Working on my 04 3500 with the 11.5 AAM rear axle. What type of synthetic fluid can I use in place of the $27 a quart factory stuff?

 

I use Castrol 75w90 synthetic gear lubricant. Its API GL-5 rated and has worked good for me. Its much cheaper that the dodge stuff.

 

i use amsoil,changed after 90k and was almost as clear as the stuff i was putting in

 

I have Amsoil Severe Gear 75-90 going in. Used it on my Duramax with great success as well. About HALF the price of the $27 a quart stuff.

-J

 

I've always used Mobil 1.

 

Same here, always use Mobil 1.

 

I have used amsoil, but have changed to mobile 1 , works fine. I also add the additive from dodge for the limited slip, costs about $10 bucks.

 

I have mobil one up front and amsoil in the rear both work well.

 

If you are getting any chattering, switch to a full synthetic 75-140. It cured mine about 110,000 miles back. Always comes out looking like new.

 

I pulled the original stuff at about 10,000. It looked like my wife's gravey when we first got married (she's is a much, much better cook now). Smelled a lot worse. Replaced with Mobil 1 and I change it about every year. It comes out looking clean and smells like new. 258,000 and going strong.

 

On the first change mine looked terrible too. It reminded me of my dirt bike trannies. Had to break in I guess. Now with changes at a much higher mileage interval than I'm proud of, it comes out clean and the magnet is just the slightest bit of gray. 208,000 miles and all is well.

 

No chattering but when I did the brakes in June I didn't get the preload right on the wheel bearings because I couldn't find the right socket for that goofy nut Dodge uses. They weren't tight enough and I developed a roar. I tried just adding some preload but the roar is still there. I pulled the left drum today and even though the bearings look and feel good, they show signs of rotating on the axle tube so I'll replace them all. I'm hoping that is all the problem is. Keeping my fingers crossed. I caught a deal a NAPA for the bearings. They're not Timken's but considering the size, I think I'll be OK. I found the correct socket this time at NAPA as well, $16 and change out the door. All I had to do was hit the inside corners of the tangs with a file. Took less than 5 minutes and it fits perfectly. I'll post up the part numbers when I finish.

 

Amsoil or Mobil 1 is what I would use. I use Amsoil in my truck but everything else get's Mobil 1. 75w90

 

The only advantage to a true synthetic is it's ability to handle the heat.

Most trucks that are driven empty or with a light load/small trailer, son't get hot enough for it to matter. Any good synth or semi-synth will work fine.

Last summer I checked my diff temp with a infra-red thermometer. It was only 220*. Small trailer, light load (about 5K#), 75mph, I-70, Kansas, in Aug. Trans pan was a lot cooler.

A dually with a big load can make the diff pretty hot. So, for you, a true synthetic would be important.

AFAIK, there's only 3 true synthetics on the market: Royal Purple, Redline, and Amsoil. Mobile 1 is not a true synthetic.

 

Can you expand on this?