Mike2000Z28

Yeah so far I have been in a serious chase to figure out what is going on with my rearend vibrating at 70mph. I just replaced both axles, wheel bearings/seals, I had 3.73s and all the bearings professionally installed, and I have a brand new aluminum driveshaft installed. Now the car has gotten noticeably better after each install but once 70mph I have a slight vibration. The pinion angle is dead on and at speed under 70mph the car is like silk. Are the tires bad or the rims bent? If so shouldn't they be able to tell me that when someone tries to balance them? Also is it easy/any different to get the u-joints replaces in aluminum driveshaft then a steel one.?

I just can't keep throwing money at this problem.

Mike2000Z28

Having the tires rebalanced this weekend. Has anyone had problems with their street tires after doing some racing at the strip?

Mr_president

iTrader: (38)

i have the same problemmm grrrrrrr well ever sence i put the new 9 inch in ive been have a badd vibration!! what is your pinion angle set at??

Mark98SS

iTrader: (1)

I had a pretty good vibration at highway speeds on decel when the pinion angle was past about -4. I got it that way trying to cure wheel hop with the street tires & 17" DRs so I decided to bring it up just enough to get rid of the noise/vibration. It's probably about -2 now & no wheel hop on the 17" tires as long as I don't let it spin too hard in 2nd or 3rd. Of course with the 15" ET Streets wheel spin is not as much of an issue.

Mike2000Z28

mine pinion angle is dead on from what Mike from New Era said. I just don't know whatz giving me the vibration, its silky smooth till about 70mph.

Mike2000Z28

After wheel balancing I still have a vibration. I might have to go get another set of u-joints (third time) on the new aluminum shaft. I get up to 70mph and all hell is going on in the rear. I might pull the shaft this weekend to do the joints, but I hate to only to have them get wreck in another week. I have replaced everything in the rearend (bearings, axles, seals), balanced the wheels, I'm at a lose. HELP.

99PontTA

pull the carrier and have it balanced...its worth a shot.I just had a new auburn carrier installed and now i have a slight vibration...only thing that was replaced was the carrier so i know its the trouble.....its getting pulled and replaced.I also had a 87 GTA ta that had the heavy cone clutch type carrier that vibrated above 70 mph....drove me buts...tried all sorts of things but never tried balancing the carrier...Its the heaviest rotating *** in the rear so i think its a good thing to look at if you have tried all the obvious.Another thing i found helped was moving the driveshaft 180 in the yoke.Also try using two large worm clamps on the driveshaft torwards the rear end to change the overall balance of the entire driveline.you can easily move the clamps away from each other in a circle (the heavy screw part of the clamp is enough to change the balance)to change the balance and quickly see any results.Then if you find it helps its easy to make the changes.

ramairws6

iTrader: (33)

The question is did you ever crack or break a tailshaft? If so, I would say your tranny outputshaft is probably bent. I had the exact same problem as you, after 70 MPH it would start shaking, and I replaced everything I could think of. No luck! Then I heard about bending output shafts and checked mine, and sure enough it was bent! Just a thought?! Traver

Mike2000Z28

ramairws6 how hard is it replace the outputshaft on my tranny(I didn't notice any rings on the old shaft when I pulled it a while ago)? Also do you think that the poly tranny mount that I installed causing the problem?

99PontTA

another thing most everyone overlooks is the drive shaft thrust angle.There are two angle to consider,the pinion angle and the same thing applies to the thrust angle.If you looked from the top down over the trans and rear you will see there is a angle involved..its not perfectly straight...the trans and rear offset angles must add up the same way the pinion angles do or you will get the same vibration.

Mike2000Z28

How can I measure it to get the right position?

99PontTA

like i said its the same as the pinion angle only you are checking it on on a different plane...look at it like this..look down through the car as if you were superman( i know this sounds crazy)now look at the engine-trans center line as it sits in the frame.So you are looking straight down...now look at the center line of the pinion shaft THOSE ANGLES GOTTA BE CLOSE TO EQUAL.Another way to look at it is the pinion angle you set by raising or lowering the engine-trans or raising-lower the rear...the trust angle is changed by moving the engine center line right or left or the rear pinion centerline right or left. If you have a modded rear suspension i'll bet the trust angle is way off.It just as important as the pinion angle...it has the same effect on the driveline.

Not to confuse you but the engine-trans -rear center lines don't need to be inline with each other....only the angles need to be equal...geez i hope this makes sence to you.Example would be the engine-trans center line could be dead on center of the frame....the rear pinion shaft center line could be 1 inch off center of the frame.BUT they both need to be at equal angles to each other.

On more way to look at it to take the car and flip it on it side and then look at the drive shaft angle.

ramairws6

iTrader: (33)

The trans will have to come apart to replace the outputshaft.I bought a used one for $30.00 and it worked out real well. Traver

5.7LoFuN

iTrader: (1)

mike i have the same problem it sounds like... i recently got my car lowered with all sorts of new install items. STB, SFC, PHR, LCA w/ relocation brackets, shocks, springs and all of it proff. installed. and it was all done in stages and the last thing i had done was put on the wheels and tires (i bought wheels used) then the trouble started. the vibration started out at all diff speeds but i have had the wheels and tires balanced 3 times and its settled in right about 80-85 and gets worse the faster you go. All the people i talk to say that if there was somehting wrong with the wheels it would show up when you balance them so i have no idea what could be the source of this vibration. any thoughts or suggestions ?

Mike2000Z28

Ramairws6, I might have to go through that over winter if the angles are off.

99PontTA, I appreciate the examples, I understand exactly how to measure the angles. Thinking about it I might have pull the poly tranny mount cause there was a metal bracket with kit that may have messed up the angle. However I believe that driving around to much may have wrecked the output shaft. Either way I have to start measuring and take it from there.

99PontTA

can you feel the vibration more in the rear or the frt? Even though a wheel-tire is balanced it can still vibrate from too much runout or a slighty bent wheel or a tire deforming under load ...all kinds of strange things can happen.I've noticed when tires get worn past half tread you start to feel everything in the road.I had a slight vibration in the rear with a little bit of a thumping noise...sure enough it was one of my 160 dollar BFG tires..its about half worn and when we pulled off and checked it for balance it was perfect BUT its running a little out of round...that all it takes.You can try using air to see if its the tires......running them a little low will smooth things out....running higher air pressure will stiffen everything.Usually tires that are out of round or balance you can feel right down to a stop...but not always.

I'm gonna give you an example of how things can change.I had a new carrier installed,I get the car back and it had a slight vibration at all speeds and a terrible rumble in the driveline if you let off the throttle @ 45 mph....it felt like the DS was loose or worse something in the rear.We checked the DS ,it looked fine and was in the same index as before the carrier was replaced.Luckily all we did to fix the problem was change the DS index 180 degrees.NOMO vibration or rumble @ 45.I would have never expected this to change just because we replaced the carrier,but the overall balance and interaction of parts changed.The old carrier was a Torsen...the new a Auburn.The driveline acts COMPLETELY different now.Also my steering acts different now...it drives like a 60's muscle car instead of a 99 TA.

So you can imagine the changes you might have if you replace suspention parts...i just woke up and cant tyope or think hpw to spell so no wire cracks

i noticed the factory use very soft bushings on these cars in the rear ...must be for good reason to try and soakup vibration and give you a smooth ride...change all that stuff and its normal you'r4e gonna have some vibrations....nothing wrong with that....don't think a small vibration is gonna hurt anything.

Mike2000Z28

I am going to check the angle of the tranny first then check my u-joints second. Since I just had my tires rebalanced I think I will wait for next season when I get the car out of storage get new rims and tires, if the angles and the new drive shaft I put in doesn't show to bad of wear marks on the tranny output end. Since I have rotated my wheels also I don't see a difference in vibration, so I don't think its just the tires or rims. I am almost 100% sure the ujoints on the new shaft are gone.

CrimeSScene

iTrader: (9)

Shot in the dark, but I just had some vibration issues at exactly 70 mph and above. Don't know exactly what kind of vibration you have exactly, but I just moved my exhaust and it was slightly touching my axle where it was going over it when under load at that speed and above. Moved the exhaust back about 1/2 inch and vibration went away. I could actually tell a difference in vibration between 5th and 6th gear though. Probably nothing to do with your vibration, but thought I would mention it.

CW00BlackTA

iTrader: (31)

I've been dealing with a similar issue ever since installing a Ford 9 inch. I'm still not done. The one thing that's made the biggest difference was replacing the pinion yoke. I had about 0.006 runout which caused vibration as low as 50 mph. After changing the yoke, I'm good up to about 75.

I've already had the driveshaft rebuilt and balanced by the best shop around, adjusted the pinion angle 18 different ways and gone through a handful of u-joints. The vibration in mine is located somewhere in the center section. That's coming out next for an inspection.

Mike2000Z28

I have been thinking about changing that out but since I have been going through ujoints left and right I really want to check out the tranny angle and see what is going on their.

As far as the exhaust, could be a problem. Right now the driveshaft/vibration is starting to cause the Ypipe hit the heat shields. Until I can get the time and the car up on a lift/stands, I am starting to think cause of all the time the vibration has been around that I might have to replace the output shaft on the tranny along with the pinion yoke.