rpmauto

iTrader: (14)

I dont know for sure yet, i am grasping at straws. A few weeks ago i put a set of 4.11s in my strange 12 bolt, everything is in spec. The only thing i was not able to check was pinion depth in relation to axle centerline(dont have the tool for that) So i just reused the shims under the rear pinion bearingfrom the 3.73s. The next day i got to take it out for a little longer drive and it started grinding going into 5th and has a pretty good vibration in 6th gear only. (above 60mph)

So i figure synchro was out of 5th and maybe something went through 6th to make the vibration. Has to be fixed so i pull the tranny. Havent got it back in yet to verify, but the only and i mean only issue with the tranny was some burrs on the back side of the 5th synchro. Will have tranny back in later this week.

I just cant for the life of me figure out what would cause a gear specific vibration. ONLY in 6th. I dont think it is possible to be the rear end, it doesnt do it in any other gear at any mph or rpm. I also wouldnt think it to be the driveshaft for the same reason, (Shaft was new this spring and is a PST unint from EPP.) But i dont know. I marked the driveshaft this time and i will put it in the opposite way and see what that does.

Does anybody have any other ideas on what would cause a gear specific vibration??

cherryelky305

iTrader: (2)

if its gear specific, I would say its a trans problem. if you can get to the speed it vibrate's in 5th or 4th, and there is no vibration, then your driveline should be fine, must be something specific to 6th gear, a bearing maybe (but not the output shaft bearing that would cause vibration in all gears.)

alamantia

iTrader: (10)

Rotate the driveshaft 180 degrees in the pinion yoke and try it again. Worth a shot.

rpmauto

iTrader: (14)

yea, that is what i am going to try. I figured that it had to be a trans problem, being only in 6th. It just stumped me when the only think wrong in the tranny was the 5th/6th synchro. And oddly enough it happened the day after i put the gears in. Before i had zero issues. Obviously it is pure coincidence. What are the odds??

cherryelky305

iTrader: (2)

well its unknown if the gears are set up properly since you put the original shims in but it could be close, but the pinion could still be out of spec. it just depends it guess. if its not making noise is might be ok.

rpmauto

iTrader: (14)

yea, that is the only possibility in the rear. I have reused shims on tons of rear ends i have set up, but i am usually not changing the gear ratio. The backlash is perfect, and the pinion preload is perfect. I wanted to use the 2 piece solid spacer that the 3.73s had instead of a crush sleeve, but they didnt send any shims in the master install kit. I have the nut and pinion marked and nothing has changed.