What gear lube grade and quanity for my 05 dually.I plan on using amsoill and I tow heavy.

 

Are you referring to gear fluid for the rears or transmission lubricant?

 

I've had the best UOAs and results (3 out of 4 times) with RP. RP 85w140 in the diffs and synchromax in the nv5600. Out of the 4 boxes that I tried Am. and RP, there was only once that RP didn't do a MUCH better job. My 97 5 spd shifted too stiff with RP. The other 3 times and boxes was no contest. Craig

 

as stated 85w-140 in the diffs. the nv5600 must have two quarts over full of a 50-50 blend of the following. Delo Synthetic Transmission Fluid SAE 50
Delo Synthetic Transmission Fluid SAE 50 delivers exceptional all-climate, year-round performance in heavy duty truck transmissions. A unique additive package can protect gears without using the “active sulfur” agents commonly found in automotive axle oils. This results in little to no corrosion and long life for copper-containing parts, such as oil coolers, bushings, and thrust washers. Good pumpability in extreme hot or cold temperatures promotes smooth shifting and efficient power transfer. It is specifically formulated to meet the latest extended drain requirements for Eaton transmissions, with drain intervals of up to 500,000 miles.
Synchromax is recommended for manual transmissions
that specify an automatic transmission fluid or motor oil.
It is also ideal for transfer cases and 2-cycle motorcycle
gear boxes.
Synchromax is formulated with Royal Purple’s synthetic,
proprietary Synerlec additive technology, offering
improved shift quality over a wide temperature range and
reduced gear noise.
Synchromax is fully compatible with all types of friction
materials and offers excellent corrosion and oxidation
protection without affecting the soft metals commonly
found in manual transmission synchronizers.
Performance Advantages
• Greater wear protection
• Smoother shifts
• Excellent rust / corrosion protection
• Reduces friction for more power
• Lowers operating temperatures

 

I personally think the 85/140 is unnecessary in light duty trucks. 75/90 is good enough for semi trucks to run, and carry more weight and run more miles than our trucks. Get a quality synthetic gear lube and save a litter parasitic drag.

 

I agree with Dragonslayer above on the 75/90 weight. Unless you lived in Arizona. I know the fiver you tow, and while that maxes out your truck where the GCVW is concerned, it isn't "that heavy" compared to what many others tow here. I have a 36' Montana that I tow.

I use Schaffer's gear lube in mine. The moly additives tend to be superior. RP and Redline are also good choices. To be completely fair, there really doesn't exist "bad" choices in gear lube now days.

Go to "Bobstheoilguy" dot com for a good education on lubricants. You will see oil and flame wars galore from the readers there.

There is more to lubricants than just additives, synthetic vs dino, viscosity or brands. Things like air saturation is extremely important and rarely gets discussed.