The Project Pad

i recently started working a single seater sand rail restoration that i want to sort of modernize. for a transmission i have chosen one out of a 1989 audi 90 FWD 5 cylinder car. i figured this is a great tranny because its pretty much a quattro tranny less the center differential, their pretty strong in stock form, their dual bell housing pattern so i can use 4 cylinder, 5 cylinder, V6 and V8 VW/audi engines and trannys from early B5 passat/A4's are dirt cheap and extremely similar. anyhow, the first problem i see is that i will have 5 reverse gears and 1 forward gear if the trans is mounted the conventional way with the engine out back. i found a bit of info where people spoke about flipping the ring gear to the other side of the pinion so that it rotates the opposite direction thus making 5 forward gears and one reverse gear but no one ever had any solid proof that they actually made it work properly. this is the only problem i for see at the moment. shifter is going to be a hybrid setup with an MK4 VW cable shifter with custom cables and special linkage, clutch setup is pretty straight forward and mounting it is as simple as fabbing up some brackets on the chassis. the buggy will be power by an ABA 16V turbo hybrid engine running on digifant 1 EFI. the engine choice is the reason why i want the audi trans, with the audi trans there's no special adapters or clutch sets needed, the bug/bus transaxles are getting rare and expensive today and the audi transmissions are dime a dozen and as cheap as 75 bucks a piece.

I've heard people talk about turning the Trans upside down, not sure if that actually works, you'd obviously have to plug the vent...

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scubagli wrote:I've heard people talk about turning the Trans upside down, not sure if that actually works, you'd obviously have to plug the vent...

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i heard that too but i cant picture how that works. still trying to grasp how it all works in relation to the gears and rotation.

Turning the transmission upside-down seems like a lousy idea to me. As mentioned there's the problem with the vent, and fill/level/drain plugs will be in the wrong place.

Also transmissions are designed to be lubricated a particular way... it's not always obvious but there are often various channels & passages, hollow shafts, etc., that capture oil thrown by rotating parts and route it to bearings and bushings that are not exposed to the splash. And when the trans is upside-down, those mechanisms won't work.

I will say I too have heard of moving the ring gear to the opposite side (generally not by changing how it's attached but by flipping the diff around) but can't point to a specific example and have never personally seen it done.

elaw wrote:Turning the transmission upside-down seems like a lousy idea to me. As mentioned there's the problem with the vent, and fill/level/drain plugs will be in the wrong place.

Also transmissions are designed to be lubricated a particular way... it's not always obvious but there are often various channels & passages, hollow shafts, etc., that capture oil thrown by rotating parts and route it to bearings and bushings that are not exposed to the splash. And when the trans is upside-down, those mechanisms won't work.

I will say I too have heard of moving the ring gear to the opposite side (generally not by changing how it's attached but by flipping the diff around) but can't point to a specific example and have never personally seen it done.

i have a friend who claims he's done the differential flip in old air cooled trannys and it worked just fine for him. i think he did it when he was building a mid engine instead of rear engine buggy.

That sounds like the solution.

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scubagli wrote:That sounds like the solution.

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agreed