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post #1 of 3 (permalink) Old 05-16-05, 12:06 AM Thread Starter
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From 3 Speed auto to 4 Speed auto in EA

Hey. I have an EA Fairmont Ghia Series I. it only has a 3 speed automatic, but i want a 4 speed automatic. is it possible to replace the 3 speed auto to a 4 speed auto without having to rewiring or changing the computer? would it make any difference to the fuel comsumption as well as reliability and speed?

if anyone is selling a cheap 4 speed auto please PM me. thanks

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post #2 of 3 (permalink) Old 05-16-05, 06:34 PM
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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!

Good luck,


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
AU thermofans
Explorer intake manifold
Contra 16x9 rims, rubber: 225(f)/245(r)
Custom cupholders
Chiptorque HP2 chip
illegal tint

ET: 14.78 @ 91.48mph, 137rwkw!
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post #3 of 3 (permalink) Old 05-17-05, 02:33 AM
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Re: From 3 Speed auto to 4 Speed auto in EA

Different computer. Different engine bay harness. Different Dash Harness. Different Pedal Box (can get away without changing it though). Different gearbox crossmember mount. The 4 speed crossmember won't bolt in. '88 and '89 have a different bracket welded under the floorpan. There may be a crossmember from a certain model that will allow the fitment, but I don't know. Personally, I drilled out all the spotwelds on the underfloor brackets from a 1990 EA and fitted them to my '89 model. Lots of work.
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