Junkyard treasure! Oil recommendations for future.

As many know my d35 abs rear end is on its way out after only 338 thousand miles. I have been scouting for a couple of months and have came up short until today. I went to pick n pull, (which is a long drive for me,) for a bunch of grand am parts and lo and behold, out of only 2 xjs, one had a d35 abs rear end! Not only that but it has the larger optioned rear brakes with the finned rotors, which I had only heard about and never seen before! After I clean it up and go through it, should I run the heavy-duty 85-120 since I subject it to severe duty carrying mail and towing way too heavy trailers? What kind of change interval should I change to rather than my patent whenever I remember it schedule? Should I drill and tap a plug since I'm going to be doing it more often? Taking off the cover every time and re cleaning the surfaces is why I tend to avoid it.

Congrats on the JY find.

I can't speak to the gear oil choice with authority. I would say look for a local shop that specializes in setting up gears. Their advice will be suited to your particular climate/environment.

What I will suggest is that you get a Lube-Locker gasket for your diff. Having been in and out of my D30 many times on account of the ARB locker I have come to really appreciate the Lube-Locker. No more fussing over silicone stuck to the cover, the axle, the threads of the bolts and in the bolt holes. Just a quick wipe down with solvent and everything is ready to go back together. It is a game changer.

Drilling and tapping the sheet metal cover would probably not work. It is just thin sheet metal. You would need to weld in a bung. Alternatively you could buy an aftermarket cover with a drain provison. I would just get the Lube-Locker gasket. Try it out and see if that doesn't make your life better.

Follow the Factory Service or Owners Manual recommendations for the severe duty maintenance schedule, and the recommended fluids. Synthetic is specified for towing and heavy duty usage.

Have a bung welded to the diff cover, or buy an aftermarket cover with a bung and a drain plug.

And a MAGNET!

I had the ruff stuff heavy duty diff cover on my Chrysler 8.25 it came with the screw in fill plug plus a screw in drain plug on the bottom.

I dont have a manual, it would probably be in Japanese if I did anyway. I was just hoping for good recommendations since after 20 years of being out of production we have all learned the manual isn't always the best option any more anyway. What does the manual say the severe use change interval is?

For towing and serious off-road use SAE 75-140 synthetic

Engine Oil
-2.5L (4cyl) - 4.0 Quarts (3.8L)
-4.0L (6cyl) - 6.0 Quarts (5.7L)

Cooling System
-2.5L (4cyl) - 9.0 Quarts (8.5L)
-4.0L (6cyl) - 10.5 Quarts (9.9L)

Automatic Transmission

-4.0L (6cyl) The AW-4 Automatic Transmission uses Transmission Fluid labeled Dexron-III/Mercon.

- Drain and Re-fill = 4 Quarts (3.8L)
- Filter and complete fluid exchange = 8 Quarts (7.8 L)

-2.5L (4cyl) Chrysler/Mopar Automatic Transmissions use ATF+3 or ATF+4 Type 7176

Manual Transmission

Chrysler now recommends that 10w-30 motor oil be used in XJ Cherokee manual transmissions

Many Jeep owners report good results with Synchromesh fluid.

-AX-5 5 speed manual - 3.3 quarts 75W-90 GL3 or GL4 (NOT GL5 or GL5 compatible as incorrectly stated in some Owners Manuals)
-AX-15 5 speed manual - 3.32 quarts 75W-90 GL3 or GL4 (NOT GL5 or GL5 compatible as incorrectly stated in some Owners Manuals)
-NV3550 5 speed manual - 2.1 quarts Mopar fluid part # 04874464AA or Snychromesh (meets Mopar MS-9224 specs)

The NLGI specs are important - typical NLGI GL-5 gear oil carries added sulphur used as an Extreme Pressure (EP) lubricant. Especially when heated, sulphur is antagonistic to yellow (copper-based) metals - and the synchronizer rings and any bushings in the AX-15 are bronze. Most synthetic gear oils are rated GL-5 and are listed as "safe for use with yellow metals."

Unlike API specs (to API Service SL/CJ-4,) NLGI Service specifications are not reverse-compatible. Well-stocked parts houses will have both NLGI GL-3 and NLGI GL-5 mineral-based gear oil in stock all the time.

If you want to use a synthetic (RedLine, AmsOil, etc.) either check the back of the bottle or check the manufacturer's website to make sure it's safe for use with yellow metal - using sulphur-bearing gear oils usually results in draining your synchronizer rings at your next fluid change...

Transfer Case
-NV231 Part-Time (Command-Trac) - 2.2 Pints (1.0L)
Dexron III/Mercon

-NV242 Full-Time (Selec-Trac) – 2.85 Pints (1.3L)
Dexron III/Mercon



Front Axle
-Dana 30 - 2.5 Pts (1.2L) SAE 75W-90

Rear Axle
-When equipped, Trac-Lok Limited Slip rear axles require 4 ounces of Friction Modifier Additive

-Dana 35 - 3.5 Pints (1.66L) SAE 75W-90
-Dana 44 - 4.0 Pints (1.89L) SAE 75W-90
-Chrysler 8.25 - 4.4 Pints (2.0L) SAE 75W-90

How often should it be changed?

Gear oil should be changed. Eventually. Anyone giving you mileage intervals is trying to sell you diff services. The only important interval is the post break in oil change.

I wouldn’t recommend drilling and tapping for a plug.

Ain't nobody trying to sell me nothing. I haven't set foot in an auto shop since I worked in one 20 years ago. This isn't some weekend toy that i can do maintenance on whenever the mood strikes me. I rely on my my jeep being able to drive a 170 miles a day, over severe conditions for my livelihood. An ounce of prevention is worth a pound of cure. I want this unknown mileage rear-end to last as long as possible, repairs and downtime affect my bottom line. I keep all my fuel and maintenance on an app so I get alerts for when it's time for fluid changes. This is the only fluid i haven't been keeping track of, and I can't find a recommended interval anywhere.

Unclewolverine said:

Ain't nobody trying to sell me nothing. I haven't set foot in an auto shop since I worked in one 20 years ago. This isn't some weekend toy that i can do maintenance on whenever the mood strikes me. I rely on my my jeep being able to drive a 170 miles a day, over severe conditions for my livelihood. An ounce of prevention is worth a pound of cure. I want this unknown mileage rear-end to last as long as possible, repairs and downtime affect my bottom line. I keep all my fuel and maintenance on an app so I get alerts for when it's time for fluid changes. This is the only fluid i haven't been keeping track of, and I can't find a recommended interval anywhere.

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If you Google "recommended differential fluid change intervals", you'll find most sources say anywhere between 30,000 and 60,000 miles.

I would go with somewhere in that range, maybe towards the 30,000 mark because it appears you are probably in the severe duty category. It never hurts to change fluids sooner than recommended.

Thank you. I change my rotella under recommendation and it's kept this junkyard engine that sounded like it's about to come apart from day one going for 56k!

Another factor with gear oil changes is water crossings. I don't know if you end up having seasonal streams to cross, but if you do, that should up your change frequency to at least once a year at the end of that season.

And no, it is not just a matter of breather height. The quick cooling off of a warm pumpkin can lead to water getting sucked in through the axle shaft seals. I learned that one from a San Diego Navy guy who shared what was happening to their trucks when they would launch water craft.

I can't reiterate enough - Do not use cheap gear oil in the manual, even GL3. GL3 without the EP additives might be safe for the brass, but in my experience it still shifts like crap. Use something meant for it, like synchromesh or Redline MTL or MTL90. Lots of folk report running synthetic 10W-30 motor oil with good success too.

lawsoncl said:

I can't reiterate enough - Do not use cheap gear oil in the manual, even GL3. GL3 without the EP additives might be safe for the brass, but in my experience it still shifts like crap. Use something meant for it, like synchromesh or Redline MTL or MTL90. Lots of folk report running synthetic 10W-30 motor oil with good success too.

Click to expand...

Fwi this thread is about a Dana 35 junkyard axle

Yeah, just wanted to follow up on the fluid recommendations above.

Just had a look at my "Maintenance Schedules" & for normal use (Schedule "A") there is no reference to the diffs. at all but according to my Haynes "Book of Lies" (which generally aligns itself with Schedule "A") it's 30,000 miles.

Schedule "B" - which is for "frequent short trips, frequent driving in dusty conditions, towing, extensive idling, off-road driving &/or commercial service, e.g. delivery vehicles - sound familiar? (there are some others but of less relevance to OP) it's 12,000 miles. Now that did surprise me, plenty of folk don't change their engine oil that often.

Oh & it specifies different weight oil for tow package equipped vehicles (seemingly whether you use it or not).