1 of 3 Vibrations Left to Cure
 

After reading this post: https://www.thirdgen.org/techbb2/sho...hreadid=207667 , I was able to correct a couple vibrations. It was the BEST post I read on isolating vibrations by far. Unfortunately I still have at least one. First vibration was corrected with new ignition system. Didn't need the MSD 6A and coil or Taylor 8mm wires, but the wife said to fix it RIGHT! Installed... No more miss! Second vibration cured by going back to a rubber tranny mount. Had an Energy Suspension Poly in it. Can't remember which thread, but this poly mount IS DEFINITELY taller that the OEM rubber by the thickness of the pre-load plate they tell you to put in. Anyhow, replaced it and positioned the trans crossmember to where the factory put it (it wasn't in the same place after the last mount was put in). After installing the crossmemeber, I had to force the trans towards the drivers side to get the bolt in. Have read this is normal also. Verdict - vibration between 1700 - 3000 RPM with mild throttle is gone.

The last (I hope) vibration is a high speed vibe. About 65-70 it starts and gets worse the faster I go. It sounds like a rumble and I would have to catagorize it as a small oscillation. For reference, tires out of balance would be a large oscillation. Just balanced the tires today. Watched him like a hawk while he did it. Got the car home and after replacing the trans mount, I jacked the rear up and put it on jackstands. Started the car and looked at the driveshaft. It had a pretty large wobble, but the shaft into the trany (yoke?) looked fine. The driveshaft does have some pretty large weights on it though. Also, the shaft that slides into the trans (yoke?) is pretty loose. Can easily move it sideways about .010". What is the tolerance?

Things I have done to isolate vibration:
Rev engine in neultral/Park to 3500. Smooth after above repairs
Drive at 80mph, shift to neutral and turn off engine. Still vibrates.
Place in drive while on jack stands and observe drive shaft and wheels.

To summarize my questions...

Is the driveshaft wobble normal if the shaft into the trany is turning true?

What is the tolerance for play in the trans extension


AND,
Does anyone have any other ideas?

BTW, I think it's the extension bushing or the driveshaft.

You should not be able to move the drive shaft inside the transmission, by hand, AT ALL. If you can wobble it by hand, it's wasted.

It could be that the bushing is worn, or the yoke on the drive shaft, or both.

The bushing costs about $0.50. Last time I had somebody replace it in the car (there's tools for that, a puller that reaches into the ext hsg and pulls the old bushing, and a driver that goes around the trans mainshaft to knock the new one in) it cost me $20.

i'd suggest you just get a junk drive shaft out of a LS1 car and stick it in, and not futz around with your existing one. It won't cost a whole lot more than just balancing by itself, let alone replacing the yoke; and you'll get an aluminum one instead of steel that way, and it'll come with a (probably) much less worn yoke, with no extra work.

RB83L69 - Thanks. That was my plan. Just wanted to get someones concurrence. I'm calling around to the junkyards now. I'll post again when I have new info.

BTW, Really appreciate the time you spent on the thread I listed in my previous post. That was a very thorough and the info was invaluable.

I think I read somewhere that all driveshafts are the same length for all 3rd/4th gen man/auto, but I can't remember. Yard has alum drivesahft from a 97 with a manual trans. Will it fit my 350/700R4 car with stock rear-end?

Short answer, yes.
As for what to look for there are a few differences. IIRC, the 87-92 1LE driveshafts are 2.75" in dia., the 93-97 are 2.75, and 98-02 3". Try to find one from the later models that had the dampner on the tranny yoke - seems like it helps alot. The weight difference is marginal - even compared to the stock steel shaft, but every 1lb of rotating mass you lose = ~7hp. Try ebay also - that kinda stuff is always abound.

Thats the info I was looking for. I'm gonna hold out for a '98 or newer. Yard wanted $100 for the '97. I guess it's a back-up if I can't find a newer one.

Double post.

Called a couple trany shops and they said if its not leaking, the bushing and seal are probably OK...

So off to the junkyard I went. Got a DS from a '97 Camaro. It has a dampner on the yoke end. Not sure if it was really a '97 or not. Don't really care. Pic is below. Let me know if that's not a dampner but it sure looks like one to me. And it was only $100. Brought it home, cleaned it up a bit and put it in. OPTEST SAT.

Now the bad news... The vibration when the RPMs are up is back. Not as bad as before, but back. I think the DS vibration was covering it up and the rubber mount just didn't transfer the vib to the frame like the poly one did. I get the vibration really bad in 3rd gear, but is noticable at about 85mph and up in 4th. Since it is RPM related (after about 2700 RPM), It has to be engine or trany. Right? Reading the other post, I guess I have to pull the trany out and run the engine up to speed. The guy at the salvage yard said the 3rd gens have inherent problems with out of balance torque converters also. True or not?? Don't know. Would be a good reason to buy a TC and shift kit though.

Let me know your thoughts.

Don't know if this applies to you or not, but after I dropped my 9 bolt for a new pinion seal, I got a vibration just as you are having. Somebody suggested I put the pinion yoke on out of phase with pinion. So I give it a look and my pinion yoke has a counter weight spot welded to the outer perimeter. So just for giggles I rotate it 180 degrees and no more vibes. I don't know if it is in the exact same place as before but it must be close.
Before everyone second guesses me, I wasn't a total idiot by not marking the relationship of the yoke, pinion and nut because I measured the total rearend pinion preload with an inch pound torque wrench and put it back to this same measurement.
I don't know if 10 bolts have balanced gear sets with the yoke but I know my 9 bolt is.

The other owner didn't have the knowledge to pull the rear end. The reason I got it so cheap was that he couldn't change the fuel pump and power windo motors. That and I haven't pulled the rear end apart. I did install a Spohn torque arm, but did check the pinion angle.

Since I posted the original thread, I pulled the intake to fix a coolant leak. While at it, also replaced the fuel injectors. When I got it back together, it ran like new and the vibration was gone. Believe my problem was clogged injectors the whole time.

Zig