ND1. 2.0L
on a future part of my build project ive got shortlisted a new rear diff. looking at the 3.45 ratio.
im just having a browse around and trying to confirm some bits:
- is it only the Abarth 124 which has the 3.54 ratio AND lsd? so as a complete diff this is my only option?
- i couldnt find any easy/obvious options to simply purchase a new final drive. does this exist? is it expensive?
- @AdamR28 did a great little post about a year ago about the ecu acceleration tables that need updating. i noticed on SPS ‘s2000 package’ they hadnt specifically called that out, when fitting the 3.45. is this because its ‘‘in range’’ so to speak? any info here would be good. (i am wondering if as the 6 gears are unchanged, does the final drive make a difference to the ecu? are the acceleration tables only required if the 6 main ratios are changed, e.g an NC gearbox swap?)
- finally, what is the going price for a final drive/diff? im looking at ebay and its not too shy of £2,000!! seems immense money! engines are less
You will need the tables updating properly. Use Maurici at CleaR Motorsport 
The short diff totally transforms the car, worth doing!
What if I’ve got an ecutek? Can the tables be modified independently? As I don’t recall seeing accel parameters within log data on my tek
They can, not shown on logging though.
You’ll have to use whoever you bought the ECUTek setup from.
The SPS Motorsport package requires the factory LSD to be removed from the car then disassembled, reassembled and reinstalled. It’s much more labour intensive than swapping the LSD with an Abarth 124 equivalent.
If local or nationwide scrap yards do not have an Abarth 124 LSD, you may have to source one overseas. One issue is that such part will be of unknown quantity unlike SPS Motorsport package where the parts will be brand new.
Understood.
After a bit more looking. SPS seem to do 4 variations:
3.45, 3.58, 3.9, 4.1
(Not included the 2.866 currently fitted)
The 3.45 and 4.1 both were on an ND, somewhere in some form. Dont recognise the others.
But for the work and effort involved of swapping i assume(?) that finding a complete diff with the drive I want the cheapest way to swap.
I hadn’t thought about overseas market… the Abarth may be more readily available elsewhere?
Forgot to mention that I did look into buying a brand new Abarth 124 LSD from a local Fiat dealer around 3 years ago. If I remember correctly, I was quoted around £2,000.
Parts dealers in the US are still offering the LSD but whether they can actually source it remains to be seen:
https://parts.moparonlineparts.com/v-2019-fiat-124-spider--abarth--1-4l-l4-gas/differential-and-drive-line--rear-axle-assembly