8 3/4 rear went in a few weeks ago, new leaf springs.... I had the driveshaft cut and re-balanced...put 1" lowering blocks under the rear (figured it would sit too high with the new leafs...it sits perfect for me now)... But now i have a vibration/growl from 40-60mph, faster it goes away, it's a constant one, not pulsing... had nothing of the sort before the swap... also, i put in 3.55 gears, which changes my rpm range, but before I could do 70-80 and there was no vibration...

i'm thinking that the lowering blocks are causing the pinion angle to be off... i haven't checked it yet... Front B/T joint is good, greased up. New U-Joint in back....

Incorrect pinion angle can cause vibration, but I would also check the modified driveshaft for runout and balance.

64 Convert has a good suggestion, I swapped to 3.55 gears and they broke in fine, but I get the same vibration and going down some steep grades I get a little whine and clunk depending on the side of the teeth the gears are pushing on each other(coast vs. power).

Recently a discussion came up in another group about the gear manufacturer's have different 'softness' in their gear material. My are Richmond gears I believe, but I've heard some stories about the Auburn ones being a bit softer (and some race sets are very soft...)

Are the gears new, or are they 'transplants'?

-D.Idiot

the gears are used, i don't know the manufacturer... vibration is there with power ON and coasting, also it's there in neutral...

also, the rear U joint has only the grease inside that it came with, i didn't squirt any more in the zerk fitting... but i don't 'think' that this would cause the vibration...

My dart had a vibration afte I put in the ss springs. They made a big change in the ride height and changed the pinion angle. I flipped the front spring hangers to lower the car and that vibration went away
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I don't think that a 1" block would affect the pinion that much.

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My 63 Valiant
http://www.readersrides.com/rides/class ... aliant.htm
<img src="http://www.readersrides.com/slant6-02.gif"/>

Sometimes a simple step can resolve a driveline vibration. Try removing the straps on the rear U-joint, rotate the shaft 180 degrees and reinstall.

yeah, i've heard about that one... i'll try that first, then see about the angle thing....

oh, here's something else... when i purchased the chunk the yoke on it had a stripped out hole for the strap bolt, i tried taking the yoke off and changing it but the damn yoke nut was too tight (had a 5' bar on a breaker, with axles locked and something felt like it was going to snap) So i drilled out the strap hole and re-tapped it with a course bolt, a little bigger than the other bolts. So one bolt head is 7/16" and the others are 3/8"... i don't think there is much weight difference in the bolts... but this "repaired" yoke might cause the vibe... watcha think?

I doubt the bolt change would cause a significant out-of-balance condition, but it could contribute to an already existing condition. You might consider replacing the strap and installing a heli-coil in the stripped out hole.

the guy that I bought my Valiant from had it cut and a spline installed. The shop that did the work (I was told) didn't balance the driveshaft when they were done, so I would need to get it balanced. You can't tell, until you drive the car over 65.

- A buddy of mine sugusted that I put 2 or 3 hose clamps on the driveshaft and just get them snug... drive the car fast and the hose clamps would move to the right spot to balance the shaft. Tighten them up and it's a cheap drive shaft balance job.

I haven't tried it yet.. I'll let you know when I do.

Joe

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My 63 Valiant
http://www.readersrides.com/rides/class ... aliant.htm
<img src="http://www.readersrides.com/slant6-02.gif"/>

It's almost gone, the vibration is about 75% better since i flipped the U joint 180 in the yoke. Now it's more of a little growl between 50-60 then it smooths out... could be the pinion angle, could be the bearings in the chunk... still have the 1" lowering blocks installed....

I don't get this. Is this problem with a pickup truck? I don't recall ever seeing a spline on the driveshaft of an early '60(and later) Mopar pass car. If this is some kind of a 'farmer' job, you definitely wouldn't put a spline on the rear of a driveshaft! There's way too much slop in any spline(let alone a used one), to have it back by the rear axle.
OK, reread postings. We've got two different apps going, I see, now.
I think Thropar has pretty much figured this out. I would be inspecting that driveshaft pretty carefully, if it's out that much. I, also think the quality control is pretty spotty on these driveshaft shops!

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

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