I have been complaining to the dealer about a slight whine around 50 mph on slight acceleration. This started around 8,000 miles. I changed out the rear axle fluid at 4,000 miles using the DC stuff specifically made for the AAM axles. Yesterday with just under 12,000 miles on the truck I changed the oil again before we head south. In my opinion the fluid had the consistency of water, grey water. Very thin. Anyway, it was my intention to go with Redline 75W140 this time. There were no chips in the old oil or on the bottom of the housing and the oil smelled fine. There was some grey paste on the plug magnet. I inspected the teeth of the ring gear and noted that the pattern on the acceleration side goes all the way from the heel to the toe and appears to have scoring marks running from heal to toe. It has been a LONG while since I have done any ring and pinion work but it seems to me that the wear pattern should be smooth and long egg shaped positioned about the center of the teeth. I will go back to the dealer after my trip south but I would appreciate the opinions of anyone out there with rear axle experience. Have a great weekend.

 

Here is a pretty good link for showing wear pattern and the effect of varying the pinion depth and backlash.

http://www.drivetrain.com/ringpinioninstal.html

Did the score marks remain on the teeth after wiping the teeth with your finger or a rag?

Synthetic oil is "thinner" than regular oil. If you drained the oil when it was warm or hot it will seem even thinner.

 

I drained the oil when it was lukewarm. Yes, I wiped the old oil off the teeth with a lint free cloth. I didn't have my digital camera available or I would have posted a picture of the wear. Hindsight ya know.

Casey

 

Mine has 256,000 on it and it is wining, but it has always had a full wear pattern on the pull side.

 

Is that pattern scored or shiny?

 

Not what you wanted to hear, shiny. It is a Dana 80