Swapping my SROD 3-speed w/OD transmission for a 5-speed in my 1981 ford f100. First timer, Any suggestions for a compatible five speed transmission that will fit my truck?

 

Mazda M5OD from an '87 up truck. It will require a hydraulic clutch.

T5 will work with an adapter on your existing bell and clutch.

What is your axle ratio?

 

I am not sure what my axel ratio is.

 

If you post a picture of your door cert sticker we can de-code it and tell you if it has not been swapped / changed out.
My 81 F100 that had a 3sp w/OD (SROD / TOD) had a 2.47 rear gear (code 07).
My other 81 F100 that had a T18 4sp (now a NP435 4sp granny first) granny first has a 2.75 rear gear (code 13). I added over drive, making it a 8sp, when I swapped in the NP435 .
Both trucks were 300 six trucks at 4700 GVRW.
Dave ----

 

Here's a couple in Indiana. Your speedometer may not read correctly, the reason they wanted to know your rearend gear ratio. Apparently you can't change the speedometer gearing on the Mazda 5 speeds. These were listed under a 3.55 ratio.

1990
Transmission Assembly
Ford Truck F150 MT 5 SPEED,4.9L,05/90; RATIO ?? X 220252 $Call Wise Auto Parts, Inc. USA-IN(Richmond) Request_Quote 765-962-0602 / 765-962-5525 Request_Insurance_Quote
342 1989
Transmission Assembly
Ford Truck F150 4.9L MT 4X2 MAZDA 5SPD SHIFTER LOOSE 153,968 A X-6569 $300 Burkhart Automotive Inc USA-IN(Greensburg) Request_Quote 800-933-3805 Request_Insurance_Quote

 

Dave I did not know it could not be changed.
I know the later ones used the ring tone gear off the rear axle to feed a computer.
On the transmissions that can take a speedo cable wonder if you could use adapter to change it to match.
I used one on my 86 K5 Blazer when I swapped to lower 4.11 gears to get it to read right again.

One of the reasons I would like to know the ratio and what he will be using the truck for is how happy he will be with the M5OD.
If he plans on heavy loads he needs a lower first gear like in the T18 / NP435, maybe the T19? To get the load moving.
Or could go with a lower (higher number) rear ratio with the OD could work.

Also the high (lower number), over drive and large tires depending where he lives, hills / mountains, he might be staying it 3rd gear and never use 4th or 5th OD.
I say this based on my truck.
I plan on using my truck to pull my car trailer of about 5k, so kept the granny first trans.
Wanted over drive to keep the motor RPM down for less wear on it and may be better MPG.
My truck also has a 2.75 rear gear and 235 / 75 / 15 tires factory size.
That works out in 4th (1:1) and over drive (.72) to a final rear ratio is 1.98
I know the truck would never pull the trailer in OD and may even have a hard time in 4th with the 2.75 rear gear but in 3rd over drive I have 3.544.
Is that not what the M5OD has for a rear gear ratio?
Dave ----

 

Here are the different Mazda transmissions listed for a 1989 f150. I am sure you could fudge the speedometer somehow, but car-part lists their interchanges as bolt ins with no fudging.

MT, 5 speed, Mazda (Toyo Kogyo manufactured), 4x2, 2.73 ratio
MT, 5 speed, Mazda (Toyo Kogyo manufactured), 4x2, 3.08 ratio
MT, 5 speed, Mazda (Toyo Kogyo manufactured), 4x2, 3.55 ratio
MT, 5 speed, Mazda (Toyo Kogyo manufactured), 4x2, 4.10 ratio