Bad vibrations

[robvas]

It vibrates less now, but it's still noticeable.

It's just weird because if I only go 1/4 throttle it's smooth as can be.

Going to take it on Monday and let them take a look while they do the pinion seal.

One thing that looks really weird is there is a circular cut-out near the bottom right shifter bolt, in the tunnel. I almost wonder if it was either drilled or cut intentionally, or somehow the trans moves enough in that direction to have created it? I don't really feel the shifter moving though.

 

[MG0h3]

Strange. Looks like it something was bumping up against it.

So are we talking about a high load condition that causes the vibration?

If so, def look at Ujoints, pinion angle stuff which could happen if you have some trashed mounts.

Leaking pinion seal could be a sign of something amiss.


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[OX1]

Could try this app for $100, might help narrow it down.

NVH For Android - Apps on Google Play

Diagnose truck and car vibrations with the NVH for Android app

play.google.com

 

[robvas]

One last thing: I have these UCA's on the car along with LCA's that have poly bushings. Never had spherical bushing uppers but I have had poly LCA's before and never noticed any NVH from them.

This isn't something that's expected from UCAs like this, is it?

 

[Blkkbgt]

How did you test your u-joints?

Did you use a screwdriver to pry them in each direction?

I ask because what you're describing screams bad u-joints.

 

[Bdubbs]

U-joints are easy to replace.

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[robvas]

How did you test your u-joints?

Did you use a screwdriver to pry them in each direction?

I ask because what you're describing screams bad u-joints.

I just did a quick check by wiggling and yanking on the driveshaft with both hands, I did not put a big screw driver in there to check like you said

 

[Blkkbgt]

I just did a quick check by wiggling and yanking on the driveshaft with both hands, I did not put a big screw driver in there to check like you said

Next time you're under there give it a try. I did the same the first time troubleshooting mine and missed it.

Make sure you check each joint in all 4 directions. Don't be gentle about it because the joint will go bad and stick in one spot. Mine popped loose and had at least 1/4 inch of play.

 

[MG0h3]

One last thing: I have these UCA's on the car along with LCA's that have poly bushings. Never had spherical bushing uppers but I have had poly LCA's before and never noticed any NVH from them.

This isn't something that's expected from UCAs like this, is it?

Can’t believe that I missed this was straight axle.

Changes everything.

Most likely deal is your pinion angle is off after the control arm install or bad ujoints due to the angle being off.

This can even cause the pinion seal to let go or even pinion bearings.


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[robvas]

Most likely deal is your pinion angle is off after the control arm install or bad ujoints due to the angle being off.

This can even cause the pinion seal to let go or even pinion bearings.

Let's talk pinion angle

Transmission measured at -3 degrees

Driveshaft was -5.5

Rear end measured +5

I figured I could just adjust the upper control arms and bring the rear end to -3 (?) and everything would be good, right?

BUT I could only break one of the jam nuts loose. Going to have to pull them off the car and stick them in a vise or something to break them free.

 

[MG0h3]

Driveshaft angle doesn’t matter in this case.

It’s transmission output vs pinion.

If the trans is pointed down 3, pinion should be pointed up 3. They cancel each other out.

On a straight axle car, you usually want the pinion to be a little less pointed up and the trans is pointed down. Gives you a little room for axle wrap, but with those upper and lowers, I don’t think you need to worry about that.

If you could get to 2.5 on the pinion go for it but I’m sure 3 would work just fine.

Slap some penetrating lube on there and be mindful that one jam nut is possibly reverse thread.
Maybe Google some destructions on the innerwebs.


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[robvas]

Pinion angle change seemed to clear it up.

 

[railroad]

Most set ups try to run pinion down 2 or 3*, trans up 2 or 3*.
Even with IRS there is some deflection causing the pinion to rise minutely, even more with a live axle.
The neg pinion is to off set the tq rise.