Tech article by Jon Hanna (Admin)
Automatic Transmission Intro
See also Manual Transmission Introduction

C4 3 speed automatic
1973-1977 Broncos as well as several other Ford cars and trucks from 1964-1981
Unlike the other transmissions in this article, the C4 has a removable bell housing. Also see the transmission pan image above for identification.
Adapter required?
Because the C4 was a stock option on Broncos an aftermarket adapter isn't needed if you can find a stock unit. If not there are aftermarket adapters available.
This is the simplest, most straightforward and least expensive automatic transmission option because it was originally available on 1973-1977 Broncos. Find a donor Bronco with a C4 and transfer parts. Although the C4 was originally designed for smaller V8's it has a strong aftermarket following and can take a lot of abuse if built properly.
The C4 has a fairly high first gear without the modern advantages of overdrive. In completely stock form the C4 can be a little weak for high output engines.
Cost: (Approximate)
Transmission: $150-500 used and $500-1400 rebuilt (expect to pay near the upper end of this range if you are getting your C4 out of a 73-77 Bronco.
Adapter kit: $500-550
Drive Shaft Mods:
Total transmission is approximately 1.5" longer requiring some drive shaft modifications.
Bell housing:
The C4 came behind small block Ford engines and will bolt up to your 289-302-351 engine.
Modifications needed:
Very few modifications are needed if using a C4 out of a Bronco.

Manual Transmission Gear Ratios1st2nd3rd4th5th
Bronco 3 spd (6 cyl)3.411.861.00
Bronco 3 spd (8 cyl)2.991.751.00
NP 4356.693.341.791.00
Toploader (Close ratio)2.321.691.291.00
Toploader (Wide ratio)2.781.931.351.00
Toploader (Overdrive)3.291.841.000.81
NV4500 (Dodge)5.613.041.671.000.73

Automatic Transmission Gear Ratios1st2nd3rd4th5th
Bronco C42.461.461.00
AOD w/ low gear set2.841.551.00.67