[garretthes]

I have a 59 Suburban with a transplanted 74 Camaro rear axle. The axle is posi with 2.73 gears. When I swapped it originally I had the pinion angle wrong. The pinion was angled up towards the front while the transmission is almost level. This resulted in some vibration at low speeds under mild acceleration.

After a year of driving it like this I finally was able to change the pinion angle to match the tranny. They are now parallel.

However, the test drive yielded the same vibration, actually a bit worse. It doesn't vibrate under acceleration but as soon as I let off it starts.

Also, a few weeks ago I started hearing some rattling during coasting at interstate speeds. I'm pretty sure the U-joints are OK. I can't get the drive shaft to move at all. So I'm wondering if I have a dying rear axle. It's old.

I'm in the Birmingham Al. are now but should be back in the Nashville area by Monday if you have a shop to recommend.

 

[garretthes]

OK I just re-read the post on pinion/drive shaft/rear drive angle. I wish I knew why I was thinking the tranny and pinion were supposed to be paralel.

 

[poncho62]

I would check the "U"joints anyways....may not have any movement, but could be worn or dry and seizing

 

[NEW INTERIORS]

On all my chevy set up's,, The trans shaft is down 3*, Then I set the rear at 3* up.. Work's great for me.. Now if It's in a drag car I will set the rear a little lower..Hope this help's..

 

[S10 Racer]

What driveshaft did you end up using and did it need cut? May be out of balance. A u-joint can have no play but be bad. I just replaced the ones in my Duramax because they were making a clunking noise. They had no play when I tried checking them but as soon as I took them out, what needle bearings were left fell out on the floor and was rusted. A lot of times a u-joint will make a squeaking sound when driving slow or a clunking sound when putting it in gear.

 

[dsraven]

what i have always done with a driveline vibration that is difficult to find, is first jack up the unit and place it firmly on some axle stands. make sure that the u joints are in good shape, block the wheels, set the park brake, put the unit in neutral and check them with no load on the driveline. check the centre bearing if you have one, check for looseness in the pinion bearing and also the pinion yoke for tightness. check if the ujoint fits the pinion yoke nice and tight with no slop and the circlips are the right thickness for the pinion where it fits. if the trans has a slip yoke check the bushing and slip yoke for slop the trans bushing can wear and allow the yoke to move.. check the axle bearings on both sides for up and down movement, sometimes you need to take the brakes off to do this, or pull an axle to see if the bearing surface on the axle is pitted or peeling off (last case scenario). make sure the ujoints are in phase, especially if it has a 2 piece driveshaft. then have a buddy start it up and run it in gear till the noise starts. (gotta let the park brake off for this one). next i get on the creeper and listen, if possible, to where the noise is coming from. make sure to stay away from the turning parts with any loose clothing etc.check to see if the shaft is straight and not rotating around an eccentric at one end or the other. that would mean it isn't in the centreline and you may have a bent yoke or dirt under a ujoint cap surface where it is mounted on the yoke. you can use a stethoscope or a piece of hose to your ear to help find it. if it still checks out as good you may have to take the shaft off and check each ujoint to make sure it turns easily and it isn't easy in the middle but sticky at the ends of it's travel cycle. this is also a good time to check if any weights have fallen off, or take it to a driveline shop and have it balanced. if you still can't find it then you may have to take the cover off the diff and inspect it for worn out bearings etc. if you had the shaft shortened or lengthened make sure to check the ujoint phasing. they should all line up and each shaft should have the ujoints the same at each end of the shaft and inline with each other.
ok, this is getting long winded, sorry. it is a start though.

 

[RWENUTS]

OK I just re-read the post on pinion/drive shaft/rear drive angle. I wish I knew why I was thinking the tranny and pinion were supposed to be paralel.

You were thinking they should be parallel because in fact the should be parellel.
Are you checking angles with the chassis loaded?

 

[garretthes]

What driveshaft did you end up using and did it need cut? May be out of balance. A u-joint can have no play but be bad. I just replaced the ones in my Duramax because they were making a clunking noise. They had no play when I tried checking them but as soon as I took them out, what needle bearings were left fell out on the floor and was rusted. A lot of times a u-joint will make a squeaking sound when driving slow or a clunking sound when putting it in gear.

We had the drive shaft made.

 

[garretthes]

You were thinking they should be parallel because in fact the should be parellel.
Are you checking angles with the chassis loaded?

I think the problem was the tranny was while I did get the tranny and axle paralel, the tranny was so much higher than the axle it created too much angle at the shaft. I checked my angles while the truck was on level ground and the transmission was level, the drive shaft was at 6 degrees and the pinion was at -3 degrees.
We fixed this last night (all night) and now we have almost a straight line front to back. That is what I missed the first time.
Big mistake but lesson learned.