Wanting an Overdrive Gear for my 73 Mach 1

[CarNPlaneNut]

I have a 1973 Mach 1 and I want a better driving gear. Is it better to put an overdrive kit onto the existing 3-speed transmission or replace it with a 65-66 transmission with an overdrive? My mechanic has one of these that he removed from a 66 that changed to a manual and can install it for a reasonable price.

 

[c9zx]

Are you talking about a T85N manual 3 speed with an overdrive from a F-100 truck? Chuck

 

[giantpune]

Your car's a manual now and you want to switch to a manual with an overdrive?
I vote T5 for the budget build, or TKX/T65 if you want to be moar bulletproof. T5 was put behind millions of small block fords.

If you're doing automatic, I'd vote C6 with a gear vendors behind it.

 

[Hemikiller]

The 73 351-2V came with either a 2.75:1 rear, or a 3.25:1. Which does yours have? What's your cruise RPM at a specific speed?

Define "better driving" - is the engine too noisy? does it lack power?

Which transmission is your mechanic proposing to use? If I'm reading your post correctly, he removed an overdrive automatic from the 66 when doing the 5 speed swap. A very common trans to use is an AOD, which is not a bad transmission if it's built properly.

The common "add on" setup is to use a GearVendors overdrive, which runs around $3000 plus installation, plus driveshaft modifications.

 

[jpaz]

How does your mechanic think a transmission from a 66 will bolt up to an engine that hadn’t been made yet? I don’t think that’ll work. He thinks a transmission for a 289 will be proper for a totally different car? I think your mechanic doesn’t know what he’s talking about. Sorry, no disrespect but that doesn’t make any sense to me, maybe I’m missing something here.

 

[Hemikiller]

How does your mechanic think a transmission from a 66 will bolt up to an engine that hadn’t been made yet? I don’t think that’ll work. He thinks a transmission for a 289 will be proper for a totally different car? I think your mechanic doesn’t know what he’s talking about. Sorry, no disrespect but that doesn’t make any sense to me, maybe I’m missing something here.

The 289, 302 and 351C all share the same bellhousing pattern. A toploader from a 66 Mustang is a direct swap into any small block 65-73 Mustang, the basic architecture did not change. A C4 from a 73 would pop right into a 65.

 

[jpaz]

The 289, 302 and 351C all share the same bellhousing pattern. A toploader from a 66 Mustang is a direct swap into any small block 65-73 Mustang, the basic architecture did not change. A C4 from a 73 would pop right into a 65.

Ok so I was definitely wrong. I didn’t know that they all were had the same bellhousing pattern. My apologies to CarNPlaneNut.

 

[AcesArneson]

The bell housing pattern is known as Essex and Ford used this in auto's and standards. If you are looking for a really good automatic upgrade you can get a 4R70W from a 2003/4 Mustang V6. This is an electronic transmission and requires an electronic driver like the 'Quick 4' stand alone shifter. If you are going this route ensure the transmission has the gear style speedometer cable port in the tail. I didn't even know it was there until I started researching how to convert the electric pulse speedometer to the analog speedometer in my '73. The 4R70W was rated for 506 foot pounds of torque in 2003 (the 70 in 4R70W stands for 700 Neuton Meters which converts to roughly 510 foot pounds). You can also purchase a J-Mod for the 4R70W which increases shift speed and firmness which also helps the transmission run cooler and prolong life.

Or you could find an ECM (EEC-V) from a 2003/4 Crown Victoria to power this transmission. WARNING, "do not use the transmission from the 2003/4 Crown Vic". It is a 4R70W as well but it uses the Mod Motor Bellhouse pattern and requires a $1500 adapter plate to install on a motor with an Essex bellhops pattern.
I will let you know how mine works when I get my project completed. I am currently rebuilding a 351C into EFI using the EEC-V from a 2004 Lincoln Town Car (same as the Crown Vic) that will drive my 2003 Mustang V6 4R70W.

https://www.usshift.com/usq4.shtml?...-DLWjB7GE76HGRBxeCiP6BajhMXoU80UaAnxuEALw_wcB