"Thunk" from rear when stopping / letting off the brake (1 Viewer)

[Jeff Elliott]

Hi All -

When I come to a stop and then release the brake to pull away from said stop, I get a "thunk" from the rear end and I can see the shifter move - like something is bound up in the driveline. If I very gently come to a stop and lighten up significantly on the brake as the rig comes to a stop (like I was driving the Pope around), I can avoid the thunk / jolt.

Any ideas? I'm thinking u-joint but I recently had them checked by an old-school driveline shop and they were good. Maybe slip joint?

Thanks all

 

[ajax1]

Ujoints rear upper and lower arms bushings

 

[thegadgetguy]

I had a similar issue and replacing the rear driveshaft (so, new slip yoke) made it disapear, for awhile at least. I would also add, make sure your engine mounts are not broken.

 

[Jeff Elliott]

Thanks @thegadgetguy - two questions:

1) for a little while - did it come back?
2) any advice on checking for broken mounts (do I need to lift the motor)?

 

[Rwhat]

Grease your rear slip yolk

 

[Rwhat]

Thanks @thegadgetguy - two questions:

1) for a little while - did it come back?
2) any advice on checking for broken mounts (do I need to lift the motor)?

Pop the hood start up the engine. Then put it in drive and while holding down the brakes and giving it gas. Look to see if the engine lifts. You will know by sound when the fan hits the shroud.

 

[leonard_nemoy]

Haha, you might want to have someone else look at the engine while your holding the brake and giving it gas. Just make sure they aren't standing in front of the vehicle!!!!!

 

[thegadgetguy]

Pop the hood start up the engine. Then put it in drive and while holding down the brakes and giving it gas. Look to see if the engine lifts. You will know by sound when the fan hits the shroud.

My two front mounts were completely sheared off, for how long I don't know, and I never had any radiator shroud issues.

Jeff, I honestly don't know how you tell if the mounts are okay without removing them. I have an inkling mine might need to be replaced again.

I do have a little bit of a clunk again. I'm not sure if it's the slip yoke again, or some other issue.

 

[Rwhat]

My two front mounts were completely sheared off, for how long I don't know, and I never had any radiator shroud issues.

Jeff, I honestly don't know how you tell if the mounts are okay without removing them. I have an inkling mine might need to be replaced again.

I do have a little bit of a clunk again. I'm not sure if it's the slip yoke again, or some other issue.

Well, next time if you are unsure. So the same thing i mentioned, but put the transfer case in low gear and report back.

 

[Feldrian]

I'd check in this order (agreeing with what every one else posted):

1. Rear driveshaft ujoints
2. Rear driveshaft slip yoke
3. Control arm bushings
4. Caliper mounts (look for missing/ sheared bolts or excessive corrosion allowing movement)
5. Engine and cross member mounts
6. Transfer case output bearings (they'd have to be really smoked to clunk and there would be other symptoms like vibration)

My money is on the driveshaft somewhere or maybe control arm bushings.

 

[Heckraiser]

As others have stated, I'd bet it's your driveshaft (u-joints or slip yoke) or control arms (either worn bushings or the bolts have worked themselves loose). I had a front end clunk that took me a while to diagnose, but it turns out I just needed to re-torque the radius arm bolts. 130ft lb is a lotta torque!

 

[Jeff Elliott]

Well, the new drive shaft solved it!

Untitled by Jeff Nada, on Flickr

Untitled by Jeff Nada, on Flickr