Supra 5-speed or Th700 into 420?

Hello All.

I have a ´67 420 with an autobox that needs replacing. I bought all the bits for a supra conversion and was about to begin the job today.
However a few hours earlier I drove a 3.8 mk2 with the th700 conversion and thought itsuited the car really well, quick, smooth and relaxed…

So now I suddenly find myself considering converting to a th700 instead of the supra 5-speed…

I would be happy to hear your thoughts on the matter…


I have the T700R4 conversion from John’s Cars in my S-type.
And I am very happy with is.
Nice shifs, and great is the top gear overdrive and Direct drive.
And you do not need electronics for the Direct drive.
There is on 4e gear a pressure switch you can use to engage Direct drive.
And you need a oil cooler.

Peter Jan

Thanks for your reply.

I know this conversion very well and I agree with you.
I just can´t decide if I want to do the one or the other… :stuck_out_tongue_winking_eye:

But the Supra ( just a few sold here) is a manual, seems more involving to me.
And a car like a 420 ( or S-type ) is more a cruiser, Auto box is more suited I think.
80% of the cars sold here are manual, and auto boxes are for luxery only.

Peter Jan

Thanks for your thoughts :slight_smile:

What domyou mean by direct drive and pressure switch?
I have the T700 in my Mk9 and like itba lot. But itbwants to go into 4th, far too early, so I take off on 3rd, and only switch to D when on a motorway or country road with higher speeds.
Works well for me…
I have the Supra box in a 140 and it is very nice.
I think the 420 and S are sporty saloons and much more fun with a manual box. I have an S-type (my fatherś old car, ordered with wire wheels, Webasto sunroof and MOD.

Okay…good advice…thankyou…

Hi Peder,

How do you engage the direct drive clutch? ( may only be engaged on 4 )
There is a power connection as you now on the left of the box.
The direct drive connection ( 12V ) is on there.
I used the pressure switch ( only on 4 ) inside the box to engage the direct drive.
I rerouted the wiring to get this working that way.

Peter Jan

I got a complete kit from Jons Cars in Texas, including lock up kit.

Hi Ralph,
Personally I would go with the manual gearbox. I am looking for a 420 4sp. The 420 is a sports saloon so a 5sp would be great fun in it. It would be more enjoyable on twisty roads than a slush box.

My 420 had the MOD 'box, and it was a BALL to drive!

Thanks for your thoughts.
5 speed it shall be :slight_smile:

I have a Supra W57 5 speed behind a V12 XJ, and it does depend on whether you like manual gear change. Not usually an issue unless the vehicle is a daily driver in traffic.
As you have all the parts for the Supra conversion, I doubt you will be dissappointed

I will start the conversion as soon as posisible. Only snag is the gearlever postion which is a good deal further back on the supra than on the original. But I found a conversion made in australia that takes care of this issue…

Yes, that is Dellows Engineering in Sydney, that is where my conversion came from