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post #16 of 35 (permalink) Old 12-08-2011, 10:10 AM
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My 75's driveshaft is out, let me know if you need measurements and pics.

1987 Milano Gold 3.2 24V + JK Cams
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post #17 of 35 (permalink) Old 12-09-2011, 06:42 AM
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Well, for those who like riddles, here's a pic I took this morning of three Alfa 75 driveshafts. The one on top is from a 3liter, the middle one from a late (post 1990) 1.8T and the bottom one from a 'regular' 1.8T. Other than the splines, its interesting to note the diameter of the tubes, front and rear. I can't make sense out of this but its nice to know they all have the same length (the bottom one just looks longer as the 'nose' is a few inches off the ground). I'm still trying to decide which one to put on the 24v car... Maybe a roll of the dice?
Jim K.
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post #18 of 35 (permalink) Old 12-09-2011, 07:04 AM
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Hi Jim,

For what its worth, being used to my early GTV6(which has no splines) I remember I was surprised seing the splined shaft on a newer GTV6. I have always considered the splined shaft as a simplification of dismantling the propeller shaft.

G.K.
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post #19 of 35 (permalink) Old 12-09-2011, 07:18 AM
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I would go with a hybrid, get both halves which have the smallest diameters, then have the whole assembly balanced. No sense in getting a thick shaft there.

1987 Milano Gold 3.2 24V + JK Cams

Last edited by 75evo; 12-09-2011 at 07:21 AM.
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post #20 of 35 (permalink) Old 12-09-2011, 07:31 AM
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Hey, Gabor, I don't suppose you feel your car had some kind of disadvantage not having the splined joint? I think I'm leaning in favor of not using it in the 24v.
US owners haven't seen cars without this feature! Here in Greece its the other way around -very few 3liter cars because of tax problems. In fact, they didn't believe this feature appeared on some later 1.8T's, until they saw my 1990 1.8T a few years back.
75evo, the hybrid idea sounds good; I'll also weigh the parts for more info.
Jim K.
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post #21 of 35 (permalink) Old 12-09-2011, 06:01 PM
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my gold has the non spline I would have swaped in one from grant if the thin center were not so hard to get.

my gold length is not quite right and the I think the car was rear ended at some point.
so I get some zigzag on the flex. and I have had the front go bad on this car.
The verde with the splines I can get perfect every time and the flex seem to last way longer.
also it makes taking out the drive line a lot easier.



looking at one and two it looks like they just swapped the thick from the front to the rear.

I kinda thought my were thin at the front to make room for the shifter but after seeing this I have 2nd thoughts.
I will have to take a look the next time I am under.


I would go thick and thick with the extra RPM of the 24V you don't want the drive line to play jump rope

1987 black Milano Verde, 1987 (made in 1986)blue $200 gold with ABS and LSD
1972 White spider 2000 Veloce

Last edited by slyalfa; 12-09-2011 at 06:07 PM.
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post #22 of 35 (permalink) Old 12-09-2011, 07:07 PM
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Now that is interesting! Somewhat typical of Alfa Romeo to do a bunch of stuff differently and seemingly illogical .
Logic says that the larger diameter shaft has the highest torque capacity. It will also wind up less with the torque that is applied to it. But the guibo's will take care of that.
Logic also says that the chain is only as strong as its weakest link. So there doesn't seam to be any reason for using 2 different diameter shafts tubes.
In other words, what is the point of the larger diameter shaft being used if it's followed by the smaller shaft and visa versa?

Combining the 2 smaller diameter shafts would give a tailshaft with the lowest moment of inertia and so the best acceleration and deceleration rates. Pre-gearbox (just engine) torque is hardly going to stress these parts. For a 2 piece tailshaft, this should/would be the best performance design.

Slowly Progressing Vortech Supercharged 1990 Alfa Romeo 75 Potenziata. Out of Action Twin-Charged 1988 AW11 MR2. Current Daily Driver, The Glorified Taxi 2006 BF FPV F6 Typhoon.

Last edited by Duk; 12-09-2011 at 07:11 PM.
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post #23 of 35 (permalink) Old 12-09-2011, 11:11 PM
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Heheh, are you guys paid to confuse the issue? You all have valid points rooting for thin or thick shafts... And yes, the factory Luigis and Giovannis very often did stuff which was not documented -especially on Fridays?. They must've thought 'thick or thin what the hell, they all work the same so just bolt'em up!. As for torque capacity, 1.8T's here with 480-550Nm (350-400lbft) are happy with either tube type, so any na V6 is safe with them.
Just for info, I'll weigh the parts today; stay tuned!
Jim K.
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post #24 of 35 (permalink) Old 12-10-2011, 06:28 AM
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So, the 3 driveshafts weigh ~10kg (22lbs) each give or take a half kg (1lb) -with my flimsy cheapo chinese scale which broke after the last shaft, hahah! Therefore, no significant difference.
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post #25 of 35 (permalink) Old 12-10-2011, 09:23 AM
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I thought it would be interesting to see what alfa ended up with on the final and ultimate 75: the SZ!
Surprise, its the solid front shaft without the splines! Well anything can happen in the Alfa world! Was the solid shaft the ultimate choice after all?

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post #26 of 35 (permalink) Old 12-10-2011, 09:56 AM
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Those jerks just rolled a dice.

1987 Milano Gold 3.2 24V + JK Cams
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post #27 of 35 (permalink) Old 12-10-2011, 12:16 PM
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Right, the SZ microfiche... I looked through most microfiche slides for about an hour and I can't find the splined part in any of them! I tried many editions of America, Milano, Super, gtv6, Turbo, whatever! I faintly remember finding it in the past, just don't recall in which fiche! I also looked in all factory manuals and it was nowhere to be found! This really is strange!
Clever thinking to check the SZ, Gabor! I am now sure I'll ditch the splines, since it was not deemed necessary for the SZ -who am I to disagree! That leaves me with two spare splined shafts and 4 spline couplings. Good, I can take the shafts apart and pick the best parts!
Jim K.
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post #28 of 35 (permalink) Old 12-10-2011, 01:45 PM
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I think it is wrong to assume that the shaft used in the SZ is some how the best. Remember that Alfa Romeo were broke and a shaft that has a welded on drive flange is cheaper to make than the splined shaft. They may also have bean using up left over parts.

Slowly Progressing Vortech Supercharged 1990 Alfa Romeo 75 Potenziata. Out of Action Twin-Charged 1988 AW11 MR2. Current Daily Driver, The Glorified Taxi 2006 BF FPV F6 Typhoon.
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post #29 of 35 (permalink) Old 12-10-2011, 01:48 PM
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Hm, I really got you searching, Jim

I have the splined version of GTV6 on picture L1 ed. 8-1985. If you donīt have it I can scan it for you!

G.K.

Duk: I could agree about late production problems with the GTV6. Fiat took over in 1986 and production of the SZ/RZ was in 90-93. Donīt you think that by that time they could afford the shaft they thought best for the job?

Last edited by Gabor K.; 12-10-2011 at 03:11 PM.
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post #30 of 35 (permalink) Old 12-10-2011, 04:31 PM
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well if not the splined you will need a way to stretch/shorten the car or at lest the gearbox vs the motor. I did not see a way to do this on the gold. but I might have missed something. but I did not see any slots where I could change the length. the spline is easy to get the length right. and even if there is slots on the gearbox some where. it seems like it would be a real pain to set up. vs the pinch.

also I still think the thicker would be better at high RPM. the stock redline was very slow
I think the 1.8 revs a lot more and the 24V too.

1987 black Milano Verde, 1987 (made in 1986)blue $200 gold with ABS and LSD
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Last edited by slyalfa; 12-11-2011 at 03:42 PM.
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