Building a better Vanagon automatic transaxle

[jlaudin]

I have been reading and re-reading this valuable thread over and over again.
My burning question for the group and especially Kourt, is: Is it the additional cooling or the 4 planetary gears that gives Kourt the feeling of reliability.
I ask this selfishly, because I have about 4,000 miles on a rebuilt transmission that was rebuilt locally by my go-to machinist, who has never before built a VW transmission, and it has performed flawlessly behind a Bostig conversion hauling a 1984 Adventurewagon High top (4,800lbs) in Colorado two years in a row, including Monarch and other high Colorado passes.

I have the original transmission that I removed on my workbench, and my dilemma after reading this thread is given that the tranny in the bus that is working could go for thousands of miles (I do have the Go Westy Auto transmission cooler installed), is it worth the hassle of sourcing an Audi or Porsche 944 for the extra planetary gears, or just rebuild the one I took out as a backup tranny.

It's a classic cost-benefit question.

Best,
Jeff

[danfromsyr]

while more beefy inside parts are always better.
with the ~130hp of the Bostig engine I'd say that the stock internals are just fine.

if you were going Chipped 1.8t or 3.0H6 or SVX or TDI then I'd certainly source the beefier internals (as I have done for my 1.8T intended swap)

and well possibly for a subie 2.5 @ 165hp but IMO the van internals can take ~165 reasonably driven HP

[kourt]

For me it's both, but I primarily believe the additional cooling capacity is most important.

I agree with Dan--the Audi internals are nice, but not necessary for most applications.

Knowing what I know now, I could have kept my original transmission and just worked with the extra cooling capacity. I've driven Subaru conversions and Bostig conversions. My Bostig does not have the power delivery of a Subaru. My Bostig is not a transmission-buster.

kourt

[jlaudin]

Excellent and clear answers. Very helpful to me and perhaps others’ on the thread. Thanks for generously sharing with the community.
Jeff

[vwhammer]

Realistically you are looking at an extra $250 to $450 to upgrade to the Audi parts.
That practically triples the cost to rebuild the trans yourself.

I have some wild aspirations of slapping a turbo on my beefed up ABA and maybe getting somewhere close to 200hp so I figured why not do the upgrade since I had the trans out of the van and it needed rebuilt anyway.

Is it necessary?
Who honestly knows.
I don't think anyone has thoroughly tested one with enough power to the point of failure then determined that it was the weaker van parts that failed.

I can say that it is very unlikely that there is any real negative to running the upgraded parts other than cost and perhaps some assembly issues.

I think if you wanted to go all in then you would do the 4 gear planetary, the Audi forward clutch as it has the extra friction and maybe snag a kevlar brake band.
Without getting super custom that's about as strong as you can build one of these simply.
There is a possibility that you can change some springs in the valve body to increase pressure in system but so far I have not seen anyone do this.

I am going to run one spring from the Audi valve body that was different from the van valve body to see if that does anything.

Beyond that I do believe a serious cooling system and as much extra capacity and filtering as you can add is likely the biggest bang for the buck as far as longevity is concerned.

If you were limited on cash I would definitely start with the cooling system for the trans.

[danfromsyr]

well fwiw the Audi 5000CS/200 turbo were ~165hp
https://www.automobile-catalog.com/car/1989/234740/audi_200_turbo.html
same rating as the Subie 2.5

the 1989 Porsche 944 turbo is ~250HP.
https://www.google.com/search?q=1989+porsche+944+turbo+specs

[MarkWard]

This is out in left field, but 4 planetary gears might create more friction = more heat to dissipate. With the 2 recent builds failing in such short time, for a 1st time DIY overhaul, I would stick with the parts that came with the vanagon transmission for my first one.

While there are no snakes or spiders in these, trying to mix and match parts for your first overhaul, might lead to an early failure. Using the parts that came out of it and staying neat and orderly, might lend itself to a more successful overhaul out of the gate. Building experience on success, not failures can be more enjoyable.
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[kourt]

I agree with Mark here. I got lucky, in that my first Audi build came out good despite my being a relative novice to transmissions.

I had three transmissions and tore them down/rebuilt them several times to overcome the unfamiliarity and fear of working with them. Once I had lost my fear and knew the hardware, playing with the Audi internals became an easier risk to accept.

I've just finished helping a friend build up a new auto transaxle for his 87 Westy. This friend is not one who steps away from mechanical challenges, but even he was hesitant to play with the automatic transaxle, and I was mostly there to help him learn and push him to explore the core maintenance tasks, like installing 2nd gear brake band pistons, adjusting the 2nd gear brake band, measuring for shims, changing back-to-back seals, checking piston/return spring function with compressed air, mating the trans+diff without destroying splines or snap rings, etc.

What got me started was mechanical curiosity.

BTW, I think my Audi internals do run hotter than my old OEM transmission.

From page 2 of this thread:

Planetary gear trains provide high power density in comparison to standard parallel axis gear trains. They provide a reduction volume, multiple kinematic combinations, purely torsional reactions, and coaxial shafting. Disadvantages include high bearing loads, constant lubrication requirements, inaccessibility, and design complexity.

The efficiency loss in a planetary gear train is 3% per stage. This type of efficiency ensures that a high proportion of the energy being input is transmitted through the gearbox, rather than being wasted on mechanical losses inside the gearbox.

The load in a planetary gear train is shared among multiple planets, therefore torque capability is greatly increased. The more planets in the system, the greater load ability and the higher the torque density.

The planetary gear train also provides stability due to an even distribution of mass and increased rotational stiffness. Torque applied radially onto the gears of a planetary gear train is transferred radially by the gear, without lateral pressure on the gear teeth.

I'm glad this thread is a lifeboat for 090 transaxle lovers.

kourt

[Butcher]

Most, if not all the heat of an automatic transmission comes from the torque converter. I'm no engineer but it's highly unlikely that the additional gear will be something to be concerned about.

The Euro Audi 200's were pushing close to 200hp. I believe it was about 190hp.

I'm pretty certain the 944 Turbo's did not get an automatic transmission. If it did, I highly doubt if it was this version.

As for load on a gearset, if you have 100hp on three gears, I can only imagine there would be less load [on each gear] if you had 4. I would agree there would be a bit more friction, but I highly doubt it it would run dramatically hotter.

[vwhammer]

I am also of the opinion that one more gear is not going to make or break this trans on the temp front.

However, I do know that heat is the enemy when it comes to auto transmissions.
I also know that I don't want to have to worry about it so I am running a 30 row trans cooler with a thermostatically controlled fan and dual remote mount filters.

On another note I was just thinking about the kevlar brake band for my rebuild.
Isn't the Audi direct drive clutch drum bigger in diameter than the van drum?

The clutches are bigger and diameter and the shell that mates with it is larger.
Would this not mean the drum is larger and therefore the band needs to be longer?

I am at work so i don't have the parts to look at right now but this might be an important factor in the Audi trans parts van upgrade.

[danfromsyr]

I don't think any 3B 20v Audi 200 turbos were automatics..

ahh, so if only the NA 944s then those were ~164hp as well.

soo based on 2 OEM manufacturers upgrading the internals at around ~165hp, It may not be a bad idea if you are planning for a HEAVY loaded camper with BIG tires & a 2.5 Subie,

at the moment there are several Porsche 944 automatics out on fleabay as trans donors.
make them a low ball offer if you are local to pick it up.. the Porsche people don't want the automatics.. there's nearly zero resale market on used 944 automatics.
I found a local 944 enthusiast who's dismantling and parting out 944s for the other bits. so search your regional Porsche CL ads and inquire.. they just may give it to you.

[Butcher]

You're probably right but the 2v Euro 5 cylinder turbos had much more boost that what was offered here and produced 190hp.

"2.2 L I-5, 200 PS (147 kW; 197 hp), fuel injection, turbo (1988−1990); 190 PS (140 kW; 190 hp) with automatic transmission"
https://en.wikipedia.org/wiki/Audi_100

[MarkWard]

In my experience, the only automatics that had failed planetary gear assemblies were vehicles that were towed on the drive axle. It was common at the dealer to have a no start vw towed in for something as minor as a dead battery and we'd get it started only to find the automatic was shot.


Most failures I came across were hardened apply pistons. Often the steels and fibers still looked good.

I've cleaned my share of valve bodies as part of an overhaul, but other than the normal wear on the pistons, they do pretty well. The intermediate plate where the balls seat does get hammered and a samba member is selling reproduced plates here. In production I recall some valve bodies had 4 balls and some had 5 balls. So you needed to pay attention when you took the valve body apart. They can roll pretty far.
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[h00drat]

Have you guys seen the two paper gaskets that go on either side of the separator plate sold individually anywhere? I am only seeing them in kits...and this is the cheapest I've seen:

https://www.fcpeuro.com/products/vw-audi-auto-trans-gasket-set-010398007b
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<<Tyler>>
1987.5 Wolfsburg Weekender / CHC / 2.0 ABA
CHC Top Thread
Engine Conversion Thread (2.0 ABA Swap)
ABA Swap - Image Gallery
Auto Trans Rebuild - Image Gallery

[Gruppe B]

[danfromsyr]

OK so here's a question for the experts, how do you get the 2nd gear piston out if it's stuck in the bore. Yes I've tried compressed air in the port from under neath.. even scribed the outline with a scribe and penetrating fluids.
tried to compress the piston a smidge to break the stiction & crud
we get some corrosion up here in the salt & brine belt.

[MarkWard]

Is the cover stuck or the piston under it? Once the circlip is removed, clean the area as best you can and spray the od with pbblaster. Often whacking the cover with a rubber mallet or dead blow will walk it out. It is spring loaded and will want to pop free. Short of that, it may take some heat around the case to expand it.

Worse case, drill and tap the cover. Using a slide hammer to work it out. Don’t think there is the room to do that installed. You can then use a set screw to plug the hole you made.
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[vwhammer]

[vwhammer]

[kourt]

Have you removed the valve body and compressed it like this? Seems like it would come out pretty easy. I've had some stubborn pistons, but they usually give in to compression. Also, ATF+acetone rinse.

kourt