Rear end vibration

[Poirot]

I have a strange issue. It started when things began to cool down this fall. I was driving and the car started to vibrate as if I was driving on 4 concrete squares rather on tires. The feeling went away after a few min, so I thought it was just road imperfections. The issue went away for a few weeks then it came back again with a vengeance. I had the tires rotated, but the issue remained. It appears to be localized to the rear. The issue tend to be very prevalent on cooler mornings. The vibration will come, then after a while it will go away. The issue appears to be temperature/time related. This weekend for example, when on the highway, the vibration began around the 10 min mark from a cold start. It was in the 50's. The rear started to vibrate, and remained that way for about 10 - 15 min, then started to slowly go away at highway speeds. The issue also happens in city driving, but takes longer to fully manifest. The vibration appears to be speed independent, but can be felt above 30mph. If I were to hit traffic or slow to a crawl, and then speed back up after a bit of time, the vibration returns, and then will slowly go away. So it is like the rear is 'warming' up, something is vibrating, and when it reaches a certain temp range, the vibration goes away. I read a thread where one user had a seized rear caliper. Not sure that this is the same issue, as I had both calipers replaced a couple years ago. Anybody wish to share some wisdom on this?

Poirot

[VStar650CL]

There isn't much in the rear that won't be "speed related" unless maybe the body is reacting to bad subframe bushings. That's pretty unlikely, and even a wobble from a bad control arm will get slower when you drop the throttle. If it's in the drivetrain, using a sirometer to find the frequency will allow you to pinpoint where in the system it's occurring. Knowing the road speed, the vibration frequency, and what gear the car is in, you can calculate the ratios from transmission back to the wheels to see what corresponds to the frequency. If nothing does, then you know it's something non-rotational in the body or suspension.

[VStar650CL]

https://www.treysit.com/english/how-to-use/

[LIBRILZ]

How many miles on the car? I had a bad transmission mount and same symptoms. Maybe replace that with a low mileage used part. Car feels amazing now.

[Poirot]

How many miles on the car? I had a bad transmission mount and same symptoms. Maybe replace that with a low mileage used part. Car feels amazing now.

She has 126K and change on the clock. Additional detail and a new symptom. On a cold start after work, I shifted from park to reverse and there was a definite clank. I then shifted from rev to neutral, then to drive. Got a clank. Shifted between neutral and rev/drive a few times and each time I got a clank. I did the same thing this morning and didn't get the clank, and it was MUCH colder outside. While driving today on the highway, during the shudder/vibration, I didn't notice that I did not feel it in the shifter.

Thanks for the feedback. I am tempted to just replace the motor and trans mounts to save on any future expense. If I can grab someone, I will have them look and the engine as I shift to see if they see any undue movement. My valve passenger valve cover was leaking a while back, and I had it replaced. I bet some oil may have damaged the motor mount on that side. I want to try and get this sorted before the snow setts in.

[VStar650CL]

On a cold start after work, I shifted from park to reverse and there was a definite clank. I then shifted from rev to neutral, then to drive. Got a clank. Shifted between neutral and rev/drive a few times and each time I got a clank. I did the same thing this morning and didn't get the clank, and it was MUCH colder outside. While driving today on the highway, during the shudder/vibration, I didn't notice that I did not feel it in the shifter.

Sounds a lot like a rusty U-joint. Have you checked the driveshaft?

[Poirot]

That is the next think I will be doing. Been a bit wet here as of late. Thanks for the info.

[Dbarry]

How many miles on the car? I had a bad transmission mount and same symptoms. Maybe replace that with a low mileage used part. Car feels amazing now.

We'll include the transmission mount when we inspect this M45 project. Time for new tires so we ordered a set from 4Wheelonline and would do the brake pad replacement as well.