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GTV6, 75 TRANSAXLE SWAP

Posted: Mon Apr 14, 2008 9:39 pm
by smashigcraft
Hi
I've read extensively (thanks to all who have contributed) about the issues of putting a 75 TS transaxle into a GTV6 and plan on doing this to benefit from the better gear ratios and LSD.
I am wanting however to install the GTV6 trans into the 75 and use the car as a daily driver. I'm assuming the only issue will be with the speedo! and if so how will I resolve this and will there be any other things to consider?

Posted: Tue Apr 15, 2008 2:18 am
by sh0rtlife
you will have to swap out the rear axle stubs(for lack of a better "alfa" term the short output shafts exiting the transaxle) as the bolt sizing and i think some offset is different

that speedo...i think your only way out is going to be a SGI-5 dakota digital calibration unit..theres a dealer on ebay 75$ shipped(in the states that is)

i was told the 75 has a reversed clutch slave...on the gtv6 you need to pull the studs for the slave and swap them into the 75 box(or atleast i had to)..so the reverse would be true for you

the clutch piviot ball MUST be swapped as well as clutch fork

shift selector (simplistic) must be swapped(iso vs normal shift)....if you make the mistake most ppl make and forget to drop the transaxle back into Neutral you pull the reverse switch out and you can pop the shift lever into Neutral with ease

since your going to have to break open the case for the shift selector...hose it out with some brake clean..this will make re-sealing it that much easier as you dont risk minor amounts of oil getting onto the sealant or mating surfaces ....meaning MUCH less risk of it leaking "alot" on you later down the road

something to consider is filling the case just before putting it into the car..lets face it the fill plug isnt in the ideal spot and a few quarts of oil doesnt add any real weight to it

if your creative and patient you can actually pull and remove the brakes and clutch slave WITHOUT bleeding or draining them..its just tricky........i rebuilt the brakes late last year and had fresh ate blue in the whole system so i didnt want to crack open an air free system..........if you do break the system open vacuum bleeding is imo the only way to do it



just did a 75 box into my gtv6 a few months ago..so its all VERY fresh in my mind :? ......so i think thats everything.....well pretty sure thats everything

Posted: Tue Apr 15, 2008 7:44 pm
by smashigcraft
Great thanks. It doesn't sound like too much trouble

Posted: Mon Apr 21, 2008 5:18 am
by PietereQ
sh0rtlife wrote:you will have to swap out the rear axle stubs(for lack of a better "alfa" term the short output shafts exiting the transaxle) as the bolt sizing and i think some offset is different
Refreshing the topic a bit as I will be soon doing the same thing... Shortlife you mean these?
thanks,
Pete

Posted: Mon Apr 21, 2008 5:52 am
by Mats
Yep. Stub shafts or stub axles. The bit with the flanges that goes into the diff itself.

Posted: Mon Apr 21, 2008 6:10 am
by PietereQ
Crap, I'll have to look for a spare then :?

Posted: Mon Apr 21, 2008 1:48 pm
by sh0rtlife
yes those...they use a diferent size bolt and i think have a diferent offset

i thought you were swapping from 1 car to another?...if thats the case you should have them already.....its a 4 allen bolt swap VERY simple

Posted: Mon Apr 21, 2008 7:16 pm
by Daniel
Offset is the same, bolt size is different - either M8 or M10.
There is a spacer that fits with the shorter half shafts/drive shafts which I think are the ones with the bigger bolts (GTV6 & 90 ?), while the 75TS has the longer shafts, no spacers and smaller bolts.
The PCD of the holes on the stub shafts is the same, just the size is different, so worst case you could drill and tap them M10 to suit the short shaft and spacer setup.

Maybe mine was easier because I replaced a GTV 2.0 trans with a 75TS trans and the shafts and bolts were the same.

Posted: Tue Apr 22, 2008 4:16 am
by zar162b4
Hello,
I'd like to ask a question related to the swapping. There is a bearing located near the head of the pinion (I mean the one not located in the intermediate flange)... in the v6 alfas and in the 75 turbo this bearing is different from the one adopted in the 4 cylinder carburetted and twin spark engines. My question is: can the bearing of the twin spark box sustain the increased torque of the engine? If not, since I have found an Alfa Romeo mechanic who has all the tools for pinion head positioning, bearings preload and crown pinion clearance check, can all the gear set of the alfa 75 fit in the gtv6 box, so that the v6 pinion bearing can be moved to the twin spark pinion?
Thank you
Regards
Oscar

Posted: Fri Apr 25, 2008 12:42 pm
by PietereQ
sh0rtlife wrote:yes those...they use a diferent size bolt and i think have a diferent offset

i thought you were swapping from 1 car to another?...if thats the case you should have them already.....its a 4 allen bolt swap VERY simple
Not a fast reply here, It's been a crazy week...
I have snapped all of six bolts on 2nd gear exiting the corner... Yes i also keep wondering how did it happen... Had to look for my rear rotor wich was several dozen meters behind :lol: Also the rotor broke my rear caliper mount so that's a new caliper to add to the shopping list. But to the topic, I think that threads on the output shaft flange are not good for anything now, hence my idea to look for a spare...

Posted: Fri Apr 25, 2008 2:35 pm
by sh0rtlife
YIKES thats scary

Re: GTV6, 75 TRANSAXLE SWAP

Posted: Fri Nov 21, 2008 12:58 pm
by jaco
Hello everyone. I live in south africa, and drives a gtv6 with 280hp. The short gearing is a real pain, and i would like to swap to 75 gearbox with the taller ratios. The 75 was not available in south africa, so i was hoping someone could help me source such a box and ship it to me. Any help would be appreciated!

Re: GTV6, 75 TRANSAXLE SWAP

Posted: Fri Nov 21, 2008 1:03 pm
by Mats
You do know there is only really a difference on first and second right?
Quite a big project for such a small gain I'd say. :)

Re: GTV6, 75 TRANSAXLE SWAP

Posted: Fri Nov 21, 2008 1:17 pm
by jaco
Sorry, i must have been mis-informed, as i understand the 2.5 has a ratio of 4.1 with no lsd, and the 75 has a ratio of 3.55 with lsd?

Re: GTV6, 75 TRANSAXLE SWAP

Posted: Fri Nov 21, 2008 1:46 pm
by Mats
Only the 75 3.0.

I thought you meant the speed gears, the final drive would be a good swap if you want taller gearing.