bad rumble from transfer case

[lovetoski]

I'm sure I need to rebuild my transfer case, but have noticed a noise lately that might indicate more than a simple rebuild.

This noise sounds like rumbling, or maybe like marbels. Can be very rough sounding.
1. It happens only in 4W High.
2. Cannot hear in 1st, can hear quietly in 2nd, pretty loud in 3rd, sounds like somethings going to break in 4th.
3. Noise only when transitioning from on the throttle to off the throttle, or vice-versa.
4. Noise lasts for 2-3 seconds, then silent until next change in throttle.
5. No metal flakes in gear oil.
6. Transfer is full of oil.
7. Both front and rear output seals are intact, and the bearings feel tight. Maybe a little wiggle in the rear output, but none at all from the front output.
8. There is a noise in 4L, but it's different. Sounds like it's trying to come out of gear. The 4L noise only happens under high torque situations. (All engine mounts and tranny mounts are intact.)

I can't tell from the FSM what might be the problem. What I think is that a gear is loose on a shaft. When the load changes direction, the gear walks on the shaft a bit until something stops it. But hey, I'm just taking a flyer...

I know it will be obvious when I pull it apart. But it's a DD, and if it's obvious in advance what additional parts I'll need (besides the standard rebuild kit) then it will reduce the down time. Or, if this noise means it's really badly worn, I'll scrape up the $ for a rebuilt one.

Thanks in advance for any input!

 

[dogboy2]

i'm calling a bad bearing on your output shaft. since you only hear it in 4wd, my guess would be the one that services the front output shaft.

a bad bearing may feel tight, but still be shot. it will sound exactly as you describe, especially when you throttle on or off. if the t-case is not exercised in 4wd on a regular basis, half of the front bearing sits submerged in gear oil, the other half recieves none until the case is engaged in 4wd and gives it cause to spin. over time, the exposed part of the bearing will corrode and eventually fail, hence the owner's manual recommendation to drive in 4wd monthly.

been there done that,
hth,
-dogboy- '87 FJ60

 

[foxtrot4elk]

Hey guys. My 1st time on this board. Awesome amount of info everyone has contributed. I've learned more about my cruiser in a week of lurking here than I thought possible!

I have the same rumble,only mine is in 2wd, going down hill @ hiway speed & ease off the throttle. Not bad but its there. u-joints hav been in a long time so I'm changing them but have a feeling mines in the transmission.
Thanks to everyone for a great board!
Brett Flodin

 

[brett76]

Hey guys. My 1st time on this board. Awesome amount of info everyone has contributed. I've learned more about my cruiser in a week of lurking here than I thought possible!

I have the same rumble,only mine is in 2wd, going down hill @ hiway speed & ease off the throttle. Not bad but its there. u-joints hav been in a long time so I'm changing them but have a feeling mines in the transmission.
Thanks to everyone for a great board!
Brett Flodin

just posted this in another thread on here but thats classic differential in need of rebuilding from what i hear and have experienced


also lovestoski- you been catching any of that awesome powder at crystal lately? its phenomenal

 

[60wag]

lovetoski - You might take a peek in the PTO cover hole before tearing it down. I doubt you'll see anything obvious but its worth a try. It might be a bearing on the tcase output shaft but I think its odd that its different depending what gear you're in.

 

[Cruiserdrew]

A rumble is a classic bad bearing sound. If I had to guess, it's your pinion bearing in your rear diff, especially iif it's loudest off throttle.

Check the magnetic drain plugs for metal. If none, you have a bit of time to plan your rebuild(s).

The rear diff/pinion bearing thing is very common. Check for off-axis play at the diff and at the t-case. Also look for seal leaks, which can indicate the bearing is on it's way out.

 

[lovetoski]

Hey guys,

Good info and suggestions. I didn't really understand that a rumble would be such a clear sign of bearing failure. Good to learn something new. Since this happens in 4W only, I'm pretty sure it rules out anything regarding the rear diff, or the rear output bearing.

This would leave the front output bearing, or the front diff. No leaks from either. Good question though about why the noise changes with gearing...could it be as simple as it's related to the speed of the driveshaft? Higher gear = higher speed?

Second question - can I replace a transfer case output bearing w/out a complete transfer case teardown? As in, can I do it laying on my back in the driveway? Easily? If it's easy and not too expensive...

brett76 - ya, I've had some awesome powder days at Crystal! One of them ended with a seized air pump on the drive home though! No biggie - a powder buzz powers through any little thorn...

 

[Cruiserdrew]

Second question - can I replace a transfer case output bearing w/out a complete transfer case teardown? As in, can I do it laying on my back in the driveway? Easily? If it's easy and not too expensive...

Make absolutely sure it's the t-case before you go tearing in there! You could rebuild the whole case in situ, but to do the bearings, you will have to split the case. If you are going to do that, rebuilding the entire case is only about 15 extra minutes-that's no joke.

Look very carefully at u-joints, and your differentials as a source for the rumble.

Put some heavy weight gear oil in the t-case (85w-140) and see if that quiets the rumble, if so, it probably is the t-case.

 

[dallen341]

I would consider pulling the front drive shaft and see what happens. I believe you said it happens in 4HI only. You can quickly eliminate the d/s as the culprit this way. While you have the d/s off, check the pinion on the front 3rd for slop/wear. I'm guessing the rumbl;e might be d/s bad or out of phase.

Don