Changing T40 for T50 gearbox...

[jondee86]

Just out of curiosity, has anyone ever changed out a factory
fitted T50 with a T40 gearbox ? I was wondering if a T40 plus
a 4.1 or 3.9:1 diff ratio would be reasonable setup for road
use plus the occasional track visit ?

I find the fifth gear on the T50 a bit awkward when changing
in a hurry, and wouldn't mind eliminating it. Plus gearing up
in the diff would raise the super-low first gear up a bit.

Cheers... jondee86

[Dell'Orto]

Aren't they the same ratios, with 5th just being overdrive?

[jondee86]

Aren't they the same ratios, with 5th just being overdrive?

Exactly... but by going to a 4.1 or 3.9:1 diff all the gears get a bit taller.
With the stock 4.3:1 first gear is a bit low, so it can stand being effectively
a bit taller. And by making 4th taller the need for a 5th overdrive gear is
reduced. I'd guess that 4th with a 4.1 or 3.9:1 diff ratio would be quite
a usable gear... more responsive than 5th with a 4.3.

In the early 80's Toyota was making a few different models fitted with T40
and 3.9 rear ends from the factory. But I never got to drive one, so I don't
know if the spacing between gears gets too much for a 4AGE.

Cheers... jondee86

[Stealer Of Souls]

I used to have a K50 / 3.9:1 on the back of my 4AGE. It was okay, but not great.
Now have a T50 / 4.1:1 and it is much better.

On the previous setup used to run out of oomph at about 165kph on the long straight at Taupo.
The current setup is still pulling very well at 140kph. I haven't had an opportunity to see just how far it will go, but given the performance at 140, I think the 4.1 will top out higher.

Just to note, nothing else in the car changed, just box and diff. After I destroyed the K50 I was lucky enough to get my hands on the T50 almost straight away.


I don't see the reason for losing the 5th gear.
Isn't it just a case of remembering not to use it?

[Grrrrrrr!]

I don't see the reason for losing the 5th gear.
Isn't it just a case of remembering not to use it?

^^^^ This. Drive your car round without using 5th, you now know what a t40 would feel like on current diff ratio. Figure out if you can fit a wheel with the appropriate profile to simulate a 4.1 diff under your guards, borrow a set for a day and go for a quick drive to see how the engine pulls thru the gears. ie, if you are running 205/50-15 now, a pair of 205/50-16s is pretty close to the same difference as a 4.3 to 4.1 swap. 195/45 -17s are almost perfect.

[jondee86]

I don't see the reason for losing the 5th gear.
Isn't it just a case of remembering not to use it?

Good point that The annoyance comes with the accidental 2nd to 5th
change under pressure I have a spare 4.1 CW&P in the shed, and by
way of an experiment, I might throw that in to see the effect.

There is another reason for looking at T40's, and that is the rising price
of T50's and the drying up of the supply. Given that a T40 should pretty
much be a drop-in swap for a T50, if you can live without the overdrive
gear you open up a low cost alternative to the W-Series upgrade.

Cheers... jondee86

[85AW20v]

You can fit heavier detent springs in it too to help stop the accidental 5th - they're in the top of the box around the shift linkage I think.

It's also about your change technique. Don't move the gear lever across like you do for a four speed - let the detent springs do what they're supposed to and center the lever in the 3rd-4th slot. It doesn't take long to get used to. My brother had to learn to shift again when he went from his rally Mini to a Starlet with T50 and didn't take long to sort it.

[jondee86]

It's a long time since I hit 5th by mistake But what I have
discovered, is that if you double de-clutch while changing from
5th to 4th, it seems to defeat the reverse gear lockout. So if
you are not careful, you can find yourself in the reverse gear
slot rather than the 4th gear slot. I'm a reasonably quick learner,
so I just pull the lever thru without doing anything fancy now.

I think the detent springs are doing their job, as there is a
reasonable amount of resistance when pushing the lever across
to select 5th. Might still hunt down a T40 and stick it in the back
of the shed, so if anyone has a known good condition 22 spline
T40 that needs a new home... let me know.

Cheers... jondee86

[fangsport]

have only recently (events-wise) gone back to the T-50 in the Levin.
rocked T40 for many years, as there was not great gain except backstraight of Levels, where the short (4.5:1) diff would max the revs in 4th.

and no, my T40's are staying were they are, in case you were gonna ask