High Speed vibration, can't find what's causing it.

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MopaR&D said:
One thought I had is the rear leaves could be starting to wear out and allowing too much axle windup (dynamic pinion angle) when on the throttle since OP mentioned it goes away when letting off
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calvert split monoleafs. 1 year old. I would think axle windup would be worse with more torque in 1st and 2nd gear. I think it is mph related.
 
I read you didn’t change pinion angle, have you checked to see if it changed? I think 1 and 2nd wouldn’t linger in the “bad” rpm as long.
 
Did you inspect the driveshaft for dents or missing weights? I agree with others, if it was fine before and just started your slicks need re balancing.
 
justinp61 said:
Did you inspect the driveshaft for dents or missing weights? I agree with others, if it was fine before and just started your slicks need re balancing.
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Yes inspected everything after the transmission tailshaft. Slicks balanced coming next.
 
I bought one of those 50-60 year old bubble balancer for the right price years ago. But to do my 14 inch slicks I bought a Harbor Freight balancer as I couldn’t do my slicks on my other one. If you pre level the balancer right it works great. I have to do that job when I’m fresh because by yourself it’s a little tricky.
 
pittsburghracer said:
I bought one of those 50-60 year old bubble balancer for the right price years ago. But to do my 14 inch slicks I bought a Harbor Freight balancer as I couldn’t do my slicks on my other one. If you pre level the balancer right it works great. I have to do that job when I’m fresh because by yourself it’s a little tricky.
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I have a tire sponsor who is going to put them on his machine for me.
 
I don't know if you can go to test and tune but try shifting into neutral right when it starts see if it goes away...if it does its trans forward if not its in the drivetrain etc. come up with a way to pinpoint. after that listen feel for frequency if the vibration is with the speed of the wheels etc.
 
Dartswinger70 said:
I don't know if you can go to test and tune but try shifting into neutral right when it starts see if it goes away...if it does its trans forward if not its in the drivetrain etc. come up with a way to pinpoint. after that listen feel for frequency if the vibration is with the speed of the wheels etc.
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Thanks but I would have to back off the throttle to shift from 3rd all the way to neutral, and simply backing off the throttle causes the vibration to stop so there would be no need to shift to neutral at that point.
 
RockinRobin said:
Thanks but I would have to back off the throttle to shift from 3rd all the way to neutral, and simply backing off the throttle causes the vibration to stop so there would be no need to shift to neutral at that point.
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Yeah you are racing that method I described is probably more low speed and RPM etc. Do you think its misfiring at all? or maybe engine/trans or driveshaft back?
 
Dartswinger70 said:
Yeah you are racing that method I described is probably more low speed and RPM etc. Do you think its misfiring at all? or maybe engine/trans or driveshaft back?
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Not misfiring. The symptom is not rpm related it is mph related. Only happens after 90 mph and stops as soon as I get out of the throttle.
 
well Im sure its been said start with wheel balance then drive shaft then out put shaft bearings, pinion bearings axle bearings etc. driveshaft and or axles could be bent or twisted un fortunately you wont know till you start checking things...
 
This is speed AND load related. That being the case, I cannot see these parts being the problem: wheel/brake balance, bent axles, axle brgs.
 
There are even some published procedures using hose clamps on driveshafts. I think it was likely in the Mopar chassis book, and maybe other places.
 
"simply backing off the throttle causes the vibration to stop" says it is torque related and not a balancing issue. I'd really be looking at U joints, pinion bearings, trans mount very closely. I'd think you'd know if the engine was missing.
 
I believe a torque converter that's going out can shake/vibrate upon acceleration.
 
pittsburghracer said:
It’s just not a popular way of doing this job.
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Popular or not, balance beads work. You never have to worry about balance weights falling off or having to use gorilla tape to keep them on. The tire re-balances itself every run... You wouldn't use them in a Top Fuel car but for every day vehicles and some drag cars they are great. I have them in my slicks and the street tires for the car. It's all personal preference but they are an option to using weights that like to fall off...
 
RSM said:
Popular or not, balance beads work. You never have to worry about balance weights falling off or having to use gorilla tape to keep them on. The tire re-balances itself every run... You wouldn't use them in a Top Fuel car but for every day vehicles and some drag cars they are great. I have them in my slicks and the street tires for the car. It's all personal preference but they are an option to using weights that like to fall off...
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Ok you do it your way and I’ll do it my way. I’ve proven to myself at 160 mph my way works.
 
pittsburghracer said:
Ok you do it your way and I’ll do it my way. I’ve proven to myself at 160 mph my way works.
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I never said you had to do it my way. Why do people get so butthurt over comments? It's dipshits like you that give a site a bad name...
 
As a former driveshaft builder, check runout near each joint and in the center,at joints it shouldn't be more than .010
 
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