Diff oil

(back again!)

Trying to find out what sort of oil to use in rear diff, i have gone to Volvo in Dublin, and they are not sure. I have a 96 2.3 940 estate (230FK). I have been warned that the wrong oil could cause damage

[dave r]

I'm just quoting my 940 handbook here, it says........

Rear axle:
Oil quality: Volvo rear axle oil, API-GL-5 (MIL-L-2105 B or C)
Viscosity: SAE 80 or 80W/90
Capacity: 1.6-1.75 Ltr (2.8-3.1 pints)

Bear in mind that my car is a '92. It's strange that the Haynes Manual doesn't mention the viscosity at all.

Hope this is of some use.
Cheers Dave

[ivor940]

From 700/900 FAQ on Brickboard.com:

Differential Oil Maintenance

Checking the Oil Level:

Solid Rear Axle. Remove the fill plug at the top, insert your finger, and make sure the oil level is up to the bottom of the plug hole. When you reinsert the plug, coat it with antiseize so you can remove it from this rusty environment next time. Snug it up and don't overtighten or strip the threads.
Independent Rear Suspension Rear Axle. [Dennis James] To check the oil level on an Independent Rear Suspension differential, look for a threaded plug about even with the driveshaft on the driver's side. It is not on the back side of the assembly, but on the front where the driveshaft bolts to the pinion shaft about three inches to the right (looking at it from under the car at about the position of the rear-driverside seat.)
Why Change the Oil? [Tips from Brake and Front End Magazine, Jul 02 by Larry Carley] [Volvo] differentials use hypoid gear oils that also contain extra amounts of "extreme pressure" (EP) additives. Limited slip differentials also require their own special additives. Most of these lubricants are long-lived and hold up well for tens of thousands of miles. But none will last forever. The combination of heat, shearing action and oxidation eventually breaks down the oil and reduces its ability to lubricate and protect. Normal wear inside the gearbox and differential also produces metallic debris that ends up in the oil. Since there’s no filter to remove these contaminants, the fluid becomes more and more abrasive as the miles add up. The only way to get rid of the contaminants and restore the lubricating qualities of the oil is to drain and replace the fluid. The oil level inside a manual transmission or differential is critical for proper lubrication because there’s no oil pump to route the oil where it’s needed. The oil is churned by the whirling gears, which "splash lubricates" the moving parts. If the fluid level gets too low because of a leak, therefore, the bearings and gears won’t get enough lubrication. The result can be galling, seizure and total destruction of the unit. Oil is also necessary to cool gears and bearings. The total oil capacity of most manual transmissions, differentials and transfer cases isn’t very much (typically a couple of quarts or less), so it doesn’t take much fluid loss before parts start running dangerously hot. If a transmission or differential is whining and making noise, it’s too late to add oil. The damage has already been done. Adding a higher viscosity oil may quiet it for awhile, but once wear has taken its toll on the gears and bearings there’s no magic cure other than to overhaul the unit and replace the worn parts. Another reason for changing the lubricant inside a manual transmission, transaxle, transfer case or differential is to improve cold weather operation. Most conventional oils thicken as the temperature drops. This increases friction, drag, fuel consumption and the effort needed to shift gears. ...Synthetic gear oils have a lot of advantages compared to conventional petroleum-based oils. Synthetics are more stable, flow more easily at low temperatures, reduce friction and operating temperatures, improve fuel economy and generally provide superior all-round lubrication and protection under a wide range of operating conditions. [Editor] Highly recommended for all seasons, all temperatures, all uses: synthetic 90 grade differential oil. Mobil 1 75W-90, or Valvoline, Castol equivalents in 75/85-90 grades. See below for LSD/ALD oil information.

Differential Oil Vent Tube. If you change your oil and find it frothy or foamy, make sure the differential plastic vent tube is not allowing water into the lubricant. Re-orienting this might be necessary.


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Re-Filling Rear Axle Lube.

Identifying Leaks. [Tip: Editor] I make a habit of every so often spraying a little cleaner on the rear axle housing just aft of the pinion seal, as well as the gas tank near the seal, and washing the car in one of those car-bottom automatic washes. This allows me to see a clean axle housing when I inspect it occasionally and know at once when the rear pinion seal is leaking. The seal is a wear item and I have gone through them most frequently when the car is used in short trips on bumpy roads. Sure enough, I looked underneath last night and found the telltale spread of dark oil being blown both aft under the axle and sideways onto the gas tank. These are prime indicators of a leaking seal.

Draining the Differential Oil. Before you drain any oil out, make sure you can open the fill plug at the top of the differential.

Earlier Axles With Drain Plugs. Drain the oil by removing the fill plug at the bottom of the differential case.
Later Axles Without Drain Plugs. [Query] How do I drain and refill my rear axle housing when it does not have a drain plug? [Response: C. McGrew] The later axles do not have drain plugs. A suction tube will not work because of access, so just remove the bottom cover bolt and let the oil drain through the bolt hole.
Refilling the Axle. If you don't have a suction gun, buy a quart of axle lube for $2 at Walmart and an eight-foot piece of 3/8 inch vinyl tubing at a hardware store. Hook the oil bottle up to the tubing, route the tubing over the rear wheel, have wife hold the bottle in the air while you put the other end into the fill port, and slowly the oil will siphon down the tube into the axle housing. It took a little while, but it didn't leak and was a quick and easy way to refill the axle. [Tip: Abe Crombie] I've pumped hundreds of quarts of diff/gear lube at home by cutting the screw on top to a size that will take a piece of clear vinyl 3/8" tubing with a very snug fit. The you puncture a small hole near top of gear lube jug. With tube on very bottom of container and sparing application of air from your compressor via a blower nozzle, you can make quick work of adding the lube w/o assistance. Don't rush it or you'll rupture the gear oil jug.
[Tip: Peter Cohen] StaLube sells small pumps ($5) that afix to gear oil bottles; visit NAPA.

Refill with Mobil 1 or Valvoline synthetic in a 75-90 grade.


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Limited Slip Differential Lubricants. [Editor] If your car has a Limited Slip Differential (a dealer-installed option in the 1031 axle), then use a rear axle oil with a limited slip additive. The axle may have a tag specifying "anti-spin oil", which means an LSD additive.


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Automatic Locking Differential Lubricants. [Note from Michael Asmussen, Torque Control Products Division of Eaton Corp.] We recommend the following lubrications for our 1041 automatic locking differentials:
1)Texaco 2276; Synthetic 75 W90; GM Part # 9986115
2)Texaco 9622; Mineral based 80W90; GM Part # 9985290
3)Texaco 2080; Synthetic 75W140 (heavy duty applications); GM part # 9985991
Note - All of the above lubes are preblended with friction modifier. No additional modifiers are necessary or recommended. As far as other lubes are concerned, any standard GL 5 lube will work, but the units perform optimally with the three listed above.
[Comment from Castrol:] Thank you for contacting Castrol regarding Syntec 75W-90 GL-5 gear oil in your Volvo 1041 differentials with an Eaton Automatic Lock. You may use SYNTEC gear oil with full confidence.
[Comment from Mobil:] Mobil 1 Synthetic Gear Lubricant meets the GL-3, GL-4 and GL-5 API ratings. If the manufacturer requires the use of a GL-4 rated lubricant ONLY, then you should not use Mobil 1 Synthetic Gear Lubricant.



ivor940

I am none the wiser! I have not got a clue if the diff is “automatic locking” (or not)!
I did read ivor reply (thank you), but I may as well be looking into a hole on the ground, way over my head!

Thank you all the same, I’ll motor on (no pun intended)

[Peter Milnes]

Go with the Castrol Syntec GL-5. It is the recommended grade and type.

All the best, Peter.