1990 744 GL (Regina) AW70L and 4.10 open rear diff

Soooo... Long story short I've been rehabbing this car for a while, and I had some driveshaft vibration about 6 months ago that was noticeable especially on the highway and especially after installing new rear shocks and doing not much to the front suspension. New engine and trans mounts were also installed.

And then the vibration really set in.


So then I got a new driveshaft support bearing and rubber mount, 3 new universal joints (Dana/spicer 51310X) and ended up having to replace the rear axle because it had a bad bearing in it somewhere.

Anyway ... the same exact thing happened (except the axle) with my last 90 744 turbo - new rear shocks, left the front unchanged, new engine and trans mounts, new u-joints and still vibrations. I don't remember how I fixed that back then, since it was 15 or so years ago.

Maybe I need to do the front shocks... is that a silly idea? I can shim the support bearing down, which is the only thing I can think of being a solution at the moment.


I am totally fine with taking it in for a balance job, I just need to actually do that.


I did notice that the vibration comes and goes sort of randomly. It came on as I crested a climb of about 1200ft on a 6.5% grade (highway 26 in Portland) at about 53mph and changed with little relation to load on the driveshaft. I'm hoping it's a balance issue, but what about the front shocks and the angle of the universal joints? Does the rear have enough range of motion to change the angle appreciably?


Cheers,
Will