tires and wheels Whole Car Shakes At 60 Mph

[Malagatii]

So 2 weeks ago I replaced the rear control arm bushings with Polyurethane on my 74tii ( still need to do the subframe inserts).   At that time I also rotated the tires and installed new steel braided brake lines.  2 days later on the way to work the car started to shake around 60 mph. The shaking/vibration can be felt throughout the whole car (in the seat and the steering wheel, etc...).   The frequency of the vibration reminds me of a warped rotor, but it's happening all the time at a constant 55-65 mph (it's still there above 65-70, but not nearly as noticeable).

• Thinking I had thrown a weight on a rear wheel, I got the wheels balanced....  minimal improvement.
• I also visually checked for a tire out of round, but nothing that i could notice.
• Trying to identify if I had a bad wheel, I tried rotating the tires back to original position.  Again, maybe minimal improvement.
• I've checked the guibo, but it looks in reasonable shape.  It was replaced about 20 k miles ago.
• Center bearing seems OK.
• half shafts seem ok too.

So my question(s):

• Could it be the guibo?  I've read/heard that when these are going, the shakes come on around 30-40 mph.  Also I would assume the frequency of the vibration would be much faster.  Are there typical visible signs of one about to fail? 
• Could it be due to the new bushings and a change to the alignment in the rear?  Not sure I understand the physics of how alignment could cause shaking, but....  And if it is, what options do I have since there is no adjustment to the rear alignment?
• Could it still be a bad wheel?  I may need to borrow a friends set of wheels to test this...

What else could it be?

 

[GreenSwede]

As I´ve experienced it both guibo and center bearing approaching toast tends to be much more obvious under load. Take off, uphill or just acceleration. So I don't think it's the drive line.

Maybe the alignment could do it. Not heard of it that bad, but two rear wheels struggling in different directions must reveal itself some how.

I've got a shaking steering wheel at some speeds, the wheels have been checked and rechecked for balance and trueness, and I can't find anything else. I read somewhere on the forum that someone got a shaky steering wheel after installing poly sway bushings, but I donut know.. Maybe in cahoots with the ET17 wheels widening the track? I'm also not sure I preloaded the steering column when I reinstalled it, but I don't think that should cause a wobble.

 

I drifted off there. My sole point being - I don't think it's drive line related. Unless you had the diff loose? Moving the diff back or forth might do something, changing the tension on the center bearing and guibo. 

 

Another thought, could it be water in the tires? I recall a customer having used his own compressor not having a water separator having something like that going on.

[esty]

put the wheels back where they were before you rotated them....

[Malagatii]

Thanks, Esty.  that was one of the last things I tried to no avail...

 

 

Trying to identify if I had a bad wheel, I tried rotating the tires back to original position.  Again, maybe minimal improvement.

 

 

BTW, can I send my car off to you for summer camp for an interior refresh...  I love the photos of what you've done to most of your cars.  And yes i do have a carpet order coming to you one of the these days....  Soon I hope.

 

 

My sole point being - I don't think it's drive line related. Unless you had the diff loose? Moving the diff back or forth might do something, changing the tension on the center bearing and guibo.    Another thought, could it be water in the tires?

 

Thanks, Ola.  The car is my daily driver, so I am hoping it is not the driveline or something that could put an abrupt halt to my commute.  I don't know how water could get into the tires over the two days that this started to happen, especially in this dry climate in California.  I'll take a look at the Diff.

Edited July 11, 2014 by Malaga74tiiDD

[Buckeye]

Did you loosen diff? If so, should follow specific procedure.

Trailing arm bushing must go on in certain way. Did you consider that?

[Malagatii]

I double checked and I did install the bushings the correct way. (Thanks for the photos, Buckeye. - a side note, but I'm assuming you are either in Columbus or went to OSU. I went to OWU.)

I also checked the diff and it's solid. We did not touch it when we installed the bushings.

I'm starting to think I really need to swap out the wheels. It must be a damaged rim. Can't hint of what else it might be.

[Mike Self]

One more thing to check...

 

The rear tranny mount.  I had a very annoying vibration between 55 and 62 mph that drove me nuts for nearly a year--checked everything you did to no avail--was close to getting rid of the car 'cause I couldn't find the vibration.  Was under the car checking something else and noticed the rear tranny mount had turned to black goo...replaced it with one from a 320 (you can also use a Bavaria one) which is larger and sturdier.  Problem solved.  

 

BTW, I've been using urethane sway bar bushings for many years with no vibration problems that can be traced to them.  

 

One more thought:  This wasn't happening before you did the bushing work....so doublecheck everything you did.  If you can get the car up on a frame lift, then put it in gear (wheels off the ground of course) and accelerate to 60 mph and see what happens...

 

good luck, and let us know whatcha find....

 

mike

[Malagatii]

Great suggestions. This wasn't happening prior to the bushing upgrade. When I swap the wheels out, I was thinking about doing just what you recommended: running it up to 60. I had not thought about the rear transmission bushing being an issue, but I did notice the last time it was on the lift that it looked more like a squished donut than a squared up racing slick tire. I'll certainly be taking a closer look at that.

[Rocan]

Rotating tires on my car has the same effect (vibration around 55-65). Until the tires wear in their new place, it will vibrate a little. If you drive them like this and then swap them back, then they will still vibrate. Rotate, deal with the minor vibration till they wear in, and you should be okay. 

 

Of course, double checking that the wheels are mounted properly is a good idea. Remove the lugnuts and check that the seats are clean and not damaged. When tightening, tighten by hand at first and use a cross-tightening pattern to make sure everything is nice and true. 

[kbmb02]

If, after checking other things you still have the issue, look for an old-school tire shop which will check and true the tires while mounted on the car (we've got a shop here in Southern California ... action photo included). -KB

[jgerock]

Your post says you replaced the trailing arm bushings with urethane ones but not the subframe inserts.  Does that mean your tii has old subframe (carrier) mounts?  You may have transferred an existing (but not evident) problem (old trailing arm bushings) to another area without replacing everything in the rear. 

 

Did you completely remove the trailing arms when replacing the bushings?

[Dev02]

I did rubber and not Ur, so am not sure of the proceedure. When installing Ur bushings do you preload the suspension and did you do that? Just wondering if that could cause issues.

[Malagatii]

Did you completely remove the trailing arms when replacing the bushings?

 

 

Yeah, still need to put new Subframe and poly inserts in.   Hope I can can get around that int he next couple weeks.

And we did completely remove the trailing arms to get the old bushings out and the new ones in. 

 

When installing Ur bushings do you preload the suspension and did you do that?

 

I hadn't realized we need to preload the bushings and then do the final tighten the trailing arm mount bolts once the car was under load.  I'm certainly going to doing this when I install the subframe bushings.

 

Another update:  I decided to go back to the tire shop that balanced the wheels for me and apparently one of the tires failed the road force test where the tread was wavering a bit.  They checked the wheel and it was true, but the tire needs to be replaced.  The tires only have 9k miles on them but they are 18 months old so out of warranty.  Now if I could just find a shop that has one in stock.  Anyone know where I can find a BF Goodrich G-Force Sport Comp 2  195/50 r15?  

 

My guess is that this is a majority of the cause, but I still need to look into everyone else's suggestions because there is probably more to it.  Thanks for all the comments!

[Dev02]

I hadn't realized we need to preload the bushings and then do the final tighten the trailing arm mount bolts once the car was under load.  I'm certainly going to doing this when I install the subframe bushings.

 

I don't know that you need to preload with Poly, it might be that you don't.

[Mark Newman]

replaced track control arm bushings and this made it WORSE