Nasty noise

I have a 61 3B ...stock F-Head T-90 D-18 and Saturn OD. When driving under load no abnormal sounds. When decelerating (completely off the throttle) no abnormal sounds. At part throttle there is a loud vibrating grinding noise that doesn't change even with the clutch engaged. It sounds sort of like its coming from under the drivers seat. Drive shaft slip joint is snug but moves, and both U-joints are tight. I'm thinking intermediate gear or OD. Any ideas?

 

sounds like a bearing failing, only does it when you are coasting? my road tractor is doing the same thing, and i believe it to be a bearing also, does it do it cold or after you have put a few miles on it, like enough miles to get the transmission transfer gear oil warmed up?

 

This noise only happens under light load conditions. It happens when cold and gets worse as it warms up. I'm going to pull the trans/t-case this weekend. I'll post an update of what I find.

 

you can drop the transfer case pan and inspect/remove/replace the int gear shaft/bearings without removing the units
just an FYI

 

I will do that first for a quick look-see but the jeep is new to me and I want to check out the trans. too. Thanks for the reminder.

 

Just so you start with the easy stuff, make sure the slip joint is completely full of grease. The grease should squirt out the pin hole in the plug in the ujoint yoke when it's full.

Also make sure your rear output shaft endplay is just barely noticable (0.004-0.008") ... not sloppy. It could have been shimmed incorrectly (not too noticable at slow speeds).

 

After much gnashing of teeth I found the cause of the driveline noise that I had under light light load conditions. The rear driveshaft yokes were out of phase, ie; clocked 90 degrees to each other! What a simple fix! Too bad I took the trans and transfer case apart without noticing it. Oh well. I hope this will be of help to someone else. Craig

 

Anytime I have seen a driveshaft out of phase like that, It would about shake you out of the jeep!

 

A buddy and I rebuilt his trans case and still had the vibration. We just couldn't figure it out. Then a friend of ours who had gone blind and couldn't even look under the jeep asked if the u-joints were in line. You don't have to be blind, to be blind, I guess.