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

AOD 4 speed automatic with overdrive
1980 -1993 Ford cars and trucks with small block engines. In 1988 some design improvements were made making these newer models more desirable. A common swap is to take the 5.0L engine and AOD (or AODE or 4R70W depending on year) transmission out of a 1989 or newer Mustang. Look for one out of a small block V8.
As with most automatics the case and bellhousing are a one-piece design.
Adapter required?
A tail housing adapter is required as well as a new spud shaft and new (or machined) output shaft.
The overdrive is one of the prime reasons people upgrade to the AOD. For those looking for lower gearing you can purchase a "low gear ratio" set. This will give you 2.84 first gear and 1.54 second gear.
The AOD transmission doesn't have the best reputation in high abuse applications. However, several transmission shops specialize in correcting the factory weaknesses and beefing these up to handle real 4x4 duty.
Cost: (Approximate)
Transmission: $200-500 used and $800-2000 rebuilt
Adapter kit: $550-620
Drive Shaft Mods:
Total transmission is approximately 1.5" longer requiring some drive shaft modifications.
Bell housing:
The AOD came behind small block Ford engines and will bolt up to your 289-302-351 engines.
Modifications needed:
The cross member will need to be modified and relocated to make up for the 1.5" longer AOD. The stock transfer case shifter also requires some modification and a larger hole needs to be cut in the floor. An aftermarket transmission shifter or modification to your stock automatic shifter will be required. Transfer case to floor may be tight if you don't have a body lift installed and the front drive shaft may be very close to the transmission pan depending on your lift. A smaller diameter front drive shaft or transmission pan modification may be required.

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