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Discussion Starter #1 (Edited)
Anyone following my GTA progress thread will know I've been having issues with the original gearbox. I sourced a good 2nd hand box as a temporary replacement whilst I consider my options for the original box. My plan was to to have it rebuilt and sling it back in...

But, OMFG!!! I don't know whether the car is running better with new primary lambdas, maf and cam belt but ef-me it's absolutely manic! I was going into a 60 from a 30 tonight, 2 seconds behind a dawdler doing 25mph and I was grabbing 3rd before I'd even passed them...

I thought the same when I built my first 156 3.2 but that was a different experience, I didn't have a baseline comparison, I went from a half remembered cf2 156 2.5 to a cf2 156 with a 3.2 dropped in it.

As the GTA is a 2nd car now and consequently mpg is not a consideration, I'm really tempted to have the GTA box rebuilt but not fit it. Just sell it with the car.

It's thaaaaaaat much fun!!!
 

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Anyone following my GTA progress thread will know I've been having issues with the original gearbox. I sourced a good 2nd hand box as a temporary replacement whilst I consider my options for the original box. My plan was to to have it rebuilt and sling it back in...

But, OMFG!!! I don't know whether the car is running better with new primary lambdas, maf and cam belt but ef-me it's absolutely manic! I was going into a 60 from a 30 tonight, 2 seconds behind a dawdler doing 25mph and I was grabbing 3rd before I'd even passed them...

I thought the same when I built my first 156 3.2 but that was a different experience, I didn't have a baseline comparison, I went from a half remembered cf2 156 2.5 to a cf2 156 with a 3.2 dropped in it.

As the GTA is a 2nd car now and consequently mpg is not a consideration, I'm really tempted to have the GTA box rebuilt but not fit it. Just sell it with the car.

It's thaaaaaaat much fun!!!
I agree.. although I've not tried a 2.5 box. I have a 3.0 gtv box.. so a half way house as it's a commuter.. but it makes it fun on slip roads : ) Hey, if those south african crazy tuners are all sticking them in as part of 'stage 1' .. it can't be a terrible idea.. Enjoy it :thumbup:
 

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i think 2.5 gearbox is a great idea, it doesn't make too much of a difference in 6th.
or at least if you look at the speed you lose it doesn't concern me since i dont travel that speed....much lol

if my gearbox ever goes i would defo be considering fitting a 2.5 in and then fit the Quaife in aswell :)
 

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People always seem to forget the box when trying to get a bit more "fun"

I remeber putting a 1.3 box on a 1.5 ti SUD and could not belive the difference in accleration and torque!!!
Not much could beat me away fromte lights :biglaugh::biglaugh:

Sounds cool to me.
Only thing would be resale as it wouldn't be standard.
But thats only an issue if you're not keeping it.
 

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Is it not the same box with different ratio's anyway ????
 

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Interesting. Here's a question, can the 3.2 GTA clutch kit fit in the 2.5 gearbox? I JUST had my clutch replaced and I'm seriously considering doing the 156 GTA SW a once over...from full suspension (coilies, ARB's and bushes) to headers and then the obligatory diff, it would be great to fit a 2.5 box while at it.
 

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Discussion Starter #7
Interesting. Here's a question, can the 3.2 GTA clutch kit fit in the 2.5 gearbox? I JUST had my clutch replaced and I'm seriously considering doing the 156 GTA SW a once over...from full suspension (coilies, ARB's and bushes) to headers and then the obligatory diff, it would be great to fit a 2.5 box while at it.
Yes, the gearboxes are all but identical. - I've used the GTA flywheel and clutch with a 2.5 box and a Q2 diff.

The clutches differ though - the GTA pressure plate has twice as many mounting points. But again, a GTA clutch will marry up with the 2.5 flywheel and gearbox with no issues.

And vice versa, a 2.5 clutch will FIT a GTA but there's a reason why they doubled the number of bolts so I wouldn't recommend it.
 

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a 2.5 clutch will FIT a GTA but there's a reason why they doubled the number of bolts so I wouldn't recommend it.
I cant understand the reasoning though unless the clutch pressure spring is much much stronger on the GTA
I have lorrys with less bolts.. the drive is taken up on the three small steel pegs so all the bolts do is hold the plate against the flywheel and after running much heavy clutches on other cars with less bolts i thought it was very odd the first time i noticed it
 

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Externally the boxes are identical, you need to look at the crown wheel to see whats fitted. We've pulled boxes out of GTAs being broken up for spares before only to find they've got a 2.5 box fitted rather than a GTA box.

I'm pretty sure gear ratios 1-6 are identical 2.5, 3.0 and 3.2, the only difference being the final drive (pinion to crownwheel tooth count).

I'd like to build up a 2.5 box but fit it with the 6th gear cogs from a 1.9 JTD 16v box, that would be perfect for hooning about in without sacrificing fuel economy on a long run. 2530rpm at 75mph with 225/45/17 tyres.
 

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I have a 3.2 GT with the Q2 diff and a 156 V6 2.5 gearbox. It is noticeably quicker throughout the rev range than my old GTV 3.0. Some of that will be the extra power and torque low down but most will be the shorter final drive. I do very little motorway driving and only around 5000 miles a year so for me, it's ideal.
 

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Yes, the gearboxes are all but identical. - I've used the GTA flywheel and clutch with a 2.5 box and a Q2 diff.

The clutches differ though - the GTA pressure plate has twice as many mounting points. But again, a GTA clutch will marry up with the 2.5 flywheel and gearbox with no issues.
Interesting...:scratchchin:

So in my 156 3.0 conversion, I could put in a GTA clutch without any worries? Straight swap? :)
What exactly would be the difference? Stiffer pedal? ...

:beer:
 

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Interesting...:scratchchin:

So in my 156 3.0 conversion, I could put in a GTA clutch without any worries? Straight swap? :)
What exactly would be the difference? Stiffer pedal? ...

:beer:
Yes exactly. Very little difference in feel compared to a 2.5 clutch. I don't think you'll notice the difference. Its supposed to handle more torque than a 2.5 clutch.
 

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Yes exactly. Very little difference in feel compared to a 2.5 clutch. I don't think you'll notice the difference. Its supposed to handle more torque than a 2.5 clutch.
Great! That's exactly what I wanted, because the 3.0 has a little more torque than the 2.5... ;)

Thanks Pud!

By the way, forgot to mention my gearbox is the original 2.5.
 

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Great! That's exactly what I wanted, because the 3.0 has a little more torque than the 2.5... ;)

Thanks Pud!

By the way, forgot to mention my gearbox is the original 2.5.
As was my 3.0 conversion, used 2.5 gearbox. When the conversion was originally carried out the 3.0 dual mass flywheel and 3.0 clutch was retained, but later in life a solid flywheel and 3.2 clutch was fitted. I can't recall if the flywheel came from a GTA or a 2.5 but a GTA clutch will fit either of them anyway.
 

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Externally the boxes are identical, you need to look at the crown wheel to see whats fitted. We've pulled boxes out of GTAs being broken up for spares before only to find they've got a 2.5 box fitted rather than a GTA box.

I'm pretty sure gear ratios 1-6 are identical 2.5, 3.0 and 3.2, the only difference being the final drive (pinion to crownwheel tooth count).

I'd like to build up a 2.5 box but fit it with the 6th gear cogs from a 1.9 JTD 16v box, that would be perfect for hooning about in without sacrificing fuel economy on a long run. 2530rpm at 75mph with 225/45/17 tyres.
Thats a good idea! I personally find the GTA 6th a tad too short as in V max trials you end up taking at 6800rpm which is past peak power.
 

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Is it not the same box with different ratio's anyway ????
Externally the boxes are identical, you need to look at the crown wheel to see whats fitted. We've pulled boxes out of GTAs being broken up for spares before only to find they've got a 2.5 box fitted rather than a GTA box.

I'm pretty sure gear ratios 1-6 are identical 2.5, 3.0 and 3.2, the only difference being the final drive (pinion to crownwheel tooth count).
Yes, ratios are all the same on the V6 boxes, final drive ratio is only change. 2.5 the shortest, then GTA, then 3.0 GTV box the longest.
Interesting. Here's a question, can the 3.2 GTA clutch kit fit in the 2.5 gearbox? I JUST had my clutch replaced and I'm seriously considering doing the 156 GTA SW a once over...from full suspension (coilies, ARB's and bushes) to headers and then the obligatory diff, it would be great to fit a 2.5 box while at it.
The clutch sits on the flywheel - the gearbox just slots in. Yes GTA clutch kit fit on 2.5 flywheel. If you want to mate a 2.5 box to the GTA, then only the box matters, Clutch can stay 100% as is.

Thats a good idea! I personally find the GTA 6th a tad too short as in V max trials you end up taking at 6800rpm which is past peak power.
If GTA box is short, in your opinion, then the 2.5 box is even shorter - the GTV 3.0 box is longer.

7% between the boxes - redline speed in 6th gear:
2.5 = 260km/h
GTA = 280km/h
3.0GTV = 300km/h
 

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If GTA box is short, in your opinion, then the 2.5 box is even shorter - the GTV 3.0 box is longer.

7% between the boxes - redline speed in 6th gear:
2.5 = 260km/h
GTA = 280km/h
3.0GTV = 300km/h
GTA box isn't halfway between the 2.5 & 3.0, it is much closer to the 3.0.. If you displayed redline speed on a scale it'd look something like this:

(2.5)....................................................................(3.2)..............................(3.0)
 

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OK pud - you called me out and I had to double check my figures :smoker:
We can bring one more box into the equation - the 166 2.0TS (the bell housing is different so you have to swap internals)
Final ratios
2.0 = 4.06
2.5 = 3.94
GTA = 3.73
3.0 = 3.562

So sorry, my mistake - you are wrong... :jester:
3.0% between 166 2.0TS and 2.5 - then 5.3% between 2.5 and GTA and 4.5% between GTA and 3.0

So to correct the approximation: redline speeds
2.0 = 250km/h
2.5 = 260km/h
GTA = 275km/h
3.0 = 290km/h
 
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