Re: From 3 Speed auto to 4 Speed auto in EA
Hi phongus, welcome to the forums :)
Unfortunately you need a different ECU to run the 4 speed auto (since it's an electronic box and the 3 speed isn't), and I suspect looms are required too.
I dunno if "Dellboy999" is on these forums or not, but do a search for him. He successfully did this same mod to his EA a while ago.
The 4 speed has a taller 1st gear I believe (I can get to 100kph in 1st <mine's a V8>, and I have a 3.27 diff!), however the fuel consumption should drop a fair way especially when cruising.
3rd gear in 3 speed box = 1:1 ratio. 4th gear in 4 speed box = 0.68:1 ratio. BIG difference in revs here!
PS I think it may be easier to do a T5 conversion (less electronics to worry about!), this is what most people with 3 speed autos seem to do when they feel it's time to change.
'91 EB Fairmont Ghia V8.
Pacemaker PH4000 extractors
Meaty semi-twin system
AUII XR8 t/b & maf, ELGT snorkel
BA semi-manual shifter conversion
Electronic shift kit
4.11 Hydratrak LSD
Explorer intake manifold
Contra 16x9 rims, rubber: 225(f)/245(r)
Chiptorque HP2 chip
ET: 14.78 @ 91.48mph, 137rwkw!