Diff and gearbox ratios

[Macaco]

More manne..

I hope someone can help me with advice pls, I have a problem with my ratios, at 120kph my revs are between 4100-4300 and it's killing me on petrol, now I heard changing diff ratios is a solution, but then I hear also it's my gearbox ratios that aren't mixing well with the diff and it would be cheaper to change the gearbox instead cause if I change the rear diff ratios the front ones must be changed too, I got a gearmax diff with a cressida gearbox, any advice would be greatly appreciated.

[Haboob]

Bigger tyres will also help with the revs...

[Macaco]

I've alredy got 31" tires

[Gunta]

Very strange that it's revving so high. Where was your diff from? Cressida gearbox is the same as the 22R so shouldn't make a difference. What motor have you got in there?

[Macaco]

It had a full 5m conversion, gearbox and all, all I did was change the motor to the 7m, one person in spoken to says maybe the gearbox ratios and diff ratios aren't mixing well, another guys says just change diff ratios, then another says it's too expensive cause once you change the rear diff ratios the front diff must be changed too so it's more cost effective to just changed the gearbox, but then to what gearbox would best suit.

[Gunta]

You can't change the rear without changing the front ratios otherwise you will damage your diffs, gearbox and transfer case. Easy thing would be to change the gearbox. All Toyota gearboxes will fit your bell housing. Running 33" tyres will help too by about 10%. Something seems wrong with your box if it's revving so high.

[Macaco]

That's the first thing that went through my mind, cause if it really is a cressida box then it should naturally have long ratios and especially for cruising in high gear, unless it's not the gearbox I was told it is, but then even my mechanic confirmed it was a toyota box, he actually thought it was the standard hilux box, I then told him it should be a cressida box and he said it could be they almost identical, so I don't know but now it's the second time I hear the gearbox is the problem, but now what box would I be looking at to resolve my problem.

[Gunta]

A standard 22R box. It's a R151 I think. You might have a stout gearbox because they were made for low gearing.

[Macaco]

That makes alot of sense, thanks Gunta, for all the advice, now I need to go gearbox hunting and one strong enough for the motor, any suggestions?

[Gunta]

R151 gearbox. Try Japan motors 0113976789

[Gunta]

Have you changed your transfer case at all because that could also be the problem?

[Macaco]

No not that I know of, it's the original transfer case that's on the gearbox.

[Gunta]

Try Japan Auto then.

[Vlak vark]

you are running a 6 cylinder on a 4 cylinder cluster so your rev counter will be out by at least 1500 rpm.

[Gunta]

If you are running a 6 cylinder then that explains everything. You need to have your rev counter recalibrated for a 6 cylinder.

[Scott]

What is the revs at 120km/h on the SFA box ?

[Gunta]

About 3750