01ssreda4

iTrader: (96)

If your driveshaft is oriented correctly where the fixed u joint is pointing down, this gives you the driveline angle. That flat surface doesn't look level to me and I wouldn't trust it regardless, why would you when the correct way is 6 inches away.

Sam Strano

iTrader: (41)

I hate to say it, but just adjust it around and see if you get it gone. I had a guy show up here years ago after having been to the other side of the state having an adjustable TA put on. It shook so badly and he was pissed.

I looked under the car and could clearly see the diff pointing down. I got it in the air and changed it, took an educated guess judged by looking at the diff vs. the driveshaft. It was better. Did it once more, took a little more angle out and it was cured. No measuring, nothing. The installer "measured" and screwed it all up. The guy was originally bend at me for doing it that way, but once I fixed it and told him I could care less what the number someone came up with was, he was happy.

Kevin97ss

Hey, sorry to hear you're still dealing with this. Just want to give you a heads up, that is NOT a good place to measure from.

I see the driveshaft shop is trying to help you out but you need an inclinometer or a small digital angle finder. What tool are you using?

Legal Tender

I felt compelled to bump this thread. I have dealt with many of the same issues other users have posted. I upgraded parts expecting performance gains but ended up getting horrible drivability with vibrations in the driveline. I tried lots of stuff to reduce the vibration including axle bearings, u joints, drive shaft replacement, transmission rebuild ( which the car needed anyway), rotated wheels, measured driveshaft run-out, and more. I did a series of modifications in the beginning of the season 2 years ago including new engine mounts trans mount, Tunnel Mount torque arm, 3 point subframe connectors, and a panhard bar. The car has been a double D powered ***** since then.

Simply adjusting the pinion angle in relation to the DS did almost nothing. The car was running 4.10s which amplified the problem and made it a miserable pos to drive at more than 60mph.

After finding this thread and doing a bit more research, I was hopeful there would be improvement. I purchased the digital angle finder that is linked in the thread and went to work.
It takes some patience and attention to detail to get the correct readings, but once you have it it's easy to make these adjustments.

I'm happy to report that the car is totally different to drive at speed now. It's very smooth under hard acceleration and I feel almost no vibrations until 85. I had been driving with these vibrations for so long that I subconsciously correlated the vibration I felt to the speed I must have been going. Now I end up looking down and seeing 10 to 20mph more on the speedo than I expect. The car also feels like it coasts a little smoother too.

I plan on making one last tweak after a few more miles, I think I can get it a little better yet. I'd say I reduced the vibrations by 75%!

This was a 94 z28 t56, with full tubular UMI suspension front and rear, ALL poly bushings, Denny's HD driveshaft, 3pt SFC bolted in, and a tunnel mounted torque arm. Stock springs, sway bars, and bilsteins all around.

2JAWZ

iTrader: (1)

Ive been in the same boat and I know this is def gonna be good help**

2JAWZ

iTrader: (1)

Have any definitive answers been found on this yet? I believe that Sam Strano has one of the best approaches yet. Adjust,, and re-adjust until its good! I agree that numbers are gonna do you no good as every car is just a slight bit different from every other car! Im in the same boat but being I have no where to get my car in the air I guess its going to the pro's*

KStornadoes

How difficult is this procedure to perform? I ask because I had my slave cylinder replaced three weeks ago and ever since I have been getting the same bad vibrations at 70-80 mph. My mechanic doesn't do a lot of work on these F-bodies and I want to be 100% clear on what I am talking about when I take it back in to him. He seems to think that "All F-bodies have that kind of road noise at highway speeds" which it definitely did not before I got the slave cylinder replaced. Follow up question, I'm getting a noisy rattle right underneath my stick shift (Is where it sounds like it is coming from) between the RPM range of 1500-1900, only under load in any gear (also started after replacing the slave cylinder.) Does not do it in neutral. Thanks for the help guys!

1hotroc

I just wanted to please inform all you guys that after reading all your driveline angle issues and vibration complaints it puts me back to an unhappy place. After all your driveline angles are checked and within spec. Don't overlook a collapsed motor mount. Just make sure they are ok by jacking up slightly under the pan with a block of wood of course! Obviously determine if your vibe is there with or without spinning the driveline and wheels on jack stands. Try to duplicate vibe then apply jack pressure at that given moment when its happening. I spent hours and hours and insane amounts of money swapping rears, trannys, trans mounts, torque arms, driveshafts! No correction! It ended up being a slightly collapsed cheap p.o.s Left Chinese engine mount the whole time! Car was a third gen Iroc but principle remains the same for our 4th gens! After reading this Im scared to death to lower my 99 HOSS! I was entertaining the 1.2" strano kit with bilsteins or the AGXs but don't want to open up pandoras box of vibrations! r Right now she rides like glass but really don't like how high it sits. Any good suggestions on best route for this mod? Do I really need the rear lower control arm reloc brackets and adj panhard with the lowering kit? Thanks

FirebirdStud

iTrader: (5)

What fixed these vibrations?
I am very curious what your angles ended up being: working angles specifically.