Help with my gearbox

[nickpadgeth]

I've fitted a 1.6 diesel into my 1971 bay, using the original bay gearbox, I've also fitted the largest rear tyres I can fit to raise the gearing, does anybody know what gearbox I could use to raise the gearing? Thanks

 

[68_early_bay]

Quite a common conundrum with the guys fitting larger Aircooled motors, to raise the gearing some fit a late bay 091 "6" rib gearbox but this requires a few modifications to mount, there's also "5" rib, but both of these are now getting harder to source due to their popularity,

The easiest way is to contact the likes of bears Motorsport or cogbox, and have the gearing in your existing box increased :mrgreen:

 

[madmike]

5 rib is only 4:86 R&P
get the 6 rib it's a 4:57

 

[madmike]

5 rib is only 4:86 R&P
get the 6 rib it's a 4:57

 

[Trikky2]

Or of your gearbox is in good condition you can get the 4.57 crown wheel and pinion fitted to it.

 

[nickpadgeth]

Quite a common conundrum with the guys fitting larger Aircooled motors, to raise the gearing some fit a late bay 091 "6" rib gearbox but this requires a few modifications to mount, there's also "5" rib, but both of these are now getting harder to source due to their popularity,

The easiest way is to contact the likes of bears Motorsport or cogbox, and have the gearing in your existing box increased :mrgreen:

Thanks for the advice, i shall lie under the bus tomorrow and have a look

 

[Tofufi]

I'm doing a 5 speed conversion on mine.

 

[jonboylaw]

I'm doing a 5 speed conversion on mine.

Do tell more...


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[Tofufi]

I'm doing a 5 speed conversion on mine.

Do tell more...

I'm planning on fitting a Porsche 901 gearbox. I've not done it yet, so I don't have any first-hand knowledge, I'm still collecting the parts (only starter motor and a few bolts to get now, I think). I'm hoping (by doing the work myself) that I can get 5 speeds for under £1k, although my gearbox is an unknown quantity in terms of condition, so may need a rebuild... and be aware, Porsche parts are pricey compared to VW stuff! My bus will be keeping its stock 1600 with twin DRLA carbs.

I've got a 1970s magazine article I can upload later if anyone is interested - it details someone in the US doing the same conversion, but there isn't much detail.

The Porsche 901 gearbox is ideal for an aircooled engine, as it doesn't lower the revs *too* significantly. With a torquey diesel you may be better looking at a later Porsche 'box, the 915, as it has taller ratios again.

I've done a graph to show the 901 gear ratios against the standard 3 rib gearbox. 1st and 2nd gears in the Porsche gearbox are taller (so it's not great for those who live in hilly areas), 3rd and 4th approximately the same as standard, and the Porsche 5th drops the revs from 4th, but I'm hoping not enough to cause my microbus any problems with overheating due to reduced fan speed.

 

[Tofufi]

As promised...

Note however that you're still doing 3000RPM at 60. If you have a diesel/watercooled and want to lower the revs much more, you'll want to look for a later Porsche box, as they were designed for much lower RPMs that won't suit an aircooled VW engine

And some gear ratio tables for the 901 5 spd manual box...