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Discussion Starter #1 (Edited)
My mechanic after some persuasion by me bought a Q2 differential in order to find if it is possible to retrofit it to an existing Alfa. Here's what we have found so far.

First of all, the Q2 is an epicyclical torque-biasing diff of type Torsen B without a preload spring, like Quaife's ATB. Here is a drawing of it:


Its shell is of similar dimensions with the free diff of the TS versions but the ring gear spigot is a little wider. Also the driveshaft spigots are longer; about twice the length of the ones in the free diff. Therefore in order to fit the Q2 to a TS gearbox you would have to machine away a portion of the spigots and fit the ring gear of the JTD Q2 version. This ring gear however is quite "long" in ratio, 57 teeth. For a 1.6 147 like mine it could be combined with a 14-tooth pinion gear, from an earlier 155 model instead of the stock 15-tooth pinion gear and the final ratio is really close, (57/14=) 4.07 from (61/15=) 4.06. For a 2.0 TS i am not sure because we haven't found what kind of ring/pinion combination they use.

Unfortunately the Q2 cannot fit into a V6 gearbox because the V6's ring gear is larger than the TS or JTD one and its bolts are totally different.
This is not true, read ahead in the thread.

I'll keep you informed about anything new we may find.
 

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I am in the process of doing the same thing on my JTD, the diff I have matches a Quaife V6 diff in dimensions are you sure it wouldn't fit a v6, what am I missing, are you telling me the internal teeth are in a different location and I might need new driveshafts? it looks to me like I can use my existing ring gear, I was going to look into what I could chnage for slightly longer gearing when I have more power.

The measurements from here seem the same as the diff I have in my hands which toes in with what I have been told that the V6 and JTD have the same diff? I was told it wouldn't fit a TS but Alfa provide the Q2 to the 2.0JTS don't they?

http://www.quaife.co.uk/shop_files/QDH6E12222.jpg

Are there perhaps 2 part numbers one for the 2.0 and one for JTD or I am missing something obvious ?
 

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sandys said:
I was told it wouldn't fit a TS but Alfa provide the Q2 to the 2.0JTS don't they?
Do they? I thought it was just diesels for now, and other models later?
At least thats what I read on Alfas web site recently. of course it may be out of date.

Cheers,
TB
 

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I'm sure Q2 is just 1.9JTD for now.
 

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Hi,

Would one of these diffs fit a 147 gta 6 speed box? I've been considering a quaife unit until i saw this thread.

John.
 

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Discussion Starter #8
I am under the impression that Quaife provides a custom ring gear together with their ATB, at least that's what this drawing suggests.

Our initial intent was to fit the Q2 to the V6 versions because they need it the most, but according to my mechanic's memory (for now) the ring gear of the V6 is a lot more massive and has a different PCD and bolt pattern which makes it impossible to bolt onto the Q2. Also its tooth pattern is different. However we cannot be certain until we take a V6 diff off a car and examine its ring gear or spigot. We have already ordered a Q2 ring gear so that we can inspect it closely and compare it to the ring gears of other TS's and V6s. JTDs are very rare in Athens because diesel-engined cars are banned from Athens "for environmental reasons". :rolleyes:

By the way, the final ratio of the JTD Q2 is a little shorter than the 3.2 V6 because the latter has 56/15=3.73 ring/pinion ratio and the JTD is 57/15=3.8

Also, note that Quaife's ATB seems similar to a Torsen T-2R.
 

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alfasud.ti said:
I am under the impression that Quaife provides a custom ring gear together with their ATB, at least that's what this drawing suggests.
I'm sure they don't.
Given that the final drive ratio varies between different models it just adds unnecessary complexity for them to do the crown wheel too. Your existing crown wheel would bolt to the LSD.
 

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Discussion Starter #10
Just came back from my mechanic. After he saw this drawing and did some measurements on the Q2 that gave exactly the same numbers as the Quaife diff for Alfa V6s he promptly removed a ring gear from a gearbox/diff assembly, tried to bolt it on the Q2 and ...guess what? It fits perfectly! :D

The rest of the dimensions seem identical as if the Quaife drawing was actually one of the Q2 itself! The only extra thing you will need is the twelve bolts that bolt the ring gear on the Q2 diff because they are a little longer than the ones of the stock free gear. My mechanic will be fitting the Q2 to his GT 3.2 V6 on Friday.

The big surprise is the cost. The diff and its bolts costs about €400 (£250), so the whole conversion will not take more than €500 (£320) considering the fact that in V6s you don't have to take the gearbox off the car to change the diff, you only dismantle the front subframe and driveshafts and remove the diff/ring gear module. I know that prices are higher in the UK, but how high can they be? ;)
 

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That is good.
I think I checked through ePER some time ago and fount that the std diff case was the same on the V6 & JTD. It is good to see that the whole thing will swap.
Good price too
 

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Good stuff, you had me worried for a mo that my diff was going to be a pain in the arse. I did the same measurements but only roughly and didn't want to recommend it to the V6 boys for fear of being wrong.

You probably want the new bearings too which are about £40. still under £300 for the parts is not bad. It'll be interesting to see how well it works when fitted next week, I would find it quite useful with the wet roads at the mo, the TCS light is on all the time when gunning it through a series of bends.
 

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sure these are the parts I picked up might not need them all.

bearings x2 7655061
misc spacers/seals etc. 7704728 and 95720273
diff 55208952
crown wheel bolts if you can get them are 7581411

I found this when I was going to do my GTA years ago ( bookmarked it :lol: ) helped me to understand where the diff fits in, its much the same for the Alfa, though getting all the stuff out to get to that point is another matter, if my stepdad wasn't ill I would have done a how-to unfortunately I now I have to pay someone else to do they job as I'm not confidernt.
 

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That's definetely on the to do list then!
 

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Discussion Starter #17
Well, the Q2 diff is on the GT 3.2 since Saturday. The transplant was like i described earlier. The car has a lot more traction when exiting a turn even in slippery roads (many of those here in Greece) and ASR/VDC activation is considerably delayed. Absolutely no reaction to the steering wheel like the one you'd have with a conventional LSD with disks.

Great mod, well worth its cost.
 

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Hi guys!

Anyone of you knows if this Q2 diff could be retrofitted in a 166 V6 6-speed gearbox? It sounds as if the 147 and GT have the same gearboxes, but does it match the 156/166 as well? Would have been great if it did, could use a bit more grip och the winterroads here in Sweden.
 

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You should look if your diff is the same as the JTD 16v diff (95721110). The Eper parts dvd says they're the same. So that's a start.
 
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