Mixing grades in an LSD? Multiple questions

[AZjeff]

OK, I recently bought an 02 Nissan Xterra. Was happy to find it has a limited slip rear diff. While out trying it out I got opposing tires light on a diagonal erosion ditch in the trail and was dismayed that the light rear tire just spun and made no effort to move the X forward. Some searching on Nissan forums turned up info that the break away torque (BAT) on these is pretty low and what some owners do is drain the LSD lube with the friction modifiers and fill with straight syn lube. This supposedly gives more friction on the clutch plates but not so much to get tire chatter on pavement while turning. This sounds reasonable, anyone see anything wrong with it? Second question is the weight recommended by Nissan. Operating temps under 104f calls for 90 wt, above calls for 140 wt. We do see temps above 104 here in the summer on occasion, even for a week at a time or more. I currently have a quart of M1 75W-90 and a quart of SuperTech syn 75W-90 on hand. The diff holds just under 3 quarts. If I were to add a quart of 75W-140 syn to what I already have would it make sense? Kinda killing 3 birds with one stone, straight syn in the LSD, using what I have onhand, adding some 140 wt for the hotter days.

thoughts?

 

[Bluestream]

Mixing the oils you mentioned, you would end up with more like a straight 90 weight gear oil.

 

[AZjeff]

Could you explain why? thanks

 

[sicko]

I was always under the impression that you should never mix gear oils. Return one bottle you already have and buy two bottles of the one you kept, that way you have three bottles to fill the LSD.

 

[AZjeff]

Well that's good to know before I dump them in together. Can't really return them, been in my garage for a while. Should I just go with 75-140 because of the temps we have in the summer?

 

[AZjeff]

Should you not mix brands or weights or both?

 

[Colt45ws]

Buy a 75W110 like Amsoil's Severe Gear. Is thicker than a 90 but thinner than a 140. Basically what you are trying to do.

 

[AZjeff]

I use the Amsoil 75W110 in my 2500 Duramax with the LSD. It's LSD compatible so it must have the friction modifiers that I want to get away from, although the bottle says something about using an additive if you get wheel chatter.

 

[michaelluscher]

An LSD rated GL-5 80w-90 is what Nissan specifies

Castrol, Valvoline, and Mobil all make fluids suitable for this application.

I'd prefer you refresh the specified LSD fluid and see where that gets you before resorting to forum hearsay and pseudo science.

 

[Colt45ws]

Yeah it does... But so does the Mobil 1 I think....
I think of the syn gear oils only a few don't have LSD modifiers.

Mobil Delvac 75W90 (Can be had in 1 gallon containers)
Redline 75W90NS
Redline 75W140NS
There might be others, but I haven't looked in awhile. Some of the Schaeffer's oils I dont think have modifiers, but those are hard to get ahold of...

Blend the two Redline oils. Ive blended Valvoline Synpower 75W90 and 75W140 together before. I dont see why its a problem.

 

[Greasymechtech]

You can mix gear oils no problem. You can thin a 140 with 90, or thicken a 90 with 140. My only recommendation is to stick with the same brand, even though I've topped off and mixed with whatever was available and never had a problem.

In tired, weak, or worn LSDs, I've run non-lsd gear oil without issue. Although, you could still get some chatter.

Motul Gear300 and Motylgear, Torco, and Redline NS are some nonlsd gear oils. Most semi OTR gear oil is non LSD. Visit a truck stop.

For your weather, you'd have no problem running a 75w140 year round. But, just about any GL5 full synthetic SAE90, 75w90, 75w110, 80w90... will work just fine.

 

[AZjeff]

Thanks for the replies, really appreciate the input. The Xterra has 126K road miles on it, it lived in Co and Az and is in great condition. Don't know what would wear out an LSD but I don't think this truck led a hard life before I got it.

My main goal is to tighten the clutch action up some for better off-road ability, it's what I bought the thing for. Filling with factory spec LSD lube isn't going to do that, if anything it might free them up but the PO is an indie mechanic and stated he serviced all the fluids. Nobody has said I'll ruin the clutches so I'm going to give it a try. Maybe stick with another bottle of 75W-90 instead of the 140. I'll try to measure the BAT with a torque wrench on the lug nuts before and after and see if it goes up at all. Right now it doesn't take much effort to slip the clutches by hand, hardly better than an open diff.

 

[Colt45ws]

They are probably worn. My CVPI has a factory clutch-type LSD and it would lock up on dry pavement but asking anything else wasn't going to happen. I ended up rebuilding it because the axle end-play was over 1/8". Since its an 8.8 its c-clip and the clutch packs set up the end play.
Anyway, its much better with fresh clutches.

 

[dailydriver]

Originally Posted By: AZjeff
I use the Amsoil 75W110 in my 2500 Duramax with the LSD. It's LSD compatible so it must have the friction modifiers that I want to get away from, although the bottle says something about using an additive if you get wheel chatter.


ALL of the limited slip additive containing gear oils make this disclaimer, as they do not know just how much friction modifier your particular limited slip needs, (and YOU do not know exactly how much of it they put into their product).

Case in point; I ALWAYS have to add the full 4 ounce bottle of XL-3/Ford Racing additive to every gear oil which claims to have additive in it already, in order to not get the; chatter/groan/creaking out of my eaton Posi's carbon friction plates during low speed, coasting, turns.

I am going to try the NON limited slip formula Motul Gear 300 next (for it's sky high, 222 VI

) next.
Who knows how much friction modifier I will have to add to that to keep from getting a cocaphony from the pumpkin on slow/coasting turns.

LOL

 

[Bluestream]

The LSD additive does no lubricating, therefor only add the bare min needed to eliminate clutch chatter.

 

[artificialist]

Redline oil has advice on their website for controlling LSD slip, and some guys you can talk to for advice.

Their gear oil is high quality stuff.