1961 CJ3B "Gator"

[Shark49]

Transmission question.  I have an overdrive on my 3 speed.  Works great.  However, when I am driving and I let off the gas it often shakes and rattles.  Is that a bad bearing?  Under throttle it's fine if a bit noisy.  I emptied and replaced the gear oil.

[Rus Curtis]

How did you determine it was the OD?  Have you applied tension (forward/rear/side-to-side) to each shifter to see if the rattle changes?

[Shark49]

I was just stating I have an OD.  The shifters rattle but its like a whole tranny thing when I lift off throttle and then reapply it will vibrate whole jeep

[Rus Curtis]

Ok.  How about shifting out of OD into direct drive.  Same?  This is in 2WD, right?

That description also makes me wonder about your U joints.  Especially when you say it vibrates the whole jeep.  May be hard to twist by hand but another way is to jack up wheel and turn the tire back and forth.  Watch the yokes to see if there's movement between the yoke and driveshaft ( both - at the transfer and differential).  This works for front or back. Lifting both wheels on an axle will just get the other wheel spinning.

If you can rule out the U joints, there may be some other things to look at.

[Shark49]

YEs 2wd.  yokes are brand-new but ill check that. 

[Rus Curtis]

Also check phase.

[SteveKfl]

QUESTION... When did you start noticing it?  Was it after any major "changes", or "incidents" (like off roading)?  Pinion angle too extreme, bent drive shaft, worn gears in transmission or OD, etc.

[Shark49]

No big changes just getting it on the road for my first time.  The transfer case handles rattle some but there's something else going on when alifting off throttle and then back on with slight throttle the whole things vibrates

[SteveKfl]

This may be a strange question, but.. Are all of the tires the same size and condition, or if not, might it be that when you take it off "load" and then power back the differences "translate" back thru the tires to the drivelines trying to "catch up" at different speeds or conditions (like balances, tread types, wear factors, alignment, etc)?

[Shark49]

all the same and radial tires at that.  Im going to check all of the mounts etc. for loose nuts.  But it feels as if something is off balance but under load it's fine.

[SteveKfl]

Can you recreate the vibration with the vehicle up on "Jack stands under the axle housings" for FREE WHEEL spin and proper "ride position"... spinning the wheels with load and "no load"... and with the assistance of a helper make observations that way from underneath?  Maybe see if just one axle does the vibration, or elewhere, like a drive shaft, or the tranny itself.