AT gearbox maximum torque

Discuss VW transaxles and transmissions. Gearheads wanted!

Moderator: Henryhoehandle

TZepeSH
Posts: 209
Joined: Wed Nov 03, 2004 1:55 am

Re: AT gearbox maximum torque

Post by TZepeSH » Tue Jul 04, 2017 12:26 am

Thanks for your feedback Clone. It seems i can get away with no mods. I'll drive a bit like that and see what happens. If gears start spining on hubs, then I'll decide whether to rebuild with bus gears or get another gearbox. I hope it won't happen during a vacation if it happens.

SC3283
Posts: 33
Joined: Thu Nov 19, 2015 9:10 am

Re: AT gearbox maximum torque

Post by SC3283 » Mon Jan 29, 2018 11:13 am

Any updates?
70, 74 beetle, 81 Chenowth, 66 Fastback, 83GTI, 85GTI, 02 GTI, 72 Std Beetle

TZepeSH
Posts: 209
Joined: Wed Nov 03, 2004 1:55 am

Re: AT gearbox maximum torque

Post by TZepeSH » Mon Jan 29, 2018 1:13 pm

Hello, no updates yet. I wanted to have the type4 engine ready this year but I got too deep in the pocket for suspension, steering and wheels, and now the engine is behind schedule. Also bigger family leads to other priorities. I guess this year I will continue shopping for the missing parts ( about 5000 bucks for everything else that I need) and put everything together during winter or beginning of next year. Meanwhile I will drive it as it is, and then I will still use same gearbox with the type4 (maybe 140hp), and if it breaks I will buy a rancho or similar stiffened box...

User avatar
Udo Airbus
Posts: 163
Joined: Thu Oct 23, 2014 8:22 am

Re: AT gearbox maximum torque

Post by Udo Airbus » Wed Jan 31, 2018 9:06 am

I'm running a stock AT box in my vw splitscreen (1600cc dual carb) (tires are 185/65/15) And towning a caravan (750KG max) No problems!!

Now I installed my type 4 1971cc single weber turbo engine.. and im afraid I will kill the gearbox.. we will see
VW T1 1964 - Mouse Grey - Pearl White OG paint

Bagged, Porsche steeringrack/brakes..IRS, AMR Supercharged 1600 (sold) building a 1971cc EFI turbo/supercharged engine

User avatar
petew
Posts: 3584
Joined: Sat Oct 07, 2006 6:05 pm
Location: Sydney/Australia
Contact:

Re: AT gearbox maximum torque

Post by petew » Thu Feb 15, 2018 4:36 am

IIRC correctly, there were a bunch of guys running stock AT trans behind subaru EJ20T turbo motors over here. Some of them were just street beetles, but a few guys were using them for track days and doing the 300hp upgrade on the motors to STi spec. I was astounded that they stood up to the abuse, but they did. I think most guys used them with great success. I remember a few of them upgrading the gears for better ratios and adding quaife diffs, but I don't actually remember anyone blowing them up. I think the key is mechanical sympathy. That would be more torque than you'll ever see with your type 4.

P.s. if you do decide to do a rebuild, I was seriously consider a subaru 5 speed. Everything for them is cheaper, more plentiful and stronger.

TZepeSH
Posts: 209
Joined: Wed Nov 03, 2004 1:55 am

Re: AT gearbox maximum torque

Post by TZepeSH » Thu Feb 15, 2018 6:21 am

At some point I considered a 5 speed conversion. However, I do not like the gearing, as it would drop the RPM at high speed and cooling would not be so efficient.
A friend of mine who has a Subaru conversion on a Bus is now considering also a Subi gearbox, because not even the 091 can take his abuse (heavy camper, boat trailer behind, heavy foot). We have a transmission shop in our town, and the guy has a Subi gearbox in his yard. He opened it and said he would try to put the differential on the other side to reverse the output (otherwise there will be 1 forward and 5 backward gears). His opinion was that it does not need the special R&P from SubaruGears, just some clearancing on the other half of the gearbox to swap the differential. It's like in the beetle gearboxes where you can install the diff on either side to change rotation. He looked at the pics from the website and said that there is no reason for the mis-alignment between R&P shown there (http://www.subarugears.com/About/About.html) if the diff is properly aligned. He will try to do it in the following months, and it would be MUCH cheaper than the SubaruGears conversion. I will give an update if this works.

User avatar
sideshow
Posts: 3265
Joined: Mon Oct 27, 2003 2:00 pm
Location: suth'ern oraygun yusa
Contact:

Re: AT gearbox maximum torque

Post by sideshow » Thu Feb 15, 2018 9:04 am

Hypoid R&P can be reversed...by inverting the entire transmission (making it work upside down).
Yeah some may call it overkill, but you can't have too much overkill.

User avatar
Pablo2
Posts: 404
Joined: Sat Jun 25, 2011 7:37 pm

Re: AT gearbox maximum torque

Post by Pablo2 » Thu Feb 15, 2018 9:20 am

Yeah, I don't think your buddy's going to have much luck flipping a hypoid diff in an OE case. The only way I've seen it done involved extensive main case welding. Good luck altering the side adjusters' off-set ..

Straying from the OP's subject, but your buddy might like to know that we've been gathering all the bits required to upgrade Vanagon Syncro transaxles to reliably withstand high horsepower engines (SVX & TDI). Most of these parts (billet intermediate housing, reduced helix gears, etc) can also be used in 2WD Vanagons ..
Image
.
Thread:
https://www.thesamba.com/vw/forum/viewt ... &start=200
.
aka Pablo, gears, Geary
9.36 @ 146 in '86

TZepeSH
Posts: 209
Joined: Wed Nov 03, 2004 1:55 am

Re: AT gearbox maximum torque

Post by TZepeSH » Thu Feb 15, 2018 10:34 am

Well, I am no expert in gear meshing in that detail. I just got that info from my buddy and remebered the beetle gearboxes in which the differential could be swapped to the other side (the dual side cover versions?). I am curious too about the result, but I do not know when they will do anything about it, as this is just a test/learning mule. Maybe I'm thinking about the R&P arrangement and differential shape as a symmetrical design, so this is why I would have also thought just swapping it to the other side and some clearance on case ribs would be just about it and it would mesh the same on one side or the other. Of course if the big bearings are not symmetrical in the case halves and there is a difference of even a few millimeters, the R&P would not be in the same position equivalent. But if I were designing a gearbox, I feel it would be easier to make it symmetrical. But yet again, I am no mechanical designer, I am HW designer (funny, I design ECUs for gearboxes - automatic, dual-clutch, CVT, center diff, rear diff, etc).
I'll also let him know about your gears, but I think he was looking for a cheap solution, not an expensive rebuild. He changed two gearboxes by now, as he could find them at ~100 bucks.

User avatar
Pablo2
Posts: 404
Joined: Sat Jun 25, 2011 7:37 pm

Re: AT gearbox maximum torque

Post by Pablo2 » Thu Feb 15, 2018 4:39 pm

In Bug transaxles and Porsche transaxles up through '86 you can flip the diff. Beginning with '68 002 Bus Box, VW went to a hypoid R&P that doesn't allow flipping the diff.

I don't know what year Subaru went to hypoid, but it's WAY back .. probably 1970
aka Pablo, gears, Geary
9.36 @ 146 in '86

TZepeSH
Posts: 209
Joined: Wed Nov 03, 2004 1:55 am

Re: AT gearbox maximum torque

Post by TZepeSH » Thu Feb 15, 2018 4:54 pm

So what type is the bug R&P? Spiral bevel? I thought all were hypoid. What are the differences? Is a bug pinion aligned with a symmetry axis of the ring (as in diameter axis is collinear to pinion axis)? Or is it also off-axis?
Strange, wikipedia says hypoid is an older design better for torque, and spiral bevel is more efficient so most cars use it.

Google did not make me understand yet.This is an interesting read, I learned something new today.

User avatar
petew
Posts: 3584
Joined: Sat Oct 07, 2006 6:05 pm
Location: Sydney/Australia
Contact:

Re: AT gearbox maximum torque

Post by petew » Thu Feb 15, 2018 9:09 pm

Todd from Subaru gears tried all manner of different ways around the issue. The custom R&P was the only sensible way to fix it. Otherwise there would have been another cheaper kit.

Bruce2
Posts: 6822
Joined: Sat Oct 13, 2001 3:01 am

Re: AT gearbox maximum torque

Post by Bruce2 » Mon Feb 19, 2018 4:51 pm

TZepeSH wrote:
Thu Feb 15, 2018 4:54 pm
wikipedia says hypoid is an older design better for torque, and spiral bevel is more efficient so most cars use it.
Depends on what the designers want. The spiral bevel is more efficient at transmitting torque, but it has the lowest contact ratio. Hypoid gear sets have higher contact ratio so they can transmit more load before things break. Due to the hypoid offset, the force of the pinion is not being applied in a direction that is perfectly perpendicular to the radius of the ring gear. This makes the hypoid gear set less efficient.

The Suby R&P has a massive 30mm hypoid offset. Unless your friend is intending on raising the diff in the trans case by 60mm when he puts it on the other side, he's an idiot for trying.

The big thing that separates humans from all other animals is that we have the ability to learn from the mistakes of others.

User avatar
petew
Posts: 3584
Joined: Sat Oct 07, 2006 6:05 pm
Location: Sydney/Australia
Contact:

Re: AT gearbox maximum torque

Post by petew » Mon Feb 19, 2018 8:50 pm

Here, I fixed it for you...
Bruce2 wrote:
Mon Feb 19, 2018 4:51 pm
The big thing that separates SOME humans from all other animals is that we have the ability to learn from the mistakes of others.

I can't tell you on how many levels that applies to my life and many around me. :roll:

User avatar
raygreenwood
Posts: 11792
Joined: Wed Jan 22, 2003 3:01 am

Re: AT gearbox maximum torque

Post by raygreenwood » Tue Feb 20, 2018 12:40 pm

Just for a little historical...but odd..reference....VW used a hypoid differential from 1968 to the start of model year 1975 in the VW 411 and 412 manual transmission (type 004) and also in the 003 Automatic on the same vehicles and type 3. Very quiet, smooth...but no flippy differential.

Ray

Post Reply