156 3.0 V6 racecar, the best gearbox? - Alfa Romeo Forum
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(Post Link) post #1 of 17 Old 25-09-14 Thread Starter
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156 3.0 V6 racecar, the best gearbox?

Hey.
I have a 156 3.0 V6 racecar, with the 3.0 gearbox from a 166.
The gearbox have to long gears for the track, i had a 2.5 gearbox in the start but it broke down.(it had been used for 195000 miles/314000km) I have a diff 50% from Bacci&romani and a paddle clutch.
What i consider is a JTD gearbox, will this fit the V6 engine and will the diff fit this gearbox? And will it be stronger than a petrol gearbox?
Anyone knows?

Lars

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V6 and later JTD gearboxes (GT/147/156 family) are the same, they differ just in gear ratios.

What did break in your 2.5 box?

Last edited by yan.ko; 26-09-14 at 20:39.
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I think it was a combination of long milage on the gearbox, paddle clutch, brutal diff and very hard down shift from 200 km/h...
Okay, i have seen that the gearbox house is almost the same from V6 to JTD, so potentialy the diff also will fit?
The gear rations on a JTD will probably fit better for the circuit than the V6(made for the autobahn i think).
But the question is will it tackle the power better? Diesel engines have more tourqe, so maybe its a better gearbox for race also?
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yes, also the diff is the same.

JTD gear ratios are MUCH longer than V6
JTD: 6th gear -> 240km/h @ 4500rpm
2.5 V6: 6th gear -> 240km/h @ 6300rpm

so if you'd put JTD gearbox into V6 156, all you would get is top speed of 300+ which is useless.

Last edited by yan.ko; 26-09-14 at 20:54.
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No it's not useless, its great for autobahn cruising :>
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I think they have more strict highway limits in Norway than we have in CZ
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(Post Link) post #7 of 17 Old 25-09-14 Thread Starter
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Okay, then we put the idea of diesel gearbox away. I didn`t tought the diesel version had so high gear ration.

Just as you know this is a race car only and not for roaduse
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The best box would probably be another from a 2.5 V6 156, preferably with less than 300,000km on it.
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I would choose a 156 2.5 V6 6-speed manual gearbox or maybe 156 GTA 6-speed manual gearbox.
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2.5v6 would be probably cheaper , more available and had less of a hard life than a more rarer and expensive Gta box. I put one in my Gta and I couldn't tell the difference , apart from the shorter 6th gear but for track should be better.
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I used same 2.5V6 gearbox on my trackday 156 with 2.5V6 engine, then with 3.0V6 from 166 on same chassis - not much of a difference - never used 6th gear.....Have option here to manufacture shorter ratio 3th and 4th gear for better response, but my project takes another route for now......And IMO that's maybe only reasonable solution with OE boxes.....
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The gearboxes should all handle +/- the same power. As most have said the ratio's of the 156 2.5 V6 is the shortest and thus best for track.

In sequence of gear lengths:
156 2.5 V6
166 3.0 V6
166 3.2 V6
156 late GTA
GT 3.2 V6
156 early GTA
GTV 3.0
147/156/GT 1.9 JTDm

Quaife and Autolusso is working on a sequential box:
Quaife® / Autolusso Sequential Gearkit for Alfa Romeo 147 / 156 GTA models - Quaife
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There's also the 166 TS 6-speed gearbox, which was a C630 but with different bellhousing to mate to a TS engine. Likely this box has the shortest gearing of them all, but would require swapping the bellhousing to fit to a V6.
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yes, you are right. The latest 2.0TS CF3 (2001+?) have different final gear (65/16 vs 63/16 on 2.5V6) and slightly shorter 6th gear (31/36 vs 31/38).
The shafts and differential gear ring would be interchangeable as differential is the same as on V6s. It's pity I didn't know that sooner

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Last edited by yan.ko; 05-10-14 at 19:29.
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Quote:
Originally Posted by Gertie View Post
The gearboxes should all handle +/- the same power. As most have said the ratio's of the 156 2.5 V6 is the shortest and thus best for track.

In sequence of gear lengths:
156 2.5 V6
166 3.0 V6
166 3.2 V6
156 late GTA
GT 3.2 V6
156 early GTA
GTV 3.0
147/156/GT 1.9 JTDm

Quaife and Autolusso is working on a sequential box:
Quaife® / Autolusso Sequential Gearkit for Alfa Romeo 147 / 156 GTA models - Quaife
Wow!
Any indication of what the price of this would be ?
Can imagine a good few thousand pounds...
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Quote:
Originally Posted by cannotstop View Post
Wow!
Any indication of what the price of this would be ?
Can imagine a good few thousand pounds...
It says 4500 pounds or there abouts in the link, before vat or install.
Which seems like a lot, but I'm sure one gta with it fitted would sell it to many others
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Quote:
Originally Posted by Scortho View Post
It says 4500 pounds or there abouts in the link, before vat or install.
Which seems like a lot, but I'm sure one gta with it fitted would sell it to many others
So it does
That is not a bad price if you want to take your GTA racing. A replacement straight cut gear set from AHMotorsports is 4750 pounds (ex. VAT)
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