E30 vibrations under load over 35mph and while rolling in idle

[bmcf1lm]

Lately my e30 has developed a problem with a lot of vibration. I recently replaced the CSB, guibo, and transmission mounts on my 1987 BMW 325is. I had my driveshaft out, got a friend at a shop to replace the CSB on the driveshaft. Once the car was back together it felt great. Best the car ever drove. Fast forwards a month and 2000 miles later and im getting this terrible vibration when I pull it out of storage. When i put it up on the lift i saw there were no bolts in the transmission bracket.

So now to the vibration. Under load the car shakes violently above 35mph. But if I take my foot off the gas, all the vibration is gone. Rolling in 5th gear at 60mph theres no issue. If i put it in neutral, the problem is back only slightly. Its strange. Really stumping me.

As for the cause, a friend guessed a bent input shaft. Another possible cause is the driver side axle has both CV boots torn ans has about an inch of play in and out. That is a problem but im not sure if that would be the full cause of the problem overall since the axle wouldnt change speed between being in neutral versus in gear.

After researching the issue a bit I saw someone say differential mount or u joints. Im really stumped on this issue and if anyone could shed some light on a possible fix, it would be greatly appreciated.

Thanks,
Ben C

Sent from my SAMSUNG-SM-G890A using Tapatalk

[estoguy]

Another possibility - Are you having any steering issues to boot?

Check your trailing arms for play. I was getting vibrations similar to what you describe. In my case, I don't think I had tightened the trailing arm bolts enough when I did the bushings. The outer bushings had actually worn against the bolt - the threads on the bolts were worn flat, and that few mm of play was causing the vibration. Jack up one side at the rear, and grab the wheel at 9 and 3 o'clock and move it back and forth. If you get any noticeable back and forth movement, then you'll need to replace the bushings at the least, and if they have worn the bolts, those too. If you find this to be true, don't worry about getting the bolts from the dealer - I found replacements at Canadian Tire here, and they were cheap in comparison. The only difference was the pitch of the threads. The OEM bolts are 1.5, my replacements are 1.75.

[ak-]

Did you install the guibo backwards? That is something that will fail prematurely if done.