Team MightyBoy

ok so iv been googling to find this info and cant find
i wanna know what the gear ratios r in the f5a auto box or what rpm the engine revs at 80k-90 kph
its for a diesel conversion(legal this time)
thanks

I don't know the exact ratios, but the final drive is roughly equivalent to an F5A manual. So the answer is that at 80-90kms your RPM is about 4500.

According to the SS40 manual

ok so lemme see if i have this correct

using 175/70 r13 wheels, the diameter will be 452mm
.452 x 3.14 = 1.419 metres circumference
1000 / 1.419 = 704rpm at 60kph at the wheel or 704 / .6 = 1174rpm at the wheel at 100kph

final gear ratio on r4burns chart is 1 to 1 and the other ratio underneath that is im guessing the diff ratios which i dont really understand that much, but if i use the 4.684 as a multiplier...
4.684 x 1174 = 5501 engine rpm at 100kph which is ouch

from my searching on the forum, 175/70 r13 are the biggest wheels that will fit on a stock mb without scrubbing on full lock
its not an issue for me to use slightly bigger and just not use full lock but i wanna second opinion on my figures before i get excited

at 80kph it would mean 4400 rpm so pretty close to what brayden said

175/70 R13 tyres have a diameter of 575mm, and you'll be very lucky to fit them in the rear wheel arches. Assuming they would fit, you'd wind up with about 4300RPM@100kph.

thanks for that, i forgot to count for 2 sidewalls in my calculations thanks for putting me on the right track
so something like a 500 tall wheel is the max i can go

do u know of any auto boxes that would fit and has a taller final ratio?
i was thinking of using a cvt from a sherpa or justy but they r pretty rare

My 17's are 545, and they just squeeze in. F8B auto has a taller diff, same kind of difference you get going from F5A to F8B with a manual box.

whats the turning circle like? do yours scrub? and what offset r your rims?

im guessing a f8b auto box is gonna be a real mission to find

I have 165/75 13 on the rear these are "just fits" as any wear in the rear shackle bush's will result in scuffing under heavy braking (spirted driving).On the front 155/75 13 is as big as I can go without adjusting the steering stops and limiting the turn.

arklan wrote:whats the turning circle like? do yours scrub? and what offset r your rims?

Turning circle isn't affected by the wheels, and they don't scrub but the arch lips have been folded flat. Offset is +42.

Do you have an updated build thread anymore Brayden?

Nope, I haven't really done anything to it over the past 2 years. Moved on to other projects.

last question
is it possible to 'break' the gearbox so it just changes gears at the same rpm every time?
a little 3 speed or something would be better but google isnt my friend at the moment

If you disconnect the vacuum switch then it will shift to 2nd at 40kph every time, or 60kph if you have your foot to the floor.