Diesel conversion - transmission options Options

[bfrymire]

Thanks for all the info guys, keep it coming.

When I think of front engine fwd I always think of a transverse layout. I forgot that audis/passats came front engine fwd longitudinal. So it seems like I am looking for a diesel passat (long. engine layout) tranny if such a beast exists. Or look in to gear interchangeability between later transverse diesel trannies and earlier longitudinal gas trannies. Or re-gearing of the 914 tranny, which sounds unlikely with the drop necessary. Hmm.

Thanks,

Chris

Not meaning to stir the pot.. Just a thought. Subaru has a new diesel engine out now. If the bolt pattern and engine layout is the same as the EJ25, then there are already parts available to make the swap. You can also get the parts to use the suby tranny. Wouldn't that solve all the problems? (And you might have room to put the radiator into the engine compartment.)

The real hurdle here, is getting one of the new engines.

-- brett

[type11969]

Yeah, its the "real hurdle" that I am trying to avoid. But, by the time I actually get around to this that might be a viable solution!

-Chris

[VaccaRabite]

I am so waiting for that engine to be released stateside. That is when I'll likely trade in my daily.

Zach

[type11969]

Some good intro info over on the tdiforums on the thread I started. To summarize:

It "might" be possible to mount the engine and stock transmission tranversely . . . quick measurement between the nuts on the suspension mounting points reveals 32" of clearance . . . guy online measured one setup he had at 34". Yeah, I know, too big but that is between the crank pulley and edge of the tranny. If I can get the pulley ahead of or behind these points the clearance opens up. Gotta figure out the distance between the crank centerline and tranny output shaft centerline . . . I'm sure the trunk will need to be hacked in this config but I can rotate the engine towards the front of the car to hopefully minimize this. Also, since I will not be using the driveshafts to compensate for the steering angle like in a fwd setup I will have some more flexibility with engine placement relative to the stub axles in the 914. Mating the stubs to the VW driveshafts is another headache though.

Longitudinal tranny options:

The DHY unit has a 3.700 final drive and 1-5 ratios of 3.500, 1.934, 1.300, 0.943, 0.789 B5 passat v6
The DHL unit has a 3.889 final drive and 1-5 ratios of 3.500, 1.934, 1.226, 0.838, 0.683 B5 passat diesel
DQY====3.778=2.118=1.360=1.029=0.755=3.389==Jetta/Golf TDI, for reference

I'm sure it is impossible to find the DHL unit, not sure how tough it is to find the DHY unit, Cap'n? So, just for comparison, at 3000 rpm with a 195/50 r15 tire in fifth gear with a DQY tranny I would be going about 80mph. With a DHY tranny I would be going 70. Could always use a bigger wheel/tire combo too to drop the rpms further. I know this is only part of the picture but cruising rpm is a pretty big part.

So there do seem to be some options to make this work. It will be interesting to see what comes up as I dig deeper.

-Chris

[type11969]

Potential tranny candidate, seem to be plenty out there:

http://cgi.ebay.com/ebaymotors/98-05-VOLKS...sQ5fAccessories

Same ratios as DHY. Hmmm

[type11969]

Oh yeah, doc, when you have a minute, how close can you get to the DHY ratios in a 914 tranny? Is there a taller R&P out there?

Thanks,

Chris

[Dr Evil]

There is a taller diff in certain years of sportomatics. I dont know what the difference is off hand, I need to look it up.

[Dr Evil]

Actually, I have a sproto diff and pinion that I can hook you up with. It is the set from the sporto that is not the perfect fit for a 901 box, but with a 902 or 912 aluminum plate which is shorter I can make it work I think. It would take some work, but we could do it.

[Dr Evil]

R&P in a sporto is 7:27 vs 7:31 in stock 901.

[type11969]

Hmm, interesting, that would result in a taller set of ratios than the passat tranny. Question is, is it going to be more work/$$ to mod a 914 tranny to use the sporto R&P or fab tranny mounts, cable shift, and output shafts to use the b5 tranny. I gotta chat with okieflyer about what he did. I do like the idea of an updated tranny, especially if I can swap in TDI gears at some point.

-Chris

[rohar]

I don't think I'd let tranny mounts influence your decision. They're pretty simple on the boxster/Audi box conversions and you're going to have to fab motor mounts anyway.

I'd personally be a little nervous attaching a TDI to a 901. That's a whole tone more torque than it came with (IMG:style_emoticons/default/wink.gif)