I went with what the user manual said, which was 75W-90 gear lubricant. I checked for the differential, and it said the same thing. I got full synthetic cause' there's no leaks, transmission seems to work well and doesn't have excessive wear, so I figured full synthetic would last a lot longer.

 

I'm just not sure if I should add friction modifier or not for using this in the differential.

 

Well you posted that your truck is "2WD LSD" so if the fluid does not have the modifier, yes you need the FM. If the fluid has LSD written on it, that means it's already added and you don't need to add. What does it say on the bottle?

One gripe with the Dodge diff. Why the hell couldn't they include a drain plug?

 

The bottle says "Limited Slip" right on it, that's why I figured it has the friction modifier, but I've never done this and wasn't sure if that's what it meant, or if it meant that it was the appropriate viscosity for Limited Slip diffs, but still needed the friction modifier. I guess I was just looking for confirmation that the words "Limited Slip" on the bottle did indeed mean it already has friction modifier.

 

Yes, that means it has it. You don't need to add it separately.

 

Cber, you put that Valvoline 75w-90 in your transmission - a MANUAL transmission?

If so, get it out, NOW. I guarantee that the manual does not approve that fluid. It will destroy your transmission. The sulphur (see the PDF) in the gear oil will eat the synchronizers. There are big differences in the oil requirement for a transmission and a differential.

This is from the FSM: Required lubricant for the NV3500 is Mopart Manual Transmission Lubricant, P/N 4874464. This is the only lubricant to be used in NV3500 transmissions. No other lubricants are acceptable, or recommended.

There are "syncromesh" fluids NOW that are compatible. But it MUST state "syncromesh."

This is the PDF on your gear oil - it says "axles" not transmissions.

http://www.valvoline.com/pdf/synpower_gear.pdf

 

Call it the placebo effect, but since having the new fluid, the truck seems to overcome internia a bit better. It feels a little less heavier when moving off from zero.

 

Dan is 100% correct. Get the gear oil out ASAP. I have an NV 3500 and use Pennzoil Synchromesh in it. You can buy it at any parts store and it is just as good if not a little better than Mopar MTL but costs half the price. It only takes 2 quarts and I change it about every 25,000 miles. Synchromesh is good stuff and my transmission runs very quiet and shifts super smooth even when cold.

Jimmy

 

I'll dig through the trash and check the bottles. I don't "think" the ones I put in the tranny said "Limited Slip" on the bottle, or at least I didn't notice it. That's part of the reason I got these bottles specifically for the rear-end, because I noticed it said "Limited Slip" on the bottle. I know it was full synthetic Valvoline 75W-90 because that's what the user manual that came with the truck said to put in it (75W-90), but I don't know for sure if it was the one labeled "Limited Slip" or not.

Worst case scenario I'll just drain it and re-fill it with the same stuff and make sure to get the one that is NOT labeled for Limited Slip differentials.

 

The point is Cber that the transmission and differential take VERY different fluids.

If the differential has the additive, even if you don't need it, it won't hurt it. But, put the wrong oil in your transmission and in short order, you'll be rebuilding it.