Gearing questions

richbaker78 · Teacher of Padawans Joined: 31 Jan 2006 Posts: 1298

I've got myself confused by gear ratios can anyone explain?

Inspired by all the box flipping that's going on I considering flipping a 20v turbo passat box and mating it to my scooby wrx. I thought I would compare the ratios .....

My scooby had
3.454/1.947/1.366/0.972/0.738 FD 3.9

20v
3.778/2.176/1.429/1.091/0.865 FD 3.89

Most important to me is cruising on motorway so if I'm getting this right, the lowere the FD the better? So 20v is better for this slightly? Does the FD account for the ring and pinion ratio? Do I need to consider anything else when thinking gearing? Obviously things like turbo coming on boost etc but how do I convert all this numbers to real world driving / accounting for wheel size etc? I don't want to start this all only to find its terrible to drive!

This is to replace a 091 box with a 0.77 4th....what's better ???

Kai · Posted: Thu Apr 10, 2014 7:34 pm Post subject:

I can't help you out on the gear ratio question specifically

However on the Subaru gears website and plenty others out there you can get gear ratio calculators. Enter the ratios and the wheel size and you can work out the road speed in every gear. Probably an iPhone app for this too.

20v turbo box and an adaptor plate seems like a pain compared to fitting the Subaru box alone.
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Think......

Don't sleep and drive!!!

richbaker78 · Teacher of Padawans Joined: 31 Jan 2006 Posts: 1298

Cheers Kai I'll have a play with the calculators.
Ideally would love to go 5spd scooby but the cost difference is massive.....vw boxes from £50 and even with machining etc that still leaves me a lot of change out of £2k ish the Subaru gears would cost. Only down side I can see at the mo is the driveshaft angles.

rusty69bus · Jedi Master Joined: 24 Apr 2006 Posts: 467 Location: essex

i remember taking about the passat boxes years ago, maybe look at it from a slightley different angle.... from what i remember theres no spare to flip the crownwheel? hence the flipping of the box.........so to get the drive shaft angle down how about looking at the sump as that must be the lowest point still, maybe dry sump it and drop the engine down further.

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