Drivetrain clunk

Hoping to get some opinions on this before I bring it in to get looked at.

Issue: When I let of the gas and then back on it, I get a clunk through the drivetrain. I can feel it in the gas pedal. I notice it at low rpm's like 1k-3k. I do not notice it in parking lots, seems to be at speeds over 10mph up to highway speed. I can make it do it on demand if I let off gas and then back on it right after. I can also stop it from happening if I'm very light on the gas pedal when starting to accelerate again.

History: Truck is a 2021 TRD Sport auto trans with 31,000 miles. 3 months ago I had (under warranty) the transfer case input shaft seal replaced. The tech forgot to tighten the carrier bearing mounts back up. 2 days later the vibration got really bad and I crawled under to find only 1 of the 2 bolts barely holding on. The problem seemed to start then and has been getting worse, but not 100% positive it's related.

Any insight before bringing to the shop would be greatly appreciated!

 

Try tightening the u-bolts on the rear axle/leaf springs.

 

So if this were a two wheel drive vehicle Id say to put it in neutral, crawl under and see if there is play in the differential by rotating the prop either way. Given that you have an extra gearbox in the mix you might want to drop try the same thing but holding both the input and output shafts and rotating the input either way first. Loose spring bolts or worn shock mount bushings could give a little clunk too but not usually at 32k. The missing bolts on the prop would just make me want to check for play on either the 4w box or the rear diff.

 

@DerekO thanks for the reply. I don't think it's the suspension. I can feel it in the drivetrain and the all the suspension components are tight. I will check the shafts for play.

 

I get the same thing if i let of the gas momentarily and at the same am between shifts. Rare occurrence, it is like slack smack!

 

This is not uncommon on these vehicles. There is play in the rear gears, in the slip yoke, and in the transfer case. If it is a manual, there is more play. All this play can make a clunk when you unload and reload the driveline.

 

Bad universal joint.

 

That is exactly what it feels like! My concern was mostly with that it was a non issue prior to the dealer forgetting to bolt up the carrier bearing after service work. The issue was getting worse, but now seems to be getting better (but still doing it).

 

I was thinking this too, but I can't replicate the issue at low speed in parking lot which I would expect to be able to do if it was u-joint?

 

slip yoke might be sticking bc of the lack of grease in it. You can pull it apart and grease it well and put new clamps on the boot for it.

 

I have 2016 access cab 4cyl/AT/4X4 and frequently drive up hills where I live. Near top of hill I back off on gas to slow the truck for a cross street. If I apply throttle before vehicle completely stops, I get a noticeable clunk in driveline. You can hear and feel it. If I come to a complete stop and apply throttle to get going again, no clunk. Just smooth acceleration. Usually go to 4 on transmission selector going up or down these hills. (SF) I have 80k miles and no other problems in nearly 10 years with this vehicle. Are my symptoms same as what this thread is discussing?

 

I'd say it definitely sounds similar, I think my truck would do the same.

 

It may be normal for these transmissions

 

My 2016 does exactly the same.

 

My 2020 with 86k miles has had a rear end clunk on acceleration and letting off the gas for years, although it doesn’t do it every time. It’s not too bad with it in 4hi, but it’s annoying driving around town. I probably need to do a trans drain and fill sometime soon.

 

Dang, sounds pretty common. I'd love to hear if a drain and fill on the trans fluid would help this. I've heard some people reporting their trans fluid was under filled from factory.

 

I have a 2017 2WD and have the same issue. I have inspected the driveline all u-joints are ok and suspension is tight. However there is play in the driveshaft. I did a trans service and D&R Diff fluids with no change. Looks like this is normal?

 

If you had an issue that made a similar noise under similar conditions, I would suspect that you are now more aware of it. So now you are noticing the normal play in the system that you tuned out before the issue.

If you have thoroughly checked the driveline and have found no issue, I would suggest continuing monitoring it and if it doesn't get worse then eventually you will tune it out.

My stepson recently purchased a VW Jetta with a TDI in it. He complained to me about a noise when going on the highway and off. When I checked it out, it turn out to be the dual-mass fly wheel and the way it loaded up and unloaded during the speed transitions on and off the highway... it was normal operation for the system. I told him the same. Be aware and observe, let me know if it gets worse. He has since tuned it out because it wasn't getting worse.