Is there a higher ratio 5th gear available for the B4 Passat TDi?

My 96 Passat has plenty of torque available at 1900 RPM (90% if I remember the VWOA propaganda) so why can't I cruise on the highway at lower RPM. I heard they exist somewhere, any ideas or sources?

Any experience or results with using these on a TDI?

http://www.spiretech.com/~vw6spd/

E-mail Vince, the owner of the above company. He can probably help you out. He built me a custom ratio box for my Golf and did a great job.

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couple of Rabbits, a Golf and a Passat TDI

As far as I know, there is a slightly taller 5th gear available for an 02A tranny, but the difference is only about 5%, not worth it in my opinion, but ask Arizona Mike who did it to his car. (Do a search.)

Those 6-speed conversions are generally close-ratio boxes, the ratio in 6th may not be any taller than our present 5th...

Brian P,
'96 Passat TDI mit UPsolute

1900 rpm is the peak of the torque curve, 100% of 149 lb*ft. The rpm range in which at least 135 lb*ft (90%) is available extends from about 1750 to about 2750. 80% (120 lb*ft) range is from about 1500 to about 3500.

Thanks for the info. It sounds like with a torque curve that flat, We should be able to use higher gearing for crusing purposes - I suspect true horsepower, which is proportional to torque X RPM, becomes the limiting factor and not actual torque. (If I am remembering those old dynamics and physics formulae correctly)

I think that for steady crusing, we need to find out the road horsepower required to maintain say, 80 MPH and check the HP curves to see at what RPM we fall below the road horsepowder needed. Road HP could be calculated by mass and coast-down tests (how many Gs) or perhaps we can ask one of the ECU-mapping brethren to tell us via boost or specific fuel consumption, etc. what the instantaneous HP is when road testing at 80 MPH.

We could then use documented HP curves to see how low of an RPM we can produce the same HP (with more pedal, of course)

How high of gearing can we go in 5th for near-flat crusing. I bet with enough pedal and stock ECU, we could cruse at 80 MPH as low as 1900 RPM.

Any ideas? Sounds like a thesis project.

I want to ask our non-Northamerican brethren how their crusing RPM compares to ours. Maybe VW uses different gearing in Europe or across the globe. I will start another topic for this one.

I'm pretty sure that a taller top gear would be necessary in order to increase top speed, especially when chipped. Beyond 4000 rpm the torque/power curve falls off a cliff, and my top speed is limited by the power dropping off at 4000 rpm. As for how I know this, don't ask.

I've heard that the Euro 6-speeds have about 1600 rpm at 100 km/h in top gear (read 3200 rpm at 200 km/h!!) compared to our 2200 at 100 km/h. That might be a tad too tall for our conditions, but I'd like about 1800 - 1900 rpm at 100 km/h ... I'd say 1900 rpm at 80 mph / 130 km/h would be too tall, you probably want to be around 2400 - 2500 at that speed ...

Brian P.
'96 Passat TDI mit UPsolute