I have an '87 Sammy with what I THINK is a noisy rear differential (could be transfer case?*), and was told that I could simply remove the entire FRONT differential carrier from the axle and bolt it into the REAR axle, and I would have a low-use "new" one for just the labor of swapping them.

Obviously, the front one gets at most 5% of the use of the rear one given that most Samurai miles have been highway miles w/ the front hubs unlocked.

Is this true, and has anyone actually done it successfully?

Bob
*At first I was told the noise was transmission, but I switched to LO range, and the noise was not present until reaching the road speed of 35mph, where the whine started in HI range, so the noise is ROAD SPEED related, and not engine or transmission output RPM related.
I am losing faith in the "experts" advising me.
The noise is a whine on pull, and howl on coast, worst in 4th and 5th gear above 35mph, though appears to be more speed dependent than gear dependent.

4th and 5th gear noise is commonly bad trans bearings, the T-case is not part of the
transmission system so it still could be a bad trans.

One easy way to tell is to pull the rear drive and take the trucklet for a spin in front wheel
drive and see if the noise is still there. Be very careful driving in front wheel drive, the front
doesn't seem to drive as well as the rear, spins easily

Wild

I have an '87 Sammy with what I THINK is a noisy rear differential (could be transfer case?*), and was told that I could simply remove the entire FRONT differential carrier from the axle and bolt it into the REAR axle, and I would have a low-use "new" one for just the labor of swapping them.

Obviously, the front one gets at most 5% of the use of the rear one given that most Samurai miles have been highway miles w/ the front hubs unlocked.

Is this true, and has anyone actually done it successfully?
 

The sidegears are different spline between front and rear diffs.  So you would have to change the sidegears to match, if you wanted to swap a front third (diff) into the rear, or vice versa.

4th and 5th gear noise is commonly bad trans bearings, the T-case is not part of the
transmission system so it still could be a bad trans.

One easy way to tell is to pull the rear drive and take the trucklet for a spin in front wheel
drive and see if the noise is still there. Be very careful driving in front wheel drive, the front
doesn't seem to drive as well as the rear, spins easily

Wild

That's what I was first told, but if it WERE my transmission bearings, wouldn't the whine have occurred in LOW range at the same engine RPM in LOW range as in HIGH range since the 4th and 5th transmission output rpm would be the same in either range?

In my case, the whine is occurring at the same ROAD speed in both transfer case ranges, and the only things rotating that the same rpm in different T/C ranges, but at the same road speed, are the transfer output shaft and the driveshaft and axles?

I am not against rebuilding the transmission (since I have a noisy input shaft bearing I can hear in neutral with the clutch engaged, but goes away with the clutch disengaged), but I would like to eliminate the whine first (if it's NOT the transmission).

I may have located a front axle from a wreck for $100 that has bad hubs and spindles (is that reasonable?), but hopefully a good gear set. That would mean less disassembly of my OWN Sammy. If I read it right, I'd only need to swap the diff end gears from my rear assembly to the donor assembly, then install the donor assembly complete in my axle housing?

Bob

The whine is load and speed related, otherwise you would hear it all the time regardless of the
gear you are in, so the only way I can see to easily check if it's the diff or trans is to isolate one
of the probabilities, which should save you time and money, and the other noise is the throwout
bearing, and will go for a while, the pilot bearing is so small they don't make enough noise to hear

Wild
 

The whine is load and speed related, otherwise you would hear it all the time regardless of the
gear you are in, so the only way I can see to easily check if it's the diff or trans is to isolate one
of the probabilities, which should save you time and money, and

the other noise is the throwout bearing, and will go for a while, the pilot bearing is so small they don't make enough noise to hear

Wild
 

I agree that load enters into the whine, though trying to increase the load at lower speed doesn't seem to increase the whine. It is inaudible below about 30mph regardless of load, and is roughly equivalent (maybe slightly louder in 5th in high range) in all gears and transfer case ranges starting at about 30mph.

I like the idea of removing the rear driveshaft and driving it in 4WD (front wheel drive). That would eliminate the rear differential from the equation (but not the transmission vs. transfer case). That should take only 20 minutes to remove the rear shaft, too. I think maybe that's the next thing I should try, as it may tell me something useful. I once did this w/ a Datsun truck I was flat towing (since the rear shaft was removed for towing and I needed to reposition the truck), and it drove really badly, with HUGE torque steer, but I should be able to get up to speeds where the noise was loud in RWD.

As far as the bearing noise you identified as the throwout bearing, I seriously doubt it is that.

The conditions when the noise is present are with the clutch engaged (foot off clutch) in neutral, and the throwout isn't spinning at this point (if the clutch cable is properly adjusted).

The noise goes away when the clutch is depressed and when the transmission input shaft coasts down (maybe 2 sec after clutch is depressed). It's also quiet with the transmission in gear and clutch depressed. Under both of these conditions, the throwout IS spinning.

Beside, I changed all of the clutch components when I had the engine out for rebuild only 100 miles or so ago. The noise was identical w/ the old and new throwout and pilot bearings, though with the clutch engaged (foot off clutch) the pilot bearing is also not rotating.

As far as not hearing a pilot bearing, I had a Corvette once with a dry throwout bearing, and it started "chirping" like a bird with the clutch disengaged (foot on pedal), but was silent otherwise. Before I replaced it, it was a steady loud squeal w/ the clutch disengaged, easily heard over the engine and exhaust noise. The clutch was only 50% worn-what a PITA to pull the tranny just to get in there to replace replace a pilot bearing (what really sucked was that I replaced the whole clutch kit thinking I was doing a good deed, only to find I'd gotten a defective NEW pressure plate, necessitating pulling the tranny a SECOND time).

I'll report back in a couple of days after I do the "rear driveshaft removed" experiment.

Thanks,
Bob

Ahh, I misread your post on the other noise, but I will say, now knowing you
changed the clutch, that it could be the trans input shaft bearing, furthering
my first thought that the trans bearings are going bad

Wild