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Discussion Starter #1
Could some one set me straight on what i need to convert my 1600 Duetto transmission with the old style syncros - to the new type?
Do i need to change ALL the sliders as well? Could I just leave the 5th gear slider/syncro as is?
TIA
 

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Do i need to change ALL the sliders as well? Could I just leave the 5th gear slider/syncro as is?
TIA
I think you'd have to change all of them because they use different types of tranny oil. The non-moly ribbed syncros call for Shell Dentax and the newer moly syncros call for Spirax (sp?). I think the change occured around '66-'67. Are you sure that you currently have non-moly syncros? I think the non-molys have a yellow sticker on the tranny case and the molys have a red sticker. I'm interested in the responses on this as well. I have a couple of each type and am wondering what parts are useable and what's just garbage.

Bill
 

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This might help:
 

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Thanks Ruedi, excellent info. I have heard that you can get away with changing the dog teeth that are on the gears along with the sliders and syncro rings. Since Alfa apparently never sold the dog teeth seperately they would have required that you buy the whole gear. In either case, it's probably not worth it.

Ray40: If all you need is a ribbed syncro ring to make your non-moly transmission work I have a couple NOS rings still in the bags. $50 each. I also have a couple of long rod transmissions with moly syncros that would work with your bellhousing and be a lot easier to rebuild. $125 each + shipping. A third option would be to modify your Duetto's bellhousing to accept a later short rod transmission ('74 and later). I have done this and can explain in a different thread if you like. I don't have a short rod tranny to sell but they show up frequently on ebay.

Bill
 

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A third option would be to modify your Duetto's bellhousing to accept a later short rod transmission ('74 and later). I have done this and can explain in a different thread if you like.
Please do! I think this would be very valuable information for all owners with non-moly transmissions.
 

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Discussion Starter #7
thanks for the responses all - it appears that all gears (except 4th?) are also supposed to be changed along with the sliders/syncros - i suppose if i canabilize another tranny it might work out but the cost of gears are crazy.

Bill S : are you saying that the pre 74 boxes will fit on my bellhousing with no modification? In that case perhaps that makes the most sense for me if i want to go to the moly. But if i just change the ribbed syncros on my own box - whats the real downside to just stick with the non-moly?
 

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whats the real downside to just stick with the non-moly?
The only downside I'm aware of is the limited choices of oils that are available.
 

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OK : Can someone tell me what is the difference between the metal composition
of the moly and the pre moly synchro assemblies ?
By looking at the sliders and dog teeth of a moly and pre moly gear case the teeth look the same .
Is one set a lot softer metal than the other ?
What is the difference in the 2 lubricants for the moly and pre moly synchro case ?

Thanks
 

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Bill S : are you saying that the pre 74 boxes will fit on my bellhousing with no modification?
One difference would be that the reverse lockout would be the gated style instead of the push-to-reverse style. Much prefered in my opinion - no more rattling shifter. I'm not sure if the rear mount bracket may require shimming to line the tranny output shaft up with the driveshaft. I'll try to take some measurements tomorrow to see if the rear mount is in the same place.

The main disadvantage to using the ribbed syncro rings is that other than the two I have, they don't seem to exist. Also if you need to replace a syncro slider they're even harder to come by. If all you need to do is replace a couple of worn rings then my two are a good option - until the next rebuild.

Ruedi: I hope to have my Duetto on the road in a week or two, at which time I'll write up the bellhousing procedure (described to me by Tom Sahines) - provided everything works!

Rocco: good questions. Hopefully someone smarter than me can answer them!

Bill Sinclair
 

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What is the difference in the 2 lubricants for the moly and pre moly synchro case ?
Pre-moly: vegetable oil
Moly: mineral oil
 

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Hello all
Is there a spec on Dog Teeth to know if they are Marginal or Good
There is the obvious Bad Teeth but how is one to tell if you have acceptable
dog teeth
Can Some one post some pics of Acceptable as compared to over the limit Dog Teeth
( I cant wait to see what pics you guys post )
Thanks
 

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Gear Box Oil

Pre-moly: vegetable oil
Moly: mineral oil
I am not saying that you are wrong, it was my understanding that the original Dentax had whale oil in its make up, and as the whaliing declined there was a shift over to Spirax. (fact or fiction I don't know)
The Dentax is still available in 40 lb. pails.
 

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I am not saying that you are wrong, it was my understanding that the original Dentax had whale oil in its make up, and as the whaliing declined there was a shift over to Spirax. (fact or fiction I don't know)
The Dentax is still available in 40 lb. pails.
Thought I better look up what this oil is really made of. Page 21 of this Shell Lubricants Product Data Guide (2.6 MB PDF) says the following:
Shell Dentax 90 is high quality, straight mineral oils intended for certain automotive transmissions.
• Manually operated gearboxes
• Spiral-bevel and worm axles – Use where gear loadings are relatively mild and extreme pressure oils are not required.
Not recommended for heavy-duty transmission applications.
API Service Classification: GL-1
Another source says:
Shell Dentax Oil is a gear lubricant designed for manual transmissions where the manufacturer specifies either a "straight mineral" oil or an oil meeting API Service GL-1. A time-tested additive system inhibits oxidation at high temperatures, maintains excellent flow in cold temperatures, and controls foaming.
I'll try to find the reference I recall from the '60s or '70s that said it was vegetable oil -- which it apparently isn't.
Thank you for prompting me to check.
 

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in order to do this you must change all of the internal pieces of the gear assembly. Then change the sleeves and rings and you should be good to go, with out the worry of any oil issues. Good luck
 
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