Author Topic: Low speed shimmy?  (Read 1693 times)

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Offline s ǝoɾ

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Low speed shimmy?
« on: September 12, 2008, 10:19:29 PM »
Ok this is a new one to me.

Best way to describe it, is the sudden violent shuddering, that feels like the front axle is going to fall out from under neath me.

This ONLY happens at very low speeds when braking at a traffic light. I would say it begins some where below 5mph down to zero but stops if I release the brakes.

Does not happen at highway speeds or when coasting to a stop. No real noise. When cruising I can release the steering wheel and it tracks impeccably well.

This slow speed part confuses me, as I am at barely a crawl when it takes place. A violent shaking and wobbling action.

Front suspension and steering parts feel tight.

Any ideas?

One would assume this to be the brakes, but it just doesn't add up right.

Oddly enough, it's the drivetrain itself, that I'm worried about.
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Offline BradicusX

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Re: Low speed shimmy?
« Reply #1 on: September 12, 2008, 10:33:02 PM »
Hmmm...    I had that happen to me many years ago in my Dad's 79 D150. I used to jump the truck all 4 wheels off the ground, and drive it in the creek. One day my dad was driving it into town and when he slowed down for a light, it began to wobble and shake badly. We tried to make it home, but half way there we stopped for another light, and the right front wheel fell off and we skidded into the median.

The R/F spindle had sheared into.

When's the last time you checked your wheel bearings?  ???
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #2 on: September 12, 2008, 10:41:31 PM »
When's the last time you checked your wheel bearings?  ???
{think}  ::) You may have a point. Damn unit bearings  {flame}

I only guessed that bad bearings would wobble all the time ???

This will only wobble when braking to a stop, and only below about 5mph. This wobble is incredibly violent, especially for the extreme low speeds at which it happens.
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Offline SuperBurban

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Re: Low speed shimmy?
« Reply #3 on: September 13, 2008, 05:00:11 AM »
I agree, Most likely the bearings.
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Re: Low speed shimmy?
« Reply #4 on: September 13, 2008, 05:43:00 AM »
also check your track bar
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Offline BradicusX

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Re: Low speed shimmy?
« Reply #5 on: September 13, 2008, 07:36:28 AM »
You know... it could be GREMLINS!  :o   :-X
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Offline SuperBurban

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Re: Low speed shimmy?
« Reply #6 on: September 13, 2008, 07:39:50 AM »
You know... it could be GREMLINS!  :o   :-X
Isn't it illegal to drive over Gremlins?
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Offline BradicusX

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Re: Low speed shimmy?
« Reply #7 on: September 13, 2008, 07:40:44 AM »
Isn't it illegal to drive over Gremlins?

Not in Texas  ;D
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Offline some zilch

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Re: Low speed shimmy?
« Reply #8 on: September 13, 2008, 06:00:11 PM »
might check your rotor too, if it goes away when you release your brakes
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #9 on: September 14, 2008, 11:50:37 AM »
Track bars exhibit a high speed "death wobble" that doesn't cease until you come to a stop.
Not the case here.

Wheel bearings should exhibit a wobble that increases with speed and is present most all of the time.
Also not the case.

Rotors usually exhibit a pulsating brake pedal.
None.

I'm not saying one of these couldn't be causing the problem, but something just don't seem right.

I'm really hoping it isn't rotor or wheel bearing, either one. In order to pull the rotor, the hub has to come off. When pulling the hub, it's common to destroy it.
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Offline newrc93

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Re: Low speed shimmy?
« Reply #10 on: September 14, 2008, 12:17:22 PM »
i had a similar problem with my 76 corvette(i know not a dodge truck!)the shimmy was in the rear when i braked at slow speeds. it ended up being a halfshaft u-joint. i dont know if this would apply to your front u-jounts our not but i thought id share this info
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #11 on: September 14, 2008, 12:38:50 PM »
i had a similar problem with my 76 corvette(i know not a dodge truck!)the shimmy was in the rear when i braked at slow speeds. it ended up being a halfshaft u-joint. i dont know if this would apply to your front u-jounts our not but i thought id share this info

I was actually considering this possibility. Front driveshaft or axle shaft ??? I don't think this should apply since power shouldn't be applied to either of these.

Front axle shaft also equals good chance of breaking the hub upon removal.

If it didn't cost $1,000+ then I would consider a full floating upgrade on the front.
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Offline newrc93

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Re: Low speed shimmy?
« Reply #12 on: September 14, 2008, 12:44:24 PM »
how do you change front roters if the hub allways breaks and causes such expensive damage ??? im not to fimiliar with 95 ctd hubs so exuse me if thats a dumb question
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #13 on: September 14, 2008, 01:26:39 PM »
VERY carefully. I haven't changed rotors yet.

The hub is pretty much identical to a front wheel drive hub.

Apparently from what I'm told, the hub eventually rusts to the knuckle. When you attempt to pull the hub and rotor (pressed together) the bearing separates from the hub. It is non seviceable bearing and can't just be stuffed backinside the hub assembly.

So you go to NAPA or autozone and pony up another $200/side for a new hub/bearing assembly, and have your rotor pressed on.
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Offline ducktail

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Re: Low speed shimmy?
« Reply #14 on: September 14, 2008, 02:01:08 PM »
u joint. Once I had one freeze up and it felt like you were about to be thrown from the vehicle at low speed.
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #15 on: September 14, 2008, 02:29:33 PM »
front u joint? My rear joints "feel" fine, I'm about to go outside and see what I can notice with a prybar on the fronts.
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #16 on: September 14, 2008, 02:53:35 PM »
Hmm.

Went and check the front driveshaft. No play, spins nice and free.

Went and checked the front axle joints with truck on the ground. Have minimal twisting play, but quite a bit of up and down play. Almost looks like the whole shaft is moving up and down slightly.  {think}

I assume the whole knuckle needs to come off?

Any pointers?
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Re: Low speed shimmy?
« Reply #17 on: September 14, 2008, 03:03:58 PM »
Went and checked the front axle joints with truck on the ground. Have minimal twisting play, but quite a bit of up and down play. Almost looks like the whole shaft is moving up and down slightly.  {think}

The stub shaft should be solid in the hub. If the whole shaft is moving, the bearings and/or hub have to be bad.  try jacking the wheel off the ground, and see how it feels. rotating, shake in and out at the top & bottom, and side to side.
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #18 on: September 14, 2008, 03:11:43 PM »
The stub shaft should be solid in the hub. If the whole shaft is moving, the bearings and/or hub have to be bad.  try jacking the wheel off the ground, and see how it feels. rotating, shake in and out at the top & bottom, and side to side.
I'll do that as soon as the stores open up. My "high-lift" doesn't cooperate with this stupid bumper and I need something more than a 2 ton trolley. Ah, hindsight.

I was thinking the stubshaft should be solid, but was not sure.

Shouldn't i feel this all the time, if the hubs are shot?

Quick! Someone find me a 78-79 ford HP D60! LMAO  {hammer}
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Re: Low speed shimmy?
« Reply #19 on: September 14, 2008, 03:22:07 PM »
VERY carefully. I haven't changed rotors yet.

The hub is pretty much identical to a front wheel drive hub.

Apparently from what I'm told, the hub eventually rusts to the knuckle. When you attempt to pull the hub and rotor (pressed together) the bearing separates from the hub. It is non seviceable bearing and can't just be stuffed backinside the hub assembly.

So you go to NAPA or autozone and pony up another $200/side for a new hub/bearing assembly, and have your rotor pressed on.

 yup / only the 94 to 98 3/4 tons have this forked up design
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Re: Low speed shimmy?
« Reply #20 on: September 14, 2008, 03:32:12 PM »
I'll do that as soon as the stores open up. My "high-lift" doesn't cooperate with this stupid bumper and I need something more than a 2 ton trolley. Ah, hindsight.
You don't have the factory jack?  High lift is good for some things, but I'll take a bottle jack to change tires on the road any time.
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #21 on: September 14, 2008, 03:35:58 PM »
O shiat! I forgot, it's under the seat still  ::)

Anyone want to sponsor me on a "strong fix" for this thing? Here

I might be able to justify some of this cost with the simple fact, I'm due for a brake job soon...
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #22 on: September 14, 2008, 04:30:34 PM »
Hmm, lets play a little game called piss-joe-off  ;D

Ok. For the first time ever, I just dug the oem jack out. Never used this mechanical screw jacks before.

It actually works, but I really should have started with a piece of 4x4 under it, 33s take FOREVER to lift.

Then I find out someone else drained my impact, so no charge. So back to breaker bar and impact socket.

Got it off after making a bed of pine branches to keep me out of the mud (this is a flooded area)

Ok. So first thing I notice, um where is the inner brake pad??? It's there, but not much more than a backing plate. Wonder how long that's been going on?

Ok. Now to check hub. Absolutely no play laterally, radially, or any other imaginable way.

On to axle shaft u joint test. Actually stub shaft isn't moving. I lied. The inner shaft moves a little. The u joint is also loose, it will need to be replaced as soon as I learn how to remove the outer knuckle...

So with everything else that is or could be faulty, I believe I may have found a slightly unusual culprit.

Could a caliper cause this? I think it could.

When facing the rotor, the caliper has minimal up and down play. Also has no "front to back" play. That may be confusing but keep in mind since I'm facing the rotor, that would be from driver to passenger side.

I then pulled it "left to right" (actually front of the truck to the rear of the truck) and noticed as much as 3/16" of movement, from the top bolt, while holding the bottom of the caliper steady. When holding the top the bottom has hardly a movement.

So, what I mean is, my upper caliper bushing (rubber) is either shot or missing. Kinda dark, couldn't see for sure.

Real cheap part, but I may end up replacing both calipers here real shortly anyways.

Might consider the "strong fix" as well.

By time I'm done, I will have completely re-engineered this thing into a "For-dodge-rolet"  ::)
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Offline my90LE4x4

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Re: Low speed shimmy?
« Reply #23 on: September 14, 2008, 04:41:58 PM »
I would say that the violence of the shudder has caused the bushing in the caliper to wear. I had a 97 2500 V10 the front rotors came off like a front wheel drive car they were not pressed on once you remove the unit bearing you should be able to pull out the axle shaft without removing the entire knuckle. You might want to consider replacing the front axle seals while it is all apart.
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Re: Low speed shimmy?
« Reply #24 on: September 14, 2008, 04:42:49 PM »
Hmm, lets play a little game called piss-joe-off  ;D
Ok. So first thing I notice, um where is the inner brake pad??? It's there, but not much more than a backing plate. Wonder how long that's been going on?

Ok. Now to check hub. Absolutely no play laterally, radially, or any other imaginable way.

So with everything else that is or could be faulty, I believe I may have found a slightly unusual culprit.

Could a caliper cause this? I think it could.
Yes, and the worn/missing pin bushing can explain why you do not feel the roughness in the pedal.

Real cheap part, but I may end up replacing both calipers here real shortly anyways.
Always a good idea to replace both calipers, pads,hoses, and flush the fluid. ;)


By time I'm done, I will have completely re-engineered this thing into a "For-dodge-rolet"  ::)
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Offline s ǝoɾ

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Re: Low speed shimmy?
« Reply #25 on: September 14, 2008, 06:23:25 PM »
Ok. Further update. I knew the front brakes were getting bad before this, but really I was delaying the inevitable.

The bushing is GONE. Not gone like wore out, but it popped off the slider bolt, my guess is right about 1 week ago or whenever that last hurricane was.

I came over a hill right into about 10" of water. I hit the brakes, and since that point this has been occurring. Guess my hard water landing made the bushing go bye bye.

One more re-engineer trick. This really shoulda have had a washer on the caliper bolts to retain the bushing. Guess I will be adding some. I also notice the sleeves have lube holes drilled into them, but the bolts do not. Maybe they make a standard hex type bolt that is gun drilled, instead of the allen head cap screw?

I cannot really see me ever wanting to pull the unit hub off and putting another one of those POSs back on, just for it to take a crap on me again.  :'(

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