On the dutch forum they said it was from a gta sa but it seems it doesn't have a limited slip diff so that sounds a little strange.
ahum, it was me who thinks it's from a GTA SA...
Be aware that we are talking about the crown wheel and pinion. The limited slip diff is mechanicaly a separate unit. If the rear axle has this unit whether or not, depends perhaps more from the history of the axle...
Second remark, the axle came from a non-original (2L engine, ...) GT 1300 Junior.
The owner is building a GTAm Replica
The following final drives were mentioned in the various parts catalogues and the Alfa Romeo Options Performance Catalogue:
6/41 - 7/41 - 7/43 - 8/41 - 8/43 - 9/41 - 9/43 - 10/41 - 10/43 - 11/41 - 11/43
I couldn't find a 12/43 but maybe it is in a 2000 Berlina/GTV/Spider catalogue? Or it is an option for racing? Anyone?
Well Olaf, those ratio's are also mentioned on the FIA Homologation documents for the GTA (and GTAm) to allow them to race in Group 2. The ratio's you wanted to use, had to come from the production cars (or had to be at least available as an option).
The GTA SA raced according FIA Group 5 rules
: gear and diff ratio's were totally free! (They only had to fit in the original housings).
According Tabucchi's book on the GTA, a GTAm gathered a maximum speed of about 230 km/h on the Monza track using a 11/43 (=1:3.73) ratio in the diff. Using 9' x 13' rims, no info about the tyres ...
Engine speed: about 7800 rotations/min.
My guess is that they produced a 12/43 (=1:3.58) for :
- Experimental reasons
- To be used on the GTA SA (a bit more horsepower at about 7500 rot/min, say 300 rot/min less then the GTAm)
According to Pignacca/NADA, the GTA SA used 5,5M x 14 'tyres' (?) ...