Final drive for turbo track use (oe toyota 3.90?)
 

I have a 2013 FRS with 4.10 stock gears. I use the car for time attack/lapping/autox, and have ordered an OS Giken differential for it. I run out of gear on the back straight at my track, and was thinking about going with slightly taller gears to help alleviate the problem.

I see a lot of 8 inch toyota gears for Hiluxes and other truck models. What is the cross compatibility on the 8 inch ring and pinions for these cars? I suspect the is300 units are different from the truck units. Am I basically looking for any 27 spline 8 inch toyota unit?

Bottom line, what's the most cost effective way to source a 3.90 R&P which I can install with my new LSD when it arrives? Are there other vehicles which came with the ratio I'm looking for other than the is300? I suppose I should do some googling to confirm the tooth number on the gearset I'm looking for to ensure I'm ordering the correct part, if it ends up being a used Lexus take off or the like.

If anyone has done the same swap and could provide any tips it would be super :)

What is wrong with the is300 units? An is300 m85 diff with a 3.73 or the m98 with the 3.9 would seriously be your best option. Alternatively, you could get gearing from weir or another company that replaces your 4.10

It appears I should have searched first lol

https://www.ft86club.com/forums/show....php?p=2861994

An oem solution is what I'm looking for. I might be able to find one in a junk yard even.

I see how I worded my OP made it sound like I didn't want the is300 unit. That's not the case, just wanted to see if there were other options to widen the search net. In all likelihood an is300 r&p is what I'll end up with. It seems like the weir 86-92 supra r&ps are also compatible and avail in 3.91. The thread I posted above has folks suggesting that's an option.