which turned out to be leaf springs as well. GM Rep and dealership found leafspring/axle bolts not tightened to spec. They cranked them down and the noise was greatly reduced. Still does it occasionally, especially when wet. I've been meaning to get some clamps to see if that solves it.

Definitely worth the little bit it costs. I feel mine rides and shifts more firm now.

Stevens03 · May 12, 2015

Well, I did this on my 2003 about every 10k-15k miles.. and never had an issue in nearly 70k. Maybe it's not good to do on the new trucks, but it sure fixed the issue on my 03.

nadrojcote · May 12, 2015

Well, I did this on my 2003 about every 10k-15k miles.. and never had an issue in nearly 70k. Maybe it's not good to do on the new trucks, but it sure fixed the issue on my 03.

Ya you cant do it on the newer 4x4's. My problem was almost as if I could feel the whole rear end of the truck moving front to back, jerking and slipping in between shifts.

fondupot · May 12, 2015

I was told there's a TSB that says you can grease the slip yoke on 2WD, but not 4WD models because the grease will get into the transfer case. II came across this info because I was chasing a very similar clunk/pop which turned out to be leaf springs as well. GM Rep and dealership found leafspring/axle bolts not tightened to spec. They cranked them down and the noise was greatly reduced. Still does it occasionally, especially when wet. I've been meaning to get some clamps to see if that solves it.

So the leaf spring mounting bolts and the u-bolt clamps?

Jackseric · May 22, 2015

OK ProjectSummit, I've got questions.

How many miles did you have on your truck when you put the shackles on?
How many do you have now?
Any wear problems or downsides to doing this?
Was the main/only reason for doing this the clunking on shifts?
How long are leaf springs supposed to last? I've never heard of them being worn out or replaced before your post. Well, aside from people doing stupid things like pulling 15,000lbs trailers with light duty trucks or something like that.

Thanks! :-)