131mirafiori forum

i own fiat 131 1979 1600 twin cam and know there is two type of rear axle  the fast one and the slow one   and i want to know what i have in my car without open my rear axle
is there something help me to know

i am asking because i buy a new ( used ) rear axle for my fiat 1979 1600tc , the new rear axle was from fiat 131 Estate station with desiel motor
i want to know it that rear axle good for my car

As far as I know the estate and saloon axles are different I think with their mounting points.

Perhaps the diff from the estate axle can be fitted to the saloon casing.

I imagine with the high torque and low revs that it would be a fairly tall final drive ratio.

In 1990, my 131 racing was fitted with a rear axle that came from a 131 diesel. As a result the topspeed was lower than a standard racing and I had to shift gears a lot sooner because the ratio of the rear axle was much shorter than the original racing rear axle. So bear this in mind. The car was good in pulling up to about 140 km/h but the top speed wasn't that high anymore.
The reason why the diesel axle was fitted was that it was much stronger than a standard racing/sport axle which was apparently a 1600cc rear axle, (so I was told by the Fiat Garage at that time), and this axle was too light to transfer all that horsepower onto the road.

I think the Auto or the super2000 had a 3.5 diff check the spec sheets in garage

  Roger........

the estate axle is different to the saloon as the shocks are not inside the springs but mounted lower down to help with load space. the diff will swop over, however the half shafts are thicker and longer. they will have to be machined down to fit. (idid this modification in 1997, in the days before the internet you made do with what you could find!)  most estates had 3.9 ratio.

1600tc & sport had 3.9 ratio

2000tc supermk3 had 3.6 ratio

2000tc mk3 automatic had 3.5 ratio, (unlikely to find one now though)

All the automatic 131's I ever had or worked on in the uk had 12/43 rear axles, 12 teeth on the pinion and 43 teeth on the crownwheel,
I once had  a 131 sport and a past owner must have had the axle go and he had fitted a 12/43 automatic axle and it was awful and top speed was only 102mph on the clock as the axle wouldn't go any quicker. I changed it to a 10/39 and the car was fine.

Was going through some n.o.s the other day and found a brand new 10/41 and a 12/43 pinion and crown wheels. Was wondering what the 12/43 was off. Cheers for that David.

My data shows the following ratios :

10/ 41 or  4.1: 1  in CL manual) and 12/43 or 3.58: 1 in  CL automatic

Supermirafiori had in 1300 - 9/40 or 4:44:1 , 1600 - 10/41 ( 41:1 ) and 2000 12/43 (5.381:1).

I also understand there was a short series for Panorama ambulance made specially for South American high Andes. I am not sure what it was.

The Panorama diesel 2.0 diffs were considered the strongest ( made to handle most torque)

Miro

PS: I should have spare one for the 2.0 diesel.

Miro  

The axles I came across in the UK were :
                                                             10/41   1400 CL  mk3 saloon
                                                             10/39   1600 CL  & 2000 sport  mk2 saloons
                                                                          (also 1600 supermirafiori)
                                                             12/43   1600CL   automatic mk 3 saloon

I did fit 10/41 1400CL axle into 131 sport and I prefered it to standard 10/39 as it would rev slightly higher and made fifth a proper pulling gear although this was the wider mk3 type axle it still fits to mk2's as shell was the same.