Wicked vibration problems

[arveetek]

I'm having real trouble tracing down a wicked vibration/shaking problem with my truck. The vibration/shaking feels like a wheel is out of balance, and is in sync with wheel speed, not driveshaft speed. The problem occurs at 45 mph and above, and is worse around 65 mph. It's gotten so bad that I can hardly stand to drive the truck anymore, it just starts shaking me to pieces.

The problem originates from the rear of the truck. I've had the rear wheels jacked up off the ground and ran the truck up to 70 mph sitting still, and the shaking occurs without the front wheels moving.

I've had the wheels (custom aluminum rims) and tires (about 20,000 miles on BF Goodrich) balanced numerous times. I've even had the tires separated from the rims and moved around, trying to locate the problem. I've swapped the wheels and tires from front to rear, and even ran my spare on but it doesn't appear to be a problem with the wheels.

My transmission mount was getting pretty bad, so I replaced it (energy suspension this time). The slip yoke on the rear of the tranny was getting a bit sloppy, so I installed a new bushing in the tailhousing of the tranny, and that fixed another minor vibration I had. I replaced all the u-joints, some more than once. Carrier bearing (center driveshaft support for 2-piece driveshaft) is in good shape. There is a small amount of looseness on the splined slip joint on the second driveshaft, but it's always been that way. I'm basically left with the rear axle (14 bolt SF).

The yoke on the axle is a bit sloppy, and it's starting to leak oil out of the front seal. It's been a bit sloppy for years, but never seemed to be a problem. I jacked up the rear end to check for looseness in the axle shafts and outer bearings. There's a small amount of movement up and down between the hubs and backing plate, but no more than on my Tahoe which has a silky-smooth ride.

I'm rather stumped. The axle doesn't appear to be in that bad of shape, but the shaking is getting worse with every repair I've made. I know the yoke on the axle needs attention, but can it cause a vibration that would match wheel speed, not driveshaft speed?

I've checked around on 14 bolt FF axles, but they're getting hard to find. I've found a couple, but they're out of 30 year old trucks with lots and lots of miles. I found a couple of late model 14 bolt SF axles, but they cost around $500. I found a 4WD shop locally that will rebuild my SF for $275 plus parts. That sounds good to me, because I've been into these axles before, and I don't want to do it again.

Any thoughts/suggestions?

Casey

[gmctd]

Remove both rear tires\wheels, install couple lug nuts for safety, run it up to speed, drums only, observing axle-hub action.

[arveetek]

Remove both rear tires\wheels, install couple lug nuts for safety, run it up to speed, drums only, observing axle-hub action.

I've actually already done this. However, I didn't look at the axle/hub while it was running, just feeling for vibrations. It's barely noticeable without the wheels on. In fact, I have to apply the brakes slightly to put a load on the system in order to feel it at all, but without the extra mass of the wheels and tires, I couldn't really come to any solid conclusions.

Casey

[gmctd]

I suspected you might have done - is it a gov-loc limited slip differential?

[arveetek]

Standard open diff.

[gmctd]

Do the aluminum wheels center on the lugs, or the axle hub?

[arveetek]

Do the aluminum wheels center on the lugs, or the axle hub?

On the lugs. They come with center caps that are held on from the backside of the wheel. The center caps are still loose when the wheels are bolted on.

Casey

[BobND]

I've got a 1984 Sub with a similar shake.

I've...

....Had the wheels balanced several times, and tried 3 different set of wheels and tires, one brand new.

...Jacked it up, and run it with just the rotors and drums. (Doen't seem to shake.)

...Replaced the driveshaft with a used unit.

...Replaced the motor mounts, timing gears/chain, waterpump, fan and clutch, removed the A/C compressor.

...Replaced the torsional damper.

...Checked for the presence of the flexplate balance weight, and that the flexplate is located properly to the crank by the dowel.

...Replaced the IP and injectors. (It WAS "missing" at idle.)

...Removed torque convertor bolts, and turned it 1/2 turn in relation to the flexplate. (Didn't help.)

I think the problem IS an out-of-balance rotor or drum, but it sure didn't show up when I ran in up on the jackstands, with the wheels removed!

[arveetek]

I've got a 1984 Sub with a similar shake.

I think the problem IS an out-of-balance rotor or drum, but it sure didn't show up when I ran in up on the jackstands, with the wheels removed!

I wondered about that too, although it seems that the drum would have to be way out of balance to cause such a shake, but why doesn't it manifest itself with wheels removed?

Casey

[gmctd]

As I tho't - have you tried a matched, dynamically-balanced pair of tires - for brand, tread pattern, size - on a matched pair of oem wheels, which center on the hubs?

Also, because that is an open differential, you can lock either-side brake with a pair of vise-grips on the respective cable, then run the speedo at half speed to test each side separately at 70mph.

If tests are extensive and the diff gets hot, let it cool between tests.

Think maybe you gotta outta balance drum.

The spring-eye insulators may be shot, or a rusted-solid spring pack can contribute to the symptom.

[arveetek]

As I tho't - have you tried a matched, dynamically-balanced pair of tires - for brand, tread pattern, size - on a matched pair of oem wheels, which center on the hubs?

Think maybe you gotta outta balance drum.


I have not tried a set of oem wheels yet. I've wanted to but have been unable to borrow any as of yet, and hate to purchase a set for testing purposes only. My spare is mounted on an oem steel wheel, but it's an older model with a different size tire, etc. Not a very good test specimen.

Casey

[gmctd]

Brake the rr drum, try the spare on the lr hub, then switch it to the rr hub, locking down the lr drum - see whatcha got.

Make sure it is dynamically balanced before testing.

[Subzilla]

Same problem with my '83 for 8 or 9 years and I've tried most of the same solutions ya'll have tried. I've even been through new shocks, wheels and tires, suspension lift kits and I keep coming back to the imbalanced brake drums or worn out rear axle bearing theory. But I keep getting funny stares when I ask locally about balancing brake drums. They usually say there ain't no way the drum can cause that or they've never had to balance a drum before. I still think it's a possibility but can't find anybody to check them. My bearings have a ever-so-slight movement when I try to move the wheel up and down. I assumed they should have almost no play as in the front? I haven't made the time to replace them but I'm trying to talk to myself into trying this solution. I just hate to get disapointed again. My vibration will shake the console and seats enough to mix a margarita while holding in your hand! (well, sort of).

[gmctd]

That type vibration is usually associated with 2-pc driveshaft clocking - all the crosses must line up, starting at the transmission.

The trans yoke must line up with the slip-joint yoke with the diff yoke.

The three 'yokes' welded to the driveshaft tubing should then be in exact alignment.

[arveetek]

Same problem with my '83 for 8 or 9 years and I've tried most of the same solutions ya'll have tried. I've even been through new shocks, wheels and tires, suspension lift kits and I keep coming back to the imbalanced brake drums or worn out rear axle bearing theory. But I keep getting funny stares when I ask locally about balancing brake drums. They usually say there ain't no way the drum can cause that or they've never had to balance a drum before. I still think it's a possibility but can't find anybody to check them. My bearings have a ever-so-slight movement when I try to move the wheel up and down. I assumed they should have almost no play as in the front? I haven't made the time to replace them but I'm trying to talk to myself into trying this solution. I just hate to get disapointed again. My vibration will shake the console and seats enough to mix a margarita while holding in your hand! (well, sort of).

That's exactly the problem I'm having. My vibration has been there for some time, but is now gotten bad enough I can't hardly stand to drive the truck.

My u-joints and yokes all line up....they will only go on one way. The splined slip-joint between the two driveshafts has a notch that will only allow it to slip together with u-joints and yokes lined up.

Casey

[Subzilla]

And my Suburban has a one piece driveshaft that I've had balanced. My vibration doesen't seem to vibrate to the same speed as the driveshaft turning. It seems to vibrate slower like an unbalanced tire. We use our Sub for alot of traveling and that's been my biggest thorn in the side.

[arveetek]

And my Suburban has a one piece driveshaft that I've had balanced. My vibration doesen't seem to vibrate to the same speed as the driveshaft turning. It seems to vibrate slower like an unbalanced tire. We use our Sub for alot of traveling and that's been my biggest thorn in the side.

Yep, that's what I'm experiencing. Vibration is wheel speed, not driveshaft speed.

I went ahead and made an appointment to have my axle rebuilt....it needs done anyway. I'm going to look into having the driveshaft balanced while I'm at it.

Casey

[Subzilla]

http://thedieselpageforums.com/tdpforum/showthread.php?t=23037
This was my latest plea for help and the responses. Please let me know if your axle rebuild helps.

[poolmike]

I had a very similar situation with my M715. Did all of the above checks and then found 17 teeth torn off of my ring and a totally shredded pinion. That was a Dana 70 with 5.87's. Rebuilt it with new gears and it was all good.

[arveetek]

I dropped the truck off at the axle shop today, and they just called and said that the axle is fine and doesn't need to be serviced. They said that the axle couldn't cause the vibration I'm having. They were more than happy to take my money, they said, but were sure it wouldn't do me any good. They suggested wheels or driveshaft as the culprit.

I'm still stumped! :confused:

Casey

[john8662]

Need some stock wheels?

Got a set of stock steel rims off my '95 6.5, caps, rings, all of it.

I had a problem with my '86 that was like this. I had the u-joints replaced and the carrier bearing replaced. The shop that did it CUT the old carrier bearing off with a torch. Guess what? When you heat something like that, well, it kinda warps it. Anyways, was put together and the thing wabbled badly under lower speeds. That driveline was essentially ruined, cause I had a driveline shop re-do it again, they balanced it, it was MUCH better, but not perfect. I ended up buying a good driveline from the salvage yard (that still had the original u-joints in it) and had it rebuilt, that's what I'm running now. It's smooth now.

Do you have a driveline shop that actually balances the driveline?

If not I can get it done locally.

[Subzilla]

Casey, I'm disappointed. I was hoping you would find the problem for me. But I wonder that when the shop said the axle could not cause the vibration, was he meaning that your axle is good or did he mean that any axle could not cause that vibration?

[arveetek]

After nearly a full day of trial and error troubleshooting, a set of new tires reduced my vibration problems by 90%.

I hated to replace a set of tires that had a lot of life left in them, but that was the final conclusion my brother and I came to. We jacked up the rear of the truck again, and watched the rear tires. One tire wobbled in and out, the other up and down. I found a set of chrome rims, and installed a pair of tires I had from the last time I changed tires (almost forgot I had them). We went for a drive, and the problem was nearly eliminated. We finally got out a dial indicator used for measuring runout, and determined that my aluminum rims had just a slight amount of runout, but that one tire had an extreme amount of runout.

I was running BF Goodrich Long Trail T/A's, size 265/75R16. I only had about 20,000 miles on them, and they had lots of tread left, but they were simply bouncing me out of my seat. My previous tires were the same brand and model, but size 245/75R16, and I got 50,000 miles out of those. I went up one tire size last time simply for looks. I don't know if it really makes a difference or not, but I'm wondering if the larger tires were just too big to expect such long life. So I decided to go back with the smaller tires, again same brand and model.

I can still detect a small amount of vibration, but only because I know every tick, wobble, and vibration there is on this truck. The casual passenger would never sense anything.

Thanks for all your help, guys!

Casey

[arveetek]

Do you have a driveline shop that actually balances the driveline?



I found a local shop and was going to have the driveshafts balanced today, but my brother talked me out of it. He was convinced that it would not help. He had his hand on the carrier bearing with the axle turning at 65 mph, and he couldn't detect any vibration at all. I still may have it done (only $60), but it looks like I've got it figured out now.

I think my truck is riding as smooth as a 25 year old 3/4 ton pickup can be expected to now.

Casey

[arveetek]

Casey, I'm disappointed. I was hoping you would find the problem for me. But I wonder that when the shop said the axle could not cause the vibration, was he meaning that your axle is good or did he mean that any axle could not cause that vibration?

I took it to mean that they thought it would be highly unlikely.

I think that if I balanced my driveshafts, replaced the shocks, and replaced all the suspension bushings, I'd have an even smoother riding truck. I do believe that my Energy Suspension motor and transmission mounts are transferring a lot of engine vibrations back into the body, though. I can really feel the engine singing to me at 70+mph. It's not that bad, though. At least I don't have to worry about my drink spilling due to the shaking!

Good luck with your vibration!

Casey

[HH]

Did your tires require alot of weights for balancing? Many times just spinning the tire 180 degrees on the rim will solve a tire/wheel balance issue. Most wheels are drilled for the valve stem at either the heaviest or lightest point (I can't remember which) and usually the tire is marked for the opposite, with either a branded "v" or possibly a paint mark. Most "tire busters" don't know this and just mount the tires as fast as possible, and throw them on the balancer, and add extra weights to compensate. I would not give up on your "new" tires just yet.

If there is a problem, the place you purchased them from should cover them under warrenty, probably prorated, but better than paying full price. It may be possible a belt is starting to seperate internally. Good luck.

[arveetek]

Did your tires require alot of weights for balancing? Many times just spinning the tire 180 degrees on the rim will solve a tire/wheel balance issue. .

Yep, one tire in particular had all the weights the shop could possibly get on it, and it was still out of balance a little. I had the shop break the tire from the rim and move it like you suggested, but it didn't help.

Of course, it doesn't help that my custom rims only allow weights to be attached on the back side of the wheel. There's no lip to attach weights on the front of the wheel.

I do have a set of BF Goodrich LT265/75R16 tires for sale! :D They're in great shape, really, and would probably be just fine on someone else's truck. I'm just so anal about these things, and most other folks couldn't tell what I was talking about.

Casey

[Subzilla]

Hmmm, I've got the factory steel wheel with tires sitting out in the woods. I wonder how dryrotted they are from 12 years of collecting spider webs and rain water?!?! I think I'll pull them out and see about putting them back on just for fun. I guess the thing that keeps baffling me is the fact that moving the tires and wheels around doesn't seem to move the vibration. I have never felt it in the front (best I can tell). It seems to me that if my wheels/tires were bad, I would feel the vibrations more in the lighter springs up front and not as much in the HD 3/4 ton springs in the rear. I guess I'm thinking the heavier springs would be more prohibitive of vibrations and flex. Thanks for posting back your findings!

[arveetek]

I guess the thing that keeps baffling me is the fact that moving the tires and wheels around doesn't seem to move the vibration. I have never felt it in the front (best I can tell).

I found the same thing...in fact, my results seemed to be inconclusive. I could never put my finger on which tire was the problem.

Casey

[arveetek]

Well, after driving the truck for about a week, I came to the conclusion that I had not solved the vibration problem completely. My violent shaking is gone, but I still have a vibration coming through the seats that is still driving me nuts. I believe that the shaking tires covered up this vibration enough that I couldn't separate them out.

The current vibration feels like a bad u-joint. I took the driveshafts out last night, and they have now been to the shop and have been balanced, and I will put them back in tonight and report back with the results then.

I did have the rear wheels up in the air again last night and could definitely tell that the new tires have zero runout or up and down motion, mounted on the same wheels as before. So I know my wheels are fine, and the new tires helped considerably. Hopefully the balanced driveline will solve this last piece of the puzzle.

I've come to realize that I had several problems added up together instead of one large single problem causing the bad ride.

Casey

[arveetek]

The shop added several weights to the driveshaft, but I don't think it helped any. If anything, I have a worse vibration at 40 mph that feels like a bad u-joint. Above that speed, however, and I don't feel that particular vibration. I still have a wheel-hopping sensation though. I'm stumped. I have no clue where to go from here.

I'm going to double check my front suspension and wheel bearings, but I doubt there's any problem there. I have no idea what else to check. I ran the truck up to 70 mph with the back of the truck in the air, and it's really pretty smooth now, except for the 40 mph u-joint problem. Maybe there's a new tire problem in the front??? :confused:

Casey

[More Power]

Some of the better equipped shops can balance a tire/wheel/hub assembly on the vehicle. If you have this done, it's important to mark the lugs so if the tire/wheel come off at some point in the future, it can be reinstalled with the correct orientation.

Back in the mid 70's I bought a new Plymouth Satellite Sebring, but requested that the new tires (60-series belted bias) I had on the trade-in ('69 Baracuda) be moved to the new car. As I discovered many months later, they sourced a set of steel wheels from an auto salvage wreck to mount my tires onto that would fit the disc brake equipped car. I went through the imbalance problems you guys are reporting here for nearly two years till I discovered the problem.... bent wheels.... Multiple re-balancing jobs never helped - including dynamic balancing on the vehicle.... I finally installed new wheels, which cured the imbalance.

So, I'd recommend checking runout - both longitudinally and laterally, in each wheel - while mounted to the axle. Possibilities include out of round tires, bent wheels, warped hubs, bent axle, corrosion/rust causing an out of line mounting surface, and so on.... Lug-centered wheels are generally not as true as hub-centered. I'm told GM uses hub-centered.... at least for their factory wheels.

Jim

[Subzilla]

Jim or anyone,
What would be considered acceptable runout? I'll recheck my set to see what I have. Thanks.