Diff Ratios

[NiftyNev]

I hava a '92 2.4 SSR-X Manual with 31x10.5x15 tyres and a diff ratio of 4.875.I am considering changing to a 4.3 ratio for better fuel economy and lower revs at highway speeds.Interested to know what others have.
Manual transmission only.

(1) Tyres
(2) Diff Ratio (or code)
(3) RPM @ 100KPH

Thanks
Neville

[TonyN]

Nev, you may be approching this the wrong way, the 31's will have already made the gearing taller if they wern't fitted at the factory, giving you less revs for a set road speed, trouble is the motor is working harder cos of the higher gearing, so using more fuel.

Most regears after fitting bigger tyres are 4.88 for 33's and 5.29 for 35's, lowering the gearing gets the powerband (therefore most efficent engine performance) back in the right place for road speed.

The above No's are based on petrol motors, deisels, having more torque is the why you'll have taller 4.88's anyway. Our V6 4Runner should have 4.56 gears or even 4.10's

4.3's will give you a lower RPM, but, only if your motor can handle the extra load without needing the go-pedal buried in the carpet.

Talking about gearing sucks! I aways end up getting confused!

[Elvz]

'89 Manual Surf

(1) 10.5 31 R15 Bridgestone D689's
(2) 4.875:1
(3) 3200RPM in 4th