Hi lads,

i have some vibration in my rearend (no not haemmoroids). Only appears when driving between lets say 55 and 65.
The wheels/tryes are new and balanced.
the axles, housing, diff is new
the gearbox is new
driveshaft length is ok
It doesn't matter what gear i'm in (happens in 4th, 5th and neutral)

I guess through isolation the only thing left is imbalanced driveshaft. The driveshaft i got was used from 66 automatic. it looked good, but before I take that for balancing, does anyone have another idea of what it could be?
I couldn't think of anything anymore

Kalli

 

I would start with checking balance on tires and wheels. Sounds like a axle issue to me. Can you get someone to follow you? They might help you see the issue.

 

Try rotating the driveshaft 1/2 a turn in the mount at the differential. See if that makes any change for better or worse. The driveshaft and companion flange may have an imbalance and SOMETIMES this can help the issue.

Also try putting a couple of large hose clamps on the driveshaft and drive it and see if it improves or degrades. Keep the two worm gears aligned together when you tighten them. This is like adding small weights to the shaft. Rotate them around the shaft and drive again, check vibration. Repeat as necessary.
This is kind of a poor man’s driveshaft balancer but it might prove or disprove an out of balance driveshaft.

 

hiya blue66mustang... thanks a lot for that info
I've seen what you mean with the clamps in the shop manual. I'll definetly give that a try.
the diff is brand new and the shaft used. so i don't guess turning the thing will help much (i've heard that they're sometikmes balanced together). I'll def try the thing with the hoseclamps or just bring the shaft for balancing. I've seen they mention as well doing this with a bit of chalk with car driving in gear to find the spot (i guess you know what i mean)

rbrown: wheels and tyres are new and balanced. I know that wheel imbalance in the front can be annoying at steering wheel, but i don't think it could have suc h a massive effect on the rear. Anyway if i can't sort it with the driveshaft, then it's back fro re-balancing.

 

i'll bet it's your u-joints, i had that problem over 55 and went away when i got new u-joints

 

My money is on drive line (balance or u-joints) or bent axle.

You can check the axle real easy like I did.

Remove brake drum

take a solid object like a brick and tape something ridged to it I think I used a framing square. This whole thing sits nice and steady on the floor with the framing square sticking up towards the ceiling/sky

now take a pointed object and tape it to the square so its point can touch the axle flange. you want it to touch the thin side not the face. (so if they tire was on it, the pointed object would be facing the tread of the tire...like running over a nail)

have the point just touch the axle flange and rotate the axle and watch to see if the axle flange pulls away from the point....if it does thats your runout and it must be less that .004

basically we just made a real crappy dial indicator...but real cheep and fast too and it works.

-Gun

 

hmmm. u-joints are new, but maybe i fried them with the bad pinion angle i had in the past.
the rear axles shouldn't have any problems as I'd go berserk otherwise. they're brand new moser axles
So I have a plan for now. balance the shaft and change u-joints. i'm quite sure that should sort it ...

thanks all !