So I've gotten my Jeep back on the road, after my engine swap, and am now trying to track down a noise. The noise was there before the swap, so I don't think it's related to that. It seems like a rubbing type noise, coming from somewhere under the truck. It seems like it's coming from from the rear, but I'm not positive. The U joints in the drive shaft don't have any play that I noticed, and I just greased them this past weekend, and it made no difference. I checked the rear brakes, and they rub on the drums a tiny bit, but the sound doesn't change as brakes are applied, so I don't think it's that. The sound is most noticeable under acceleration, and seem to go away when I let off the gas, but then it comes back again just as I'm about to come to a stop, so from around 10mph to 0. It isn't really a continuous sound, and by that I mean it's like it pulses, instead of being a constant rubbing noise, kind of like when you have a flat spot on a tire. I can also feel it slightly through the floor boards. Anyone have any ideas what I should check first?

 

Could be your tires rubbing on the leaf springs... If you have bigger tires, and the wrong backspacing on a wheel...

 

Factory wheels, 235/75/R15 tires.

 

ring and pinion

 

I would take the drums apart, and look for something unhooked or rubbing.

 

"The sound is most noticeable under acceleration, and seem to go away when I let off the gas.."
ring and pinion

 

Already did, everything was connected like it should be.

 

Assuming that's the issue, is it worth trying to fix it in the D35 I have, or should I plan to pick up a C8.25 from the junkyard?

 

Then do what he said and check for a roasted pinion bearing or maybe some slop somewhere in the gears...

 

first of all check the play, apply hand brake, put in N and turn the shaft.
if it's less than 1/2 inch, and u don't drive on the highway, get a carton of grease and squirt in the diff. will last another couple of years.
if it's more and u drive on the highway, u have a wide choice:
new ring and pinion
new diff
new diff with locker
new(scrap) d35 (check ratio)
new(scrap) c8.25 (ratio)
new(scrap, if ur very lucky) d44 out of a '87 (solve ratio problem later)
I don't know what is cheaper where u live, i would upgrade to a locker.

 

ah, in case of another axle, check also if it has ABS or not...

 

Ok, I'll see about checking that when I get a chance. It's not my daily driver, and while I was driving it recently, I've stayed off the highway mostly because of that noise, so most driving was around 35-45 mph.

As far as axle costs, the junkyard I usually go to doesn't differentiate between the different axles. All they care about is if it's front or rear, and how much brake hardware is on it. I believe a rear axle with everything except the drums is like $120. Last time I checked they had a good number of 8.25 equipped Jeeps in there. There were a few D35s, and I didn't see any D44s. I think there may have been a D44 Commanche, but it looked in bad shape, and I think all the hardware had been taken out of the rear end.

As far as ABS, mine has ABS, but it doesn't work. It's the Bendix 9 system, so at some point in the near future, I plan to change it out for a standard system anyway. Should I just get a non-ABS axle and not worry about it?

 

no, u need the phonic wheels on the semi-axes and the sensors in the drum plates, actually i think c8.25 came all with ABS, check for the sensor wires clamped on the tubes and get also the drums, check also the pinion u-joint measure, don't buy a cheap axle and then spend money to make it fit.
I've done this before, it's impressive how many things come out different when u compare them.
So if u have the patience to do all this, go on, otherwise just take a d35 and wish it has the same gear ratio ( u could actually calculate it by counting how many turns does the shaft make to make 1 complete turn of the wheels), and u can always use ur semiaxes and brake stuff.
ALL THIS, in case the noise comes from the rear, cause if it slightly comes also from the middle, could be the t.c., probably the chain or it stayed in 4wd full time, (np242 right?), check, check, check...

 

Interesting, I'll have to look and see what i can find next time I'm out there. It's possible it's the TC (yes, it's a NP242). Any input on how to check that? I changed the fluid on it this past weekend. Nothing seemed odd with that. It didn't even seem like it was terribly old or anything. The sound doesn't seem to change when I put it in 4WD from what I remember. I can check it again. There's a couple of good straight roads near my Dad's house where I can put it in part time 4WD without having to worry about binding anything up.

 

The np242 uses the same ATF fluid of the transmission, due to the central lockable differential, and usually makes some noise (normal) when the lever is in 4wd full time, it sometimes happens to me that when u shift back to 2wd the 4wd stays engaged until u back up or make some tough turns. Check if u are in 4wd by lifting one front wheel in park, it won't turn.
To check the chain play, put it in 4wd low, park, lift both front wheels and turn the shaft. Same story of the half inch (up to 1 inch is ok too).
What else could it be... bearings on the rear, bearing on the output shaft of the tc, these are usually accompanied with a leak.
Check the rear bearings by raising one wheel, start the motor, put it in first gear 2wd, apply a little brake and give a little gas, (a little, or u will take off!) don't bother the limited slip diff, it probably isn't working at all, let the wheel spin and listen carefully. Repeat for the other side. If none or both make the noise, it's not the bearings.
How was the oil level in the rear? if u have a limited slip diff like i think u need the additive. There is a little plate bolted on the cover that says limited slip diff.