What are you guys using in the rear axle? I've seen various references from all over the internet, from 75W-90, to 85W-90, to 85W-140, etc. The owner's manual isn't much help; I think it said that fluid changes were not required. Mine's a '97, but I think all 2nd gen Dakotas had the Corporate 8.25" rear, yes?

I've got a slight singing noise from my rear axle, and only in a certain road speed range (40-45 MPH). Only when lightly loaded, light throttle. At heavier throttle or closed throttle, the noise isn't there. It's probably either a bearing or worn gears (168,000 miles), but I'd like to pull the cover to have a peek...or at least get some fresh fluid in there.

No LSD on this; just a standard open rear. Recommended oil weight?

Thanks.

 

i dont know what fluid you need but i can tell you that my truck has the same exact singing noise at the same exact speed. I can also tell you that it has been doing it since it was brand new so Im not worrying about it.

 

i have had the sound since it was rebuilt

 

Oh really??!! That's interesting (both posts). I once had an Oldsmobile with a distinctive rear end howl, but it was constant, and would increase in volume and pitch with speed. This doesn't do that -- it's only a light singing, and only in that certain speed range. I may change out the fluid anyway (BTW, I did find that it's 80W-90, at least according to Alldata), but I'm at least glad to hear that this may not really be a destructive problem.

Thanks to you both for your replies.

 

i had them put 75w-90 in mine haven't gotten it back yet from getting rebuilt tho. sometime this week my dad should get it then ill have it on friday when i come home from school. Daks also came with the corporate 9.25 not just the 8.25.

 

My 04 owners manual says to use 75w-90, unless you tow, then the thicker stuff. Recently, on a differential service I found metal in my differential, "a keeper for the posi", pretty common from the posts on here. They rebuilt it under the warranty, and since getting it back, I have a very slight whine that appears exactly like you posted. I took it back to the garage, and they said all is OK ? I also took it to a local transmission shop for a second opinion, and he said it may go away after it gets broke in, but probably won't. He said you have to take the time to shim everything just right, but the garages shim everything to the factory service manual, so, sometimes you get this little whine. I guess it would be a pain to have to drain the differential and remove the rear cover and re shim until it was quiet. He felt as though everything was OK.

 

my buddy put a new rear in his grand cherokee and he was telling me about having to shim it. he said they took it about and respaced it about 3 or 4 times till they got it to were he liked it. i believe it has to be within like fractions of an inch.

 

i went to the dealership in my town and they have this additive ($55) that you add to the oil change in teh real and it will help lock the differental when you hit teh gas hard he said it was like a posi cuz he has it in his dakota and he can do 2 wheel burnouts and slide the truck sideways when he turns...and my truck has 176,000 and i dont hear any sound coming from the rear end at all.....i also have a strait pipe exhaust and cant hear much as it is already

 

thats the LSD additive, it wont do you any good unless your truck already has an LSD.

 

Advance Auto parts has it for a few bucks if you need it.