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The problem, a vibration. I get it above 40 mph and is bad at 90 to 100 mph or more. The vibration seems to be from the front seats back. The things I tried already, had all the tires rebalanced, still had it, had drive shaft rebalanced, still have it, tried different set of rear tires, still have it. What could it be?
Why I think it is not in the front, no shake at all in the steering wheel. I don't think it is in the transmission, the shifter doesn't shake.
Could it be in the rearend? Had it rebuilt about a year ago with new gears and all new stuff. The guy who did it knows what he is doing. I just don't know, and it is driving me nuts.

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When you say rebalanced drive shaft, I'm assuming the U joints were checked and are correct. Typically a vibration at a higher speed but not felt at lower is U joints.

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Just cruising along minding our own business when BAM!!! The LAWS show up.
Sorry, new spicer u-joints put in when the driveshaft was rebalanced.
Also have a polyurethane trans mount, could this be the cause?

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Possibly, but I wouldn't think so. I have poly trans./stock motor mounts in my '90, works fine.
Check motor mounts also.
Is it just speed dependent or RPM/load dependent ?

Pete - MotoArts Decals and Signs
'71 Sportsroof 351C-4V/4-speed - FINALLY under construction - no, wait, on hold again...
'90 Mustang 7-Up 5.0 ragtop, rolling beater
'66 Sunbeam Tiger Mk.IA, survivor
MotoArts, put on new ploy- motor mounts when I put the trans mount on.

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Afraid it's time to pull punkin.

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Just cruising along minding our own business when BAM!!! The LAWS show up.
Dang, that rearend only has about 500 miles on it. What do you think ring and pinion not set right?

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Tell you what you can try crazy as it sounds. Raise the rear and support it. Try the old screwdriver to the ear while someone rotates the back wheels and see if you hear anything. I'd check it at the rear of ring and pinion and as close to the wheels as you can get to safely. I use my stethescope from my old EMT days and it has helped on occasion. May be able to narrow it down before you do a lot of work.

[Image: 2rr7aiv.png]

Just cruising along minding our own business when BAM!!! The LAWS show up.
Are you running Magnum 500 wheels? if so make absolutely sure they balance the wheels off the lugs NOT off the center. It's hard to find a shop that knows how to do them right.

Check your driveshaft angles, both from the side and the top. If the angles are off it can cause vibrations. Check your pinion angle. Is your yoke into the transmission far enough? It should be about 1/2" from bottoming out at normal ride height.

Polyurethane can transfer more vibration to the chassis amplifying the feel.

I'm not sure on the rear gears, I've had them howl but not cause a vibration. Unless it's a bad bearing I would look elsewhere.

Jeff T.

Low buck, touring style, '73 Convertible "rolling restoration", 351c, 2v heads with a shave and a haircut, Performer intake, Holley 650(ish), roller rockers, screw in studs, guideplates, stainless valves, Duraspark / Motorsports MSD, T-5 conversion. 1-1/8" front, 3/4" rear swaybars KYB shocks and some home brewed subframe connectors. Future plans; JGC steering box, Cobra brakes and... paint, interior, etc.

When I die I want to die like grandpa, peacefully in my sleep... not screaming, like his passenger.

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Great ideas from Markmel and Droptop. Both suggestions are spot on. Chuck
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