87 4k CSQ tranny bad at 67k miles?

[Lines Peter]

If I read your previous posts correctly, you have the car in the air, with
the parking brake set and idling in 5th.  This means that the center diff if
spinning like crazy...  I'm not saying that this is the cause of your noise,
but it's probably not the best way to diagnose the problem.  The center diff
isn't supposed to take this much speed and will probably make more noise
than the high-speed vibration you are trying to find.  I'm also not trying
to start a discussion about how the diff's work!  :-)
I would tend to agree with Jim that removing the center driveshaft and then
the halfshafts would be a good way to rule out other problems before you
commit to fixing the tranny.  With the dollars involved you want to be sure.
About a year ago I replaced the syncros in my '86 4kq.  While I had the
tranny out, I replaced the motor mounts, tranny mounts, center driveshaft
u-joint, and center driveshaft support bearing.  All the bearings in the
tranny looked good at 205,000 miles.  Needless to say, with all these new
parts installed the fit up wasn't exactly the same.  I found I had a violent
vibration above 30mph in any gear.  Removing the center driveshaft and
driving with the center diff locked made the car silky smooth.  I had the
center shaft re-balanced (they did it first when the u-joint was fitted).
Didn't help the problem.  It turned out to be the alignment of the shaft and
the shims at the center bearing.  The Bentley manual has a detailed
procedure for determining the shim thickness.  It turned out that 2mm of
shim at the center bearing was all it took.  This was the difference between
a violent vibration at 30mph and car that is smooth up to 100mph.  Good luck
and let me know if you have any questions about the tranny or shaft...

Peter Lines
CAE System Administrator, WARN Industries
p: 503.659.8750 x4116
c: 503.319-3739
f: 503.786.4463
peterl at warn.com; www.warn.com