Apparently my 93 940 has some sort of a locking rear differential, although you'd never know it from the way it drives on ice. It'll spin out one rear at just about any speed.

Anyway, the question is this: I just changed the fluid that was in it, to Shell Spirax HD 80w90 (what I use). If this is a locker, it shouldn't need any special additives, correct? But I'm not very familiar with that breed of rear axle anyway, so is there something I'm missing?

Or does the 93 940 actually have one of those axles? I thought that was a 960 trait.

All '93- 940s should have a locker. You should be able to hear/feel when that sucker kicks in on bad surfaces, because its not subtle. Snow and ice are the only conditions that really provoke it - or the rare light rain/oil slickened hard takeoff from a stoplight.

You have an Eaton locking differential. Lubricant recommendations are in the FAQ in the rear axle section. Just about any good GL-5 will work fine and you do not need limited slip additives. I use Mobil 1 85-90 in three cars and Castrol Syntec 85-90 in one.

Steve,

I assume you pull the cover on the diff to change the oil, as my 93 has no drain plug (hate that crap). I've been wanting to do it, but pulling the cover is extra hassle, hopefully, they used a gasket. Thanks.

Often one or more of the bottom bolts goes all the way through to the oil.

Removing it drains the oil without having to remove the cover and replace the gasket.

I wouldn't remove the gasket/cover unless I had to clean the oil out due to contamination...if all else fails I'd just pump it out with a sucker and replace it with synthetic 80W/90 (or whatever I have on hand from Amsoil).

I tried that and couldn't fit the sucker hose past the planetary cage. I'm afraid that removing a bottom bolt or the entire cover is the only way to drain it. However, you have to make sure the gasket seals when you tighten it back up: it's a chemical RTV gasket.

I change the oil around 50k miles with synthetic and leave it in there until a pinion seal fails, then after replacing the seal I refill it.

Oops... I think I forgot to mention that I had already changed the oil.

So I rolled under the car and SURPRISE, there was no drain plug.

Anyone familiar with the movie "A Christmas Story"? From outside the shop, I think I sounded a lot like dad messing with the furnace while the mom & kids sat upstairs listening to him through the heat ducts.

Since I work on boats all the time, I have a nice brass Jabsco pump that I use for bizarre situations like that. A lot of boats don't even have crankcase oil drain plugs. The inlet hose for the pump is very thin for dipstick tubes, and I got just about all of the oil out of the diff. I was amazed, actually, by the amount. Typically sucking oil out does only a fair job at best. I thought of undoing the cover but I didn't want to mess with the gasket either.

Anyway, I did use the HD Shell GL-5 oil that I use in most axles.

Find out from Shell. Most modern synthetic gear oils work fine in "antispin" diffs without additives, but it is a case by case basis with the individual lube.

My mom's 940 has one. I think the LSD was standard all 9-series cars. Dont know about the oil, mechanic takes care of that car. I will agree that 940's suck in snow.

Does anyone know if there is a bolt that when removed lets the oil drain out?

My last response wasn't intended to sound like it does. I hit enter and posted before I was ready.

I was going to go further and say that there were different ways posted to get around the drain plug issue discussed in this thread. Check them out and you'll get good information. I used a suction pump.

There were several responses about that above.