GTAm Differential quandary - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 30 (permalink) Old 06-10-2019, 11:41 PM
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Yesterday I was reading the FIA document regarding the 1750 GTAm homologation and it states that the monoliner had an internal dia of 84.5mm
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post #17 of 30 (permalink) Old 06-11-2019, 01:25 AM
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Yesterday I was reading the FIA document regarding the 1750 GTAm homologation and it states that the monoliner had an internal dia of 84.5mm
Yep that makes 1985cc
Pete

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post #18 of 30 (permalink) Old 06-11-2019, 01:48 PM
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I have exactly the same 406 number on my LSD. Is there some identification manual for all these numbers?
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post #19 of 30 (permalink) Old 06-11-2019, 03:32 PM Thread Starter
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I have exactly the same 406 number on my LSD. Is there some identification manual for all these numbers?
Hello Larry, what is your 406 installed on?

Is my LSD, of what sort, cam and pawl, or....?

Regards, Alberto
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post #20 of 30 (permalink) Old 06-12-2019, 07:13 AM
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Aberto, your unit is ‘standard’ ZF 10544.17.043.01 LSD and I think that I finally understand that ‘small unit’-‘big unit’ is question of diff housing, so yours must be before 1972 series 25 (15?) splines one. (First series of 10551 had ‘small’ diff housing if I remember well). It is perfectly capable of governing GTAm power under ‘normal’ conditions, but you can improve it for major torques as well. To discover its ratio, you should open it to see number and thickness of plates. Standard 2-4 plates (1,90) gave 25% closure (optimal value for road ride) that you can increase adding one more plate (2.0-2.10) to major it up to 40% (already racing condition) and even (one plate more) up to 60-70% for extreme track use but not for street driving. Be careful in using diff oil. It MUST be 75W-90 (red line) and NOT 75W-140 (though indicated by producers) as it could damage seriously synchro. I would suggest to change the set of plates with new ones to obtain 25% revised unit, or by new one (attention! serious prices) at Alfaholics or Classic Alfa. Good ride!
For Lastforry; the numbers on LSD housing are ZF production code for ITALIAN MARKET, different from German standard codes. Send letter to ZF, and they will give you the right type of codes for spare parts.
P.S. For diff works you need a special tool set!
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post #21 of 30 (permalink) Old 06-14-2019, 06:17 PM Thread Starter
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Aberto, your unit is ‘standard’ ZF 10544.17.043.01 LSD and I think that I finally understand that ‘small unit’-‘big unit’ is question of diff housing, so yours must be before 1972 series 25 (15?) splines one. (First series of 10551 had ‘small’ diff housing if I remember well). It is perfectly capable of governing GTAm power under ‘normal’ conditions, but you can improve it for major torques as well. To discover its ratio, you should open it to see number and thickness of plates. Standard 2-4 plates (1,90) gave 25% closure (optimal value for road ride) that you can increase adding one more plate (2.0-2.10) to major it up to 40% (already racing condition) and even (one plate more) up to 60-70% for extreme track use but not for street driving. Be careful in using diff oil. It MUST be 75W-90 (red line) and NOT 75W-140 (though indicated by producers) as it could damage seriously synchro. I would suggest to change the set of plates with new ones to obtain 25% revised unit, or by new one (attention! serious prices) at Alfaholics or Classic Alfa. Good ride!
For Lastforry; the numbers on LSD housing are ZF production code for ITALIAN MARKET, different from German standard codes. Send letter to ZF, and they will give you the right type of codes for spare parts.
P.S.
Thank you for the info, absolutely a gold mine!

Will take mine apart and see what is in it.

Will post more details when there.

What do you mean by: "For diff works you need a special tool set!"

Kind regards,

Alberto
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post #22 of 30 (permalink) Old 06-15-2019, 07:45 AM
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LSDs

The correct lube is Redline 75-90 NS
Redline`s common GL5, "75-90" gear lube is not what should be used in either trans, or diffs..

There`s no reason to try and use 6 plates in these units.

Richard Jemison
RJR Racing

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post #23 of 30 (permalink) Old 06-15-2019, 08:29 AM
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Hi all,

As far as I am aware attached fotos are a GTAm/33 differential....15 splines!

Richard
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post #24 of 30 (permalink) Old 06-15-2019, 08:33 AM
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Missed on foto....

Richard
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post #25 of 30 (permalink) Old 06-15-2019, 12:07 PM
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Alfar7, your objection is useful clearing, 75W-90 NS is excellent choice, and six discs are for theory not common use.
Richards, about spline number you are absolutely right (I have not paid attention to the photo where you could easily count them) but it is not 33/GTAm LSD (10533.17.043.E02) suitable for GTAm only with 10551.17.300.99 15 splines axles, this LSD was of different external shape. The LSD that Alberto posted is 10510.17.043.00, 15 splines unit, used on different Alfas, included GTAm.
Alberto, for LSD work you must provide special tools, few specific extractors, but that is not problem. Problem is specific tool to calculate pretension of the mainspring (in case of changing the discs obviously), and set the closure ratio. There are some alternative methods but they are not so accurate as original tool.
Here is 10533.17-043.E02 in bad photo but it is clear that the shape isdifferent
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post #26 of 30 (permalink) Old 06-16-2019, 12:54 PM
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Hi ARGTAReg

......"but it is not 33/GTAm LSD (10533.17.043.E02) suitable for GTAm only"

You stated the above... I would appreciate knowing what you think my differential is?

Thanks

Richard
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post #27 of 30 (permalink) Old 06-16-2019, 02:19 PM
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Richards, the shape of the housing of your LSD is not familiar to me. It might be more recent and almost certainly not ZF. There are different (excellent) LSDs made by Quaife ATB (the one for 147/156 and GT is similar in housing shape), also GB072 Gripper is great LSD but its shape is more ‘classic’, similar to E02. They all exists with 15 and 25 splines. There might be other products too and I sincerely don’t know who is producer of yours. If it is 33/GTAm, it has surely high ratio (over 47%)
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post #28 of 30 (permalink) Old 06-28-2019, 08:23 PM Thread Starter
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Hello ARGTAReg, thank you for posting very interesting information that will go into my file.

Regards, Alberto
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post #29 of 30 (permalink) Old 06-29-2019, 01:47 AM
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Richards,
your LSD is the Colotti - bean typ , used from Autodelta in th 1300 injected racecars. Just often discussed in other threads.......

Alfa 1600 GTA Autodelta Alfa 1300 GTA/J Autodelta 4V Alfa GTAm Alfa GTV6 DPM GP A Ex-Dr.Marko
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post #30 of 30 (permalink) Old 06-29-2019, 02:08 AM
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Hi Ulrich

Thank you for the clarification - I purchased them from an impeccable source so confident original to something Alfa...

Richard
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