leebee

if it has been mentioned already, my apologies, make sure the wheels are torqued to spec. over tight lug nuts can cause the front rotors to warp and cause similar issues.

lee

bigtrucknwheels

Hey guys, great ideas!
Thanks!

rubber is soft, FYI. These tires aren't a year old yet.

another observation is that I have a notable amount of vibration around 15-35 only when accelerating, but at the aforementioned speeds, tranny in neutral or in gear, throttle or not, it still shimmies.

And, if the caster angle was off, wouldn't that be a shimmy that got progressively worse as I sped up? It rides like a dream (no lie) above 70.

TNRabbit

Vibration under acceleration denotes drivetrain issues. I still think it's a U-joint.

bry-an

what about CV's? if it was in neutral wouldnt the driveshaft be not spinning? this is a toughy. I hate like this, my truck makes this rapping noise under it like something is loose... i think its this one exhaust hanger that is loose swing around and hitting the pipe. im outta ideas.

bigtrucknwheels

Drive shaft will spin regardless of the transmission gear, because the rear axles are turning, which turns the differential, which turns the drive shaft. the rear end becomes disconnected from the engine when the transmission is in neutral, but both sides of the drive train still operate. i.e. the engine will simply go to idle, and the rear drive shaft will still spin from the motion of the tires spinning the diff.

hope that helps you understand.

TNRabbit

If it's a slapping noise when you hit a bump, it could be the brass bearings that support the front axles....can't remember the name of them! (senior moment)

bigtrucknwheels

OK, so after really really paying attention to my truck, I've developed two theories...

Tell me what you think.

1) anyone remember me slamming my transmission cross member off a curb? never replaced it, and I have a low speed rumble from it. Could be the whole issue, or at least part, as the shimmy, I've taken notice to, is much much worse under throttle at mentioned speeds.

2) My truck is an R Title, as you know. hit in the right rear. the impact was so strong it bent both the axle shafts in the rear end. I replaced that, housing and all, with a nice G292 with low miles out of a '95 4cyl. But I retain the same drive shaft... is it possible its bent and has a speed sensative wobble?

remember, at speeds in excess of 70 MPH, this thing cruises like a dream. seriously, had it up to 95 the other day, was firm and smooooth.

and, oddly enough, replaced the power steering gear box (massive fluid leak) with a junk yard unit, and call me crazy, but it seems to have eliminated some shimmy. my little cruise control stick doesn't shake near as badly.

redheaded step truck

warped brake roters with sticky calipers or warped rear brake drums

camo31_10.50

CHECK BOTH DRIVESHAFTS!...this is what happend to my '80 right before my front driveshaft blew apart and basically destroyed everything...t-case, tranny, front d-shaft, passenger floorboards..so yes..CHECK DRIVESHAFTS!..might as well replace the U-joints if you hanvent already...our '02 dodge 3/4 ton 4x4 has had some mean vibrations around 70 and above...it was the front driveshaft...runs PERFECT now...my dad and i both thought it was the tires..or brakes...u-joints u-joints u-joints....i wish i would have inspected mine sooner on my '80 its causing some problems now...word of advice...if you have manual hubs...do NOT leave them locked in all the time. .(i was told by people on here that it was ok...apparently its not...)

SEAIRESCUE

Man, if the azz got hit so hard to bust the axles, don't you think the driveshaft is probably bent? An out of round object will hit a natural frequency directly proportional to the out of round mass. So, I suspect the rear shaft is elliptical and its magic dance number is around the speeds you are complaining about.

Front caster is always an issue. Need a good alignment man to make those right.

Bad tires or rims can do the dance at the speeds your mentioning. Can be explained in my first comment.

I would pull that rear drive shaft tonight and roll it across a tile floor.

Your tires may not be aligned on the rims. New spin machines have a high spot detector so that the high on the rim can be matched with the low on the tire. Jack your front wheels just barely off the floor with jack under the A arm. Lay on floor and watch for out of roundness. Bet you find some. Then do the rears. I purchased 4 new Goodyear wranglers from Wallyworld and all 4 were severely out of round. That was my problem. Not buying tires from Wally World was the ultimate solution.

I would also get a buddy to ride behind and along side of the truck at the problem speeds and let him look at the springs, tires and front wheels. I bet he picks up on something that will help narrow things down.

Did you have this problem before the wreck (don't remember all the details)

This should keep you busy looking for the dance.

bigtrucknwheels

good replies guys!

good alignment, tires perfectly in round (had em' checked on one of those fancy balancers), front drive shaft is perfect. I was thinking about dropping the drive shaft this weekend and crawling around in 4Hi to see if it truly disappears.

mrnick1979

sounds like a driveshaft, check or better yet replace your u joints, also when you have it out check for a bend at the flanges, if you have access to a lift put it on the lift and run the truck in gear and watch the driveshaft for any vibration, i had a problem like yours and wasted lots of money on new tires, balancing the tires three times, new shocks, front end alignment, and a stering stabilizer, it still shimmied, i pulled the driveshaft, put two new u joints in and walla, the truck rode like a caddy with the shimmy gone, just my experience and thought it might help.

Matt16

Who will be the first to suggest SAS, I know someone will think it's a legit solution for a shimmy potentially caused by front IFS components.

b.miller123

SAS it!

bigtrucknwheels

prognosis to date:

ALL the front end is solid. nothing wrong there. all the u-joints all around are good too.

two things left on the list (already put on a different set of rims and tires, no difference). one is the fact that indeed my wheelbase itself is not the same side to side. one inch longer on the right.

the other thing could be the drive shaft itself is bent. either way, it rides almost perfectly now, but just that last little bit needs to be fixed.

thoughts?

bigtrucknwheels

yeah, I even swapped out another rear end, and am on a third set of rims and tires, still shimmys. its the wheelbase, and thats why I have a donor frame in the driveway...

problem to be solved. thanks for all the help though!

buckz6319

Hi just for though .....I have cv's on the front of my 95 4runner sr5 4x4 v6 auto freeweeling hubs and the vibration was coming from a bad inner cv on the drivers side.The boot seperated at a seam and I would't have known the boot was bad if I had not noticed black thick sludge dripping from the boot I went to inspect it and it was trashed. I suspect it may have been that way for a long time before I purchased it on July 1st 08oppps sorry i didn't read that u have solved the problem

iselloil

Are you sure the hubs are unlocked? Yank the front drive shaft ansd see what happens.Have you rotated the tires?Are the caliper pistons free?Turned the rotors?Is the shimmy really in the front?

iselloil

It aint the frame!!!!!!!!!!!!!!!!!!!!!!! Look at the drive line. If you had a 4 wheel alighment done the laser will pick up improper diemensions, if they are to far out.But you said the frame was checked.Put the thing on a lift,take off all of the tires and run the truck. BUT MAKE SURE YOU DONT HAVE A LOCKING HUB LOCKED.Pull the rear drive shaft out and run the truck.

muddpigg

iTrader: (1)

Pull the rear drive shaft and drive it, on the front. If no shimmy = rear drive shaft.