Start/Stop wobble shudder at speed - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 10-16-1999, 10:30 AM
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Start/Stop wobble shudder at speed

'88 Bronco

I've noticed a slight wobble or wiggle of what seems like the rear-end when I first start to accelerate from a stop. It does the same thing as I come to a stop. There is also a shudder/vibration above 60 MPH that gets worse as I go over 65. This is in 2WD mode (don't know about 4WD).

I've just redone the front end (bearings, ball joints, etc) so I know it's not coming from that (it was there before I did the front).

The rear driveshaft seems fine; u-joints are all tight. This leads me to believe it is the rear wheel/axel bearings... or maybe worn/loose u-bolts... ? Opinions wanted.

Those rear bearings look like a pain to change.

Thanks!


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post #2 of (permalink) Old 10-17-1999, 03:00 AM
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Re: Start/Stop wobble shudder at speed

>>>>Do you have oversized tires/wheels? Even if you don't, how many miles has been since the balance on the tires was checked? Have you had the rear drive shaft off and possibly not have it on the same way it was before? Have you checked the rear pinion to see if it is tight(worn pinion bearings can cause vibration and gear failure)? These are just a few more things to look at. You may also want to check the trans mount for tightness. Hope these ideas help. Later.

NUFF SAID
post #3 of (permalink) Old 10-19-1999, 06:18 PM
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Re: Start/Stop wobble shudder at speed

Thanks for the info. I'm still looking for it. It might be the wheels/tires since they're not in the best condition (but I didn't think THAT bad). They are not oversized (31x10.5x15 BFG A/T).

I didn't find anything obviously loose in the rear. I need to get someone to follow behind me and see if they can see what's making it wobble. I can make it wobble just by going down the street with the engine idling and the trans in drive (at about 10 MPH or so).

I don't notice anything out of the ordinary between 10 and 60 MPH...


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post #4 of (permalink) Old 10-19-1999, 10:26 PM
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Re: Start/Stop wobble shudder at speed

On Broncos' there is a double cardan joint at the front of the rear driveshaft, the center ball might be your problem. Best way to tell is to remove the shaft. The other poss might be the slip yoke. This Wobble, is it side to side, or is it a vibration??

Ford guy who dabbles in Jeeps and Suzukis
post #5 of (permalink) Old 10-19-1999, 11:07 PM
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Re: Start/Stop wobble shudder at speed

I've looked at that joint. I may need to do what you say and take the thing out and examine it. It does not look like it's been worked on recently (maybe not ever... 175k miles).

Side to side wobble. (feels like wheel lugs are loose, but they are not


post #6 of (permalink) Old 10-19-1999, 11:37 PM
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Re: Start/Stop wobble shudder at speed

If it's side to side, poss wheel bent? axle flange bent?? Check your rear diff fluid just for grins, maybe the side gears have too much play and are walking side to side??? Factory Limited slip diff or open diff???? Would be a good reason to at least check your outer axle bearings. Let me know
Andy

Ford guy who dabbles in Jeeps and Suzukis
post #7 of (permalink) Old 10-20-1999, 10:36 AM
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Re: Start/Stop wobble shudder at speed

I've checked the wheels as best I can, doesn't look like they are bent (but I'd never rule anything completely out; I'll be getting new tires/wheels shortly anyway).

I'm not sure if it's a limited slip. I didn't think to check it.

The passenger side axel seems to have about 1/16" of in/out play to the diff.

The driver side looks like the outer axel bearing has been changed recently. On this side I can see about 1/8" of clean (shiny; more than the other side) metal on the axel (by the bearing) where it looks like the axel has moved in and out, but I could not move it with my hands (even after turning it; this seems strange to me).

I need to check the fluid level in my front diff too. I'll be checking these ASAP.



post #8 of (permalink) Old 10-20-1999, 11:32 AM
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Re: Start/Stop wobble shudder at speed

The wobble is most likely a tire that's suffering from ply separation. I've had it happen twice. The car sort of squirms at very low speeds. It can also cause a different vibration at freeway speed. Raise each tire off the ground, spin it by hand, and look for tread that waves left to right as you spin the wheel, or look for a bulge in the tread area or sidewall area.
Norm

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post #9 of (permalink) Old 10-28-1999, 09:56 AM
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Re: Start/Stop wobble shudder at speed

I'm still looking into this, I just haven't had time to really work on anything (maybe this weekend). The fluid levels in both differentials was OK (maybe a tiny bit too low but nothing major). I did find metal bits/flakes on the magnetic fill plug on the rear diff though. I think it's time to take a peek at the rear insides (maybe the side gears have become loose as suggested above). Are these side gears pressed in?

I'm going to try putting the front tires on the rear too. (check for ply seperation.. but maybe all of the tires are bad

My next stop for the front is to take a look at the transfer case, I've been unable to check the fluid level because the fill plug is stuck pretty hard. It looks like someone tried to use a 1/4" rachet (too small) to get the plug out and rounded out the inside of the plug socket on one side. I'm hoping this is my front drag problem. Don't know what else it could be... does anyone know if the spindle needle bearings would cause major binding in the front drivetrain? (doesn't seem possible, there's not much load on them?)



post #10 of (permalink) Old 11-01-1999, 03:47 PM
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Re: Start/Stop wobble shudder at speed

I finally found the culprit in the rear. A bad tire. It's even leaking air in one place on the tread (through dry-rot cracks; not good). I was planning on getting new tires later anyway, I guess it'll be sooner than later.


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