Outer Limits 4x4 Board

I'm running the R150 box behind a 1UZ in my Hilux with 4.88 diff gears. I'm looking at dropping the the revs for 'highway driving' as it sits on around 3200rpm at 100km/h.

What are the options with this box ie; can you buy a different ratio 5th gear or source one from a diferent box?

Thanks for the help

Grub

The R154's (Supra 5 speed) have a 0.75:1 ratio 5th gear compared with the 0.84 ratio of the R150 5th gear. 1st gear is taller though so it'd be no good for the scrub. Best bet would be to source a R151 as the 1st and second gear are lower then re-gear your diffs. 1st gear is 4.3 compared to 3.8 in you current box. That would give you the same 1st gear crawl speed with 4.3 ratio diffs as your current box's 1st gear with 4.88 diffs. This would drop your highway revs by close to 400 rpm.

Otherwise, just get bigger tyres.

I had a R151F behind a 1UZ in my Bundy with 4.88 diffs and it sat on the highway at around 2400rpm with 35s

I might have to check my tacho once I get it running again as it seems high considering i'm running 36" tyres. I am running an aftermarket tacho that I may have not set to the 4 cylinder option on the dip switches.
Apparently you can fit 5th gear from a R452 gearbox that gives 30% overdrive. I have to pull the gearbox out anyway as it is falling out of 3rd so I might look at this opition.
I am also running twin transfers so low range gearing is fine off road. I have 4.1 diff gears sitting in the shed if I get desperate