Manual tranny, diff & t-case fluid for wheeling

[GoPathyGo]

Browsed all the forums and didn't find a topic on this - kinda surprised about that actually.

 

Anyway, what grade and brand of fluid do folks use/recommend for trannies, diffs and t-cases that see hard wheeling use ? Most OEMs recommend 75W90 or something similar for the MT and t-case with some recommending 75W140 for rear diffs. But with the whole move towards thinner fluids to meet MPG requirements I don't know how much I trust those recommendations anymore. Plus, the OEMs don't really care once you're past the warranty period. I've seen some fluids that are basically water with some coloring thrown in. Finally, I can't imagine hardcore wheeling was in the specs when they built the vehicle.

 

Since MTs and T-case take gear oil, has anyone tried 75W140 ? I know Amsoil, Mobil1 and Redline sell "severe duty" oils at this grade. The labels indicate they "can be used for differentials, transfer cases and manual transmissions that do not require automatic transmission-grade fluid." Redlines "Shockproof Diff Oil" claims to be equivalent to a 75W250.

 

Is there any harm from using a 75W140 in a manual tranny or a t-case ? Same for the Redline 75W250 in a diff.

 

I don't want to set off another "which oil is better" brand war. Just wondering if any are specifically known to be helpful when putting the trannies under strain. I did try the Redline MT90 but it actually made the stick notchier if anything!

[Precise1]

I'd say that the 75w90 is fine, most people use it for their entire vehicle life (wheeling, towing, commuting...) and I have only heard of a few tranny/rear end failures. Add some Lucas oil stabilizer for peace of mind and all will be well as long as you change it out per recommendation. If you have a WD21, make sure to 'overfill' to 5.1 liters as per the TSB pinned in the garage section...

 

I suppose you could go with 75w140 if you lived in warmer climes.

 

B

[GoPathyGo]

I'm just paranoid after the last time I changed fluids and everything came out black and in about half the quantities that should have existed.

 

Plus current truck and WD will be just plain wheeled till the tires come off - and given the way they're built, I expect the t-case to melt and the gears to grenade before that happens.

 

We shall see. Just gathering opinions. Now I can say,"I asked" before I find my tranny and t-case are essentially caked in fluid.

[Precise1]

No worries. Just like engine oil, when in doubt, fill with fresh fluid (make sure there is a magnetic drain plug) and run for a few weeks. Drain, and refill. Drive for recommended interval unless you spend a lot of time underwater and do not have the breather hoses properly hooked up...

 

B

[92Pathmaker]

I just put Redline MT-90 in my gear box and t-case, and the 75w90 in the diffs. It is what most people recommend. It feels good and shifts easier than before. Just be sure to use a gl4 in the tranny

[TacitBlue]

I know this is an old topic, but I didn't want to start a new thread unnecessarily. I have a 1998 Pathfinder SE 4WD 5 speed. Is the transmission and transfer case all one in terms of the oil in them? In my service manual it has "manual transmission gear oil" (10 3/4 qts of 75W90) and also "transfer fluid" (Nissan Matic D or Equivalent Automatic Transmission Fluid). Is the "transfer fluid" the 4WD transfer case? Since it states to use ATF, I'm thinking that can't be the transfer case? Is it separate only in the automatic transmission Pathfinders? Thanks for any help on this.

 

-Mark

[Towncivilian]

I know this is an old topic, but I didn't want to start a new thread unnecessarily. I have a 1998 Pathfinder SE 4WD 5 speed. Is the transmission and transfer case all one in terms of the oil in them? In my service manual it has "manual transmission gear oil" (10 3/4 qts of 75W90) and also "transfer fluid" (Nissan Matic D or Equivalent Automatic Transmission Fluid). Is the "transfer fluid" the 4WD transfer case? Since it states to use ATF, I'm thinking that can't be the transfer case? Is it separate only in the automatic transmission Pathfinders? Thanks for any help on this.

 

-Mark

The manual trans requires 5.375 quarts! The fluid capacity is listed in pints. Also, use GL-4 gear oil only. If you use GL-5 this can harm the brass synchros IIRC.

 

The transfer case can use either ATF or gear oil. Those of us with automatic trans generally use ATF, and manual trans pals use gear oil, just to prevent intermixing of fluids should a leak spring. Use GL-4 only here too if using gear oil.

Edited October 12, 2011 by Towncivilian

[Mr.510]

I run Chevron Delo 80w90 in my T-case and diffs. While you can run either ATF or gear oil in the transfer case I highly recommend using gear oil on a wheeler and ATF on a street truck or occasional wheeler. Gear oil for better shock resistance and ATF for better gas mileage. The transmission and T-case do not share the same oil supply, I think the OP asked about that. Also worthy of note: There is a drain slot in the housing between the transmission and transfer case specifically so the fluids cannot cross-contaminate even if both seals fail.

 

I would not run synthetic lube of any brand in a Nissan LSD as I've had nothing but problems in the past. I have LSDs front and rear in my Pathy.

 

I am currently running Amsoil synthetic ATF in my HD auto trans but may switch back to conventional because it does not shift as hard on synthetic. The harder an auto trans shifts the longer it lives. This is a good reason to run an auto in "Power Mode" any time you aren't on the freeway. Hard shifts = less wear on the clutches.

Edited November 12, 2011 by Mr.510

[1994SEV6]

 

 

I would not run synthetic lube of any brand in a Nissan LSD as I've had nothing but problems in the past. I have LSDs front and rear in my Pathy.

 

 

If you don't use synthetic lube, then I guess that means you use conventional differential oil?

[Towncivilian]

If you don't use synthetic lube, then I guess that means you use conventional differential oil?

I'm pretty sure he uses extra virgin olive oil in his diffs.

[1994SEV6]

I'm pretty sure he uses extra virgin olive oil in his diffs.

 

right. extra virgin is always better. that's what you want.

 

I don't understand why you would use conventional though. Synthetic gave you problems? That's weird. I guess so, but that means you have to change your fluids like..all the time?

[Towncivilian]

I don't understand why you would use conventional though. Synthetic gave you problems? That's weird. I guess so, but that means you have to change your fluids like..all the time?

There are vehicles on the road with 300k+ on factory fill diff fluid, and/or decades old gear oil. While it's not the best practice, they're still somehow working. I had the factory fill in for 123k myself. I put in Valvoline 80W-90 conventional gear oil, and I'll probably change it at 150k and put some synthetic fluid in and run it at 50k change intervals.

[Mr.510]

If you don't use synthetic lube, then I guess that means you use conventional differential oil?

 

Yes, Delo 80w-90. Chevron says it's the best non-synthetic on the market, but it's their product so I'm not surprised by their opinion.

 

I'm pretty sure he uses extra virgin olive oil in his diffs.

 

Oh, right... I mean, No, I actually use canola oil with a pinch of basil, it smells better when it gets hot!

 

right. extra virgin is always better. that's what you want.

 

I don't understand why you would use conventional though. Synthetic gave you problems? That's weird. I guess so, but that means you have to change your fluids like..all the time?

 

Synthetic has given me problems with my limited slips chattering and/or not tightening up progressively under load to lock the axles together as they should. I've run Nismo clutch-type LSDs in several of my street cars for 25+ years. I tried four brands of synthetic in my R180LSD and it chattered and/or groaned while turning with all of them. Switched back to 80w-90 dinosaur oil and it worked perfectly within ten miles. (It takes a bit for the new oil to dilute the old oil from between the friction plates in an LSD.) I change the fluid in my diffs and T-case about once a year, and only that frequently because I do a lot of wheeling. My Pathy has been in water over the bumpers hundreds of times, I've never gotten water in any of the fluids, and I'm just running the stock vent line setup.

 

There are vehicles on the road with 300k+ on factory fill diff fluid, and/or decades old gear oil. While it's not the best practice, they're still somehow working. I had the factory fill in for 123k myself. I put in Valvoline 80W-90 conventional gear oil, and I'll probably change it at 150k and put some synthetic fluid in and run it at 50k change intervals.

 

I would guess that at least 50% of vehicles spend their entire life in service on the original gear oil and/or ATF. I've drained oil out of rear ends that looked more like roofing tar than gear oil and there was no significant wear on the gears or bearings. For most people's use I think T-cases and diffs are so massively overbuilt that the type/weight/interval of fluids doesn't really make much difference in their longevity.