2WD Factory LSD oil?

[me4ou]

Hello, guys!
It has recently come to my attention that factory LSDs were only put in the european vans, but I hope you can assist me still.
My van has a 5-speed tranny with a 40% LSD equipped as stock. The code is ABM.
Even since I bought it I have had a bit of a problem with the differential.
When I am taking a turn and on the throttle, for instance climbing a bendy mountain road, the whole bus shakes and vibrates. Despite the fact that all wheels are spinning independantly it feels almost as if it's differential is welded. The LSD does work - on a slippery surface both wheels spin in the same direction. After changing the oil in the gearbox there is a slight improvement, but I am still a bit concerned. After thoroughly researching on forums, autodata, bentley manual and so on I poured new oil - Mobil1 75W90, which is what all of sources suggest is a proper oil for all gearboxes, however my issue still persists. Is it normal to have that kind of vibrations and noise with a LSD? I have only driven BMWs with LSD and you couldn't tell the difference between an open diff and a LSD.
I have also read that there are friction modifier additives for the oil, and also specific oils for LSDs.
As far as I know the oil for other types of diffs like the Peloquin are not applicable here.
Looking for any useful information and experience on stock LSDs in T3, as well as any technical data from the factory!
TIA!

[gears]

The 091 ZF LSD came with rather smooth friction discs from the factory*, so the fact that you're feeling chatter may signal that the discs and/or plain plates have deteriorated. Some will recommend adding an LSD friction modifier to the trans oil. While it's true that this will often eliminate chatter, it will also diminish the effectiveness of the LSD. But, it may be something you'll wish to experiment with.

In about a week I should receive some updated friction discs for this model ZF, utilizing the same type of friction disc we use in GT Porsche LSDs. These provide a higher friction coefficient than the OE discs, which may (or may not) reduce chatter in a vehicle experiencing it. We don't have any negative feedback in Porsche world, so I would expect similar excellent results with the 091 ZF.

Anyhow, if I were you, I'd continue to experiment with different oils. You may be better off with a non-synthetic oil for your application. That's certainly been true of 915-equipped 911 Porsches.

*Oddly, the 091 ZF is rated at 40% anti-slip effectiveness, even though it's equipped with 4 friction discs. In Porsche world, the 4 friction disc model ZFs (with identical ramp angles) are rated 80%, and their 40% ZF models have only 2 active friction discs. I can only deduce this difference in rating (between VW and Porsche 4-disc models) is because, as I said, the original discs in the 091 model are quite smooth, even when new.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[me4ou]

I am pretty sure that the % of slip effectiveness depends on the pressure applied to the discs, not so much on the number of discs.
Anyhow... Can you suggest a reliable way to measure how effective is my LSD right now and any friction modifiers that might help?

[gears]

There are a number of factors affecting lock-up percentages (ramp angles, Belleville preload, disc type, and disc quantity). My comment only points out the disparity between VW and Porsche nomenclature in nearly identical ZFs.

GM 88900330 friction modifier is something you could try. It's also possible something in your ZF is seizing (your "welded" comment). It might be wise to remove it and service it NOW, before you damage the NLA parts in it. Those OE discs don't last all that long.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[Waldi]

Rattling/vibration from a LSD comes from wrong oil without LS (low slip) additives. Most known comon failure after oil changes.

[gears]

What we have found is that very few transaxle oils "require" the addition of LSD friction modifiers. Virtually ALL popular oils used in Porsches (Swepco 201, 210, Delvak, Lubrication Engineers 9119, 9120, and numerous others) exhibit no LSD chattering.

If chattering is so severe as to "make the bus shake & vibrate", this is beyond normal "parking lot" or "in reverse gear" chattering, and I should have suggested an LSD servicing in my first response. Trying the GM product would certainly confirm the more severe issue.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[me4ou]

I have no idea what the previous oil was, in terms of brand or specs, but it was filthy. After the oil change with standard 75W90 oil, supposedly without an LSD additive, there is a slight improvement but it is persistant.
In all fairness I would welcome a working LSD but i do not insist on it. It doesn't bother me if it reduced the percentage or smth, as long as I can rely on my gearbox to not leave me on some random corner with gear pieces all over the road .
I will find this GM additive and see what happens with it. A gearbox rebuild/service is my last resort - i don't have the proper equipment I think aand my budget is a bit tight.

Thank you so much for the info!

[IdahoDoug]

My son and I are working on a Mark III Toyota Supra as a Dad/Son project and we pulled a used LSD to install in it. I looked around and asked and was provided with the factory breakaway torque to check its function before installing. You would be able to similarly check this important aspect without removing it - just by lifting the van off the ground.

So you might either put up a post here asking for it, or perhaps there are other sources overseas.

I agree that to shake/shimmy the van is something to look at more closely, though I have felt this from a slightly malfunctioning LSD on a classic 4WD that had a lot of worn bits. It would cause the entire drive train to twist, rebound through its entire worn-slack range and bang the other direction, then repeat. Sounded like the entire system was about to break. Later, with nothing but a diff oil change, ring lash properly set up and new joints on the drive line it was a smooth experience.

So, if you lift the rear and can feel a lot of rotational slop in your diff, CVs, and driveline then you might attend to that first and see if it tames the LSD's tendency to magnify normal wear issues.
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[gears]

Servicing the ZF is by no means as involved as a "transaxle rebuild". In fact, it's a pretty straightforward job with transaxle R&R being 75% of the work.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[me4ou]

@IdahoDoug - All CV joints have been replaced, as well as all other possible sources of the trouble. I will see what information i can find for the breakaway torque on this bus.

@gears - I have removed and reinstalled the tranny - not an easy job without a lift, but still manageable. The part I am worried about opening the differential is the measurements involved in reassembling it and the ring lash adjustments.
What would a "service" involve, apart from changing the oil obviously?

[T3messie]

VW says the LSD has to open at a torque between 20 and 50 Nm.

[gears]

Servicing the LSD would involve removing the flanges, marking the side adjusters, pulling the bellhousing off, removing the LSD, removing the ring gear, disassembling the LSD, and replacing some of the internal plates. I've got "how to" threads for both Porsche and Type I VW ZFs in the stickies. Your 091 ZF is quite similar, and we're here to help.

By marking the side adjuster position, the backlash is easily reset exactly where it was when it all goes back together.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[me4ou]

I measured the breakaway torque at around 25Nm, which I guess is considered "a bit worn, but still working". The slipping effect wasn't quite smooth though and that is probably what the chattering presents as.

Considering the upcoming "camping" season I am reluctant to open the box now, so for now I am planning to add a friction modifier/LSD additive to the oil and hope for an improvement. If it quiets down all together i might leave it as it is. If there is still anything left as a problem I will service it during winter probably.
Thank you so much for the quick replies and the valuable information I will keep you posted on my results!

[joetiger]

I've searched several threads and this one seems to be the most relevant to what I experienced at Syncro Solstice last weekend, so I thought it appropriate to post it here.

The Syncro is an '86 tin top with a fresh stock VC and no locker. I knew it had some type of LSD or Peloquin in the back, but did not know specifics.

It's been grabby in the back since I got it, scrubbing on tight turns. But after one afternoon of driving it up the rocks in Moab (where it performed admirably) it started REALLY locking up on even the slightest turns. I limped back to camp to see what was wrong.

Dan the sage Mercedes man and Westy owner asked me two questions:

1. Did anybody ever make a clutch-type LSD for Vanagons? I answered that I was pretty sure they did, recalling this thread.

2. What oil are you running? I told him Swepco 210.

He responded that it's not slick enough, and that I needed Limited slip additive.

We sourced some additive from town (thanks to a text to MSewalson's wife) and added it to the transmission fluid, which was a job unto itself with my stripped fill plug. It slowly regained its smoothness, now smoother than it ever was before. I still am getting a random grab here and there, but it's 1000 times better. Dan and also Josh (brilliant and resourceful RMW tech) suggested I put another 4 oz. bottle in to smooth it out more, which I'll do this week.

So, I'm guessing I have a ZF LSD? Somebody out there told me that ZF's were common in Europe, but fairly rare here. It did a great job climbing in sand, on rocky terrain, gravel, loose dirt, pretty much everywhere I took it in Moab and beyond.

_________________
Joe T.

'86 NAHT Vanagon GL Syncro/ supercharged ABA 2.0 "Pigpen"
'04 GTI 1.8T
'04 Golf R32

"get metaphysical with it. if it's simply a means to get to and from places, it will let you down. if it becomes your zen, it can't fail you." -dabaron

"Still, it's good to be afield."--VWagabond

Available Now! Vanagon to Louisiana--A Two-Lane Reckoning Through Past and Present

www.josephtrussell.com

[gears]

This is especially interesting to me, and I'll explain why: 1) The original friction discs in the 091 ZF aren't what I would consider an aggressive disc. 2) Porsche racers consider Swepco 201 and 210 rather ideal for their ZF and GT LSDs because these oils require no LSD additives.

I'm guessing what you were actually feeling was extremely worn friction discs that had worn so much that bare steel surfaces were beginning to gall.

I actually have a few new ZF LSDs in stock. Anyone interested can PM me ..
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[joetiger]

[gears]

You can't argue with whatever prolongs the useful life of your ZF. I definitely appreciate your sharing this solution to an irritating issue.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[joetiger]

Thanks again for the insight, Gears. I'll add another 4 oz. this weekend and report back after I've driven it a bit.
_________________
Joe T.

'86 NAHT Vanagon GL Syncro/ supercharged ABA 2.0 "Pigpen"
'04 GTI 1.8T
'04 Golf R32

"get metaphysical with it. if it's simply a means to get to and from places, it will let you down. if it becomes your zen, it can't fail you." -dabaron

"Still, it's good to be afield."--VWagabond

Available Now! Vanagon to Louisiana--A Two-Lane Reckoning Through Past and Present

www.josephtrussell.com

[akroblade954]

Interesting thread guys.

I have just learn that the van I bought recently has a factory LSD. It's a '90 Westfalia Atlantic, with 5 speed ASR 'box. I had recently changed the tranny oil to Comma 75W90 fully synthetic GL4, which is what I have put in all my 091 gearboxes as it makes them super smooth and 1st to 2nd change is a breeze - even in winter.. A few hundred miles later, the van started to vibrate and chatter on full lock, first gear manoeuvres. This led me to eventually discover it has the LSD...

So now I know I need some LS additive. But, how much do I need to add? Is that something that is specified on the side of the can? EG 1:50 or something? Is there a particular brand that works better with our type of LSD?

I found the GM additive mentioned above, so guess that is a good place to start


Thanks in anticipation

[gears]

I feel it's a mistake to add a modifier to the oil for minor chattering. "1st gear, full lock", reversing, parking lot maneuvers .. these are all situations that I would accept minor chatter. A modifier reduces the effectiveness of not only the LSD, but the synchro rings as well.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com