Got a straight 6, 3 speed, 89 fairlane looking for better takeoff..
I hear the 3.89 or 4.11 diffs are a good cheap option, any ideas as to any difficulty
I may come across chucking one in, or any better diff options??
And what other cars do these diff ratios come out of?

Last edited by Furlane on Mon Jun 08, 2009 4:14 pm, edited 1 time in total.

By 3.89 or 4.11 skyline diff into 89 Fairlane, do you mean the complete skyline diff or just the diff gears? Dont mean to be rude or anything but i dont think the whole skyline diff will go into the fairlane rear end so all you would be after is the gears (pinion gear, ring/crownwheel gear) within the diff. Lol just wanna make that clear as it kinda sounds like the whole skyline diff into the Fairlane going by the title, but anyways..

I wouldnt have a clue what ratio gears you have in the diff right now but im guessing with a 3 speed it would have terribly long gears, id either go 3.9 or 4.11 diff gears if you want good take off with short gearing and swap out the 3 speed auto for a 4 speed if you plan on keeping the car auto. If your after a bit better take off and want to keep reasonably good highway economy id go probably 3.45's or 3.7's

You'll also have to make sure that the diffs are the same type (carrier, spline etc) before you start buying gears and then realise they wont fit. Im not 100% sure on what the skyline diffs are so wouldnt be much help there, but iirc its the older type skylines (R31 i think?) that had the diff gears compatible with some fords

Being an NA fairlane im guessing its the older type borg warner diff (75 series) which is 25 spline so IF the skyline diff is the same, the gears should fit. Someone else on here with more knowledge will be able to clear that one up. But beware of buying second hand gears, depending on how they have worn in they might whine a bit, best to check the gears out in person to make sure there isnt any bad wear marks or cracks etc on the gear teeth

I thought the Skylines had 3.45's and the Pintaras in the same body shape ( RWD ), had like 3.7, 3.89 and 4.11's depending on transmission/engine package fitted to the car.
Years ago, I fitted a VL commo diff gears ( 3.45 ) into a VF Valiant diff housing....I still have it.

Being a 3spd auto, IIRC they have 2.77 gears, you will need a new housing in that case as the 2.77's are an orphan diff where no other gears fit

skyline r31 series 3 run a 3.89 diff gear and is 28 spline same as ford,commo's..etc all you need is the crown wheel,pinion and axle spacers for it to fit into the falcon diff, that's what is in mine and run's great..

Yeah it is the 2.77 diff, so would it be easier to get hold of a 3.45 xr6 complete diff and axle
and chuck that in instead?? im goin cheap and easy here.. lol
what modifications would have to occur there?