My donor truck for my 4.9 to 5.0 conversion in my 94 F150 (M5OD) is a 1991 F150 with an automatic. I originally thought it was a 1990. We pulled engine and trans (and rear-end) today. I want to use the computer and engine harness among other things for the 5.0 I'm building.

I noticed that there is one small harness going to trans, looks like 2 pins. Is this for the speedo? Auto trans in a 91 is not computer controlled is it?

Also has a small harness, looks like 2 pins, going to rear-end. I plan on using rear because its a 3.55 posi. Whats the wires at rear-end for?

Thanks

 

2 wires to the tranny are probably gear indicator(computer wants to know when it's in drive or park), the rear end has a RABS sensor in it and in some trucks this was also uses as the speed sensor. Does the tranny have a speedo cable attached? There should be a tranny code on the drivers door pillar, this will tell you what the tranny is for sure.

 

I'll check out tranny code today. Generally speaking though were 1991 auto tranny's computer controlled? I ask because I need to use computer for 5.0 build going into my 94 with a manual trans.

 

There were 3 differernt possible 4-speed auto trannys available for this era truck, the AOD, 4R70W, and E4OD, so it's impossible to say with certainty what you have. The last 2 were computer controlled and will have a multipin electrical connector attached to the tranny, so if you don't have this it's most likely you have an AOD.

 

OK, Paul here is what I have:
Trans code off of the data plate is 'T'. Connector into trans housing just above valve body looks to have 4 pin connector. Speedo cable goes into the tailshaft like a normal trans. I have a bunch of other numbers off of the tail shaft. I've tried to find a decoder on the net but cant tell for sure if this is an E or not.

If it is an electronically controlled E4OD......can I use computer and harness for the 5.0 in front of the manual tranny?

Rear-end code off of plate is H9N which I believe translates to a 3.55 posi, is that what you have?

Thanks for your continued help,

Craig

 

I believe trans code T is the AOD, it's certainly not the E4OD or 4R70W. That means you can use the computer on a manual tranny.

Diff code H9N means you have both front and rear LS diffs if this is a 4x4, that's very rare. It's definitely 3.55 gear ratio with a rear LS diff.

 

Thanks Paul, I've been really re-thinking this project. I'm wondering if I shouldnt just go ahead and use the auto tranny anyway. I've got everything I need from the donor truck, radiator, all mounts etc (am I missing anything?). My kid would prefer the manual but the old man is sponsoring it so I have the final say! A B&M shifter would look pretty cool on the floor and with the warmed over 5.0 and 3.55 should be fun to drive.

Any thoughts? Anyone......Anyone...... Manual or Auto?

 

I like manuals personally, but if you have to deal with a lot of stop and go traffic the auto is a blessing. The manual may discourage him from doing as much drag racing, but it will encourage more burnouts and clutch dropping abuse.

 

Excellent points, and when he goes away to college in a couple years with a well used Toyota Corolla (or equivalent) I will be driving it occasionally. I've gotten lazy and prefer an automatic.....

 

I like the auto.. They respond well to a B&M shift kit... Spin the tires shifting in to 2nd.... With a B&M pro stick shifter there a lot of fun... Or just leave it in drive... Best of both worlds.. The kid would like it !!!

 

Thanks for the input, you will see I have another post on this. I'm normally a pretty decisive guy but I'm all over the board on this one.