Vibration. NEED HELP

[sideways03]

I am trying to figure out a problem that has been haunting me for a while now. Here are the details:

Symptoms:

• Bad vibration around 80+ (before recent rear end rebuild the vibration came on around 45mph)
• Rotational clunking noise (can't tell if it's from trans or rear end) when NOT under load. When clutch is in it is much more prominent. Clunk is dependent on speed of car. Was there before rear end rebuild also.
• BAD humming noise from 30mph+ ONLY when under load. As soon as I let off the gas it goes completely away. Hum was not nearly as bad before gear install.
• Driveline seems to have excessive slack in it. Was there before rear end rebuild also.

Recent Attempted Fixes:

• Set pinion angle
• Tried 2 driveshafts
• Rebuilt rear end: brand new gears/bearings/housing
• Tried 2 sets of wheels/tires, current setup was just balanced
• Transmission rebuilt

PLEASE SOMEONE HELP. Give me ANY ideas you might have. I want/need to fix this so I can enjoy the car!

Only things I can think of now are:

• Bad install on the gears
• Diff was the only thing not replaced, so maybe it is bad (detroit trutrac w/ <10,000 miles) and needs to be replaced as well.
• Some sort of transmission issue?
• Not sure if there is more than one problem here either.

Thank you.

 

[speedofsound]

Does the noise get worse when going around corners? My gut says diff or gears.

On a side note, this is probably the most well written help thread I have ever seen. :beer:

 

[4a7191a]

drive shaft ? the frpp aluminum one is nice , it got rid of a vib. on my first mach1

 

[sideways03]

Does the noise get worse when going around corners? My gut says diff or gears.

On a side note, this is probably the most well written help thread I have ever seen. :beer:

I haven't noticed if it gets worse on the corners, I will pay attention next time. I think I am with you on the rear end though. The installer said I can bring it back and he will redo the gears so I guess I will see if that fixes it. I am wondering if I should be on the safe side and buy a new diff too. At this point I don't even care about an extra $300 for a new one. Would like to be able to sell the old one if it doesn't have any problems though.

As for the help thread, I am getting livid with this issue and not being able to drive so I put as much effort as I could into this thread, lol. I hate long winded all over the place posts. So my goal was short and nothing but facts. :beer:

drive shaft ? the frpp aluminum one is nice , it got rid of a vib. on my first mach1

I've tried 2 driveshafts and 2 sets of u-joints. The one that is on there now is a PST carbon fiber DS.

 

[OrangeMach23]

I haven't noticed if it gets worse on the corners, I will pay attention next time. I think I am with you on the rear end though. The installer said I can bring it back and he will redo the gears so I guess I will see if that fixes it. I am wondering if I should be on the safe side and buy a new diff too. At this point I don't even care about an extra $300 for a new one. Would like to be able to sell the old one if it doesn't have any problems though.

As for the help thread, I am getting livid with this issue and not being able to drive so I put as much effort as I could into this thread, lol. I hate long winded all over the place posts. So my goal was short and nothing but facts. :beer:



I've tried 2 driveshafts and 2 sets of u-joints. The one that is on there now is a PST carbon fiber DS.

What brand gears did you install? The reason I ask is I know there have been past issues for some people when setting them. I have heard that there are certain brands other than FFRP that are known to roar! Did he reuse the factory shims or did you install a new shim kit?

 

[4valvemach]

I am trying to figure out a problem that has been haunting me for a while now. Here are the details:

Symptoms:

• Bad vibration around 80+ (before recent rear end rebuild the vibration came on around 45mph)
• Rotational clunking noise (can't tell if it's from trans or rear end) when NOT under load. When clutch is in it is much more prominent. Clunk is dependent on speed of car. Was there before rear end rebuild also.
• BAD humming noise from 30mph+ ONLY when under load. As soon as I let off the gas it goes completely away. Hum was not nearly as bad before gear install.
• Driveline seems to have excessive slack in it. Was there before rear end rebuild also.

Thank you.

Do you have any play at the transmission tailshaft?what slack is in the drive line, front to rear or up down side to side
Is the humming noise more from the rear or the transmission area?fold the tops of the rear seat down on your next drive
Was friction modifier added to rear end when gears done?
A bad pinion bearing will cause a LOUD howl/whine and goes away when throttle is taken away.