An alternative TDi engine and gearbox conversion idea...

[SyncroGhia]

I had an idea about a week ago which I'm sure that other people have visited before but I've never seen anyone actually do it.

After the idea, I spent the next few days working out each detail of it so that I think (ha ha) that it might actually be a realistic proposition.

I want to drive a T3 everyday but the shape of it and the difficulties of the engines and gearboxes fitted in the van means that we're limited in what we can use.

I have several projects (which some of you know about) and right now, I just don't have the space, time or money to follow this through but I will hopefully in the next few years. Putting this up on the forum might seem like a strange thing to do to some but if I share my ideas, there are more chances that someone else will do it, sort the problems that I can think of, maybe pick out some problems that I've missed...

Anyway...

This is for a 2WD T3 so not much use for a Syncro.

I want to be able to use the Audi gearbox but I'm not prepared to turn it upsidedown because of the issues of either machining a one off gearbox casing, making an adaptor plate etc correct oiling for the gearbox etc etc.

So what else can I do?

Turn the engine backwards.

Not a new idea but how many people have done it with a TDi?

The engine in question is the first of the TDi engines, 1Z, AHU or AFN. The reason is that they're cheap, available and if it all goes wrong I haven't spent thousands. Also, they're one of the best for fuel economy.

So, looking at the components of turning an engine backwards.

Crank, rods, pistons:

All will work as they are although I'm still looking into whether the piston pin is offset in the piston. You cannot turn the pistons around due to the chamber in the top of the piston.

Oil pump and servo:

You can't turn these backwards so look at the drive. The intermediate shaft is driven by the timing belt. On the TDi, the belt runs around the inside of the pulley (the smooth side of the timing belt). But on other VW inline 4 cylinder engines like the 1.8 16V KR engine, the pulley is driven from the other side with the timing belt (the toothed side of the timing belt). This will reverse the direction of drive.

Camshaft:

With this being a 4 cylinder engine, the lobes are spaced equally and it looks at present like it's possible to flip the camshaft over and run it backwards. This way you don't need a one off camshaft. Driving it is a different story. By flipping the camshaft over, you lose the drive for the camshaft sprocket. So the camshaft will need to be drilled, tapped and an adaptor piece which will slot into the groove in the end of the camshaft that the sprocket can then attach to. The cylinder head needs a small mount of machining as the end-float is set on one of the bearings so the head needs machining to match.

Timing pump and electrics:

On the 5 cylinder 2.5TDi, the pump is driven by the other end of the camshaft. This means that it runs the opposite way as the 1.9TDi. So by moving the pump to where it's mounted on the 2.5TDi, it runs the same direction as it's designed to but it runs backwards in relation to the engine. I'd want to fit a small flywheel to the pump just as the 2.5TDi has to help reduce 'chatter' through the camshaft and timing belts.

Putting the pump there brings problems. First you need to mount it. Then you have to move the servo pump. I'm looking into Alternators which have servo pumps fitted to the back of them. You need to use the bottom section of the pump to drive the oil pump as the gear which is driven by the intermediate shaft is on the servo.

The coolant pipe coming off the cylinder head will get in the way of the pump so a one of coolant pipe will need to be made.

Timing sensor, why wouldn't it work backwards as forwards? Again.. more research.

Alternator and Water pump:

On the AAZ and some early TDis, you can run the aux belt on the other side of the water pump pulley running it backwards.

The Alternator... I'm looking into this but I have a feeling that they may work backwards as well as forwards. I haven't paid much attention to this as there are also Alternators which run the opposite direction from whichever engine they come from.

Starter motor:

Reverse the wiring to the brushes and it runs backwards... well this is an idea yet to tried out. You need to change the slip gear and drive so that it engage with the ring gear teeth.

Timing belt (s) tensioning:

Replace the tensioner with a pulley and swap over so that the tensioner is on the trailing side of the belt.

So... if this all works (wouldn't it be nice if life was that simple!) we would have an anti-clockwise running TDi, the ability to use a stock Audi 6 speed gearbox and hopefully, that magical 40mpg plus from a T3.

This will mean that the engine is mounted upright as per an Audi A4/A6 so either raising the bed or fitting to a crewcab/single cab.

What do you think?

MG
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[?Waldo?]

You've addressed the important parts. You might consider keeping the pump in the same place and reversing it's rotation. Any pump builder could very easily build an e-TDI CCW rotating injection pump. The case is machined slightly differently to put internal pressure on the other side of the dynamic advance piston which is flipped around, the fill port and delivery ports are offset the opposite way on the high pressure pluger and the vane pump outer ring is flipped around. All that said, if you ran the inside of the belt around a gasser cogged intermediate shaft, you probably wouldn't have enough degrees of engagement with the pump and you'd have jumped time issues with the pump. You could place the tensioner between the pump and intermediate shaft as one option. The oil pump/vacuum pump aren't timed, so the tensioner could be before them. Another option would be to keep the belt on the diesel side of the intermediate shaft pulley. The gasser intermediate shafts have the gear reverse cut along with the distributor gear. If you could use the distributor drive gear from a gasser on the bottom of the vac pump, then you could use the gasser intermediate shaft and gasser oil pump and it would all work spun in the reverse direction. Custom belt needed. I don't really like the idea of driving the cam off a bolt-on taper or the thought of a custom cam. There's info on vwdiesel.net on the various cam profiles and having custom cams made probably wouldn't be too big of an issue. What I'm getting at is that you could reverse the injection pump, use the diesel intermediate pulley with gasser distributor gears and it would all run reverse. The deal breaker would be if the piston pins are offset, which IIRC believe they are. The Quantum/Audi longitudinal 1.6TD starters spin the other way and you might play legos with their parts to come up with a workable starter. Other issues you might run into are the crank sprocket bolt or the alternator pulley nut undoing themselves, but probably not as there are already over-run loads put on them. Interesting idea.

[xoo00oox]

I have had this thought as well. I wonder how the transmission will do running in the wrong direction? Will there be loads in the wrong direction, will the syncros work right?

I have also wondered if one could adapt reduction boxes to the vanagon rear hubs to reverse direction and run the engine and trans clockwise.

[beelzibus]

I'm not so sure the box would be happy effectively running backwards. It's an awful lot of work to go through to find out that the box can't cope.

[SyncroGhia]

The only gearbox that I'm aware of that has synchronisers that are directional are early Porsche gearboxes, 901, 915.

The rest that I've seen (inc Audi) are not directional so will work both ways. The load going through any transmission has to able to cope with both directions in everyday driving otherwise we would have gearbox failures all the time.

Oiling inside the gearbox would only be an issue if there was oiling system. If not, it's splash fed and the parts are fed oil by fluid transmission from part to part. That won't change.

Re timing pump running off the cam with a taper fit is done on the 2.5TDI but I agree, the bolt on part will probably be the weak point.

Thanks for the tip re starter motor, I'd forgotten that the transverse mounted engines have the starter on the gearbox.

Re reduction boxes. I looked into this on a previous project, even to the point of buying some that were going cheap but you'd have to completely redesign the suspension and brake and they have very strange driving tendencies with the drive going backwards to the hub.

MG
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[GrindGarage]

I like the idea of reduction hubs. They can also add some ground clearance
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91 Vanagon AUTO
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[hans j]

Why not build a mid engine car using a FWD Audi trans in the rear and just bolt a tdi directly to it? It seems like building engine mounts and a bigger cover for the engine might be easier than flipping a trans that wasnt meant to be flipped.
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1986 Canadian Syncro Westy TDI - 1989 Syncro Single Cab - 2001 Audi S4 - 1981 VW Caddy ABA - 1980 VW Caddy EV - 1973 VW T-181

[gears]

Porsche engineers used to make a big deal about the helix angle of 1st-5th gears, and the way this helix supposedly counters unwanted pinion shaft thrust. They'd likely tell you that reversing input rotation of a transaxle will cause premature failure. That said, I'm sure some folks have gotten away with it .. the question is, for how long?

I've seen welding and machining performed on a main case allowing the flip of a hypoid ring gear. If there's enough diff/input shaft clearance, this could be a less risky solution. Which Audi trans specifically?

[snowsyncro]

Interesting idea..

Not really relevant, but I thought it was pretty cool...I drove a friends snowmobile recently...when you put it in reverse, it automatically stops the engine and starts it again; in reverse! No reverse gear in the transmission.

Of course the time the transmission spends running backwards is insignificant, in this case.

RonC

[rubbachicken]

i would look into what it would take to flip the diff, how ever much work you need to put into EVERYthing else surely it'd be less making it possible to flip the diff

if you can find a dead trans, with the diff out, you should be able to to work out how much you would need to cut out and there for add metal to make it work, a wooden template of the diff would give you a quick idea
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[SyncroGhia]

[?Waldo?]

Why is it that you feel you would need a reverse cut R+P if you flipped it, but not if you ran it un-unflipped but in the reversed direction?

[SyncroGhia]

The pinion doesn't sit in the middle of the crown wheel. If you try to flip it over, the teeth won't match up. They have a Hypoid cut.

MG
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[rubbachicken]

[SyncroGhia]

The Subaru is the same and that is the reason that you have to buy a new crown/pinion. They build a new one off crown/pinion.

The Beetle box and early Porsche 901 gearbox have the pinion sitting right in the middle of the crown.

Having the Hypoid set makes for a very strong setup.

MG
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[rubbachicken]

[SyncroGhia]

[rubbachicken]

[SyncroGhia]

[rubbachicken]

what about the subaru diesel gearbox, although i don't think they have cut reverse gears for that one yet


i guess a one off reverse cut gear for your gearbox would run into a LOT of money

would your gearbox be compatible with the rest of the syncro system, could it be an alternative to a syncro trans
as they are getting harder to find
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lucy our westy

lucy's BIG adventure

meet 'burni'


markswagen {mobile mechanic} san diego area all early VW's cared for.

619 201 0310 or 617 935 4182