growl/vibration at steady speed

'56 cj5 f134 t90 (from a truck with the lower first gear) d18 (from a '67) dana 44 10 spline. 2 1/2 inch lift. t/c crossmember has 2 quarter inch spacers and there's a small degree shim in the rear springs. makes a growl or vibration only when at the "sweet spot", neither accelerating or decelerating. give it gas or let it off and it stops...any ideas?

 

pinion & carrier bearings will do this as well. really wouldnt call the noise that they make a growl though, more like a low pitched whine. sometimes they will go for years and years like that. and just like you said right in the sweet spot is the only time you ever hear it.

 

What gear is the transmission in when this happens? If a higher gear like 2nd or 3rd then I'd suspect driveline/u-joint vibrations cause by angle issues.

 

the higher the speeds the worse it seems. definitely not a whine but like driveline vib. at 50 the whole jeep rattles so much its hard to talk. at 25 in 2nd not nearly so bad...but still there.

 

is the slip yoke clocked to match the other end?

 

yes, learned this lesson with another jeep...

 

Can you pull your degree shims out?
Took my rig to the wizards at MIT (http://www.mit4x4.com/) for other issues and they informed me about the (POs) shims. They removed them to correct driveline angle.

 

The one time I had this type of issue, it turned out to be tight yet wasted u-joints.
They were all powdered rust and chewed needles

 

i heard this one other place too. i put the shims in when i put the springs in without really knowing if i needed them. might as well take em out and see what happens...

u joints definitely old. does one test u joints somehow to see if they're bad?

 

When the driveline is installed check for play. The best way is to remove driveline and check for tight or loose spots in the u-joints when moving them in the range of movement. It should stay the same. If you have easy then tight movement it could mean worn joints. Have you measured the u-joint angles? I'd still start there.

 

one other thing to check, that the slip yoke is free and not bottomed out in either direction. if it is when the springs flex it will put unwanted preassure on the bearings/ gears in both the transfer and diff's

 

you could jack up rear of jeep from pumpkin ,neurtal, and spin by hand ...lok for tight spot .I say angles off or of bad joint .if they are greasable -apply grease run around town real quick and check again

 

removed degree shims and it made a world of difference. still there but much better...

 

Get a cheap angle finder from Harbor Freight or Sears and check the angles between the yokes and drive line. This is called U-joint angle or installed angle. Compare the two. They should be close to equal. Within a degree or two at most. I like to see no more than about 3-5* of u-joint angle as well. The less the better. Any more and it could be causing your problem.