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The mkiv Supra Owners Club

gearbox conversion


CJ

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Before everyone groans, "not aagain", this is not your normal conversion question :)

 

I have purchased a single turbo car that has been converted from an auto to a 5 speed manual. Yes, you read that correctly, I did mean a 5 speed. Whilst I have not yet picked up the car I have checked the VIN details and it is defnitely a TT converted and not an NA to TT conversion. It is currently running on the stock ECU (I am assuming the auto one) and therefore I have a few questions.

 

1. How will the 5 speed box cope with the single conversion (assuming that normal boost is run etc). By that I mean would it handle the power.

 

2. What would the drive be like with a 5 speed box as opposed to a 6 speed? Someone mentioned the gearing would allow for much better accelation. Is that true?

 

3. If I decided to change to a 6 speed, what parts other than the gearbox would need changing?

 

4. Does anyone see any other major issues with the above scenarios?

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The 5 spd box apparently is strong enough to take around 500bhp... but like the auto box all depends on how it has been treated.

 

I personally was tempted to get a 5spd as well, altho it has a slightly lower topend the gears are shorter so it should provide for a more entertaining drive.

 

The ECU should have some wires shorted on it, to fool the car into thinking it is in Neutral (either that or Park)..

 

As far as parts required for going 5spd to 6spd... I'd assume gearbox, prop, diff (and probably driveshafts), but I stand to be corrected on this...

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If someone has gone to the effort of getting a prop made up, then anything is possible...

 

That is of course if the prop is a different length between the auto and 5spd box...

This is where I am confused. I am unsure as to the differences bewteen a TT auto prop, the NA 5 speed prop etc. :blink:

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Easiest way, at a guess, would be to ask someone to measure a TT auto prop from donut to donut, and see...

 

While it isn't a scientific answer it might give a fairly accurate view...

 

Might be easier/cheaper to get a prop cut and balanced rather than replacing diff and everything associated with it...

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The diff centre bearing mounts are in the same place on all models as is the diff carrier mounts so if you had an auto diff, you would need the auto rear prop half, and if you had a 5 speed box then you would have the 5spd front prop half. You will be able to mix and match the prop halves to suit the set up that you want/require

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I was under the impression that the diff casings where different, and that the gearbox's also had some slightly different lengths to them....

 

This might change my ideas a little bit then....

 

yes you are right but the mounting points are generic so theoretically you just need the correct half of the prop for whichever set you are using. Mix and match :D

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