Shimmy @ 65 mph

[4x4Dreamer]

Just like the title says, my truck is smooth as silk until about 65 ,then it starts to shake, not super bad, but enough to jingle the change in my cupholder and the stuff in my center console. Could this just be a tire out of balance? I know I need an alignment, but my concern is a motormount or a balancer.
Any ideas?

[SteveMc]

Try going to 65 and little over, then put the trans into neutral and let off the throttle. If you still have the shimmy it should be behind the trans in the drive line or tires/wheels. If the shimmy goes away, you may want to check the eng mounts, damper, etc.

[Stray Cat]

Originally posted by SteveMc:
Try going to 65 and little over, then put the trans into neutral and let off the throttle. If you still have the shimmy it should be behind the trans in the drive line or tires/wheels. If the shimmy goes away, you may want to check the eng mounts, damper, etc. SteveMc is right about the testing procedure...I just wanted to add a bit. If the shimmy goes away with the trans in neutral, in addition to "engine mounts & damper, etc.", consider the U-joints, transmission and differential. If the shimmy doesn't go away with the trans in neutral, in addition to the "driveline, tires/wheels", consider wheel bearings, steering box (adjustment?), ball joints. The theory here is to cut the possibilities in half. If you get the vehicle to the point where it shimmies under drive power (65MPH), you have all of the possibilities in play. By putting the transmission in neutral, you have dropped the RPMs of the power producing half of the drivetrain (engine & transmission) way down; at the same time, you have left RPMs of power delivery half of the drivetrain (U-joints, driveshaft, differential) and ride/steering part of the vehicle (wheels, tires, wheel bearings, steering, ball joints) the same. So if it goes away, it must be in the power producing part of the drivetrain; if it continues, it must be in the power delivery part of the drivetrain or ride/steering part of the vehicle.

[4x4Dreamer]

well, it keep shimmying if I put it in neutral. I know it needs an alignment, so I'll probably go after that first. it's probably not too bad, but the center console gets shaking really hard and it makes it seem worse.

[jcomp]

I had a similar problem, it was the front driveshaft.

[mpascino]

mine did the same thing, same change in the cup holder scene....To be honest, I chased it for a year. In the end it was a 40 dollar tire balance. The funny thing is, I had two different sets of tires on the truck over that year, both must have been off balance. If you have driven the truck for a while and don't see any other signs of problems except the shake at 65 I would balance the tires. I assume you haven't had it done in a while, no? While mounts, shafts, balancers are still a good possibility most likely you would have seen the problem other times also.. The tires seem to go way out of balance pretty easily when under the weight of a truck getting bounced around the highway. Let us know how it works out.

[4x4Dreamer]

i'm going to check my U-joints this weekend, I don't think they've ever been replaced. And I'm going to get it in for an alignment soon as well. I'm hoping between those two things, that life is good.

[Iain]

Most likely your U-joints. I had a similar problem on a past truck and I changed the U-joints and it ran smooth as can be. Make sure you put the greasable type in your truck, that way you can always give them a few shots of grease every time you service the truck.

[4x4Dreamer]

I'm going to replace the Ujoints this weekend, hopefully that clears it up.

I should probably post this in a new post, but I'll try here first.

When I have my vent on (I have AC, but it doesn't work yet) I get a squeal when I accelerate from Idle to about 10 MPH. It's bad enough I don't run the vent, but with it being all rainy here, my windows keep fogging up. In the next 3 or 4 weeks I'll get my AC fixed. Is it possible my compressor is kicking on when I run the vent and it's protesting cuz it doesn't want to? My belts are new and the tension was checked not that long ago.

Just wondering.

[jcomp]

I'm going to replace the Ujoints this weekend, hopefully that clears it up. FYI: On mine the u-joints were fine, it was the slip joint that had a lot of wear.

[KEVIN MUNCASTER]

Funny, I have had a similar problem, but at 50-55 mph, very loud almost harmonic vibration, I decided last nite to pull my tranny mount (700r4), and it was whipped, bad, metal on metal, from years of oil leaks ruining the rubber. I changed the rear u-joint today, the other 2 were original but still smooth as silk, remarkable on a 20 year old truck. I changed the hanger bearing just for good measure. Will put it back together tomorrow and see how it is. Everyone is right, tires can make an awful shake.

Keep your stick on the ice !

[4x4Dreamer]

well, last weekend I had a friend re-weld that power steering bracket, and it broke already. I really need to fab up that mount on the back, unless I can pick one up somewhere. What a PITA. I noticed it was shaking a bit at idle so I checked out the mount...sure enough, SNAP.
I'll get out today (barring rain) and check the U-joints and motor/tranny mounts.

[4x4Dreamer]

Finally replaced U-joints. The ones in there were the original 83 units and I had to use a torch to melt the injecttion molded plastic retainers out. What a PITA that was. Now it has Greaseable U-joints in there with those Retaining clips that'll make it a little easeier to swap in the future. Worth the money.
Also replaced the driver's side motor mount. Truck is noticeably smoother now, though it still shakes a little bit. But @ 55 it's smooth as silk.

[Robyn]

If you are running large tires you very well may be getting a good amount of the high speed shake from tire ballance. There is a product called equal that goes in the tire and works wonderful on larger tires. I use it on my Big rigs and love it. Check out your front end alignment as well and I think the two if set right will yield a smooth truck for you

[4x4Dreamer]

I'm running stock size tires, so I don't think that's the issue. It might be that the truck sat for over a year in one spot and threw the tires out of whack.