Supra 5-speed or Th700 into 420?

Saloons
1

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…

Thanks

2

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.

Regards,
Peter Jan

3

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:

4

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.

Regards,
Peter Jan

5

Thanks for your thoughts :slight_smile:

6

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.

7

Okay…good advice…thankyou…

8

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.

Regards,
Peter Jan

9

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

10

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.

11

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

12

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

13

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

14

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…

15

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

16

I have a 420 also with a Johns Cars 700R4 kit. I’ve barely driven it since brake system rebuild started and snowballed into lots of other work.

17

With identical transmissions the 3.8 often feels quicker and more eager than the 4.2, so some of the different feel is probably engine related.

18

Just a question. Is there a reason for the 700R4 vs a 200-4R? Reason I ask is both are 4 speed automatic transmission, with 4th being OD. Both are hydraulic valve body, so no computer needed. But the 200-4R is smaller physical size and slightly better gear ratio spread (closer, less jump between gears). The trans bellhousing adapter would be the same. Same flex plate adapter, just a slight difference in trans mount location. The 200-4R was used in stock V6 and small V8 applications by GM. It was used behind the Buick Grand National turbo V6, so it can handle the Jaguar L6 power levels.

The question about direct drive is reference to the torque converter lockup. A lockup provides the effect of direct drive since no converter slip. Usually set up in non-stock applications for 4th gear only. Some factory settings have 3rd and 4th lockup.

19

see: https://www.youtube.com/watch?v=k_n6Jw0CH00

20

Although you seem to have made up your mind, there is one consideration that I haven’t seen mentioned. What is your driving environment? I like my 4-synchro o/d in my Mk2 very much, and converted the car from automatic - no regrets. BUT, if I lived in Seattle, no way I’d do a manual box. If you are doing a lot of city driving and there are hills, you would be much better off with an automatic conversion.