Differential Gear Ratio

[mikare]

Will a stock BT 20v benefit from a 4.7 gear ratio differential? or do you have to modify your 20v to fully utilize the 4.7 gear ratio?

[xero]

yes.
no extra mods reqiured. buy 4.7 diff, install (yourself or diff shop), fit back in car, cut sick everywhere chopping people left and right at the traffic light GP.


down side is you'll be doing about 110km/h @ 5500rpm on the freeway.

[mikare]

ok thanks. Cause somebody told me that stock 20v does not have enough power for the 4.7 gear ratio. Currently using 3.9 gear ratio. Is there a really big difference in terms of performance when changing to a 4.7 gear ratio?

[blair]

I think you've got the principle the wrong way around man, the higher the diff ratio the easier/quicker a motor will rev...

The only negative is your top speed will be reduced by a fair chunk.

You do much track work?

[H8CHIR6KU]

sort of on topic...

does anyone know how to make the speedo work running 4.7s? im not talking take it to an instrument place either. that seems to be all the info i can find

[Delazy]

Change the speedo drive gears to suit...plenty of threads around the net giving step by step instructions

[H8CHIR6KU]

i didtn realise there were factory speedo drives for 4.7 ratios that would fit

[Robo86]

na there isnt, you get them made! search a thread by oly86 or ae86 (i forget)

but yer i have 4.77 final, its awesome. highway may drive you a little mad if its loud, but makes up for it when sliding on or off track

[Delazy]

Its a combination of gears..parts are available new..think i saw a few threads on club4ag

[Sam-Q]

I doubt this would be the case. I think there even iis a chance it might increase. With a 4.7 ratio you would be doing 220km/h at 8000 RPM

Also of note is the engine would do 3600 at 100km/h, not exactly a strain for a 20V, albeit potentially loud.

I think a stock 20V engine has more of a need for the shorter gearing (taller?) than a modded one, this is because with the lousy stock ECU they really lack the midrange power and the shorter gearing should help it move around easier.