Bad vibration on my 4x4

[70 GMC 4x4]

I just swapped out axles on my 4x4. The rear axle housing is pointing down where the drive shaft hooks on rather than level or elevated a hair. Could this be the cause? The drive shaft is stretched to the max. Could this be the cause? When driving if you put the truck in neutral the vibration goes away. WOuld a bad rear end produce a vibration or would it just make a lot of noise? Any help would be great.

Thanks,
Tim
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[Gunny]

being pointed down will cause vib's - I just went through this on my Cherokee, made a couple of tapered spacers to line the axle up better in relation to the transfer case - and I dropped the trans/transfer case down 1 inch. - it is also recommended that whenever you do any type of driveline mod that you change the u joints also.

you will want to take care of it as soon as you can - with the driveshaft being at the max if you hit a bump too hard or jump on the gas you might drop it (I know this from experience LOL).

a couple of other things that will cause vibs are:
mud/dirt on the axle side of the tire rims and a tire out of balance

Gunny

[70 GMC 4x4]

Gunny,

The axle housing on the rear is just the opposite of the front. The front is almost level with a little elevation. The rear is only 6 inches from the ground. I had a 3/4 ton set up and went to 1/2 ton for a better ride. I remove some of the leafs on the rear and I think that change the arch of the spring. Which will not allow the rear axle to bolt up the springs the way they should.

Thanks for the info. I think you are correct. How bad was your vibration?

Thanks,
Tim

[Gunny]

Originally Posted by 70 GMC 4x4

Gunny,

The axle housing on the rear is just the opposite of the front. The front is almost level with a little elevation. The rear is only 6 inches from the ground. I had a 3/4 ton set up and went to 1/2 ton for a better ride. I remove some of the leafs on the rear and I think that change the arch of the spring. Which will not allow the rear axle to bolt up the springs the way they should.

Thanks for the info. I think you are correct. How bad was your vibration?

Thanks,
Tim

to even it back you can get a piece of 1/4 inch steel (a old leaf will work) cut it to match the axle purch and then grind it to a wedge shape this will make a tapered shim.

My vibration when I added 2 inches to the rear (to even out the lift to 6.5 front and back) was a real loud humming, which you could feel through the shifter (would make your hand numb), sounded like the whole rear was going to blow up.

I just made a 250 mile trip today with it (first road trip since I eliminated the vibes last week) and it did not have any vibes at 80 mph.

[70 GMC 4x4]

I was able to tilt the drive shaft up roughly 2 inches to the correct angle. Guess what the vibration went away. Thanks to all you replied.

Tim