red86nado

I plan to change the axle lube in my '86 with 124,XXX miles. Following the FSM recommendation (GL-5 spec), I had the parts counter order GM 1052271. Local Chevy dealer provided 89021671...they claimed 1052271 was no longer available from GM. When parts arrived I checked the label; the lube was GL-4.

Parts dealer contacted Chevy over the phone. Chevy dealer said it was per the GM spec, and that GL-4 would be fine. When I made the difference clear (GL-4 isn't GL-5 spec), they called the Chevy dealer again and had them double-check. Same answer...and they stated the GL-4 is all they use. Parts dealer sent the axle lube back to the Chevy dealer.

From API Pub 1560 (Lubricant Service Designations), GL-4 is for "axles with spiral bevel gears operating under moderate to severe conditions of speed and load or axles with hypoid gears operating under moderate speeds and loads." GL-5 is for "gears, particularly hypoid gears, in axles operating under various combinations of high-speed/shock load and low-speed/high-torque conditions." The note for both specs reads "frictional requirements for axles equipped with limited-slip differentials are normally defined by the axle manufacturer."

Of interest, 1052271 is still available over the internet, and there is plenty of forum advice on using synthetics. However, no one advocates using GL-4 in place of GL-5.

My lesson learned: read the label.

Aardwolf

Thanks for the info. I wonder what 1052358 is?

http://www.ecklers.com/product.asp?p...&dept%5Fid=121

Aurora40

I seem to recall reading within the last year or so that the appropriate rear axle lube for our cars was NLA from GM, and they only sold the stuff for newer cars now (presumably the GL-4 stuff you got).

Just two cents, Mobil1 is GL-5, and you can probably find it locally vs ordering from the internet. It might even be cheaper than the GM stuff shipped.

Aardwolf, that is the additive you put in, you don't fill your diff up with that. It's a 4-ounce bottle that you add to the gear lube.

Aardwolf

Oops! Typed to early in the morning! I thought he meant the additive not the oil.

red86nado

Complete agreement on local availability and application of Mobil 1. "Two cents" on the forum is usually worth about $200 when applied in advance of real Corvette repairs! For what it's worth, a 23 oz. bottle of the GM lube was about two dollars more than a quart of Mobil 1.

I posted the info on current GM lube simply because the Chevy dealership was insisting that they're putting the right product in C4 Corvettes...and they're wrong. In my case, I discovered the problem before I crawled under the car. Just hoping to keep others from going down the wrong road!

Gixster

I had to stop by one of the dealers here today to order a part and while I was there I checked their chemical/lube section based on this thread.

They had about 15 bottles of GL-5 spec axle lube on the shelf. I didn't catch the part number though, but it definitely appeared to be plentiful here.

Chatman

OK. Now I'm really confused.

I have two bottles of GM 1052271. One appears older (came with car) and is in a translucent container. The other is in a black bottle that I purchased within the last two years. The translucent container makes no API reference. The black container does and it says "exceeds API GL-4 requirements."

Mobil 1 is API GL-5, contains sulfur but does say "Mobil 1 Synthetic Gear Lubricant LS 75W-90 can also be used in rear axles where API Service GL-4 lubricant is recommended." at their website. Mobil also reports "Excellent rust, staining and corrosion protection of copper and its alloys."

If that weren't confusing enough, I can find no explicit statement about the capacity of the Dana 44 on my 86 and, when using Mobil 1, see reference to adding no LSD additive, 1 bottle and 2 bottles (Bogus citing Gordon Kellebrew).

In addition, I didn't notice a reference for use in transmissions calling for 75W-90 except a negative statement regarding use in transmissions calling for ATF or engine oil. I would prefer a recommendation for use in manual transmissions calling for 75w-90 oil.

So, what to do? Should my diff use GL-5 instead of GL-4 as recommended by GM part number. Is additive required if using Mobil 1? Do we really need 2 bottles if so? Wouldn't as little as needed be the better standard as it would be less wear to slip only as necessary?

Aurora40

Mobil is the one saying you generally don't need a limited slip additive. I don't see how they could say absolutely for every car. On their website they say "For axles requiring the highest level of limited-slip performance, OEM specific LS additives can be added to this fluid."

For me, I took that to mean add the stuff. I changed out my rear fluid with Mobil1 75w-90 and put in 4 ounces of GM limited slip lube.

On the question of your bottles of stuff, I guess if they say GL-4, maybe they aren't the right thing. Where did this part number come from anyway? My owner's manual is in the garage, but I grabbed the '93 manual from online. It says the rear lube is part #12345977

Edit: my '90 factory service manual says to use either 1052271 or 1052272, and specifically says it's an SAE 80w-90 GL-5 oil. Weird they say two part numbers as if you can take your pick or something...

red86nado

My '86 FSM calls for GL-5. The link below is for the API standards on gear lube. You can read for yourself, but GL-4 is NOT appropriate for a GL-5 spec. Use the GL-5...don't put the GL-4 in your Corvette.

API standards: http://www.dave-new.com/S4/API_1560.pdf

I finished my axle lube today; I used a mity-vac pump to draw out the old fluid. I refilled with 1.5 quarts of 75W-90 Castrol Syntec gear oil and 8 ounces (two bottles) of GM limited slip additive (1052358). That's just shy of two quarts total...of course, the amount you replace depends on how much you can draw out using a pump.

Of note, I couldn't get any of the bottles at a good angle to drain into the carrier housing, so I used one of the mity-vac hoses and a funnel to refill up to the bolt hole.

VenkmanP

My owner's manual calls for P/N 12345977, which I find has been superceded by 89021669, which is GL-5 and is in stock at every online dealer that I checked.

Aurora40

I bought some clear hose at the hardware store and used that. Just cut about 3-4 feet off, and stuff it in the diff hole. Then you can easily pour the fluid in. With those tapered bottles I didn't even need a funnel (one less thing to clean).

Chatman

OK. From the 1986 Shop Manual on page OB-6, Figure OB-2, there is a table with two lines. The first line is for standard differential rear axle. The second line is for limited-slip differential rear axle.

The first line's specification is "SAE 80W or SAE 80W-90 GL-5 (SAE 80W GL-5 in Canada) gear lubricant (GM Part No. 10522771)."
The second line says, "Some models require a special gear lubricant additive in addition to (GM Part No. 1052271)*."
This is also the part number listed for manual transmissions.

So, there is clearly contradictory information in the same direction. Use GL-5 but use an oil that is not GL-5. I think that it is probably clear enough that we should use GL-5 diff oil, but two things are less clear. First, it is less clear that at least those with a 4+3 manual transmission like mine should use GL-5 in the box. It could be a problem because there seems to be consensus that GL-5 is more corrosive than GL-4 and who knows for a fact whether this is adequately controlled in Mobil 1 or other GL-5 oils? Second, it is unclear whether any additive is necessary if using Mobil 1 and, if so, whether to use 1 or 2 bottles. Wouldn't using too much lead to increased wear? Isn't the correct amount the minimum that prevents chatter?

VenkmanP

Did you leave something out of the quote? Because I don't see anything in there that says "don't use GL-5"


The correct amount is the amount that Gordon Killebrew says to use.

Chatman

Please be more clear. I'll guess that you're talking about whether or not to use GL-5 in the manual 4+3 transmission. The problem is that the specs call for the GM part number for a lube that is GL-4, not GL-5. Are the specs in error again as they were on the differential where the specs, at least in 86, called for GL-5 but specified a GL-4 GM product? Or, is the transmission spec correct in that a GL-4 should be used and a GL-5 might cause problems due to its being more corrosive.
As for the Kellebrew reference, if he were to join the conversation, cool. Otherwise, I think that we're just going from something he said one time to someone? Is that right? Is the direction at least written somewhere?

red86nado

Chatman, I started this. I'll try to end it.

The FSM is correct. It calls for GL-5, and specifies GM lube 1052271 (which is GL-5). The purpose of my original post was to post a warning that GM's replacement for 1052271 (which carries the number 89021671) is NOT GL-5...it is GL-4 and shouldn't be used in a rear axle calling for GL-5.

The "next line" in the '86 FSM refers to the GM limited slip differential additive, not the lube itself. It confirms that you need to put the limited slip additive into your limited slip rear differential.

The '86 Corvette Owner's Manual provides the following for a complete refill of the rear axle: "add 4 oz. of rear axle limited slip lubricant additive GM part # 1052358. Then fill to the level of the filler plug hole (on the passenger's side of differential case) with special gear lubricant GM 1052271 or 1052272."

Regarding whether to use 4 oz. or 8 oz. of limited slip additive, there are plenty of archived notes using the "search" function of the forum. That's a choice you need to make yourself...others have already put their thoughts in old posts.

Last note: I recommend you start a new thread if you have questions on what to add to your 4+3 transmission. It requires different fluids...one for the transmission, and one for the overdrive unit.

Good luck!

Chatman

Sorry but you didn't read carefully or I wasn't clear enough.

I took the fact that GM 1052271 is GL-4 from my GM bottle with that part number. As I said earlier, the GM 1052271 bottle reports "exceeds API GL-4 requirements" on the label. Part number GM 1052271 is not GL-5. I'm not surprised that its replacement isn't either.

red86nado

You're right...I didn't understand what you wrote.

I'd figured, from the FSM recommendation of 1052271, that it was GL-5. You've poured even more gasoline on the GL spec fire!