clunking under light braking

MODERATORS: I replied to the original post in the modified tech forum without realizing it was not the OEM forum. I'm posting here as well since the jeep in question is not modified at all. Sorry about that!


Sorry to revive an old thread but searched, and didn't see a clear answer discovered in any of the posts.

This is a 99, 242, 8.25, 139k. 4 new ball joints and brakes in front along with tires. When braking LIGHTLY, there is a very low clunking coming from what seems to be the driver's side middle/rear. This is only noticeable starting at about 15mph and slower. Hard braking does not exhibit the effect, and I *think* it's not present when in reverse. I tried several times in reverse and *may* have heard it once, but never again. Really seems to only happen under very light braking going forward.

I checked the driveshaft and there does not seem to be any play in it (gripped with 2 hands and tried to wiggle it while jeep on the ground). I have no idea if the sound was there before the front end work was done as this is not my jeep, and I only heard it taking it for a test drive (my friend hadn't noticed it). There is snow outside and it's crappy weather for working on vehicles, so all I have done at this point was try to check the driveshaft. Oh, and looked at the ball joints and the front pads through the wheels. All parts said to be replaced were. Thanks for any help.

EDIT: It seems to happen about every quarter turn of a wheel

Inspect the u-joints, u-bolts, leaf springs, shock bolts, shock bushings, lug nut torque, and transmission and engine mounts. Inspect the rear brakes for any spring/hardware issues, loose brake shoes, and out of round drums.

There a TSB for 8.25 clunking


TSB Number: 05-05-00
Group: Brakes
Date: May 26, 2000
Subject:
Rear Brake Clunk Or Thump When Brakes Are AppliedModels:
1997 - 1999 Cherokee
Overview: This bulletin involves installing a rear axle shaft(s).
NOTE: this bulletin applies to vehicles equipped with a Chrysler 8.25 rear axle.
Symptom/Condition:
A clunk or thump may be heard coming from the rear of the vehicle when the brakes are applied on some vehicles equipped with an 8.25" rear axle. This may be caused by an axle shaft, which does not have a correct size brake drum pilot flange.



Diagnosis:
If the vehicle exhibits the condition, remove the rear wheels and brake drums and inspect the rear axle shafts at the center pilot for the wheel and brake drum. There must be two separate pilot diameters on this area (See Figure 1). The outboard diameter for the wheel (2.812-2.808 inches) and the slightly larger inner diameter to support the brake drum (2.832-2.826 inches). The brake drum pilot may be missing or may not be deep enough to support the drum. If the drum pilot does not adequately support the drum, some movement of the drum may occur when the brakes are applied causing this noise. If this condition is present, install a new axle shaft or shafts, P/N 05018393AA, as necessary.

Thanks! Checked trans and motor mounts and lugnut torque... all good. Didn't think about shock bolts. I'm trying to do first what's easy in snowy weather

My '92 clunked on and off for a few years... I think I traced it down to rear drums that were not quite round. I've also noticed it happening if a wheel's lug nuts are put on too tight, or not evenly, by a tire jockey with a gorilla-sized impact gun. I will use a torque wrench to re-install a wheel, starting at 30 lbs/ft, then proceeding to 45, 60, then up to 80, all the while using the star pattern method. The alloy wheels on our Jeeps typically want 80-100 lbs/ft, so I shoot for the lower figure, but will check them occasionally. Ramming them on at over 100lbs one at a time with a big gun is only asking for something to warp.

heyhar said:

My '92 clunked on and off for a few years... I think I traced it down to rear drums that were not quite round. I've also noticed it happening if a wheel's lug nuts are put on too tight, or not evenly, by a tire jockey with a gorilla-sized impact gun. I will use a torque wrench to re-install a wheel, starting at 30 lbs/ft, then proceeding to 45, 60, then up to 80, all the while using the star pattern method. The alloy wheels on our Jeeps typically want 80-100 lbs/ft, so I shoot for the lower figure, but will check them occasionally. Ramming them on at over 100lbs one at a time with a big gun is only asking for something to warp.

Click to expand...

Huh... never thought of this but might be worth re-torquing them. I know the tire place just cranks them on (what place doesn't?).

Just a follow up.... no luck on retorquing the lugnuts. However, I found that it only happens once the brakes are "warmed" up. I'm thinking it's a warped drum or similar. When it's nicer out I'll pull the wheels and see what I find.

Check also for exhaust pipe knocking on crossmember when engine mounts flex.

See if there's any difference in the clunk if you put the transmission in neutral.