Car shimmy during acceleration

[drypowder]

Edit: resolution in this post: https://www.carolinafirearmsforum.c...shimmy-during-acceleration.15789/#post-416251
------------------------------------------------------------------------------------------------------
'01 Accord, 4cyl, manny tranny. There's been some mild vibration under acceleration for a few years, but topping up air pressure in the tires seemed to cure it. Then when topping up air didn't work, the tires were pretty worn and needed to be replaced, and with new tires (and alignment), the vibration seemed to go away. But it slowly returned, and again, topping up air pressure in the tires seemed to resolve it. This has gone on for some time.

Tires have about 15k on them, and this time, topping up tire air pressure did not resolve the issue, and there is a noticeable shimmy/vibration during acceleration. I don't feel it in 1st or 5th gears; a little bit in 2nd and 4th gears, and it's most noticeable in 3rd gear, especially under hard acceleration (well, as hard as a 4cyl Honda can manage). Haven't really noticed it in the steering wheel. No vibration on braking or at constant speed, so my less-than-amateur wrench diagnosis is that it's probably not a brake/rotor or transmission issue.

The shimmy has always been in the front end, and rotating tires (and they get balanced when rotated) hasn't changed that - shimmy is still in the front end.

Do these symptoms narrow it down pretty well or are there a number of potential culprits here?

 

[Mike Overlay]

Drive axles... does the shimmy/shudder/vibration calm down any during curves? Gone when deaccelerations?

 

[drypowder]

Drive axles... does the shimmy/shudder/vibration calm down any during curves? Gone when deaccelerations?

Mostly notice it on straightline acceleration, though @bigfelipe has noticed it on turns. It's still subtle enough that the vibration isn't violent unless I'm accelerating hard, esp in 3rd gear - then it's fairly violent (the intensity has gone up recently; it's been mild enough in the past that I could just keep putting off dealing with it).

Vibration dies down as soon as I let up on the throttle.

 

[Mike Overlay]

Vibration dies down as soon as I let up on the throttle.

Which unloads the axles.

 

[drypowder]

Which unloads the axles.

Makes sense. Common issue? Car has ~150k on it.

Is it worth trying to isolate the issue inside the drive axles, or just replace both left and right drive axles?

 

[Mike Overlay]

Makes sense. Common issue? Car has ~150k on it.

Is it worth trying to isolate the issue inside the drive axles, or just replace both left and right drive axles?

Yeap. Is a common symptom in cv axles.
As cheap as new axles are, replace both

 

[indie_rocker]

Not thinking its a motor or transmission mount?

 

[Mike Overlay]

Not thinking its a motor or transmission mount?

No statements of the vibrations at idle. Broken mounts tend to let the motor sit "metal on metal" allowing vibrations and buzzing sounds at idle

 

[drypowder]

No statements of the vibrations at idle. Broken mounts tend to let the motor sit "metal on metal" allowing vibrations and buzzing sounds at idle

Yeah, idles fine, brakes fine, cruises fine. Only notice vibration during acceleration.

Yeap. Is a common symptom in cv axles.
As cheap as new axles are, replace both

Copy that, thanks D.

 

[indie_rocker]

I only mentioned it because I've personally experienced mounts that allowed such symptoms.

Vehicle drove and idled fine but hard acceleration would induce vibration and excessive torque steer.

It's you're money. If you've got it like that to just start throwing parts on it and hope it fixes it. Cool.

 

[drypowder]

I only mentioned it because I've personally experienced mounts that allowed such symptoms.

Vehicle drove and idled fine but hard acceleration would induce vibration and excessive torque steer.

It's you're money. If you've got it like that to just start throwing parts on it and hope it fixes it. Cool.

Is there an easy test for broken motor mounts? Maybe pop the hood, trans in neutral, hit throttle and see if the engine shakes?

 

[indie_rocker]

Is there an easy test for broken motor mounts? Maybe pop the hood, trans in neutral, hit throttle and see if the engine shakes?

That. If there seems to be movement that is unusual. Shut it down and get the biggest prybar you can find and try to isolate the movement out of the specific mounts.

Sometimes they don't even look broken. The rubber and everything is still there. But its all just kind-of flopping around.

If that all checks out. Then I agree with the CV axle diagnosis.

 

[TSConver]

Rode with him last night and it is not CV axles. The boots are fine, the shafts are tight with no play and tight low speed corners do not produce any poping or clicking. I flet the "shimmy" I am pushing him to look at the clutch / flywheel / throw out bearing. I think the clutch is chattering and gave hima couple of tests to try and confirm.

 

[Mike Overlay]

Rode with him last night and it is not CV axles. The boots are fine, the shafts are tight with no play and tight low speed corners do not produce any poping or clicking. I flet the "shimmy" I am pushing him to look at the clutch / flywheel / throw out bearing. I think the clutch is chattering and gave hima couple of tests to try and confirm.

The vibrations are generally caused by the inner joint. Was there any play in them? Kinda like a loose ujoint type feel?

A clutch being out of balance should cause a vibration from idle all the to rev limiter..

But I am not putting hands on so no telling:

Good luck to y'all . Keeps us informed

 

[drypowder]

Shawn summarized why it seems the CV axles may not be the source of the vibrations:

Rode with him last night and it is not CV axles. The boots are fine, the shafts are tight with no play and tight low speed corners do not produce any poping or clicking.

Some observations on the vibration that may help with diagnosis:

• vibration is only noticeable under acceleration in 2nd, especially 3rd, and 4th gears
• not noticeable when accelerating in 1st gear
• not noticeable at idle, at steady speed, when I let off throttle or when braking
• vibration is not transmitted to steering wheel - my understanding is this rules out a host of wheel-related potential issues
• vibration is of lower frequency than axle/wheel speed
• vibration is not easily reproducible - we had to accelerate hard a few times before we got the vibration
• when the vibration is reproduced, its intensity can vary. Sometimes it's subtle and sometimes it's strong enough to induce a bit of fear and immediate let off the throttle
  

 

[Djstorm100]

Honda's inner joint are notorious for going bad after 100k. Slow speed test would check out "ok" but shimming still exist.

Honda would have us on a lift with the non-drive tires on the ground with a e-brake and let the wheel free spin.

Put car on jack stands, with E-brake. Take the inspection cover off under the trans report back with what you see. I don't it to believe the clutch is chattering but I haven't been able to put my eyes on it yet either.

 

[TSConver]

Honda's inner joint are notorious for going bad after 100k. Slow speed test would check out "ok" but shimming still exist.

Honda would have us on a lift with the non-drive tires on the ground with a e-brake and let the wheel free spin.

Put car on jack stands, with E-brake. Take the inspection cover off under the trans report back with what you see. I don't it to believe the clutch is chattering but I haven't been able to put my eyes on it yet either.

What goes bad in the inner that would cause an intermittent vibration. The boots are all good and the shafts have no free play in any direction.

 

[TSConver]

The vibrations are generally caused by the inner joint. Was there any play in them? Kinda like a loose ujoint type feel?

A clutch being out of balance should cause a vibration from idle all the to rev limiter..

But I am not putting hands on so no telling:

Good luck to y'all . Keeps us informed

No they were solid, no lateral or in and out play could be felt. Boots were in perfect condition.

 

[SPST]

Honda's inner joint are notorious for going bad after 100k. Slow speed test would check out "ok" but shimming still exist.

Honda would have us on a lift with the non-drive tires on the ground with a e-brake and let the wheel free spin.

Put car on jack stands, with E-brake. Take the inspection cover off under the trans report back with what you see. I don't it to believe the clutch is chattering but I haven't been able to put my eyes on it yet either.

I guess I'm lucky? My '99 manual 4cyl Accord still has the original cv axles at 209k!

 

[Djstorm100]

What goes bad in the inner that would cause an intermittent vibration. The boots are all good and the shafts have no free play in any direction.

bearings or the spindles the bearings ride on. Seen it as bad as the bearing peening the male "case" inside causing more clearance.

 

[Djstorm100]

I guess I'm lucky? My '99 manual 4cyl Accord still has the original cv axles at 209k!

My 05 civic is on 168k on the original axles. Then again I drive like a grandmother..because after all it's a civic. haha.

 

[TSConver]

bearings or the spindles the bearings ride on. Seen it as bad as the bearing peening the male "case" inside causing more clearance.

That is just it there is no play in them. Are you talking the actual cv joint or the bearing that they ride in that is inside teh transfer case where thsplines on the end engage?

 

[Djstorm100]

I'm talking about the whole joint assembly. The bearing ride on spindles that are on the axle that connect the 2 CV joints together. Those bearings ride in the male spline "bucket". Splines go in the differential on a Honda.

 

[TSConver]

like i said there was no play in th joints they felt really tight.

 

[Djstorm100]

One bearing can be bad (deformed, peened, etc) and only show while under load (torquing) from the transmission turning the axle and the resistance of not wanting to turn by the traction of the wheel.

 

[drypowder]

One bearing can be bad (deformed, peened, etc) and only show while under load (torquing) from the transmission turning the axle and the resistance of not wanting to turn by the traction of the wheel.

Do you think that could result in these symptoms?

• vibration is only noticeable under acceleration in 2nd, especially 3rd, and 4th gears
• not noticeable when accelerating in 1st gear
• not noticeable at idle, at steady speed, when I let off throttle or when braking
• vibration is not transmitted to steering wheel - my understanding is this rules out a host of wheel-related potential issues
• vibration is of lower frequency than axle/wheel speed
• vibration is not easily reproducible - we had to accelerate hard a few times before we got the vibration
• when the vibration is reproduced, its intensity can vary. Sometimes it's subtle and sometimes it's strong enough to induce a bit of fear and immediate let off the throttle

Obviously the difficult-to-reproduce symptom could the early signs of deterioration, and as things get worse, the vibration could become more frequently observable.

 

[NKD]

You're completely sure it is not an unbalanced wheel? Rotated tires?
Im sure you have, just throwing it out there.

 

[drypowder]

You're completely sure it is not an unbalanced wheel? Rotated tires?
Im sure you have, just throwing it out there.

Yep, this front end shimmy has persisted through tire rotations. Also, my understanding is if it's the wheel, I'd feel it in the steering wheel, which I do not.

 

[Coltdefender1911]

Sounds like an inboard axle joint is worn. Axle will need to be replaced. This is caused most of the time from worn engine mounts. Be sure to check the engine mounts, or new drive axles will fail in a short time.

 

[drypowder]

Just wanted to provide an update on this, and to thank everyone who chimed in with good advice/info.

Took a good look at the motor mounts and the front mount was indeed shot. @TSConver and I replaced that mount. Vibration was reduced a bit (lower intensity), but it was still there. Then we replaced the CV axles - could have replaced just the one we suspected was bad, but figured if one had been damaged by the broken motor mount, the other axle probably didn't have much life left; plus, reman axles are cheap.

That resolved the vibration issue.

 

[Coltdefender1911]

Just wanted to provide an update on this, and to thank everyone who chimed in with good advice/info.

Took a good look at the motor mounts and the front mount was indeed shot. @TSConver and I replaced that mount. Vibration was reduced a bit (lower intensity), but it was still there. Then we replaced the CV axles - could have replaced just the one we suspected was bad, but figured if one had been damaged by the broken motor mount, the other axle probably didn't have much life left; plus, reman axles are cheap.

That resolved the vibration issue.

Glad to hear the problem was corrected.