Bad Vibrations between 35-45 MPH

[HOrnbrod]

I've developed a vibration lately between 35-45 MPH. It's almost like a switch; comes on/off exactly at these speeds. It;s a bit wirse when accelerating, but when I take my foot off the gas it's still there. I can feel it both in the wheel and in the seat. I thought for sure it was tire balancing, but have had them balanced twice (the worst was 1/4 oz. off) and rotated; nothing changed. While at the tire shop the guys checked for any slop in the steering and all was tight. We jacked up the rear end and accelerated up to 65 MPH with no vibrations, so it's not the driveshaft or anything in the back end. I have not done anything lately that could possibly cause this. Last thing I did was change the gears, but the vibration was already there then, only not as bad as it is now. And it seems to be getting worse. I don't think it has anything to do with death wobble, and it's been lifted for over a year and this only started a few weeks ago. Steering damper? Tranny mount? Any ideas will be appreciated.

[rockhardzj]

Smells like a road forced tire to me.

[JeepcoMJ]

is it 2wd or 4wd? ujoints, mismatched axleshafts, unbalanced front driveshaft could all come into play.

 

only other thing is your control arm bushings.

 

is your track bar mount bolted down tight?

[HOrnbrod]

It's 2WD.

[MJ20]

I had the same problem a few months ago on my xj except the death wobble was between 35-55mph. Nothing was loose and I’ve got good ball joints and damper. I had an inner tire separation on a michilen a/t.

[HOrnbrod]

My tires are new, less than 2000 miles on them. Been under tightening everything. The steering box bolts were the only thing I found, and they weren't really loose, but I did take a turn or so with a big cheater bar. Everything else was tight. Just got back from a road test, and it's still there. Seems to be worse when lightly accelerating, then slacks off when letting up on the gas.

[HOrnbrod]

I had the same problem a few months ago on my xj except the death wobble was between 35-55mph. Nothing was loose and I’ve got good ball joints and damper. I had an inner tire separation on a michilen a/t.

 

Wouldn't that show up on the balance machine?

[opsled]

Vibrations that come in and go out repetedly at the same speeds or conditions are normally drive train related and the most common are drive shaft or U joint issues. Engine, transmission and rear end issues are usually more constant but can increase or go away under acceleration or decelleration. Drive shaft issues tend to do more as you describe and come in at a certian speed then go away again at a higher speed. Check your U joints in the drive shaft REAL good. you may have 1 froze or partially froze joint that will cause what you are describing. Make sure that the rear jount is perfectly centered in the axle yoke. I have seen where the yoke has worn and can allow the drive shaft to "off center" it self from the pinion centerline and cause the exact issue you are describing. If you think that these things are good take your drive shaft to a drive shaft shop and have them spin it to check for balance and straightness. Even though you may think your drive shaft is perfect there are many things that can cause them to go out of balance. Balance weights can fall off, internal rust on the shaft can come loose and cause an inbalance, some shafts were never straight from the factory and were corrected with balancing and every time you change a U joint you are effecting it's problems. I have been down this road many times and the driveshaft or U joints are usually the culprit.

Good Luck, opsled (Lord and mentor of JeepcoMJ) :brows: :brows:

[CWLONGSHOT]

I still say tires...New doesn't automatically mean right or fixed or eliminate them as the problem.

 

Tires begin to need to be balanced at + - 35MPH. that's where your problem begins....notice a trend?

 

Try OTHER tires, got a buddie you could try his for a trip doen the road?

 

CW

[HOrnbrod]

Vibrations that come in and go out repetedly at the same speeds or conditions are normally drive train related and the most common are drive shaft or U joint issues. Engine, transmission and rear end issues are usually more constant but can increase or go away under acceleration or decelleration. Drive shaft issues tend to do more as you describe and come in at a certian speed then go away again at a higher speed. Check your U joints in the drive shaft REAL good. you may have 1 froze or partially froze joint that will cause what you are describing. Make sure that the rear jount is perfectly centered in the axle yoke. I have seen where the yoke has worn and can allow the drive shaft to "off center" it self from the pinion centerline and cause the exact issue you are describing. If you think that these things are good take your drive shaft to a drive shaft shop and have them spin it to check for balance and straightness. Even though you may think your drive shaft is perfect there are many things that can cause them to go out of balance. Balance weights can fall off, internal rust on the shaft can come loose and cause an inbalance, some shafts were never straight from the factory and were corrected with balancing and every time you change a U joint you are effecting it's problems. I have been down this road many times and the driveshaft or U joints are usually the culprit. Good Luck, opsled (Lord and mentor of JeepcoMJ) :brows: :brows:

 

Just did another tour under the heep tightening everything I could get at. Found nothing abnormal. Checked the UCAs and LCAs, new tierod about six montha ago, and the trackbar bolts (all). About a month ago, I did regear my D35 (3.55 to 4.11), so naturally we pulled the driveshaft. I did have very slight vibes at the same speed range pre-regearing, but nothing like it is now. I marked the yoke and the driveshaft and reinstalled it the same way it came out. The U-joints I installed about 1-1/2 years ago, maybe 7K on them (don't drive it all that much). They are greasable, and I have kept them greased. There is no slop in the driveshaft, but I did notice some up and down movement on the slip yoke where the driveshaft slips into the AW4. I don't know how much movement is permissable, but the U-joint seems tight. Can my U-joints be shot already? Your logic seems right on since these vibes mostly started (or got worse) when we pulled the driveshaft and regeared. That was my first time, and it took three tries to get the preload on the pinion right. Just as an afterthought, could a too loose or tight pinion nut cause vibes in the drivetrain? I guess next step is to replace the U-joints, then check the driveshaft balance. That front slip yoke has be a bit cioncerned though. And today at the tire shop we did jack it up and run it up to 65MPH with no vibes. Wouldn't most driveline problems show up doing this?

[MJ20]

Wouldn't that show up on the balance machine?

 

The service rep found the separation while the tire was on the jeep by feel. I had a mild case of death wobble so I new it had to be steering and not drive train.

 

You may want to determine if it’s death wobble or a really bad vibration

[HOrnbrod]

I still say tires...New doesn't automatically mean right or fixed or eliminate them as the problem.

 

Tires begin to need to be balanced at + - 35MPH. that's where your problem begins....notice a trend?

 

Try OTHER tires, got a buddie you could try his for a trip doen the road?

 

CW

 

Yeah CW, tires seem like the logical culprit and that's what I'm hoping it is. But I did rotate the fronts with the rears, and it did absolutely nothing, no change. I have a set of original 235x75x15 tires and wheels over at my bro-in-law's house. I suppose I could slide over there and stick them on and see what happens. But he's 60 miles away. Wait - I do have two here (also 235s), but would putting just two on give any accurate indications? Guess I could try the front then the back. Or would a complete set be better?

[zjrog]

I'm going to side on tires too. Here is why. Last spring, my ZJ started a little DW on certain bumps, then I started to feel a vibration at 50-55... SO, I had the tires balanced again, but no change. I had some wear in the tie rods, so I replaced EVERY tie rod end and the steering stabilizer. I was back to vibration, and sometimes DW.

 

Then I did something I should have done from the beginning. I rotated the tires. DW was GONE!

 

Since that time, I have replaced the tires and wheels. One wheel was a bit out of balance, more than one would expect, and that wheel was also allowing lugnuts to loosen. They were on the Jepp when I bought it, I didn't really care for them either.

 

I put on some XJ steelies and some 30" tires to replace the 235/75R15s... No more vibes, no more DW...

 

Just my experience.

[rockhardzj]

I still say tires...New doesn't automatically mean right or fixed or eliminate them as the problem.

 

Tires begin to need to be balanced at + - 35MPH. that's where your problem begins....notice a trend?

 

Try OTHER tires, got a buddie you could try his for a trip doen the road?

 

CW

Nope. New isn't necessarily perfect. Manufacturer defects, and the occasional one that didn't have as superior of a build quality, but it's not visible when leaving the factory.

 

My buddy's TJ, all the sudden, one day, it would ride fine till about 35mph, and then all hell would break loose for vibration. Threw it up on a lift, balanced and rotated the tires, tightened any bolt you could set your eyes on underneath, shook everything checking for worn out bushings or anything, seemed perfectly fine. take it out for a test drive, did it again, but slightly different feeling, about the same speed. Back on the lift, pull all the tires, road force balance them, and quickly notice one is a little egg shaped. a section of tire, the entire width of the tire, and about 15-18 inches long was about 1/4" higher than the rest of the tire. Put that on the spare tire carrier, balanced the spare before installing, threw all the tires back on and handed the keys to my buddy. He was quite happy. When he asked what the problem was, I showed him the tire on the carrier, and he was quite surprised. The tires had under 2500 miles on them when this all happened.

 

Only thing I miss about college was the 2 post lifts and the road force balancer... :cry:

[HOrnbrod]

I still say tires...New doesn't automatically mean right or fixed or eliminate them as the problem.

 

Tires begin to need to be balanced at + - 35MPH. that's where your problem begins....notice a trend?

 

Try OTHER tires, got a buddie you could try his for a trip doen the road?

 

CW

Nope. New isn't necessarily perfect. Manufacturer defects, and the occasional one that didn't have as superior of a build quality, but it's not visible when leaving the factory.

 

My buddy's TJ, all the sudden, one day, it would ride fine till about 35mph, and then all hell would break loose for vibration. Threw it up on a lift, balanced and rotated the tires, tightened any bolt you could set your eyes on underneath, shook everything checking for worn out bushings or anything, seemed perfectly fine. take it out for a test drive, did it again, but slightly different feeling, about the same speed. Back on the lift, pull all the tires, road force balance them, and quickly notice one is a little egg shaped. a section of tire, the entire width of the tire, and about 15-18 inches long was about 1/4" higher than the rest of the tire. Put that on the spare tire carrier, balanced the spare before installing, threw all the tires back on and handed the keys to my buddy. He was quite happy. When he asked what the problem was, I showed him the tire on the carrier, and he was quite surprised. The tires had under 2500 miles on them when this all happened.

 

Only thing I miss about college was the 2 post lifts and the road force balancer... :cry:

 

Thanks Joel, and to everyone for all the replies. This is the first I have heard about road force balancing. Today I went to the best tire shop I know in my AO w. the best rep, they even do the "true" high speed balancing that makes a square tire round by shaving. My tires are 31" Goodrich T/As. They swore the tires were fine, and did a dynamic balace from scratch (I pulled the weights before going there). And I do have an unused spare. So how do I find out if any other shops have road force balancing capability? Remember, this is Alabama.... :roll: Call in advance? Must be a special Hunter machine?

[rockhardzj]

I always used a Hunter Road Force Balancer. If you can take a look at the machine, Its kind of similar to a standard balancer, but you'll notice it has a full computer integrated into it, along with a drum that comes down and contacts the tire from somewhat behind the machine. The drum looks like it's coated in 60 grit sand paper, and puts I think up to a 3500LB pressure onto the tire, and it reads the profile, and stuff, and is very sensitive. Also, there are hand drawn arms that extend out to measure the rim "runout" essentially, how warped the rim is side to side and up and down.

 

Very expensive machine, I was one of the few not to break the damn thing at school... :D It was down often from people not being careful setting the lug thing to the right size/pattern for different rims.

 

Standard wheel balancer:

 

Road force balancer (not all the extra doodads hanging off the side and computer interface):

[akamcbird]

alignment ??? caster can get fubered due to a lower rear...ie. sagging springs??

[HOrnbrod]

alignment ??? caster can get fubered due to a lower rear...ie. sagging springs??

 

New leaf packs a year ago, recent alignment after my modest 2-1/2" lift, caster was right on. Rear is about 1" higher than the front. This vibe started like a month ago, and was made slightly worse after regearing. Before all was well. Now it's getting progressively worse the more I drive it. Not unbearable yet, like DW, but need to find what's causing it before it progresses. Dayem, lots of probable/possible causes, just have to eliminate and work down. Seems the most common consensus is tires first, so I'll find another set to stick on and either lay that to bed, or move on to the driveline. All new stuff for me............. :oops:

[JeepcoMJ]

I have been down this road many times and the driveshaft or U joints are usually the culprit.

Good Luck, opsled (Lord and mentor of JeepcoMJ) :brows: :brows:

 

you've been down many roads pops. sometimes it's a wonder you came back in one piece :P :eek: :teehee:

[deziped]

I had the same shaking/vibration symptons in my 89 with new tires and just about a new suspension undet it. Thought it was tires, balance, shocks, & other things, until I finally, by accident, eliminated the problem when I added 1/8" shims to increase my caster so steering would return to center after cornering. Haven't had a vibe since. Years ago I experienced the same thing when I had a broken (worn out) motor mount. Under accel. it viberated bad, but back off on it and it was near normal. Have you looked at those areas?

[opsled]

O.K. Unless I missed something in your desrciption of the problem I think you are getting dragged down to many different roads. You said this is a vibration that comes in and then goes away with changing speeds. You didn't mention any handling issues while this is going on so I will assume they are not there.

 

If this is a vibration with no handling issues to go along with it you can eliminate any steering, ball joint, suspension problems.

 

Tires can cause very bad vibrations but a bad tire CAN'T be balanced. You have balanced your tires and moved them from front to back with no change in the vibration. You have eliminated tires as the problem.

 

You did change gears and that would have been my first guess except you said the problem was there before you changed gears and is now just more pronounced. So I don't think your gear change is the culprit but you are getting close because what you did had an effect on the vibration.

 

Wheel bearings can cause vibrations but they are usually constant and don't go away with changes in speeds. They may get better or worse with slower or faster speeds but they don't go away. Front wheel bearing problems will also cause handling issues which you didn't mention so I would eliminate them.

 

You didn't say that this problem started after a spring change or anything else. You said it just started recently and and has been getting worse.

 

You say you have some slop at the slip yoke in the tail shaft of the trans. You may have an issue in the tail shaft but they all have a little slop so what you have may be normal.

 

A drive shaft is a hollow tube that WILL amplify even the slightest imbalance. Just taking one out and putting it back in can cause one with a problem to start acting up. They are the only thing that I have seen that will cause what you are describing. Alot of the time it is pinion angle or trans/diff problems that are the culprit and the shaft is amplifying them but you didn't change any of these before the problem started.

 

I have had this identical problem on a Chevy G-van. I had maintained this vehicle since day 1 and it had over 300,000 miles on it with no drive shaft issues. I had put in a new engine, trans, complete rebuild of the front suspension, new rear axle, tires, brakes ect. It all of a sudden started with a vibration that came in a 60mph and would leave at 70mph. I had been over absolutly everything on this truck and the shaft had brand new joints. I finally took the shaft in and had it spun and it was bent. It was very slight but enough to cause the problem. The guy who retubed it said it was probably bent from the factory and that it is a common thing for him to see. He said they are balanced when new but every time you take it out, change a joint and put it back in you are changing it's original balance which can cause them to start acting up. I could not make this truck vibrate on the stand but it was very pronounced on the road. The shaft was retubed and balanced and the problem was solved.

 

My 86 Comanche diesel also had a vibration similar to what you described. It's problem was a worn yoke on the rear diff. One of the little ears in the yoke that hold the U joint centered was worn and allowing the shaft to off center itself about 1/16" from the pinion centerline. The shaft was orbiting ever so slightly around that centerline and causing the vibration.

 

Pull the shaft and have it spun by a drive shaft shop to check for balance and straightness. That is the only way to eliminate the drivshaft as the problem. Make sure your U joint sits snugly and centered in your yoke. If you still have problems after that you should look into the tail shaft on you trans.

 

I have been bending wrenches for many years on everything from 1150CI Cummings diesels in trucks to weedeaters and have seen alot of weird stuff. Oddball problems like yours need to be solved with reason and the process of elimination.

 

opsled

[HOrnbrod]

O.K. Unless I missed something in your desrciption of the problem I think you are getting dragged down to many different roads. You said this is a vibration that comes in and then goes away with changing speeds. You didn't mention any handling issues while this is going on so I will assume they are not there.

 

If this is a vibration with no handling issues to go along with it you can eliminate any steering, ball joint, suspension problems.

 

Tires can cause very bad vibrations but a bad tire CAN'T be balanced. You have balanced your tires and moved them from front to back with no change in the vibration. You have eliminated tires as the problem.

 

You did change gears and that would have been my first guess except you said the problem was there before you changed gears and is now just more pronounced. So I don't think your gear change is the culprit but you are getting close because what you did had an effect on the vibration.

 

Wheel bearings can cause vibrations but they are usually constant and don't go away with changes in speeds. They may get better or worse with slower or faster speeds but they don't go away. Front wheel bearing problems will also cause handling issues which you didn't mention so I would eliminate them.

 

You didn't say that this problem started after a spring change or anything else. You said it just started recently and and has been getting worse.

 

You say you have some slop at the slip yoke in the tail shaft of the trans. You may have an issue in the tail shaft but they all have a little slop so what you have may be normal.

 

A drive shaft is a hollow tube that WILL amplify even the slightest imbalance. Just taking one out and putting it back in can cause one with a problem to start acting up. They are the only thing that I have seen that will cause what you are describing. Alot of the time it is pinion angle or trans/diff problems that are the culprit and the shaft is amplifying them but you didn't change any of these before the problem started.

 

I have had this identical problem on a Chevy G-van. I had maintained this vehicle since day 1 and it had over 300,000 miles on it with no drive shaft issues. I had put in a new engine, trans, complete rebuild of the front suspension, new rear axle, tires, brakes ect. It all of a sudden started with a vibration that came in a 60mph and would leave at 70mph. I had been over absolutly everything on this truck and the shaft had brand new joints. I finally took the shaft in and had it spun and it was bent. It was very slight but enough to cause the problem. The guy who retubed it said it was probably bent from the factory and that it is a common thing for him to see. He said they are balanced when new but every time you take it out, change a joint and put it back in you are changing it's original balance which can cause them to start acting up. I could not make this truck vibrate on the stand but it was very pronounced on the road. The shaft was retubed and balanced and the problem was solved.

 

My 86 Comanche diesel also had a vibration similar to what you described. It's problem was a worn yoke on the rear diff. One of the little ears in the yoke that hold the U joint centered was worn and allowing the shaft to off center itself about 1/16" from the pinion centerline. The shaft was orbiting ever so slightly around that centerline and causing the vibration.

 

Pull the shaft and have it spun by a drive shaft shop to check for balance and straightness. That is the only way to eliminate the drivshaft as the problem. Make sure your U joint sits snugly and centered in your yoke. If you still have problems after that you should look into the tail shaft on you trans.

 

I have been bending wrenches for many years on everything from 1150CI Cummings diesels in trucks to weedeaters and have seen alot of weird stuff. Oddball problems like yours need to be solved with reason and the process of elimination. opsled

 

opsled, I think you are right on the money. I managed to scrounge up another set of wheels and tires this morning, mounted all four, and no change in the vibrations. ON at 35, OFF at 45. It's like a high frequency vibe, and you can feel it mostly by the seat of your pants, and is slightly worse under acceleration. So that eliminates the tires & wheels for sure.

 

I have no handling issues, but did crawl under and tighten everything up to be sure. I changed the front coils and rear leaf packs about 1-1/2 years ago when I did my 2-1/2" - 3" lift, but had no vibes at all until about a month ago, which got worse after we did the gear change.

 

So next is the driveshaft. I did find a shop in Huntsville, AL that has an excellent rep, and will bring the MJ there next Tuesday. So until then, after I cool down a little, I'll pull the driveshaft again and check the joints closely. Might put it back in 180 degrees out to see if it changes things. One thing about these vibes, they are very consistent. One friend said try fastening a stainless steel hose clamp around each end of the driveshaft just to see if things change, and attempt to do a redneck balance by moving them in or out. Don't know about that. But many thanks for your words of wisdom, and I feel like I'm finally zeroing in on the problem.

[HellCreek]

Hi, Hornbrod,

 

Road Force balancing is done by a machine that uses a steel roller to apply pressure to the tire while it is spinning. It simulates actual driving conditions as opposed to a free-spinning wheel, hence the term. I had a severe case of DW before I had my tires Road Force balanced, and it cured them.

 

In answer to a previous question, yes, u-joint can go bad quickly. We had to replace the ones on the rear drive shaft on our CJ-7 after one week. We made the mistake of buying the "Super-Duper" non-greasable ones, and they went dry. Always get the ones with the grease fittings.

 

Thanks,

Tom

[HOrnbrod]

Hi, Hornbrod,

 

Road Force balancing is done by a machine that uses a steel roller to apply pressure to the tire while it is spinning. It simulates actual driving conditions as opposed to a free-spinning wheel, hence the term. I had a severe case of DW before I had my tires Road Force balanced, and it cured them.

 

In answer to a previous question, yes, u-joint can go bad quickly. We had to replace the ones on the rear drive shaft on our CJ-7 after one week. We made the mistake of buying the "Super-Duper" non-greasable ones, and they went dry. Always get the ones with the grease fittings.

 

Thanks, Tom

 

Thanks Tom. I think I can now safely eliminate the wheels/tires now since the vibes do not change when using a different wheel/tire set. But knowing what Road Force balancing is now I'm sure will help me in the future. When I changed U-joints last year or so I used the Spicer greasable ones, and have kept them greased. But maybe they can go bad quickly too - hope so!

[opsled]

One friend said try fastening a stainless steel hose clamp around each end of the driveshaft just to see if things change, and attempt to do a redneck balance by moving them in or out. Don't know about that. But many thanks for your words of wisdom, and I feel like I'm finally zeroing in on the problem.

 

Thats a good idea (wish I would have thought of it years ago). Getting it to balance that way probably won't happen but if putting a few clamps on the shaft changes your vibration it would be an indicator that you are on the right track.

 

opsled