overdrive trans
Super Moderator
Joined: Apr 2004
Posts: 34,513
Likes: 2,824
Your bell is a square pattern or narrow rectangle.
The pattern changed in '65 to the wider "butterfly" rectangle. The '80s 4 speed OD used that pattern.
BUT there is enough material to drill the old pattern into the '80s case. '60s performance 4 speeds, which is what those OD transmissions are based on, had both patterns in some cases.
Pics here:
https://www.davidkeetoploaders.com/imposters.htm
You would want to find an iron one I think.
Some had top mounted shifters, some had turret mounted which were back and to the left, and the iron ones had side mounted external shifters like the cars.
The 2nd to 3rd gap is a nuisance. First is around 3.27 so depending on your gears and tires it might be a bit tall, especially compared to the granny low in the OEM four speeds.
These are not the strongest trans out there but for light work they seem to live.
Shifter parts are hard to find.
The other issue would be input shaft depth, and throw out bearing support...
What trans and gear do you have now?
The pattern changed in '65 to the wider "butterfly" rectangle. The '80s 4 speed OD used that pattern.
BUT there is enough material to drill the old pattern into the '80s case. '60s performance 4 speeds, which is what those OD transmissions are based on, had both patterns in some cases.
Pics here:
https://www.davidkeetoploaders.com/imposters.htm
You would want to find an iron one I think.
Some had top mounted shifters, some had turret mounted which were back and to the left, and the iron ones had side mounted external shifters like the cars.
The 2nd to 3rd gap is a nuisance. First is around 3.27 so depending on your gears and tires it might be a bit tall, especially compared to the granny low in the OEM four speeds.
These are not the strongest trans out there but for light work they seem to live.
Shifter parts are hard to find.
The other issue would be input shaft depth, and throw out bearing support...
What trans and gear do you have now?
FTE Legend
Joined: Nov 2015
Posts: 30,936
Likes: 4,124
From: Angier, NC
My 81 F100 has a 2.75 gear and it is a PITA using grant first the way the NP435 shifts and at 55 MPH is 1800 RPM.
My parts truck also a 81 F100 and both with 300 six motors, had the 4sp over drive and a 2.47 rear gear.
Someone in the 80 truck area said the truck with the overdrive and 2.47 gear is a dog to drive and looking to go with a 3.55 ratio.
Now the real reason you dont want to use that 4sp over drive / SROD transmission is they are weak and hard to find rebuild part for, the shifters get play in them and also hard to get parts for and was only used in the F100 / F150 trucks and some Ford cars and not a lot of them.
If you want a better Ford overdrive transmission go with the M5OD that is a 5sp over drive. It is a nicer shifting transmission and fond in 87> F150 / F250 trucks with small blocks 300 / 302 / 351.
The later years dont have a hole for the speedo as that truck uses the VSS off the rear axle IIRC. Also the M5OD uses a hydraulic clutch and bell housing is built on the transmission.
Dave ----
Fleet Mechanic
Joined: Feb 2019
Posts: 1,388
Likes: 92
From: California High Desert
I dont see how regearing the rear axle could change the granny first gear to a working 1st, ever try and shift out of granny low at every stop? And turn 4th into overdrive?
My 81 F100 has a 2.75 gear and it is a PITA using grant first the way the NP435 shifts and at 55 MPH is 1800 RPM.
My parts truck also a 81 F100 and both with 300 six motors, had the 4sp over drive and a 2.47 rear gear.
Someone in the 80 truck area said the truck with the overdrive and 2.47 gear is a dog to drive and looking to go with a 3.55 ratio.
Now the real reason you dont want to use that 4sp over drive / SROD transmission is they are weak and hard to find rebuild part for, the shifters get play in them and also hard to get parts for and was only used in the F100 / F150 trucks and some Ford cars and not a lot of them.
If you want a better Ford overdrive transmission go with the M5OD that is a 5sp over drive. It is a nicer shifting transmission and fond in 87> F150 / F250 trucks with small blocks 300 / 302 / 351.
The later years dont have a hole for the speedo as that truck uses the VSS off the rear axle IIRC. Also the M5OD uses a hydraulic clutch and bell housing is built on the transmission.
Dave ----
My 81 F100 has a 2.75 gear and it is a PITA using grant first the way the NP435 shifts and at 55 MPH is 1800 RPM.
My parts truck also a 81 F100 and both with 300 six motors, had the 4sp over drive and a 2.47 rear gear.
Someone in the 80 truck area said the truck with the overdrive and 2.47 gear is a dog to drive and looking to go with a 3.55 ratio.
Now the real reason you dont want to use that 4sp over drive / SROD transmission is they are weak and hard to find rebuild part for, the shifters get play in them and also hard to get parts for and was only used in the F100 / F150 trucks and some Ford cars and not a lot of them.
If you want a better Ford overdrive transmission go with the M5OD that is a 5sp over drive. It is a nicer shifting transmission and fond in 87> F150 / F250 trucks with small blocks 300 / 302 / 351.
The later years dont have a hole for the speedo as that truck uses the VSS off the rear axle IIRC. Also the M5OD uses a hydraulic clutch and bell housing is built on the transmission.
Dave ----
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