[Allergee25]

Hey guys I am currently restoring a 1985 SJ40T. I plan on retaining the F10A and 4spd box (For now atleast). I plan one running 30 or 31 inch tires once its lifted ect. I want to do a w/t swap while the car is in pieces but my question is about how the diff gearing differences going from 4.11 to 3.9 (I think that's right). I will most likely be daily driving the zuk when its done so being ably to maintain decent highway speeds would be good. Basically just curious if the standard w/t gearing will be drivable as a daily and what the ideal gearing would be further down the track? Thanks guys.

[Gwagensteve]

No, gearing will be terrible with 31” tyres.

I’d recommend 6.5 transfer gears.

[ZUZUKI]

Retaining F10A & 4spd....30/31" tyres....daily driving.....maintain decent highyway speeds.....
A whole lot of incompatable with 2019 there. I think your stated goals are outside the parameters available with that combination.
You might do it for a bit, but the 'novelty' will wear off pretty quickly.
That's a very late SJ40 1.0litre, so your t/case should be able to take the commonly available gearsets.
You'll need to go deeper than 3.909:1 with diff gearing to have reasonable clutch life to get off the mark with 30/31" tyres, but there is no 5th o/drive gear at the top end to achieve 'decent highway speeds'.
Rgs, Michael