To speeds of 50mph and below I can hear a noise similar to what tires would make on different road surfaces(a roar). After searching for the problem, a local shop has determined that the rear differential is the problem. I was advised to change oil in differential going back with a synthetic 140 weight oil and maybe adding some type of additive like Lucas.

This truck is two wheel drive, has 65,000 miles on it, standard tranny(6speed) and as far as I know has only pulled a camper trailer and smaller cow trailer. I don't know the history of the truck since I bought it used with 30k miles on it.

Will 140 weight oil make the differential run hotter than say a 90 weight oil?

This seems early to be having rear end trouble out of this truck. Any advice would be appreciated.


Thanks

 

I believe spec is full synthetic 75w90 with 15k change interval, but folks who tow heavy in hot climates often run 75-140, as I do.

The AAM limited slip system isn't supposed to require additive. I asked Redline about that, and they said using oil with additive wouldn't hurt anything and may actually run cooler.

The dif cover has a reusable rubber gasket. Don't over torque the cover bolts. Also full is something like 3/4 below the fill plug. Later dif covers have a full line stamped on them.

If it is making a serious roar, I doubt fresh oil will help.

Anyway, welcome to the forum.

 

They are very easy to disassemble, before doing anything, look inside and get back to us.

 

I agree to open it up and tale a look. If everything looks good, I'd try a tube of trans-x posi additive in it.
Most noises associated with the posi, that I know of, are all at low speed take off.
But it's an inexpensive first step.

 

Ok problem was the carrier bearing. The race was starting to "peel". Replaced the bearings with a kit and filled with Mobil 1 75w90 synthetic. Noise free.

Thanks for the responses. I still would like to hear ideas on why with just 65k miles this bearing failed. I talked to several others running 3500 Rams that haven't had any trouble with bearings with 150k plus miles on vehicle. I guess I may have just had a defective bearing.

 

A carrier bearing that early is a fluke, but not totally unheard of.

From the description- roaring, I was wondering if that would be it.

Anyway, thanks for posting back.

 

Defective bearing could be. I have close to 170k on mine with a lot of towing and high HP drag racing and other abuse. I've had no issues.

The AAM axle may not be the perfect axle, but reliability is not one of the shortcomings in general.

 

Isn't the carrier bearing supporting the two piece drive shaft?

That's where I believe my noise is coming from at 70k miles.

 

Good point. Missed that it prolly has a 2 piece drive shaft.

 

That's generally considered the steady bearing, or support bearing. The differential has two carrier bearings that support the carrier, and two pinion bearings that support the pinion shaft.