AT gearbox maximum torque

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Slow 1200
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Joined: Mon Jun 17, 2002 2:01 am

Re: AT gearbox maximum torque

Post by Slow 1200 » Wed Feb 21, 2018 7:39 am

looks like around 1967 they had a hypoid-gear-loving engineer somewhere in Wolfsburg, since 002, 003 and 004 transmissions all got hypoid final drives, and all were designed during that era

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

Re: AT gearbox maximum torque

Post by TZepeSH » Wed Feb 21, 2018 7:46 am

So what type of R&P does the "normal" beetle have? Spiral bevel? Is spiral bevel pinion longitudinal axis in line with the ring radius (meaning the difference between spiral bevel and hypoid is just that the pinion is offset in hypoid, so not in line with ring radius)? Is this why a beetle diff can be swapped to the other side? I can not see a small offset in the small pictures from the web and right now it is difficult for me to get access to my gearboxes to see in person (I have both a 002 and an IRS beetle gearbox). I am not a mechanical engineer and my eyes just see some nice curved teeth on both ring and pinion, but I still can not differentiate spiral bevel and hypoid, even after reading a lot.
This was a very nice lecture and piece of information I learned, thank you!

Bruce2
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Re: AT gearbox maximum torque

Post by Bruce2 » Wed Feb 21, 2018 9:12 pm

TZepeSH wrote:
Wed Feb 21, 2018 7:46 am
So what type of R&P does the "normal" beetle have? Spiral bevel? Is spiral bevel pinion longitudinal axis in line with the ring radius (meaning the difference between spiral bevel and hypoid is just that the pinion is offset in hypoid, so not in line with ring radius)? Is this why a beetle diff can be swapped to the other side?
You now have it sussed!

TZepeSH
Posts: 218
Joined: Wed Nov 03, 2004 1:55 am

Re: AT gearbox maximum torque

Post by TZepeSH » Thu Feb 22, 2018 6:25 am

Thank you all for your patience! I have really learned something interesting. Anyway, I will post an update if the guy manages to do anything with the gearbox (maybe he wants to go all the way with welding as somebody suggested, I don't know).
And of course I will write more on the subject of the topic, when I manage to finish the conversion. But it will not be too soon.

TZepeSH
Posts: 218
Joined: Wed Nov 03, 2004 1:55 am

Re: AT gearbox maximum torque

Post by TZepeSH » Fri Feb 23, 2018 6:22 am

I just noticed on the Subaru gearbox conversion (watched a very nice 1h conversion video on youtube): does the kit involve flipping the differential AND changing the R&P to a version that seem to invert the rotation? It doesn't make sense to me, I thought the kit from subarugears means only changing the R&P and the diff stays in the same case half. Maybe I understand wrong:
1) flipping the differential to the other side changes the output direction (generally speaking, for a bevel gear, not hypoid)
2) changing the R&P teeth direction would change direction? I think not, keeping the differential in the same half would mean same output direction as before, no matter how the curved teeth are oriented. Thinking more easily to "straight cut" teeth, curving them in any direction would not change the rotation, but the "drive" and "coast" surfaces.
So is this modification done by flipping the diff AND the teeth orientation to keep the correct drive and coast orientation? The new ring and pinion do not seem to have different thicknesses than the original ones, so where does the "raising the diff in the trans case by 60mm when he puts it on the other side" come from? Wouldn't it mean to raise the diff by 60mm with the subarugears conversion, too, if flipping the diff?

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Pablo2
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Re: AT gearbox maximum torque

Post by Pablo2 » Fri Feb 23, 2018 8:37 am

Envision reversing the rotation of the Subaru engine in a Subaru. The R&P would need to be cut as a mirror image of the original, with the ring gear on the opposite side. That's basically what's been done, EXCEPT that the engine rotation HASN'T been reversed .. and because it hasn't, the new coast flank has become the drive flank. While this isn't optimum from a strength standpoint, it seems to work OK.
aka Pablo, gears, Geary
9.36 @ 146 in '86

TZepeSH
Posts: 218
Joined: Wed Nov 03, 2004 1:55 am

Re: AT gearbox maximum torque

Post by TZepeSH » Fri Feb 23, 2018 10:39 am

Oh, only now I get it!
For hypoid, in my mind I was keeping the pinion fixed and rotating the ring/diff to the other side while keeping them meshed, and I thought it would get to the same position. But it actually meshes correctly somehow mirrored on the pinion axis, thus moving the diff higher. This is the 60mm offset, right? I always thought that 60mm upwards actually meant moving to the side. My mind was set on the normal bevel gears with pinion axis in line to ring radius... So for subaru it is not sufficient to make a mirrored ring to swap the diff to the other side, because the drive and coast flanks are wrong (maybe not wrong, but not efficient).
But doesn't that mean that in beetles with swapped differential the flanks are also swapped, so the whole assembly is not optimal anymore?

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Pablo2
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Re: AT gearbox maximum torque

Post by Pablo2 » Fri Feb 23, 2018 8:36 pm

But doesn't that mean that in beetles with swapped differential the flanks are also swapped, so the whole assembly is not optimal anymore?
No, not at all. When flipping the beetle diff, the ring gear has merely been rotated to the other side. Flanks are driven exactly as they were previously.
aka Pablo, gears, Geary
9.36 @ 146 in '86

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