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-   -   GTA-style half shafts (https://www.alfabb.com/bb/forums/gearbox-transaxle-differential-propshaft/24374-gta-style-half-shafts.html)

Alex 04-27-2006 12:16 AM

GTA-style half shafts
 
I recently bought a 2-litre Berlina LSD with a 43/10 CWP after spending far too long trying to find the non-LSD 1750 Berlina version, because of the smaller diameter of the latter version's half-shafts (then fitting another type of LSD). I've noticed that in the parts manual there is another variety of half-shaft for the GTA which has a 'scalloped' output flange where it butts against the back of the rear brake disk, part # 105.14.17.300.00 . Anyway, I've also read that some of these half-shafts were 'gun-drilled' and I wonder if someone could explain what that means (I'm thinking hollow along the length), whether the shafts are just as strong when used in conjunction with a non-locked rear end, and whether anyone has attempted to modify standard half-shafts in this manner?

Alex.

vintage prep 04-27-2006 12:53 PM

Yes they are drilled along there length. The fact is, the metal in the center if any solid rod does little to add strength, mostly it adds weight, which you would'nt want in your racing GTA. Hence the drilled center. Same idea with modern racing tubular sway bars.

70ep 05-18-2006 09:23 AM

GTA Halfshafts
 
The GTA shafts had a different number of splines than production models. Not interchangable. For SCCA racing we ended up using 2 litre assemblies with tightened up LS for reliability and frugality after several GTA type broke. 70ep

Max Banks 06-21-2006 09:10 AM

yep the only halfashaft we have ever seen broken is a GTA course spline hollow one! We use 1300/1750 halfshafts always to save weight and have never broken one.

Alex 06-21-2006 01:45 PM

So with my 2-litre Berlina LSD, I'm definitely stuck with the larger diameter half-shafts?

PSk 06-21-2006 04:16 PM

Quote:

Originally Posted by Alex
... after spending far too long trying to find the non-LSD 1750 Berlina version ...
Alex.

Would that be the same as a 1750GTV? ... because I have 2 non-LSD rear axles for my car.

Pete

Max Banks 06-22-2006 07:59 AM

yep Alex you are stuck!

PSK - no its not 1750 GTV is 4.1 ratio, not 4.3 (unfortunately)

Alex 06-22-2006 09:24 AM

Quote:

Originally Posted by Max Banks
yep Alex you are stuck!

Hmph, time to find someone with a huge lathe to turn down the shafts :rolleyes: (don't worry, that was said in jest)

PSk 06-22-2006 05:09 PM

Quote:

Originally Posted by Max Banks
yep Alex you are stuck!

PSK - no its not 1750 GTV is 4.1 ratio, not 4.3 (unfortunately)

Gee so the halfshafts are different for the different ratios? ... bugger and strange (and why?).

Pete

Alleggerita 06-22-2006 09:23 PM

Quote:

Originally Posted by PSk
Gee so the halfshafts are different for the different ratios? ... bugger and strange (and why?).

1300, 1600, 1750 have one type of half shaft, 2000 w/ and w/o LSD has another, heavier ones. Both types have fine spline. GTA with LSD's for the most part had heavy spline ones that are heavier than the 1300-1750 shafts but less beefy than the 2000 ones. Some of the GTA ones were gun drilled for lightness (referring to the process of how you drill a gun barrel).

BTW, there is a factory optional LSD unit to fit with the 1300-1750 light spline halfshafts but that is relatively rare. Consequently, some people adapt the later 2000 LSD's for use in the 1300-1750 rear end. They often use the lighter 1300-1750 halfshafts to shed weight (this involves some machining - I believe there is a thread on this). Personally I prefer use the entire 2000 assembly after having seen a few halfshafts letting go on hot 1750's.

So halfshaft don't depend on ratio but on type of rear end and type of LSD fitted.

PSk 06-22-2006 09:53 PM

Quote:

Originally Posted by Alleggerita
1300, 1600, 1750 have one type of half shaft, 2000 w/ and w/o LSD has another, heavier ones. Both types have fine spline. GTA with LSD's for the most part had heavy spline ones that are heavier than the 1300-1750 shafts but less beefy than the 2000 ones. Some of the GTA ones were gun drilled for lightness (referring to the process of how you drill a gun barrel).

BTW, there is a factory optional LSD unit to fit with the 1300-1750 light spline halfshafts but that is relatively rare. Consequently, some people adapt the later 2000 LSD's for use in the 1300-1750 rear end. They often use the lighter 1300-1750 halfshafts to shed weight (this involves some machining - I believe there is a thread on this). Personally I prefer use the entire 2000 assembly after having seen a few halfshafts letting go on hot 1750's.

So halfshaft don't depend on ratio but on type of rear end and type of LSD fitted.

Okay I'm trying to work out what Alex originally wanted :confused: .

I now think it was a non-LSD 43/10 CWP for a 1750 Belina, or whole rear axle.

Now I have a 2 x 4.1 ratio non-LSD rear axles (one with teeth off the pinion, hence why I have 2), and Alex has a 43/10 LSD rear axle. Can you not change remove the 4.3 crown wheel (from the LSD diff) and bolt it on the non-LSD 4.1 diff centre and use the 4.3 pinion in one of my type rear axles? Thus as the diff centre is still designed for the 1750 it will have the right size half shaft requirement ... and bam you have a non-LSD 43/10 1750 rear axle!!!

My point is it is the differential centre that dictates the half shaft requirements not the ratio, surely the crown wheels are interchangeable ... surely Alfa Romeo is not that stupid to make them unique, surely!

I've yet to open an Alfa Romeo rear axle, but done plenty of Ford Escort ones and I used to change diff ratios all the time by changing the crown wheel and keeping the expensive gear type LSD centre ... I had a set of diff noses (actually 4 of them) where the pinions live on these axles, all set up, etc. ... for my track car.

Pete

Alleggerita 06-22-2006 10:14 PM

Quote:

Originally Posted by PSk
My point is it is the differential centre that dictates the half shaft requirements not the ratio, surely the crown wheels are interchangeable ... surely Alfa Romeo is not that stupid to make them unique, surely!

Sorry Pete, Alfa 2000 crown & pinions are different from the 1300-1750 ones. In fact the different ratios on the 2000 are available with either an 8-bolt or 10-bolt crown wheel. US 2000's are usually 8-bolt. However, the only way to find out for sure is to open it up. Been there, done that when I changed ratio on a 2000 diff.

PSk 06-22-2006 10:46 PM

Quote:

Originally Posted by Alleggerita
Sorry Pete, Alfa 2000 crown & pinions are different from the 1300-1750 ones. In fact the different ratios on the 2000 are available with either an 8-bolt or 10-bolt crown wheel. US 2000's are usually 8-bolt. However, the only way to find out for sure is to open it up. Been there, done that when I changed ratio on a 2000 diff.

Bloody heck ... Alfa Romeo are crazy :D :D

Now it all makes sense anyway :).
Pete

Alex 04-29-2007 04:47 AM

Brief revival of this thread ...

Let's just say that I found a local company that is able to drill out my (2L LSD) half-shafts for a really economical price ;) . I've got some questions:

1. Does anyone know the bore size/depth of these lightened shafts?
2. Would the hole at the outboard end of the shaft need plugging?
3. This company can deep-bore to a tolerance of 0.001" drill wander per 1" of bore depth - would any slight inconsistency in the bore cause balance issues?
4. Max mentions that the only type of half-shaft he's broken is the coarse spline hollow type. Is this because of the splines or the hollow shaft? My intuition tells me that a tube is actually more resistant to torsional stresses than a solid shaft?
5. Is this overkill for a road car or does 'every little help'?

Just wondering on a quiet Sunday ...

Alex.

70ep 04-29-2007 06:24 AM

GTA Halfshafts
 
Can't help on # 1,2,or3 but I know where every GTA shaft broke - about 3'' from the hub and the shaft was solid at that point. 70ep


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