Jack Knight dog box
Turbo Mini Forums

Hi chaps, I'm going to be totally and embarrasingly honest now...so here goes.

I bought a jack knight dog box 3 weeks ago as I was bored of breaking baulk rings. Managed to get a good deal on a box that had been used only once from a chap in the trade. He told me it had special ratios and didn't know what they were, so let me take it away and work them out.

Being a bit simple I worked out the ratios of 1st 2nd and 3rd and ignored 4th assuming it would be 1:1. I didn't realise that the ratios of the 1st input gear and laygear have to be taken into account to calculate the final ratio of each gear.....anyway to try and cut a long story short I have a gearbox with the following ratios.

1st = 3.31
2nd = 2.13
3rd = 1.312
4th = 1

You will see that 1st is shorter than normal for a dog box, seeing as I run a 3.9 diff in mine as it revs over 8, it makes 1st gear almost pointless for me.

I was about to order a new laygear, 1st input and 3rd gear to convert this gearbox to the normal dog box ratios when my brother suggested I offer it to the turbo boys. So here I am.....for you guys running 3.1's or similar and not wanting to be pull 90mph in 1st like you would with a normal dog box I can offer you this one. At the moment, on a 3.9 mine will pull just over 40mph in 1st, although thats at 8krpm+

I paid 800 quid for the box just 3 weeks ago, and its going to cost me another 600 quid to get it how I want it, so more than a brand new one would have cost me....but anyway i'm not bitter.

If you would like the box act quick as I'm an impatient git and want to put mine right for the summer.

Apologies for the length of the post, but somebody here may benefit from this gearbox.

Cheers guys.

us turbo boys want a long first gear though dan to use the torque on

i have the dog box with the long first gear thats the same as a challenge box.

Fair do's....just thought i'd ask in case anyone wants it

no worries mate. not sure where to advertise with a short first gear. mini 7 website for the 7's?

i'm having trouble working out why it has the ratios it has, very strange and wide
unless its for tractor pulling ,lol.

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

apparently it came from a 7 racer, although it seems strange to me, I mean they only pull off the line once don't they.

i'd be amazed if it was ever fit to a circuit car,
as in all close ratio boxes 1st needs to be long so the rest can be bunched up,
not the case in this one ,
i'd say maybe a heavy rally car that uses 1st on tight hairpins a lot, and the short gear will keep the engine buzzing along .

its still a strange one though ,
are you sure you have done your maths correctly??

carl

Edited by fastcarl on 7th May, 2006.

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

Unfortunately yes....plus its in the car now which confirms the crazy ratios. Once i've changed the 1st input and laygear it'll give me the proper ratios of the 2.315 1st gear box.

http://www.usedrallyparts.co.uk ???

im sure someone somewhere will pay through the nose for it

Edited by Nic on 8th May, 2006.

can also try this US site http://www.vintageminiracing.com/

I've seen the future and tbh its Pie

or just ebay it without any knowledge or answers or consience!

LOL!

Edited by turbodave16v on 8th May, 2006.

Thanks for the advice chaps, much appreciated :)

blimey i bet your gutted thats no small amount of dosh to splash out either