ALFAGTV6.COM

[Smity42]

Hi guys,

I bought a 2.5L 75 on the weekend for parts. Included in the boot was a transaxle, apparantly from a 3L 75.

From reading on various forums, I beleive the 3L 75 transaxle should have the same gear ratios as a TS, 3.54 final drive ratio, and an LSD. I wanted to try and confirm this.

I haven't taken the transaxle out of my GTV yet so this is my first real look at one. So please forgive the nOObish questions.

The crownwheel has 39 teeth and the pinion has 11. 39/11 = 3.5454 so that is a good start.

Questions:

a) Can anyone confirm if the diff in the photos below is an LSD or not? If yes, what type is it? Clutch type 1.5 way?

b) Is there any way I can confirm if this box has the TS gear ratios, other than by pulling it down?

c) Can I fit the clutch (+housing) from the GTV onto this box?

d) Can I swap the crownwheels from the two boxes over, making 39/10 (3.9) and 43/11 (3.909) ratios?

e) Is there a difference in the selector shaft between standard and isostatic shift linkages? How can I tell which one this box suits? If different, can the selector shafts be swapped?

f) On a different but slightly related note, are the brakes on the 75 any better than the GTV? Is there any difference between the rear rotors? DBA lists two different part numbers...

[MD]

Smithy,

Straight up I dont recommend the use of this box in a standard GTV 2.5 as the ratios are too tall. They are even too tall for my liking for the 3 litre donk. I 've tried it. Great for the open road and fuel economy but who runs Alfas for fuel economy? A 4.1 is best comprimise that's why the TS uses it.

So after you work out if you want to go ahead or not, the rest of the questions can be dealt with.

[Mats]

Hi guys,

Questions:

a) Can anyone confirm if the diff in the photos below is an LSD or not? If yes, what type is it? Clutch type 1.5 way?

b) Is there any way I can confirm if this box has the TS gear ratios, other than by pulling it down?

c) Can I fit the clutch (+housing) from the GTV onto this box?

d) Can I swap the crownwheels from the two boxes over, making 39/10 (3.9) and 43/11 (3.909) ratios?

e) Is there a difference in the selector shaft between standard and isostatic shift linkages? How can I tell which one this box suits? If different, can the selector shafts be swapped?

f) On a different but slightly related note, are the brakes on the 75 any better than the GTV? Is there any difference between the rear rotors? DBA lists two different part numbers...

a) Yes. Clutch/disc type 45* ramps both drive and coast. No idea what that is called with numbers.

b) Yes, it does however involve rotating the input shaft and counting the output revolutions and calculating the ratio...

c) Housing, yes. Not sure the splines in the clutch plates are the same though, you also need the correct pilot tube for the throw-out bearing. And of course the correct slave cylinder + mount. All possible to switch over, if the splines are the same on the input shaft.

d) NO! Crown and pinion is matched. The crown and pinion from different ratios don't mesh right. Absolutely no exceptions. I.e. a 39 teeth crown wheel from a 39/10 ratio is a totally different beast then one from a 39/11 ratio.

e) Yes, they are different but completely interchangeable. The old one one has a splined shaft with a thread on the end. Isostatic only have a hole through it like the one in your pictures.

f) Brakes are the same, only difference is the interface to the GB output flanges. V6/Turbo boxes has M10 bolts while the 4cyl (except Turbo) cars have M8 with driveshaft directly on the disc.

[Smity42]

Hi MD,

Yeah, I realise that the 3.54 is miles too tall, hence my questions about the crownwheels. From the information I've been able to gather, this box should be identical to a TS box except for the final drive ratio, so If I could sort out a shorter ratio that saves having to buy a TS box .



Hi Mats,

Thanks for that info, greatly appreciated.

a) Excellent. Sounds like a 1.5 way to me.

What is throwing me is that it is behaving like an open center on the bench. If I spin one output shaft, the other spins in the opposite way, and if I prevent one shaft from moving there is no resistance to spin the other one. Is this LSD likely to be dead, or is this how they behave with no torque applied to them?

b) HAHA, yeah, I was hoping to avoid that. Markings on the box or something would be nice. Oh well, I guess I have no choice

c) Great, housing was the biggest concern as I don't have the one for this box. I guess when I get the GTV box out I'll be able to work it all out.

d) I was afraid this would be the case . Can I swap both the crownwheel AND pinion over then as a pair? Therefore making the 75 box a 4.3 ratio and the GTV box a 3.54?

e) Excellent, thats everything I needed to know.

f) Again, thanks. Are the front brakes also the same or are they any better?



Cheers,

Martin

[MD]

No, the brakes are no better hence the huge thread on the subject on this Forum.

[Micke]

a) The LSD has no locking power without incoming torque. You really cannot say just by rotating it if it's dead or alive. I guess if you have the box on a bench it would be possible to lock one wheel, apply torque on the incoming shaft and check how the other wheel feels. Then again if it's out of the car the right way is just to open and chack and replace worn parts + adjust the lash.

b) MARKINGS! This is alfa. They frobably didn't know (or care) at the assebly line either.

d) Pinion and crown wheel can be swapped as a unit. However, the old and new style boxes have different shafts which don't mix.

f) Two different front brake options. 4 bangers Alfetta, Giulietta, GTV, 75, 90 (-TS and Turbo) have non vented disks. The V6 and turbo + TS have vented disks and the brakes are superior to the first ones.

[Mats]

You can change a non-LSD gearset into a LSD box if they are both from a 75 for instance. You need a spacer under the crown gear and some tinkering to get the height right. I've done it, twice.

The other way around is more difficult since you need to remove material or at least get the stub shaft bearing more outboard somehow, shim under the lid or maybe it's possible to just remove the shim under the bearing. Never tried it.

[Smity42]

No, the brakes are no better hence the huge thread on the subject on this Forum.

Mmmm I guess I'll have to venture into that dark and scary section soon...

a) The LSD has no locking power without incoming torque. You really cannot say just by rotating it if it's dead or alive. I guess if you have the box on a bench it would be possible to lock one wheel, apply torque on the incoming shaft and check how the other wheel feels. Then again if it's out of the car the right way is just to open and chack and replace worn parts + adjust the lash.

b) MARKINGS! This is alfa. They frobably didn't know (or care) at the assebly line either.

d) Pinion and crown wheel can be swapped as a unit. However, the old and new style boxes have different shafts which don't mix.

f) Two different front brake options. 4 bangers Alfetta, Giulietta, GTV, 75, 90 (-TS and Turbo) have non vented disks. The V6 and turbo + TS have vented disks and the brakes are superior to the first ones.

a) Interesting, so no preload? I've been resisting the temptation to dissasemble it for a while now, I'm sure that won't last much longer

b) LOL! I should have known. Anyway I have now confirmed that it does indeed have TS ratios (by spinning the shaft and counting). If I can just get a better final drive ratio on to it she'll be apples.

d) Do you mean the pinion shaft is different? Does that mean you can press the pinion gear on and off the shaft or something like that, or is there just no way to use a crownwheel and pinion from and old box in a new box?

f) Thanks, I thought there was a difference. Although it would seem they are not much better...

You can change a non-LSD gearset into a LSD box if they are both from a 75 for instance. You need a spacer under the crown gear and some tinkering to get the height right. I've done it, twice.

The other way around is more difficult since you need to remove material or at least get the stub shaft bearing more outboard somehow, shim under the lid or maybe it's possible to just remove the shim under the bearing. Never tried it.

Thanks again Mats. By gearset, do you mean the crownwheel + pinion, or the internals of the gearbox itself?

What about swapping a crownwheel + pinion from and old (GTV) box into a new (75) box and vice versa

Or, what about just swapping the diff centers over (So keeping the GTV gearbox and final drive gears but put the LSD center into it)?

I guess I'll have to get the transaxle out of the GTV and compare them side by side to figure out what is doable. That might be the job for this weekend.

[Mats]

Thanks again Mats. By gearset, do you mean the crownwheel + pinion, or the internals of the gearbox itself?

What about swapping a crownwheel + pinion from and old (GTV) box into a new (75) box and vice versa

Or, what about just swapping the diff centers over (So keeping the GTV gearbox and final drive gears but put the LSD center into it)?

I guess I'll have to get the transaxle out of the GTV and compare them side by side to figure out what is doable. That might be the job for this weekend.

Gearset = crown + pinion
Speedgears = 1 through 5 + reverse.

Never tried the old vs new pinion trick but I think that's what Micke says can't be done. There are pics showing what's different in another gearbox thread on this forum. From memory it's diamters and splines that doesn't match, i.e. forgeddaboudid.

Swapping the diff into the GTV carrier (i.e. the gearbox casing) should be doable. Before getting your hopes up I should repeat that I have never split an old box and hence don't know for sure if the pilot diamere of the crown wheel differ or the flange height.
If you try this, document it and add it to the knowledge bank on this forum please.

Gearboxes are really simple as far as disassembly/assembly. If you however change anything it can be difficult in a hurry.
What I mean is that as long as you know where everything was when you tore it down it's very easy to put it together. So tearing down to have a look is not difficult. Just do it and you'll know.

[Smity42]

Gearset = crown + pinion
Speedgears = 1 through 5 + reverse.

Yeah, easy. I've always thought of 'gearset' as 1-5+R. Ie, I could buy a close ratio gearset... So I just wanted to check we were on the same page and talking about the final drive gears

Never tried the old vs new pinion trick but I think that's what Micke says can't be done. There are pics showing what's different in another gearbox thread on this forum. From memory it's diamters and splines that doesn't match, i.e. forgeddaboudid.

I'll try to find the thread you mention. But it sure doesn't sound promising. Why do they have to go changing things just for the fun of it?

I guess thats one disadvantage of the transaxle setup; it's nowhere near as easy to change final drive ratios around

Swapping the diff into the GTV carrier (i.e. the gearbox casing) should be doable. Before getting your hopes up I should repeat that I have never split an old box and hence don't know for sure if the pilot diamere of the crown wheel differ or the flange height.
If you try this, document it and add it to the knowledge bank on this forum please.

Will do mate


Thanks again for all the help guys

[Mats]

Here you can see a couple of 75 pinions at least
viewtopic.php?f=9&t=1702

[Smity42]

hmmm, that certainly does not look promising

[MD]

Does anyone know if you can still buy dog teeth for these gearboxes or are we destined to scavange from other boxes to do the job forever?

My second question is, does anyone know of a business that is resharpening the originals?

[Smity42]

Hi Guys,

Two new questions:

What is the middle switch in the picture below? I know the one on the left is speed and the one on the right is reverse, but whats the middle one? Neutral? What does it use it for?



Second, what final drive ratio do 2.5L 75 V6s have? (Aus model)

Cheers,

Martin

[MD]

Half an answer.

The centre switch I think is a neutral switch somehow related to air pollution control other gismos on the car. Forget about it, for what your palns are, it is totally irrelevant.

I am not sure of the dif ratios of the 75 although I suspect a 4.1 open dif as the 3 litres had 3.59's and that would be too tall for the smaller engine.