Need vibration help

[Nunya53]

I have a gremlin I need help with. Drove my truck home from work yesterday and it drove great. On my porch was my new spacer lift courtesy of UPS...great. Knowing I couldn't do the whole thing in one night, I decided to put the 1.5" blocks in the back last night and would do the front tonight. Install last night went great!!

Problem: With only installing the rear blocks last night, I now have a very noticeable vibration on my truck mainly between 15 and 30 miles an hour, accelerating and decelerating. There is also a slightly noticeable vibration in the neighborhood of 45-50 mph.

Has anyone else had this problem and is there a simple fix for it? I have a 2006 Access Cab TRD Off-Road 4x4 Tundra with just under 35000 miles.

Thanks,

Jerry

[DevinSixtySeven]

I can only make a few guesses and a checklist...

U-bolts torqued to spec?
Spacers centered on pin, spacer centered over leaf spring perch?

It's not the driveshaft angle...3", even 4", isn't enough to cause vibration on these trucks.

The only potential thing I can think of is the jump in the rear without anything in the front dropped your caster angle just enough that you get a slight shimmy at certain speeds, and that's a WAG. Install the front, or just remove the rear, and I bet it goes away.

Hope that helps, let us know what you find.

-Sean

[DJ]

Your wheelbase is 128 inches. By installing a 1.5 inch lift in the rear, you've raised the rear end 1.5 inches relative to the front end. That makes the vehicle lean toward the front in the amount of arctan (1.5/128) = 0.67 degrees. That makes the steering axes of the front wheels lean less toward the rear by 0.67 degrees, meaning you have reduced the caster of the front wheels by 0.67 degrees, thereby causing steering instability at some speeds. That steering instability manifests as vibration, which you feel.

Finish installing the lift and have it aligned properly, thus restoring caster to its proper value, and the vibration will go away.

[Nunya53]

Thanks for the replies. I did finish the lift on the front last night and the vibration did diminish somewhat. Now it is only from about 18-25 mph. I am going to loosen the back and make sure it is all good, then I will see what happens.

[DJ]

Don't forget the alignment. Your lift has altered it, and an alignment is required.

[Nunya53]

Well, I loosened everything in the back, double-checked everything...it's all good. Retorqued the U-bolts and still have the vibration. I will have the alignment checked and report back the results. It's a good thing my tires are junk.

Thanks for the input.

Jerry

[Nunya53]

Alright...I've corrected the problem!!!

Sometimes, I have to wonder how I manage to function from day-to-day. You would think with three college degrees and 20 years in the military, I might have acquired just a little common sense along the way

Anyway, I researched on the 'net and come across a post or two about people correcting similar problems by shimming the rear blocks and that got me to thinking....so...I once again crawled under the back and took a good hard look. Lo and behold, I had installed both blocks backwards!!!

Truth be known, when I initially looked at the blocks, I thought they were flat. The fact that I had installed them both backwards was purely coincidental. After a bit of wrenching, I turned them around and my truck drives like a new one.

Thanks for the input and I am still going to have the alignment done before I put the new tires and wheels on. Feel free to reference this post on my dumbassedness to anyone who may have a similar problem in the future.

Jerry