After more than a year of rebuilding, modding and replacing parts on this beast, the one part of the equation I didn't look into yet is the rear dif. Now that I finally got her on the road and up to speed, a distinct growl can be heard from the rear end when over about 25mph, it can be heard while traveling at a steady speed and while speeding up/slowing down. Drive shaft has fresh U-joints, axle bearings do not have any noticeable play. Even though I didn't hear this growling before starting the resto, I have gone to poly bushings which may be more effective at coupling the noise into the chassis.

Questions:
1: Is this growling consistent with the dif gears failing/wearing out?
2: Am I better off rebuilding the rear end or finding a good replacement assembly? Rebuild would consist of new gears, setting the lash, and new axle bearings.

Thank you,
jorrell

i too, have a growl in my '82 242. more like, it sounds like the driveshaft is going to come through and break my pelvis. too much tire spinning on my part maybe? my first 82 had the same thing, and though i never remedied the first one, now my "new" 82 has me really disheartened. i think it may be the center bushing where the driveshafts connect to eachother... but i dont know where to get a replacement or how much they cost. then again, i dont know how much play the center bushing should have when you push and pull on it. good luck, and long live the 240's!

Keep in mind that this car sat for a year without moving. I managed to put 40 miles on it today and by the end of it, the growl was gone! Based on this, I jacked up the rear end and pulled the back cover off the pumpkin. Fluid was low but not empty, and more interestingly, half of the ring gear was rusty... probably the half that was sticking out of the lube while it sat for all that time.

Reinstalled the cover, filled it up with fresh fluid and voila no more noise! I'll probably repeat this again over the weekend to make sure all the misc. crud is out of there, oh and yeah, I'll have to replace the pinion seal which is leaking like a sieve! Nope, didn't overfill it.

Thanks for the input folks!

jorrell

superman's dad,

sounds like either rear wheel bearings or the center bearing holding the 2 drive shafts together.

Andy, owner 4 240's over 20 years

Many years back a weird differential noise appeared on my son's car, a 244 DL 1981 with m-46.

We were thinking about bad differential bearings or gears. We let it run like that for a year or two.

It turned out that noise diseappeared after replacing the two rear bushings, the ones under the axle. We used new original ones from Volvo. Harder bushings may transfer more noise to the body as you mention.

Again it is our experience and we found we were lucky we did not rush for an other rear axle.

Good luck, hope you find what is realy there.

These are tough axles. If there is any oil in there at all I would tend to rule out the Gears being harmed. My guess would be to look at the Emergency brake shoes ( as previously mentioned) and then maybe a low oil level caused the outer bearings to run dry.

I know I may catch hell for this but if you can put the rear axle on Jackstands, run the car in drive and get under there with a long screw driver put it on the Pumpkin and the other end by your ear. then do the same by the outside of the axle, you can sometimes listen for a noisy bad bearing.
--
'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me

Before thinking about rebuilding the diff, I would first replace the oil. The diff should make more noise when turning, not driving in a straight line. The old oil should really stink badly if things are not working properly.

Klaus
--
(V♂LV♂s 1975 164, 1995 854T, 1998 V70R)

Jorrell,

I'm not sure if you serviced your emergency brakes yet but its not uncommon for the shoes to become unattached from the metal brackets making for some unusual noise. I believe your 1992 would have an Eaton locker. I've rebuilt a Dana Power Lok easy enough but not sure how servicable the Eaton is. Do you like the automatic with the 3.31's? If not then replacing the rear end with 3.73's might make sense.

Yama:

Thanks for the feedback. All brake components, emergency and service have been replaced. The exception is the calipers that I had rebuilt. The 3.31 rear end ratio, I must say, is quite sweet, I couldn't see changing it unless gas mileage goes horribly down the crapper, the exta "giddy up and go" from a dead stop is worth a few MPG.

Not sure if this is a posi rear end or not. Initially, I had planned on pulling it out and going through it before putting it back on the road, but I decided to try driving it first to see how the ratio works out. In short, I haven't drained the fluid or pulled the cover so I don't know what it actually is. I can say, however, that if it is a posi, the clutch assembly is shot as it feels like a normal rear dif while turning the wheels manually with both of them in the air... Trans in park, turn one wheel forward, and the other spins in reverse.

Thanks,

jorrell

You should actually get better gas mileage less rpm with the 3.31 that come stock with a 5 speed vs the 3.73 that come stock with an auto. Should be really nice cruising on the highway. The Eaton locker is some kindof torque sensing unit not a clutch type like the Dana power lok. I'm 99% sure 1992 was the first year for it. I don't have a hard data but it seems to me that the failure rate for this carrier is higher than for the Dana unit. Your car has ABS so if you do get another axle it will need to be from an ABS car. Different tone ring. 1991 had ABS and the older carrier so that's an option.

Yama:

I didn't realize (ain't put nuf grey matter at it yet) to realize that this thing should be running at lower RPMs. The scary part is that the G-Tech Pro says this thing is now pulling a full second faster in the 0 to 60 range than it did with the M47. That being said, engine has been bored to max, valves upsized, VX cam,intake runner polish and porting plus a few elecrical tweaks. Once I have verified everything, including the G-Tech calibration, I will post a detailed report. Technically, I'm not sure if it will be of much value as so many things changed all at once. At least, it will be a data point.

jorrell