Hi Guys, I have a 73 F100 with a C4 Auto Transmission. Recently she's been hesitating shifting into 3rd gear. Was stuck in 2nd gear yesterday for most of my ride home from work. Eventually she shifted and rather hard into 3rd gear. Toward the end of my trip she was shifting smooth and the problem seemed to go away. I asked a local Ford guy and he said it sounds like the clutches in my transmission are worn. It's likely that my transmission was never rebuilt. So here is my question.

Facing the likelihood of needing a rebuild, should I simply have my c4 transmission rebuilt and be done or purchase a new transmission with an overdrive gear. I am looking for economy more than performance. If so which Automatic Overdrive transmission do you guys recommend? Ideally I would like something that will bolt right up to my small block 302 V8. I am not interested in doing crazy modifications. If I have to spend the money I want to get the best result for my money. Thanks.

Paul
1973 Ford F100 2wd

 

Might just be time for a fluid and filter change? Also check the vacuum modulator and the line that goes to it. Check the line for kinks or other problems, make sure it hasn't come off.

If the line checks out, take the line off where it connects to the modulator. If trans fluid leaks out, its bad. If no fluid, it still could be bad.

They're simple to replace, disconnect the vacuum line, remove one bolt that holds the clamp in place and the modulator comes out. It has an o-ring seal.

Modulators are identified by the color of the stripe. Pretty much the "go to" one is the black stripe. If they don't show that one in the catalog, go with the green stripe. Avoid the pink stripe. That one is a dual diaphragm version that has two vacuum line going to it.

If by chance you have one of these, replace it with one of the other two and use the vacuum line that goes to direct manifold vacuum, cap the other line. When you pull the modulator out, be careful. There is a pin that goes in the modulator. Sometimes it comes out with the modulator, sometimes it stays in the tranny. If it comes out, don't lose it.

 

Paul, Have you tried an oil and filter change? You could also adjust the bands and make sure the vacuum modulator is hooked up to manifold vacuum. If the modulator doesn't have a good vacuum source it will hold the tranny in second gear. It could also be a problem with the governor. You can do these checks yourself with little cost with out dropping the tranny. Good luck with it.

 

Rich beat me to it. Old fingers type slow!

 

No problem, nothing like a good ol double tap of information and ideas. Plus I have all that info saved.

 

Overdrive? I'd consider an AODE or 4R70W.


Either of which will require a stand-alone controller.

 

Hey guys I have a 1973 Ford f100 with a 351M I currently have a c6 trans and I’m gonna be using it to daily drive long distances and when driving I feel like I’m constantly overworking the motor cause i drive at 60 mph for 25 straight miles no lights, I feel like I’m constantly red lining the truck.
what would be a good tranny to swap into the truck that has 4 gears possibly an overdrive that will be a direct fit??

 

I don’t think there is any direct fit. You can throw a 4 speed in but it will still be 1:1. Regear or gearvendors probably the easiest route.

my wornout 400/c6(3.54) has no complaints doing 80 (downhill with a tailwind) all day.