Chasing a Highway Speed Vibration Problem

Glad to hear you found out what it was.

 

how hard was it to replace?

 

Not terribly difficult.

I had my truck on a lift, and used a high tripod jack stand to push on the skid plate attached to the transfer case. I unbolted the tranny mounting bolts first. There's 4 bolts, 14mm, and 2 are easy to get to. The other 2 have the front axle shaft limiting your work area to a few inches.

Once the bolts are out, slowly push up on the transfer case. It'll have a bit of stiction, but it will move.

Then go under cross member with a breaker bar, 3 inch extension, and a 12mm socket. Remove the 4 bolts holding the mount to the cross member.

Then start pressing the tranny higher. It's going to go damn near as far as possible upward. Then the mount will come out. It's got a black stabilizing thingy that protrudes into the cross member, so you'll need the tranny out of the way.

The compare it to your new OEM one. (On items like this, I'm really going to advise paying the dealership price, for a high quality part like this.)

Make sure the mount wings have the same angle. The new one was a bit tight, so I bent the wing out slightly in a bench vice.

Then I installed the mount. Start with the mount- bell housing bolts first. Get them almost completely installed, and don't torque it down yet.

Then install mount to cross member bolts. Torque to 22ft/lbs

Then torque mount to bell housing bolts. 48ft/lbs.


Done

 

considering one of these if I tackle the job.

http://www.pirate4x4.com/forum/moto...846-tacoma-super-duty-transmission-mount.html

 

So, it's still not solved. Carrier bearing has gone bad after only 20k miles

 

Last time a vehicle of mine did that, it just needed new tires. Flat spots developed on the tires due to a panic stop at highway speed. The brake rotors also needed replacing after that.

 

What happened to the Tom Woods one piece? Do you still have it? If one or both sections of the two piece driveshaft were out of balance, it's possible that they could cause the carrier bearing to fail.

 

I returned the tom woods, because it didnt solve any problems. The shaking was *LESS* violent with the 2 piece and dogshit carrier bearing...

 

Does the wobble disappear witha loaded bed I wonder

 

How did you know by looking that the trans mount was possibly the problem? I don't see anything in the photo? Is it the different angle of the rubber supports that tipped you off? I would expect the angle to flatten out with the weight of the trans on it.

So did the trans mount need to be replaced after all?

I had the identical problem and it was drive shaft splines - clean/regrease fixed it.

 

Did you ever completely resolve this issue - or is the vib still there but muted?

question: you said the vibration was "rpm related." Is that in all gears at said rpm, or only overdrive?

Personally I suspect the vibration took out your carrier bearing and tranny mount; having these two replaced only mutes the vibrations....

gl

 

yeah, they only settled the vibrations down.

I have a feeling this is getting narrower and narrower.

I had a bad rear-axle bearing and seal, which when replaced changed some of the vibration, but its still horrid above 75. its tolerable below 75.

So now i'm thinking its my pinion angle, or its a driveshaft balance issue.

 

Did you install aftermarket rims? Just make sure your tires are balanced and mounted correctly. If your rims are not hubcentric, get a ring for them.

 

Nope, OEM rims, and road force balanced tires.

I need to buy a angle finder, and check my rear angles.

 

UPDATE: I loaded 5 crates of Russian ammo in hte back of my truck and took a drive to harbor freight to buy a cheapo angle finder.

Sure as shit, the vibrations died down. Still noticeable but not awful.

So weighted down, vibrations go down. This is a angle problem.

 

Update #2 (this evening):

My rear u-joint operating angle is 6*. Holy fuck.

After CV Half shaft ---> U joint ---> Rear Diff Flange
----- 11* --------------------------------- 5*


The absolute worst part about this entire thing, is that i've gone repeatedly to a *well known and prestigious* Off-Road 4x4 shop (they've been/are in shit-tons of off-road magazines, all the time). They even have a "toyota guy".

And somehow 6 fucking degrees is okay for a u-joint?

It irk's me that I told them i wanted 3* shims put in back, and they came back with "replace your CB and add some CB shims"...

 

Actually 6 degrees is ok, if it makes sense with everything else in your driveline, and your u-joints are in good shape. I have a one piece driveshaft on my '11 and the angle at each end is 6.5. Spicer, who makes the u-joints, specs them to run to 15 degrees IIRC. They just wear faster with more angle. For a one piece driveshaft the goal is to get the TC flange and the pinion flange parallel, so the angles are the same. If the angles are the same, the vibes from each u-joint cancel each other out. I have a 3" lift, and 6.5" at each end is the best it can ever get with that amount of lift.

For more info on the two piece driveshaft, there is a very long thread on TW somewhere with lots more info. But long story short, I would bet that one of your driveshafts is out of balance. If you take them to a shop to get them balanced, make sure you go to a shop that can spin them to 3500 rpm. Some shops only spin to 2300 or so, which isn't state of the art and doesn't match the reality of driving on the highway. Also, on the second gens, the easy fix is to get a double cardan joint put on the second driveshaft. In Denver, that will cost $400. Just balancing would be about $90. Some people have taken the driveshaft out of 3rd gen? (appx year 2000) forerunner, because they already come with the double cardan. There is also info on this in the other thread.

 

Excabs have a DC joint and 6* pinion angle is definitely not acceptable for that and will cause vibes. 2*+ 1* down bubble from the DC joint is the accepted ideal angle.

 

Exactly. Pre-runners get away easy because the output angle on the tranny flange, and the input angle on the rear diff must match. That's easy.

With Acc and Dbl cabs, the shaft is 2 pieces. The tranny flange to carrier bearing is nominal (try to keep within 3*), then the constant velocity (double cardan ) joint comes into play. It uses 2 u-joints with a internal bearing assy to keep the rotational velocity constant thru the curve.

From there it's straight shaft to rear-diff flange operation angle. That is the pickle for many folks. More than 3 degrees starts reducing u-joint life ~ 15% per additional degree. It also induces rotational imbalance.

That's where axle shims come into play. You want to get. *some * of the angle out, but not all. 1-2* leftover is good.

#1 rule, don't have a 0* operating angle on a ujoint. It causes the needle bearings to Brinnel inside the bearing cup (force divots into it), because they are stationary with torque applied.

 

Yep, and it also helps to "move" the grease. Pretty much 1st grade drive line stuff. I can't believe what that "shop" told you but that kind of BS from so called "reputable shops" is more common than most folks realize.