Simple question; is there a simple answer?

[YV1LW]

1998 V70R AWD time to remove and replace the rear differential fluid/grease.

I believe that a GL-5 75w-90 is called for, BUT I cannot independently confirm this. Additionally, I "believe" that all GL-5 spec differential grease is synthetic. Is that a correct assertion?

Is the angle gear grease the same spec as the rear diff? Volvo p/n 41259380 is a full synthetic 75w-90 and I've found links for it to the angle gear. I can't find ANY specs for the rear differential.

Finally, all the research I've done indicates that for this MY V70R, the rear differential is a Generation 1 haldex. Gen 2 arrived in 2003. But perhaps I confuse this AWD system using a viscous coupling and a true haldex system. I guess I may be confusing TRACS with a haldex system.

Thanks.

[RickHaleParker]

The rear differential grease is API GL-5 / SAE 80 W. Volvo part number 1161620.
The API GL-5 / SAE 75W-90 for the angle gear will do just fine. Volvo part number 31259380 or equivalent.

[Oro]

1) If you can get 80w-90, it will be a little more robust than 75w-90. However, the 75w-90 will work. It's the same concept as motor oil - get the narrowest viscosity spread that suits your climate/application. Apples-to-apples, an 80w-90 will be more robust and last a bit longer in the same way a 10w-30 would vs a 5w30. But both will fit the application.

2) I believe your 98 car has the VC system, same as mine, not Haldex. "Gen1 Volvo awd" and "Gen1 Haldex awd" are not the same. There's a very bad explanation of Volvo awd on the FCP Euro website and that may be what misinformed you. Our cars have the GKN vc system, nothing Haldex about it.

The original Volvo awd system is made by GKN, not Haldex (these are company names). TRACS/STC is independent of the awd system and is an electronic brake-and-throttle modulated anti-skid system. You can install a dash switch easily to defeat the TRACS if it is interfering with your driving style. The awd models didn't come with the switch, but the wiring is there behind a dash panel blank so you can just pop a switch in and you are in business.

[scot850]

Oro has answered the main questions you ask. Only thing I would add is that neither the angle gear and rear diff use grease. Both use an oil. I am not sure what it was as I recall at the time I did this about 8 years ago, they were a special mix sold by Volvo but I think I recall someone identifying another source. Can't even recall if they were the same. In both cases there is only a fill plug and no drain plug. I had to use a pump to suction out the oils and refill.

Neil.

[Oro]

In both cases there is only a fill plug and no drain plug. I had to use a pump to suction out the oils and refill.

Neil.

Yeah, it's a pain. There are how-tows out there on how to add a drain plug. I don't recommend it. This past summer I got inspired and I drilled and tapped a drain plug into the front diff/angle gear of my '00. Glad I did it for the future, but I do NOT recommend this unless you are fairly adept. The walls of that gearcase are thin, you need good hands to get it square, and then careful not to over-torque it. I was going to do the rear also but then decided not to.

There are how-to's on this on the web and I do not recommend doing it unless you are a real machinist or equivalent. I got away with it because my dad IS a machinist and taught me on the side some tricks and techniques.

Otherwise, just get a cheap hand-pump and pull it out if you don't have compressed air, other tools and stuff. Honestly, and it's true, even if you only pull 1/2 the bad fluid out and refill - GOOD ENOUGH. You just bought yourself another 40k miles, just repeat the 1/2 fill procedure then.

Getting even 1/2 new fluid into a system is a major thing - AT, PS, diff, Haldex. Does wonders and prolongs life big-time. Do NOT obsess about getting the last bit of fluid out of an angle gear or diff (or engine or transmission).

As an aside, I had a fabulous opportunity three days ago to take my 2000 V70 XC out in TERRIBLE conditions, and with Continental a/s tires (Conti ProContact). The Perfos were still awaiting refinishing and the Nokian snows sitting outside the garage when a big snow (for here) fell early. And it came over warm weather which froze fast - down into the teens so solid ice underneath. We still haven't had USPS, UPS, fedex get down our street for a week. Great conditions in my book.

My 2000 XC with non-snow tires cares not, just runs up and down the hills and deals with the ice. I am quite impressed. I've had three P2 w/Haldex before this and the VC system is really no worse. And way less maintenance hassle than the Haldex. I've had all kinds of awd systems including 'the ultimate' - twin Torsen T-1 mechanical systems (early 100 series Land cruiser, 1991 Audi V8 5-speed manual). Only two production vehicles I've known to be equipped with that, I've had three of them - really the VC system is NOT BAD compared to the very, very best AWD systems out there.

OK - back on track. Here's what bugs me. rickhaleparker showed above the exploded diagrams (very helpful!).

The rear diff has what is quite clearly a GM style "Posi-Trac" limited slip clutch unit built into the differential.

I did not know that was there. I've never seen these spec'd (elsewhere) w/o having to have friction modifier added to the gear oil to keep the friction right between the slip discs. Does the OE Volvo fluid include that, or should it be added if you are using non Volvo fluid like the OP is asking? Is that diagram right and there is a posi-trac LSD in the rear of all these cars? From the way the car behaves, I would say it's true - but I know what these units need fluid wise and that is not what I've seen recommended.

Suddenly sleepless in (or near) Seattle.

So I know I got long - winded above, but only because now I have more questions than answers!!!

Oh yeah, one other thought. Not fully formed; working it through. I am starting to think the negs on the VC system are because of the TRACS system overlaid on it, not the system itself. Few data points:

1) No other makes (VW, Mercedes) have complaints about the (exact same) VC system
2) AWD Volvos have the TRACS/STC overlaid automatically, sometimes defeating the awd system
3) Once I defeated my TRACS (retro-active switch installed and used), my snow performance increased dramatically

Theoretically: Once you manually defeat the TRACS, and let a viscous coupled front-rear differential work, plus a post-trac rear LSD, you are going to have a very capable awd system without any electronic control or fail-point. If you have TRACS there reading the ABS rings and then messing behind the curtain with throttle and other ECU parameters, you now have two systems working in opposition.

[scot850]

The issues that the AWD system has in the P80 are:

1) It is fairly fragile - The angle gear and the connecting collar to the trans don't like abuse. You can break the collar and in worst case strip the connecting splines in the collar and the shaft in the angle gear. This is equally try of the P2 Haldex system as it also uses the angle gear.
2) In rushing the AWD into production, the stupidity of placing the front bearing on the prop-shaft right beside the cat was dumb. Also making the center support bearing a pro-only repair.
3) The VC unit is basically a clutch with a silicon fluid in it. If not stored correctly or left for a long time the clutch plates can dry out and strip. This even happened with brand new units.
4) The only way to remove the rear diff is to fully remove the rear subframe as it is held in a cage which is bolted from the top and can only be accesses by removing the subframe.

The only issue I have found in use is a delay in the power transfer to the rear wheels which can cause the car to twitch. Otherwise if maintained and you don't use tires with different tread depths is can be pretty robust.

As for the fluid used in the angle gear and rear diff I don't know the specific specs. That is a question for Volvo. Personally, I recommend using the OE product as destroying either unit is expensive and a major PITA to fix.

Neil.

[YV1LW]

@scot850
@oro
@rickhaleparker

Thank you all for the tips, instructions and leads. Yes, I agree "grease" was not a great descriptor. Not pumping it from a grease gun but squeezing it from a bottle. However, when you look for a product such as 80w-90, etc it is frequently referred to as "grease and lube" (for example: https://shop.advanceautoparts.com/p/car ... erm=80w-90).

Regarding my malapropism of Haldex. I think after I wrote the question and then spent some time under the vehicle; I could see that the construction of the driveline allowed for no filters or pumps (Haldex) and relied on the viscous coupling ahead of the rear differential.

Thankfully at this time, the mid-shaft bearing on the rear driveline is in good condition with next to no "wiggle". I not going to get wrapped around the axle of how the system functions (not yet anyhow) just want to understand how to maintain it.

@oro
I think you may have hit the nail on the head about the FCP description. I'm sure I've read that posting (and should go back & look again) but it's nice to know the correct manufacturer & system names. Checking out the GKN name lead me to the info that the conglomerate owns Spicer and Laycock. There was something I read that stated Haldex arrived in 1998 and I think there was casual link to Volvo using Gen 1 Haldex. My knowledge stops there.

@rickhaleparker
Thank you for the link & the VIDA screen shot. It certainly does not help that Volvo uses the part numbers 1161619 and 1161620 for two vastly different differentials; the former being linked as only to be used in LSD Dana gears from Spicer and the latter linked to subsequent p/n 31259380 which some sites refer to as "Transfer Case Oil" and Angle Gear oil. If I look at enough specs, I can barely parse that the 31259380 is an all synthetic, GL-5, 75w-90, while 31367238 is said to replace 1161620, is called "axle oil", has been spec'd as GL-5 80w and has a mineral base.

What is the construction of the rear drive differential? Is it a limited slip differential? I don't have enough experience looking at the printout to know the difference.

Liqui Moly lists a GL-5 80w gear oil for hypoid gears that are NOT limited slip differentials and meets Volvo 97314 spec. I could not find any additional information on exactly what this specification properties are enumerated. This reminds me of trying to find front drive axle oil for a New Holland TT-55 that had the sun & planetary gears trashed; NH said use 20w-30, but that is not a common viscosity in the US - very much available in India, Germany and England however.

I'm keenly aware of the difference between GL-4 and GL-5 and the effect(s) GL-5 has on copper, brass and bronze parts.

In summary, I think sometimes the manufacturer fudges the specs. The solution seems to be to use the more easily acquired oil; 75w-90 GL-5 synthetic.

[Oro]

What is the construction of the rear drive differential? Is it a limited slip differential? I don't have enough experience looking at the printout to know the difference.

The part I marked from the diagram above in red is a Pos-Trac LSD differential (that is what caught my eye). The parts I marked in light green are the clutches that go inside it.

2021-12-30 (1)_LI.jpg (1.07 MiB) Viewed 3683 times

Compare to this to see what I mean:


https://www.amazon.com/Yukon-Gear-YDGGM ... 2602&psc=1

I did not change my rear diff fluid this past fall; now I am glad I didn't because I want to find out if LSD additive is required; I've NOT seen a unit that could operate correctly without the right friction modifiers either in or added to the gear fluid. If the fluid lacks the right friction modifiers and is only gear fluid, the clutch discs will rapidly engage/disengage under load instead of "slipping" ina controlled fashion. If a loud popping noise is heard under load (very hard acceleration, moderate acceleration at full lock turning, etc), that's the clutch discs slamming instead of slipping.

NH said use 20w-30, but that is not a common viscosity in the US - very much available in India, Germany and England however.

Unless you are running the tractor below 20F a lot, the unit can't tell the difference between 20w-30 and straight 30 oil. If you are using it like that, 15w-30 is widely available as an HDEO everywhere; it's the new standard in all over-the-road diesels. A lot of automotive manual gear cases spec 5w-30 motor oil as the gear case lube. You could also just put 80w gear oil in it; it's the same viscosity and you certainly don't need the motor oil additives in the gear case.

Gear oil operating (100C/212F) viscosities are roughly just motor oil viscosities +50 (random unit assigned). They are differentiated so people don't put gear case oil into engines, where a whole host of additives are needed to deal with combustion by-products getting into the oil (making nasty acids, etc). Also, gear case oils will usually nowadays have EP additives (sulphur compounds - why they have that distinct sour odor) to deal with the "extreme pressure" on the gear tooth faces during operation. They have the same base oils and viscosities, but different scales so they are more easily differentiated and not swapped inadvertently.

In an oil rating, don't over-think the first 1/2 of the rating - e.g., "5w-30" or "75w-90" vs "10w-30" or "80w-90." It's only relevant at sub-freezing temperatures and is the "winter" rating; they all flow the same above freezing. It's not the "cold start" rating like advertising would leave you thinking. It's the cold temperature/winter rating. If you live in a VERY cold climate, then you need to pay attention to them. Otherwise get the narrowest spread you can to eliminate undesirable cold-flow additives that do not lubricate and break down very easily. Example: Living in Seattle or Louisville, I'd run 10w-30 or even 20w-30 motor oil and not 5w-30 at all times (and I do). In Montana I'd run 5w-30 in winter and not care at all the rest of the year.

[YV1LW]

Thanks for outlining the relevant sections of the rear differential. Helps explain the system to know what the bits & pieces are.

I can get LM 80w gear oil from Holland or Germany, but I think I'm going to continue on with a 75w-90 synthetic LSD rated oil.

Regarding the NH front driving axle - after looking at NH specs & comparing I took the route that was simple; bought John Deere J20C. Can find it most anywhere.

Appreciate all the time, research, sharing of knowledge & experience.

[abscate]

Well, some more intrigue as I bring Kat , the 1999 s70 AWD to stage zero

Volvo calls for two different part numbers for the

Rear diff oil GL5
Angle gear oil GL5 BOT328

BOT 328 turns out to be a low foaming spec , which makes a bit of sense as the angle gear case is spinning 4x faster than the big parts of the rear differential

I’m going to use different oils In each per Volvo