Well, folks, it's been a while since I've posted, mainly because my trusty '94 Z has been faithfully taking back and forth to work every day........

Until, about a month ago, the tranny decided it no longer wanted to pull in 5th or 6th gear. Shifted in to and out of 5th and 6th just fine, just no pull and a high-pitched buzzing sound. The rest of the gears were fine.

Got her home (ever driven in 4th at 60-65 for 30 miles? ), pulled the tranny, and started taking her apart. What I found was that the 5-6 driven gear and the main output shaft splines had completely worn out, just nubs of the teeth left. No chunks or anything like that in the tranny or on the magnets.

Searched the forum for folks that had needed to repair their T56s (not that many, actually) and called D&D Performance ( www.ddperformance.com ) to get their prices on an output shaft and 5-6 driven gear. $600 for both, plus $500 for the bearings and syncros for a full overhaul. Or, I could buy a fully rebuilt tranny from them for $1500 plus core. That decision took about 3 seconds, since I hadn't even looked at the rest of my tranny.

So, what does this have to do with 4th gen steel driveshafts? I drive my car virtually all the time in 5th and 6th, she's got 150K miles on her, and I have a definite vibration about 85 and higher. I believe that the continuous vibration (even at speeds where I couldn't feel it) just slowly wore the shaft and gear splines out over a long period of time.

I now have a "new from the junkyard" LS1 driveshaft installed (although I haven't even got her off the lift yet).

So, for all of you early 4th gen'ers that have been thinking about getting an LS1 driveshaft just as an upgrade, it might actually save some wear and tear on your tranny as well.

Now I'm wondering/worrying about my diff as well. Time will tell.

Have a good one.
Mike