rear diff noise

[the1991mazdaguy]

searched and found somethings that sounded similar, but not the same. I have new u-joints, just to clear that up.

when accelarating, i get thise loud whining noise from the rear end, and when i let off the throttle and coast down (5 speed manual BTW) it makes a grinding/whining noise. I replaced the wheel bearings and the pinion bearings to no avail. the carrier bearings were replaced with timkens before i got the rig.

this noise is just so strange. it was sudden. it didnt let on, it didnt slowly start getting louder, it just came out of nowhere. i jacked it up and used a stethescope to listen for noise and it gets really loud when i put it on the diff cover. is my backlash F'd up or something? help please. this is a very loud and unsettling noise.

oh, and all of my new bearings are timkens too, so dont need to ask if i used POS made in china bearings. I'll never do that again.

oh, and is the amount of fluid in the diff critical? at my shop we have a program called alldatapro.com and spec says fill no higher then 3/8 below fill plug. why is that?

 

[the1991mazdaguy]

come on, i'm pretty sure someone out there knows something.

 

[Anime]

Is it a limited slip diff? If so, you may need to add friction modifier to the gear oil. Not doing so will cause a lot of problems with the clutches, eventually leading to wear and probably failure. Make sure to use the correct gear oil, too. Specs could be for either 80w-90 or 80w-140 (or 75W-90/75w-140).

The reason for it needing to be slightly below the fill plug is actually so the fluid doesn't seep around it. But it's also good for the diff fluid to be at that level and not under/overfilled, since underfilling wouldn't give enough lubrication and would create more heat, and overfilling would create unnecessary drag on the gears and not give enough space for them to work as designed within the fluid.

 

[the1991mazdaguy]

Is it a limited slip diff? If so, you may need to add friction modifier to the gear oil. Not doing so will cause a lot of problems with the clutches, eventually leading to wear and probably failure. Make sure to use the correct gear oil, too. Specs could be for either 80w-90 or 80w-140 (or 75W-90/75w-140).

The reason for it needing to be slightly below the fill plug is actually so the fluid doesn't seep around it. But it's also good for the diff fluid to be at that level and not under/overfilled, since underfilling wouldn't give enough lubrication and would create more heat, and overfilling would create unnecessary drag on the gears and not give enough space for them to work as designed within the fluid.

its not limited slip. 3.55 open. i ####ed up the ring and pinion gear when i got pissed off one day and dropped the clutch in reverse. went to the junk yard and got lucky. got a virtually brand new rear axle, ring and pinion gears on it have almost no wear.

gonna swap axles this weekend. thanks for the tips though. knew LS diffs need that additive, and i would like to go limited slip, but there is no 3.55 LS so people already told me i would have to change the front gears. dont know why i couldnt just change the ring gear on a LS diff and put it into my housing.

 

[the1991mazdaguy]

so, got the axle swapped. super easy. 3 1/2 hour operation, replaced the brake shoes, bled brakes, adjusted. good to go. i dont know what was up with that old axle, but my rear ABS never worked since the day i got the rig. My rear ABS works now with the new axle. couldnt figure it out.

 

[Tony H]

you failed to mention you basically knew what was wrong wit hte hrear. you hosed the Ring and pinion.
That info was important to share when asking the question.

 

[the1991mazdaguy]

you failed to mention you basically knew what was wrong wit hte hrear. you hosed the Ring and pinion.
That info was important to share when asking the question.

yes, yes i did xD i just completely spaced it, and my grandpa was trying to talk to me about things i could have done that would have ####ed it up. i dont remember how we got to it, but the conclusion was damaged the ring and pinion. but, now i have an even better looking rear diff, the only thing is i had to skip out on getting rear disc cause the junk yard wanted an extra 100 dollars that i didnt have.