front end clunk when backing up?

i have a clunk coming from the drivetrain when i am turned to the left and backing up. it has done it a couple of times going foreward, but mostly back. it is not consistant either, seems to do it after the truck has sat for a couple of minutes. i have replaced the following: all ball joints, tie rods, idle arm, pitman arm. i took it to the mechanic today, he found i have a sloppy driver side half shaft. he wasn't sure if this could cause my clunk though. i have a new shaft ordered, be here tomorrow. the noise seems to be on the passenger side though. that shaft felt tight, and the wheel bearings seem good also. any thoughts? thanks!

Have you greased the 10-11 fittings in the front end?

http://www.automotiveforums.com/vbulletin/showthread.php?t=344505

Also, check out this thread for a clunk fix I made up:

http://www.automotiveforums.com/vbulletin/showthread.php?t=302656

i greased, and installed all the above parts. i kind of ruled out the hood, because the clunk only occurs when i initially move the truck about a foot or 2. i'll check the hood out, as it's an easy fix. any other ideas?

Does it coincide with a quick dimming or flickering of the lights?

Keep us posted! I'm having the same problem. Mine is more of a loud click (sounds almost like the AC clutch coming on only much louder and from the passenger side).





i greased, and installed all the above parts. i kind of ruled out the hood, because the clunk only occurs when i initially move the truck about a foot or 2. i'll check the hood out, as it's an easy fix. any other ideas?

You might also check your anti sway bar end links. I had a clunk similar to you when backing up and turning. The top of the end link bushings were hitting the tie rod adjuster bolt and causing a clunk. It was fairly obvious since the adjuster bolt had worn a groove in the washer on the end link. I must admit these Blazers have more Clunks and pops than any other vehicle I have ever owned. I have eliminated them from suggestions on this forum, though. I still have a damn creek in the steering. :(

i stopped at the dealer to get my washers, and the guys behind the counter pulled up some tsb's for me. one that really got my attention was for the torsion bar rubbing against the frame. i'll check that out as i'm replacing my idler arm again, and installing my new half shaft. this thing has got to get better....

half shaft?

You mean inner tie rod end.

half shaft?

You mean inner tie rod end.
Half shafts are what connect the front diff to the wheel. The are generically called CV joints, even though the CV joints are just a part of the half shaft. They are some times called the front axles, too.

The problem does sound like the torsion bars. You can climb under and take a look, it is pretty easy to see if the cross member is striking the frame, because there will be a clean spot or rub marks.

if youve ever taken apart/rebuilt a CV joint/half shaft, you'd find the hub end looks like a Tibia/fibia/etc (end of a bone lol) with five (avg)hollows, five large ball bearings, a retaining ring with races and associated hardware and the axle SHAFT is attached into this ring.. usually when the joint goes out it's the disintegration of that retaining ring and its ball-bearing races, and the worse it gets, the more SLOP. In a turn, you hear a clunk... that's the combination of that slop trying to function at an ANGLE, and the sound is, understandably, different because the position is different. Replace that and I think your problem will disappear.

Also make note if it hapens while you're backing up... It could just as easily be your upper control arm bushings. Check them for dry rot/cracking on the edges. If present, that is most likely your problem.

Before going to the torsion bar mounts, do the control arm bushings...They are the more liekly culprit... Just a though is all.

well, i've replaced the following front end components:tie rod ends, inner and outer, all ball joints, idler arm, pitman arm, and driver's side front axle.they were worn out and needed to be replaced, even if they didn't solve my clunk. the truck feels so tight now, just like new! i also installed the hood hinge washers, but my clunk is still present. tomorrow i'll be looking into the torsion bar mounts. i don't regret the work i've done so far, as i'm really pleased with the results. i think this truck was rode hard by the p.o., the bastard! only 80k on this thing. i'll post my results when i've figured it out. thanks for the help everyone!

The torsion bar mounts will cause a clunk when backing up and sometimes while going forward if turning. You will normally feel it in the floor, too. It only takes 5 seconde to climb under and see if it is striking the frame.

well, i've replaced the following front end components:tie rod ends, inner and outer, all ball joints, idler arm, pitman arm, and driver's side front axle.they were worn out and needed to be replaced, even if they didn't solve my clunk. the truck feels so tight now, just like new! i also installed the hood hinge washers, but my clunk is still present. tomorrow i'll be looking into the torsion bar mounts. i don't regret the work i've done so far, as i'm really pleased with the results. i think this truck was rode hard by the p.o., the bastard! only 80k on this thing. i'll post my results when i've figured it out. thanks for the help everyone!

As I said, check the contol arm bushings... If they're dry rotted/cracked they may be your culprit vs the torsion bar mounts.

i have a clunk mostly when i take off but some times it will do it in reverse. i looked at my frame and i could see where the rubber pad on the torsion bar assably has been hitting the frame but i think this if normal since theres no metal sticking out of the rubber pad ans why else would the pad be there other then to stop it from clunking. i think its normal for it to hit it a little.

i have a clunk mostly when i take off but some times it will do it in reverse. i looked at my frame and i could see where the rubber pad on the torsion bar assably has been hitting the frame but i think this if normal since theres no metal sticking out of the rubber pad ans why else would the pad be there other then to stop it from clunking. i think its normal for it to hit it a little.

Did you check the control arm bushings?

how do i check them. they have some small dry cracks in them. is there any other way to test them?

if it's dry cracked like that they need replaced...Probably that's your problem and not the torsion bars.

how hard are they to replace?

how hard are they to replace?

I would honestly find out your problem instead of rolling the dice and guessing what it is.

how hard are they to replace?

Not very, far easier than the torsion bar mounts... As I keep saying your issue sounds more like the control arm bushings than the torsion bar. The torsion bar is more likely to knock over bumps, whereas your problem is clunking when turning or backing up which is indicative of the control arm bushings, and the fact that they are dry and cracked seems to confirm this.

well it does it when i go over bumps and when i take off. it also seems sometimes like when it does it it almost seems like when i take off like the drivers side wheel gets stuck in the rested postion and then flops down with a clunk. if that makes any sense. the only way i can get it to do it is drive it. i've tried jacking it up and droping it with no success. i've also tried jumping on it and can't find it. i did used to get a click or i could feel the clunk in the steering wheel but after looking at it i could see that the bolt from the anti sway kit was hitting the tir rod. fixed that but the clunks there. is there any way to test the bushings?

IF they're dry and cracked, they're bad.

Not very, far easier than the torsion bar mounts... As I keep saying your issue sounds more like the control arm bushings than the torsion bar. The torsion bar is more likely to knock over bumps, whereas your problem is clunking when turning or backing up which is indicative of the control arm bushings, and the fact that they are dry and cracked seems to confirm this.
I can't say for sure if it is the control arm bushings, torsion bars, or something else, because I'm not there to inspect it in person, but I do know that there is a TSB out for the torsion bar crossmember being too close to one side, making it more likely to hit the frame. The symptom listed is a clunk felt in floor pan while backing, turning, and while traveling over uneven surfaces. The fix is to shim one side so that the crossmember is centered in the frame. I currently have this problem, but it isn't enough of a nuisance to fix it right now. I'll get around to it sooner or later. I'm currently experiencing a clunk while backing to the left and occassionally when I hit a bump, it hardly ever does it going forward. Swalt was the one that tipped me off to it, I believe that he had the same issue. I think that the effected models were 98+. The year model and symptoms don't apply to metallica21156, so I doubt that it is his problem, but both do apply to the threadstarter leading me to believe it is most likely the cause of his problems.

i still have the clunk, even after installing the shims on the torsion bar crossmember. it's doing it going foreward or back, steering turned all the way right or left. i don't want to sound like an idiot, but where and what are the control arm bushings? the clunk occurs within moving the truck 2 feet or so. it doesn't do it while going over rough surfaces, or any other time. the mechanic thinks it might be in the passanger half shaft, so i might replace that next.

check your brake calipers.

The pins could be worn.

i still have the clunk, even after installing the shims on the torsion bar crossmember. it's doing it going foreward or back, steering turned all the way right or left. i don't want to sound like an idiot, but where and what are the control arm bushings? the clunk occurs within moving the truck 2 feet or so. it doesn't do it while going over rough surfaces, or any other time. the mechanic thinks it might be in the passanger half shaft, so i might replace that next.

The upper control arm bushings are at the frame. You will see a large triangle attach to the frame behind your left front wheel. the base of the triangle holds your upper ball joint, the top has a bushing in each ear. If the rubber is dry or cracked it is most likely the cause of your problem... dunno if I mentioned that before or not... :banghead:

I'm currently experiencing a clunk while backing to the left and occassionally when I hit a bump, it hardly ever does it going forward. Swalt was the one that tipped me off to it, I believe that he had the same issue. I think that the effected models were 98+. The year model and symptoms don't apply to metallica21156, so I doubt that it is his problem, but both do apply to the threadstarter leading me to believe it is most likely the cause of his problems.

Any chance that you've done this in the dark and notise your lights flicker? That's what I'm getting. Almost always in reverse - usually the first time for the day(which is @ 3am) in the dark and I notice my lights flick. I thought it might have been my automatic lights kicking in but I can let it idle for a while and it'll still happen. I'll be doing the backslide under the beast tomorrow looking for wear. Damn I hate stone driveways!!!

watch your voltage and see if it drops a little. i know drivng my truck that even cruseing i can see might lights flicker when the bass hits.

i tired to pull the upper bushings today with no luck. i did how ever got the rubber out of one and it was fine. just around the very edges that stick out where the bolt head and nut is a little cracked. i couldn't see any place it wore though. i was looking at my brakes and it looks like theres a place on the calipair that looks like the pad might be hitting. could this cause it?

i have finally solved the clunk!!! turned out that rlith was correct. it was the upper control arm bushings. $8.99 at auto zone. not the easiest to replace, but a little heat and a big vice&hammer got the job done. thanks to all who contributed. if anyone has any questions about symptoms or fixes that i had tried, fire away! thanks again everyone, she's like new again!

Not that anyone pays attention to me.. :banghead:

replaced them as well but still clunks.

replaced them as well but still clunks.

both sets of uppers? have you checked your ball joints? Have you checked your hub bearing?

replaced both sides. how do i check the hubs. upper ball joints might have 500 miles on them and the lowers are about 2,000 maybe? i did see a place on the control arm that was hitting. i'm going to put some rubber there and see if it goes away.