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Driveline vibration at speed

4

440fish

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Ok. I give up on trying to figure this out. Have a vibration that starts around 70 mph and gets progressively worse with speed. Brand new driveshaft and all associated hardware (yokes etc) Transmission is new and so is flexplate (vibration was there on my old tranny too so that can't be the issue.) Tires are balanced and re-balanced to eliminate that as a possibility. Rear end recent rebuild and it definitely is not coming from that area.

The vibration has a "roll" type of harmonic (almost like a slow pulse) to it which feels like something spinning that is out of balance. Driveshaft was built by a local shop that has been in business forever and has a solid reputation for putting out a quality product. Many local car enthusiasts insist on using their service. This is a completely new shaft that was tested before i picked it up.

This is on my 69 Bee
 
You didn't say what type of tires you have.Try letting the air out of the tires to see if you may have a broken belt. Did this with a Dart.Balance several times,even had the tires machine trued still shook at speed.Swapped all 4 wheels and tires,no more shake. Pulled the valve stem cores and found one with a bad belt. Just a thought.
 
So if it's a 69 Super Bee should be internally balanced. Harmonic balancer flex plate, and driveshaft.
 
Im pretty positive its the driveshaft. My old one was really bad and since I put the new one on it is much better but still does it to a lesser extent. Someone who went through this claimed most shops cant balance for the speeds these old shafts spin with the old school high ratio gears in the rear end? The driveshaftshop.com has a pretty good website that backs this theory
 
Does the angle coming out of the transmission match the angle at the rear axle fairly closely when loaded?? Any mods from stock on suspension height.. etc.
 
dadsbee said:
Does the angle coming out of the transmission match the angle at the rear axle fairly closely when loaded?? Any mods from stock on suspension height.. etc.
Click to expand...

all stock
 
440fish said:
all stock
Click to expand...
Doesn’t matter if it is stock. This is the most likely culprit. You’ll need an angle finder and then measure the angle of the transmission housing and the diff’s input pinion shaft axis. They should nearly equal but opposite. If the trans is pointing up 3 degrees to the rear, then the pinion axis should be pointing down 3 to 5 degrees down at the front.
 
69roadr said:
Balanced properly with harmonic balancer and flexplate and torque converter
Click to expand...
If it's speed related it's not any of these, any of those you listed would create a vibration that's rpm related not speed related. Speed related issues typically start at the driveshaft and end at the tires.
 
One more thing to check. Did you use the original u-joint straps? Make sure the c-clips are evenly spaced and make sure those cups don't move at all in and out.
 
get the TREMEC app on your i phone
you can see what is what.it you can get all angles and it tells you if your off and where
 
My ex '67, had bent axleshaft which was found out by the guy I sold it to. Not real sure how it happened but I had a mild vibration at 55-60 mph at light throttle, went away with more pedal.

Jack it up on all 4's and running through the gears and see if it's bent.

 
What have you tried for diagnosing. Neutral, drift gentle left then right, engine off etc. Put a second person in the back seat.
 
Thanks guys. Ive tried a lot of the suggestions offered but will recheck the angles. I also tried putting it in neutral at speed and it does not go away. It is slightly less when the driveline is not under a load but still there none the less.
 
440fish said:
Ok. I give up on trying to figure this out. Have a vibration that starts around 70 mph and gets progressively worse with speed. Brand new driveshaft and all associated hardware (yokes etc) Transmission is new and so is flexplate (vibration was there on my old tranny too so that can't be the issue.) Tires are balanced and re-balanced to eliminate that as a possibility. Rear end recent rebuild and it definitely is not coming from that area.

The vibration has a "roll" type of harmonic (almost like a slow pulse) to it which feels like something spinning that is out of balance. Driveshaft was built by a local shop that has been in business forever and has a solid reputation for putting out a quality product. Many local car enthusiasts insist on using their service. This is a completely new shaft that was tested before i picked it up.

This is on my 69 Bee
Click to expand...
I recently adjusted my Torsion Bars to lower the front end. Whole car started vibrating at speed 60 and up. We re balanced tires & wheels yesterday found that there might be a small amount of problem with the wheels seemed to balance out ok. Could me lowering the front end via torsion bars have caused this problem to arise?
 
Doubt this is the problem but an easily checked. Check trans yoke to see if rear trans bushing is worn? Should move less than .005? Mine was .013, in my case driveshaft was 1" to short and after 10,000mi beat the bushing.
 
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