Truck: 04 2500 Quad Cab SLT 4x4 HO Cummins, 6spd, 3.73 rear. Truck is daily driver to work and hunting vehicle on weekends. Very little to no towing.

1.24.2004: 6870 Miles Changed FRT & Rear Ends to Amsoil Series 2000 75w-90
Transfer Case to Amsoil ATF
NV5600 6 spd to Redline MTL

2.11.2005: 27,696 Miles Changed Rear end to Redline 75w-90 (regular with LS additive)
NV5600 6 spd another dose of Redline MTL

Findings: New Amsoil 2000 has a mint green color. Came out of rear as dark green liquid state, no burned smell. Very little metal on the fill plug magnet. No chunks in bottom of case. No signs of abnormal wear or chipped teeth, etc.
NV5600 MTL new is a reddish color. Came out a light-golden brown color. Only removed one bottom PTO cover bolt on drivers side to drain.

Overall: Very happy with both products. Amsoil 2000 is no longer made. I was starting to experience the grind/lockup from a stop and making left turn. After install of the Redline and driving (past 30 mins), no noise at this time.

I'm going to drive truck for a week to judge the Redline in rear before changing out the frt meatball next weekend. Probably leave the Amsoil ATF in transfer case for another 15k.

About 4 quarts of MTL in Transmission and 4 quarts of the 75w-90 in rear. Cost was $7 per quart for each product plus S&H.

 

Wow, no one had flamed me or even had a comment?

 

Nothing to disagree with. My only difference is I prefer C+ in the transfer case. I will say one thing. My 15,000 mile axle lube change is coming up in about 3,000 miles and I am thinking I might extend it. I tow (not to heavy) and use my 4wd everyday, and if the oil is fairly clean and not too much mud on the magnets I believe I will push on for a while. 15k on gear oil just don't seem like much to me.

 

Friction additive is not required with american axle anti-spin rear on your truck . I would not use it .

 

If it's in there and not needed what does it hurt?

 

My thought exactly...especially since some guys on here (including myself) have been experiencing that grind/chatter noise when making a left turn from a stop. Maybe the Amsoil 2000 75w-90 needs a friction modifier to make the rear more slippery.

From redline under the 75w-90 " Our most popular gear oil, this is the preferred product in nearly all car and light truck differentials, both conventional and limited-slip. 75W90 is preferred for most racing applications. It contains friction modifier which is recommended for limited-slip units. 75W90 Gear Oil can be used in many transmissions and transaxles; however, other Red Line lubricants have better frictional properties for rapid synchronization. Exceeds API GL-5. "

Under the 75w-90NS oil " This GL-5-type geal oil doesn't contain the friction modifiers for limited-slip hypoid differentials. This makes the transmission synchronizers come to equal speeds more quickly, allowing faster shifting and much easier low-temperature shifting. Can also be used in racing limited-slip differentials where weak spring design causes too much wheel spin. "

 

For the record - almost all gear lubes DO contain friction modifier. The recommendation from Dodge/AA is not to add any ADDITIONAL friction modifier. The amount present in the various lubes is not going to hurt anything.

 

It will not hurt anything to run Redline 75/90 with the modifier. But the helical differentials do not need a modifier of any kind because there are no clutches or cones like there are in the more traditional limited slip units found elsewhere. Those diffs require some extra "slickness" so when in tight turns the inside wheel can turn at a very different RPM when compared to the outside without noise.

It is very common for us autocrossers to run 75/90 NS in the LSD's in Camaro's (pre-Torsens which are helical) and Mustangs with the Trac-Locks. The lack of the LSD additive made the clutches more grabby. Sure it made noise, but also helped with wheelspin with stock diffs. Now that I have changed up classes and can run a Torsen unit that is a race only part, not only is there not need for that in my case, but it has no effect on way the differential works or reacts. I run 75/90 NS in my car, and in my truck both.

No reason to have LSD additive that is useless in a helical diff, and will only break down with all the extra meshing gears beyond the ring and pinion. Less additives that you do not need make for a more stable fluid.

Example follows: There are cars that take 90 weight trans oil. You can run MT-90 (same as MTL, but heavier weight), 75/90 or 75/90 NS. MT-90 shifts very nicely. 75/90 not so much because the friction modifiers work opposite of what you want for synchro engagement. 75/90 NS works almost as well when the oil is fresh, but in any gearbox that is worked hard, the NS works much better over the long run. Why? The additive in the MT fluid breaks down, just like the additive in the 75/90 does. Now, we have to run MTL since the weight is what we need, but the same thing applies. Luckily, because of the long shift throughs and most of us don't mistake the trucks for a car with a B&M Ripper, the fluid takes a lot less beating, and lasts much longer.

But, I'll tell you, as a Redline dealer that if there was something that was MTL weight, but like the 75/90 NS in the sense of NO friction modifiers, I'd run it.