j-k

I have been offered a 5speed dog box for my 93 wrx RA rally car at a very good price...

Now i know that the car at present is running a 4.11 final drive and it has VERY short gearing ie 5000rpm = 80mph with a top speed of about 120mph.

The gearbox i have been offered has a 3.9 final drive , so what would have to be changed to accommodate the new box/final drive.

I would like to keep the ratios as they are at present, so what would be the best route to upgrading?

The car currently is running standard running gear,gems ecu(no dccd),and a few other goodies..280bhp and 320lbft torque on a 34mm restrictor(group A)

thanks

jon

ZEN Performance

you would need a 3.9 rear diff.

You refer to "the" car, is this your car or the car the dog box is coming from?

You need to find out the ratios that are in the box you're considering, they may be very short and be fine with the 3.9 diff.

Paul

j-k

Thanks for the quick reply paul.."the car" referred to my car and the dog box with the 3.9 final drive is what i was cosidering to fit

So by fitting a 3.9 rear diff,(and if the ratios where the same in both gearboxes) the overall gearing would not be changed??

jon

ZEN Performance

If the ratios are idential in both boxes, changing from 4.11 to 3.9 will make the overal gearing longer, about 5% in this case. I think that is the case here, in which case you will end up with the original homologated ratios as they were intended to be run.

I'm assuming I spoke to you last week about another box you were considering buying.

j-k

Nope, not me mate....

Thanks for the advice anyway ....

jon

Jay m A

iTrader: (2)

It all depends on the gear ratios in the dog box to whether the gearing will be the same.

If you want to run as shorter gearing in the dog with the boxes available, then assuming both have 1:1 drop gears - take the front diff from your box, put it in the dog box and keep your rear diff.