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Discussion Starter #1
So I am sort of stumped. I have old-style gearbox with grooved/non-moly synchro rings that came out a 74 Spider. So I know that's not right, someone must've swapped the box at some point. It is, however, a hydraulic clutch gearbox.

But here's where I am stumped:

This gearshifter mechanism pictured below I believe is the old type where you have to push down on the gearstick to get into reverse. Have I identified that correctly?

If that is correct, I don't think there was ever a gearbox that had both a hydraulic clutch and a push-down reverse, was there? Makes me wonder if I have some sort of Frankenbox.

I have also included a picture of the inside of the shift tower case.
 

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Did someone switch the gearbox, but retain the '74 hydraulic bellhousing?
 

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There are differing out put shafts. Different sizes, different seals.
And a special seal to mix and match. I cannot remember details.

You might also have an earlier box with different ratios than the more common . You need to count the teeth on the gear pairs.

Ken
 

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Discussion Starter #6
Well, this gearbox came out of a working car, so not too worried about conversion of various components at the moment, though it would be interesting to validate the ratios. I'll save that for a follow-on thread.

For this thread what I could use help with is the original question:

This gearshifter mechanism pictured below I believe is the old type where you have to push down on the gearstick to get into reverse. Have I identified that correctly?

If that is correct, I don't think there was ever a gearbox that had both a hydraulic clutch and a push-down reverse, was there?
 

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Well, this gearbox came out of a working car, so not too worried about conversion of various components at the moment, though it would be interesting to validate the ratios. I'll save that for a follow-on thread.

For this thread what I could use help with is the original question:

This gear shifter mechanism pictured below I believe is the old type where you have to push down on the gear stick to get into reverse. Have I identified that correctly?

Yes that is correct

If that is correct, I don't think there was ever a gearbox that had both a hydraulic clutch and a push-down reverse, was there?

Probably correct but I do not know
Can I sell you a later rear housing and shifter mechanism and gear shift ??? I think it is a straight bolt on but check first.


Regards

Ken
 

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Discussion Starter #8
Yeah - that is sort of where I am going. My rear housing is cracked anyway, and I don't like the idea of the incorrect pushdown reverse going back in the car.

To that end, here are the questions that I could use input on:

  1. Is a later model year (moly gear box) rear shift tower housing just a bolt-on to an earlier model (non-moly) gearbox? In the pictures below, it seems at a minimum the rear bearings are different. Is it just a matter of changing the bearings?
  2. Is a newer model shifter mechanism without the push-down reverse compatible with the shift rods in a gearbox that had a push-down reverse?
I'd like to make all of this "correct" for the 1974 model year, but also don't want to create a gearbox that doesn't function.

Any input on these arcane questions is appreciated.
 

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Maybe count the gears and make sure you have a std box. If not it maybe worth something to someone and you can just get a correct box.

BTW there are differences between the 1750 and 2 ltr boxes in the bearings and in the shift rod length and location of reversing switch. Also 1300 boxes like 1750 but with different 5th gear.

I think a 1750 rear housing might be a straight fit and a 2 ltr not.

FWIW

Ken
 

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When you go the the later shifter assembly. It will work with the shift rods you have. But you will also need the reverse lock out plate.

If your bearings are good then just swap them out.
 

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1750 rear housing

Here are some photos of a 1969 casting from a 1750 GTV. Bearings races look same as on your older one. see no reverse switch boss on tower.
 

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There was never a reverse switch on the shift tower. The 73/74 model years had an interlock switch on the tower that was for the US federal seat belt/gearbox for engine starting.

Reverse switch was always in the bellhousing. 74 was the last year the switch was screwed to the top of the bellhousing with 2 screws and gearbox had the longer shift rods. 75 on the switch screwed into the front of the bellhousing.
 

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There was never a reverse switch on the shift tower. The 73/74 model years had an interlock switch on the tower that was for the US federal seat belt/gearbox for engine starting.

Reverse switch was always in the bellhousing. 74 was the last year the switch was screwed to the top of the bellhousing with 2 screws and gearbox had the longer shift rods. 75 on the switch screwed into the front of the bellhousing.
You are right I guess. I was thinking that when they went to shorter rods that did not protrude into the bell house that they used the switch on tower. but what you say rings a bell.

Thanks

Ken
 

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Discussion Starter #14
OK, per Ken's suggestion, I counted some gear teeth this evening. This is a great suggestion. In fact I counted them 4 times and triple checked I was counting the right gears because I couldn't believe the results I was getting. Here they are...

Gear ratio check (main shaft gear / layshaft gear):
1st: 38:15 = 2.53
2nd: 32:21 = 1.52
3rd: 27:26 = 1.03
4th: 23:30 = .76
5th: 20:33 = .61

So this is nothing Alfa spec. Would this be typical of a close ratio box?

Just to make sure I am not crazy (this is the first gearbox I am rebuilding, so never know), here's pictures of the 5th gears:
 

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Those teeth counts indicate that these are the stock ratios.
To calculate you need to divide each ratio by the "4th gear" ratio.
2.53 / (23/30) = 3.30 and so on.

I hope this helps,
Dave
 

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Here are 2 snips from a Performance Options Catalogue Feb/77. Those gears indicated as standard agree with your count.

Ken
 

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Discussion Starter #17
OK - good to know I am crazy and not my gearbox. It didn't make sense that the car I pulled this from would have had a close ratio gearbox, though that would have been a nice surprise. So is it standard in automotive engineering to calculate gearbox ratios by dividing each gear pair ratio by the 4th gear pair ratio? Or is that an Alfa thing? Always nice learning new things. Thanks all for the tutelage and info on this.

At any rate, back to the issue at hand: To recap - I have a old-style/non-moly gearbox in a 74 2L car, apparently having replaced the original gearbox at some point. This box has a cracked rear shift tower case with a push-down reverse shift mechanism, both of which I want to replace. Sounds like the gear ratios would identify this box as originally having come from anything from 1966-on. The push-down reverse would be up to 1968 depending on the car. So given that, it sounds like a rear case out of 69-71 (1750) would do the trick.

My only remaining question is given the car is a 74, what effect will not having the "interlock switch on the tower that was for the US federal seat belt/gearbox for engine starting." I am not familiar with this. Given this car was already running this older gearbox, I am guessing this won't be an issue for me?
 

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It was originally on your car. But the law was modified in 75 so dealers could disconnect it at the owners request. If everything was right you had to buckle your belt, put the car in neutral then stat the car.

If the belt was not buckled or the car in gear it would not turn over. The only thing the modified law required was for the fasten seat belt light to stay on.

If you really want it I can post the tech bulletins on how to test the system and the one on how to disconnect the system.

Whether you have the switch or not on the shift tower is not going to matter one way or the other.
 

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Discussion Starter #19
Hi Jim-

If easy to do, yes, having the tech bulletin on how to disconnect would be great. I suspect it had already been disconnected, but since I will be rewiring everything from scratch, it will be an opportunity to ensure it was done correctly.

Thanks!
 
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