5kTQw vibration under load

[Dan Cordon]

Congrads on the acquisition. I don't know that I'll be able to help much
though. I have a *probably not as pretty as yours* 87 5ktq as well. For
me when accelerating in first gear when the boost gets above 1.0 bar I
also get a vibration I can feel at my feet. I'm still trying to isolate
it. We can't tell if it's just below the passenger foot well, or if it's
in the center just behind the front seats. I also checked the shafts for
wear and engine/tranny mounts for failure. I found nothing. However, the
center support bearing does seem like it's pretty easy to move around. I
purchased a new one from someone on Ebay. It's not the MB one, but they
say it takes some small modifications at a driveline shop to install. It
was cheap though, so if it doesn't work, I'm not out much. Many people
have said to just get the replacement one and drop it in.

What I'm wondering is if it's possible to remove the rear driveshaft
(propellor shaft) and drive the car with the center diff locked. I don't
know how the diff lock works to know if it's strong enough for this. If
it was, that would help isolate if the propellor shaft was causing the
vibration or not.

Any ideas? Yours sounds a lot more pronounced than mine. I'm hoping
yours is easier to figure out so I can learn from your experience.

Good luck with the project. Let me know what you find, and I'll keep you
posted on my search as well.

--
Dan Cordon
Mechanical Engineer - Engine Research Facility
University of Idaho

> Hey, all.  Just added a very pretty 87 5kTQw to my stable (kudos to Chris
> at Force5 again, nice to do business with him). It's much better looking
> and faster than the my 86, but has a few issues of its own. To whit:
>
> The car has a very strong vibration under load.  Vibration seems to be
> located beneath and just forward of the driver's footwell, almost as if
> the diveshaft there was about to jump off.
>
> Vibration frequency is speed-dependent, but severity is load dependent. If
> I drive gently it is barely noticable or nonexistant, but at 1.0-1.1+ bar
> it becomes very severe.
>
> I looked around under the car yesterday and couldn't find anything
> obviously loose or rubbing, all CV boots appear in tact.
>
> The shocks are shot, but the mounts and bushings haven't obviously failed.
> (Some wear is evident, but nothing's loose)
>
> I only found two things amiss, I'm not sure if they could be related or
> not:
>
> 1: There is a stripe of thrown grease/oil on the body near where the
> propellor shaft goes in to the rear of the transmission. This might point
> to a failing CV on the front of the propellor shaft, but the boot
> is in tack and the vibration feels like its coming from farther forward
> and left of there....
>
> 2: Carrier bearing on the propellor shaft seems to allow more movement
> than the one on the '86. I don't know how much is too much?
>
> Any ideas?
> --
> ------------------------------------------------------------------------------
>   Rob Deis                  "Let the people know beforehand what the law
>   MiB3347                      is and what they are to expect."
>   rdeis at io.com                              -- 18th Congress, Rec. 75
>