Frankenstein R150F/R151F gearbox modifications

[adrian5800 Advanced Member Find all posts View Profile Close adrian5800]

Hi all
Been a while since I have been on here, thought I would add my latest mod to my '05 KZJ120.
The reverse gear on my box started making odd noises a few months ago so I pulled the box recently and found a couple of broken teeth on the reverse idler gear.
This box was overhauled 5 years ago by myself with new mainshaft, fully splined 5th gear and fully splined 3rd/4th synchro hub and new bearings. Some gearbox specialists call the changes a tow pack.

I have always thought 1st gear in the R150F fitted to these Prados is too tall as compared to 1st in the R151F (fitted to some 90 series and the HZJ105) and regretted not modding the box last time it was out. The R150F in the KZJ120 is 3.830:1 1st and R151F has a 4.313:1 1st gear. 2nd gear is also lower in the R151.
My camper trailer is around 2.2T ATM and 1st gear in the R150F isn't kind to the clutch..


So I bought a donor box off Facebook market place and fitted the countershaft, 1st and 2nd gears into my box along with parts needed to fix the reverse gear.

All back in now and it's just the right ratio for the 1KZ, no revs needed to set off even on a slight incline.

Cheers

[Daniel150 Member Find all posts View Profile Close Daniel150]

Nice work… Toyota seemed to insist on making 1st and reverse too high since the 120 came out.
I’ve had the same problem in prados, hiaces and Hilux’s, always wished there was a lower gear.
Doesn’t bother me now in an auto
Nice work actually being bothered to fix it.

[adrian5800 Advanced Member Find all posts View Profile Close adrian5800]

Nice work… Toyota seemed to insist on making 1st and reverse too high since the 120 came out.
I’ve had the same problem in prados, hiaces and Hilux’s, always wished there was a lower gear.
Doesn’t bother me now in an auto
Nice work actually being bothered to fix it.

Classic case of 'while you're in there'...

Thanks