Rear-end Noise After 4-link

[camarosaurusrex]

I am at a loss and not to much knowledge. I had Ridetech's 4link installed by a respected builder and now have a strange "chatter" "shudder" don't really know how to describe it(video attached). The sound shows up around 30mph and will disappear if I go higher. The builder is out of town for a bit so i can't go back to him yet and thought I would ask around. The sound comes in pretty early in the video and you can hear it though out if you can stand to watch it.
Any help or ideas to bring back to the builder would be great Thank you
https://youtu.be/SUIWBC4AY8g

[TheJDMan]

It is too fast for a wheel/tire noise. It sounds more like a drive shaft noise. Did the installer have the driveshaft out when he installed the 4 link? I would be looking at the U-joints and make sure the clamps are tight. Might also check the U-joint working angles. Tons of threads on here about drive line angles. Also, I would visually look to see if anything is physically touching the drive shaft anywhere from front to rear.

[Josh@Ridetech]

It is too fast for a wheel/tire noise. It sounds more like a drive shaft noise. Did the installer have the driveshaft out when he installed the 4 link? I would be looking at the U-joints and make sure the clamps are tight. Might also check the U-joint working angles. Tons of threads on here about drive line angles. Also, I would visually look to see if anything is physically touching the drive shaft anywhere from front to rear.

I agree. Just to eliminate all possibilities, I would check the U joints as well.

With the car at driving height, what are these measurements?:

- Transmission angle
- Driveshaft angle
- Pinion angle

[camarosaurusrex]

Thank you both for the responses. I checked for anything touching and found nothing. The clamps are on tight. Tonight I will try to squeeze under there and get some measurements.

[TheJDMan]

You may need to get it up on a lift, preferably 4 post, so you can see everything clearly with weight on the suspension. Try wiggling the driveshaft to see if there is any detectable play at either U-joint. It is safe to assume they removed the driveshaft during the suspension install and it is possible that one of the joint caps may have fallen off in the process and some needle bearings were lost. Just sayin, because the noise definitely seems to be in the driveshaft.

[dirty rick]

Get it on a 4 post lift and jack up the rear axle and run it. Then you can wander around under it and find the source of the noise.

I would closely inspect the driveshaft and joints with the DS out of the car.

I would also drain the rear axle lube to see how much metal is in it......

Between these two diagnostics I think you will find the answer.

My vote is the rear axle. But Ive been wrong before. ANY metal in the oil is a strong indicator.

[camarosaurusrex]

....

[TheJDMan]

Without seeing what you are measuring those pics do not provide any reference point. You really need to get that car up on a 4 post lift where you can keep the suspension loaded and then measure the various angles. It won't do you any good to jack up the car and try measuring. Have you contacted the "respected builder" that installed the suspension to see if they can provide any assistance? Just FYI, 3deg down angle on the engine/trans is virtually a world wide standard for front engine rear wheel drive cars.