Vibration at 80 mph

[automate33]

Hi guys,

i have dodge challenger RT 1971 340 with A904 and original drivetrain and i have vibration at 80 mph
Tires and geometry of the car was controled, but always vibration at 80 mph.
Is it possible that this vibration comes on the yoke?
What do you think?

thanks!

[GoodysGotaCuda]

What do you mean by the tires and geometry of the car were controlled?

Certainly the driveshaft is the first thing to look at. Old joints, out of balance, improper pinion angle. Then there is also the rear axle and transmission outputshaft that can contribute as well.

[sadil340]

Will be following this thread!

Been chasing a phantom vibration for 30 years. Engine/trans/rear end rebuilt, new clutch throwout bearing pilot bushing u-joints and front yoke. Axle/driveshaft trueness and pinion angle checked. Still there.

[Racer57]

I have a similar problem and I'm starting to wonder if maybe the rear brake drums (front disk) might be out of balance. They appear to probably be the originals or at least that old and with dents on edges from being dropped, rust and brake surface being machined kind of makes me wonder. New costs about $35 each so when I get around to it I'm getting new.

[Chryco Psycho]

are the ires round ? seriously , BFG usually are not !
 Check U joints , rear trans bushing

[Chryco Psycho]

It could be driveline angle too check the video above

[automate33]

It could be driveline angle too check the video above

I will controle driveline angle, My challenger rear raise some

[RusTy/SE]

Try this..

Next time you're approaching 80mph, slip the trans into neutral. If the vibration continues, look to the suspension. If the vibration stops, look to the drivetrain.

I may have that reversed - can someone verify?

I'm curious though. You mention original drivetrain - didn't all 71 340 motors get backed up by the 727-A rather than the 904?

[automate33]

Thanks for tips!
Exactly, my original drivetrain was 727 but he was changed in 76' following a problem.
I will try your tips this week end!
Thanks

[RusTy/SE]

Cool, others with a much better working knowledge than I have will likely chime in to further pin down the cause.

 

[sadil340]

Try this..

Next time you're approaching 80mph, slip the trans into neutral. If the vibration continues, look to the suspension. If the vibration stops, look to the drivetrain.

I may have that reversed - can someone verify?

I'm curious though. You mention original drivetrain - didn't all 71 340 motors get backed up by the 727-A rather than the 904?

You have it right.

The strange thing about my vibration? If I approach 70 or 80 and push in the clutch then release it quickly the vibration goes away. It's like something self centers during that process.

[HP_Cuda]

I'd pull the driveshaft and take it down to a shop that can run it up and see if there is any balance issues.

If so, you can correct them right then and there. Unfortunately it's a process of elimination so if you want to start from the cheapest and go to the most expensive that is also another way to go.

[automate33]

I'd pull the driveshaft and take it down to a shop that can run it up and see if there is any balance issues.

If so, you can correct them right then and there. Unfortunately it's a process of elimination so if you want to start from the cheapest and go to the most expensive that is also another way to go.

I have to control with a laser. if I put the laser flush the underbody, rear, I have compared to the prior 4 cm difference. is this normal? I think this should be level. no?

[HP_Cuda]

Sometimes seeing imperfections in the driveline require putting it on a machine and measuring how far out of balance is necessary.

You can try all the cheap items first like: u-joints, wheels, tires, etc...

[dodj]

I eliminated most of my vibration issues by raising the rear and running the car in first gear. Need two people to be safe!
By doing this I found one wheel was slightly wobbling. I took that wheel off and found the axle flange had been tweaked. Replaced the axle and solved the majority of my vibe issues.
Still not perfect, but a lot better than it was.