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post #1 of (permalink) Old 04-20-2003, 09:48 AM Thread Starter
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drivetrain shimmies...

85 CJ7, stock amc20 rear, stock gears (I have no idea what ratio), 33 in. tires, 4 speed T-176.

I have noticed the past few weeks that when I am in 4th gear on the highway the shifter will wobble between 2000-2200 rpm. It isn't like a loose shifter play or anything, when I hold it, I can feel the tranny moving with it. If I speed up and increase the revs above that range, it runs smooth, and below that range it runs smooth. It does not do this in any other gear. Any ideas???

Last week I had a post about my rear left axle shaft nut had backed itself out a hair, just enough to cover up the hole where the cotter pin (which was in pieces when I took the tire off [img]images/graemlins/thud.gif[/img]) goes through. Could this have anything to do with it??? Thanks a bunch!

Marcus
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post #2 of (permalink) Old 04-20-2003, 11:05 AM
 
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Re: drivetrain shimmies...

The axle might have something to do with it. Maybe a wheel bearing starting to go bad or axle shaft slightly bent. If the vibration shows up only at a certian wheel speed rather than a certian engine speed that could rule out some things like bad driveshaft u-joints. I'd check the rear driveshaft u-joints anyway; they're easier to replace than the wheel bearings.

Ken Linzmeyer
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post #3 of (permalink) Old 04-21-2003, 08:12 AM Thread Starter
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Re: drivetrain shimmies...

OK...I tried a theory someone sent me. I got it up to the speed at which I am having the vibes...about 60mph. Put the tranny in neutral, let out on the clutch, and it is still wobbling/shimmying. So, I know it isn't just under load now. Now I know that it must be the wheel speed that is causing it, and not the engine speed as I was thinking before. So where do I start? [img]images/graemlins/tongue.gif[/img] Should I replace the u-joints? I do have a new wheel bearing with seals sitting in my closet that is a spare...so I guess I could always throw that in, though I have never changed one of these personally. Thanks for the help guys, and keep it coming!

Marcus
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post #4 of (permalink) Old 04-21-2003, 11:53 AM
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Re: drivetrain shimmies...

Hey Marcus, Nice to see a fellow Cola. towner on the board. Not that I'm in the know, but I would check the U-joints then check the wheel bearings. My guess is that it is the U-joints.

I replyed to another post that you might not have seen so here is my question.

Where did you get your driveshafts "resized"? Did you get them done locally? ...where & how much am I looking at?
After I finish my NP435 swap I'll need to get some made.

thanks for the help,
mike
post #5 of (permalink) Old 04-21-2003, 03:20 PM Thread Starter
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Re: drivetrain shimmies...

Mike,
Thanks for the input...that is what I figured I'd have to look into...
I had my transmission swapped in by a shop over in Aiken (about 45 minutes away). But, they "supposedly" had the driveshaft lengths changed by somebody here in the Cola area. If you'd like I can give them a call and get the # of the shop they use for their driveshaft stuff for you. I say "supposedly" cause they don't look any different to me but they charged me something like $100 for the modification. I think they screwed me over a bit [img]images/graemlins/cussing.gif[/img]
Anyhow, I'll call down there today then shoot you a pm. By the way, where do you wheel in this area? I have been here for a year and a half and know of nothing around. Course since my cj is my daily driver, I'm not looking for anything rough cause I can't afford to fix it right now if I break something. Just looking for some fun... a little mud, a little sand...maybe a few hills.

Marcus
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post #6 of (permalink) Old 04-24-2003, 05:31 AM Thread Starter
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Re: drivetrain shimmies...

The tires were rotated about two weeks ago...It appears to only happen at that wheel speed, and not engine speed. I take it up to 60 mph and it starts the wobble/shimmy...I can put it in neutral at that speed and it does not stop the problem, which leads me to believe it is definitely NOT transmission. I crawled under it last night to check the u-joints (which I figured was not the problem, but a much cheaper fix than anything in the rearend) and found them to be fine. I have noticed the past few weeks or so that when I first start it up, and I brake on wet pavement or dirt the left rear tire will grab hard (usually lock up)...but if I let off the brakes, it releases. So I looked at the inside of that wheel last night while under the thing and noticed there was fresh lubricant (I am assuming it is gear oil or brake fluid, I still have to check the master cylinder) all on the inside of that rim, and some streaks running down the inside of the tire from where it had been parked for an hour or so.

My guess now is that it is either a wheel bearing and seal, OR possibly the wheel cylinder is shot and the brake drum out of round and it might be doing something funky??? [img]images/graemlins/confused.gif[/img] a long shot, but who knows. Any help is GREATLY appreciated! Thanks!

Marcus
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post #7 of (permalink) Old 04-24-2003, 08:15 AM
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Re: drivetrain shimmies...

1. You should be able to tell if the dripping fluid is brake fluid or axle lube.
2. IMHO... it's likely a leaking Brake Drum Cylinder that's shot...
3. Rebuild kits are about $5.00, and whole rebuilt Cylinder are about $10.
4. That should not cause the shimmy problem at speed unless the brakes are not unlocking.
5. Have you isolated it to the front or the back of the Jeep yet?
6. Have you rotated tires, front to back to see if symptoms change?
7. That's where I'd start....
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post #8 of (permalink) Old 04-24-2003, 12:52 PM
 
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Re: drivetrain shimmies...

If you just had the tires rotated 2 weeks ago, maybe they knocked off a balancing weight. I'd have them rebalance the wheels before I started everything else. Mine has a similiar shimmy on the freeway at around 55-60. When they balance them it gets lessened, but I've never gotten it to go away totally. Maybe your shop will do a better job than mine.
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post #9 of (permalink) Old 04-24-2003, 02:59 PM Thread Starter
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Re: drivetrain shimmies...

I rotated them myself (I used a z-formation: front left to front right, front right to rear left, rear left to rear right, rear right to front left-since they aren't directional), and I know I didn't knock any weights off...I probably need to check to see if it maybe fell off on its own though. I think it is definitely the rear of the vehicle (and slap me silly if I am wrong LEVE) because if it were the front, I shouldn't be able to feel the tranny wiggling as much as I do since the front hubs are unlocked, right? Since they are unlocked, the front driveshaft is not spinning, so there shouldn't be much transfer of wobble from the tires through that, should there? This might sound stupid, but, how can I tell if the fluid inside the rear left rim is brake fluid or rearend lube? Like I said, I was just going to check the master cylinder to see if it is low on brake fluid. Are you thinking that it is not the axle bearing?

Thanks again guys!

Marcus
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post #10 of (permalink) Old 04-25-2003, 07:23 AM
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Re: drivetrain shimmies...

Just a friendly bump Marcus...

mike
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