Here ya go.  Fred   

the C3 was introduced in the mid 70's and only used on the Pinto is my understanding, someone correct me if I'm wrong? I would guess a C4 would be the stock transmission for a 289. As I recall the easy way to tell is a C3 has 13 bolts on the pan and a C4 has 11 bolts

the C3 was introduced in the mid 70's and only used on the Pinto is my understanding, someone correct me if I'm wrong? I would guess a C4 would be the stock transmission for a 289. As I recall the easy way to tell is a C3 has 13 bolts on the pan and a C4 has 11 bolts

Applications (US)1974–1980 Ford Pinto
1974–1977 Mercury Capri
1978–1983 Ford Fairmont
1979–1986 Ford Mustang
1981–1982 Ford Granada
1974–1986 Smaller rear wheel drive Lincolns
1974–1980 Mercury Bobcat
1978–1983 Mercury Zephyr
1979–1986 Mercury Capri
1983–1986 Mercury Marquis (when equipped with the 2.3 I4)
1985–1989 Merkur XR4Ti

Applications (EU)1972–1985 Ford Granada
1972–1975 Ford Consul
1982–1987 Ford Sierra
1982–1987 Ford Scorpio
1979–1987 Ford Capri
1976–1982 Ford Cortina
1976–1982 Ford Taunus

I wouldn't call it WEAK, but it is weaker than the C4 when it comes to heavy duty or high torque/HP applications. It just can't handle the load is all. From what I have seen in my 73's C4 (during the rebuild), and the comparisons in the haynes overhaul manual, the way the C3 is constructed, it would be weaker. The C3 seems to have more separating parts, thus needing more fasteners to keep them together or in place, when compared to the C4 which has more cast solid parts, eliminating the excess fasteners and making things stronger.

If you have to use a fastener to keep something together, it is going to be weaker than something solid. For example, floor pans. The structural integrity of our cars is very reliant on how solid the floors are. If you are going to secure a replacement floor pan with screws, it is going to be significantly weaker than a welded or original good condition floor pan. Imagine being in a T-bone accident in a Pinto with sheet metal screwed in for floor pans vs. original good original flooring. The screwed in metal would most likely pop out/up, allowing more of the car to buckle in towards the center. If the floors were solid and original, the floor would most likely buckle, but for the most part all of the metal would stay intact, keeping more of the car from buckling inwards.

Am I making any sense at all? I think.....


EDIT: Forgot to add. I believe the C3 would be fine on any of the cars ford put it behind while it is being used as it was intended to. Continuous hauling or any type of high performance upgrades done to the car and you would want the C4 or even a C5 which is essentially a C4 with some oil gallery mods done from the factory (it also uses a slightly different valve body but it is backwards compatible with C4 valve bodies). If you planned to haul a trailer behind your Pinto and you told the dealer than when purchased, I am sure they would have recommended an upgrade to, or to choose a car with a C4 transmission if they knew about the C4s advantage in strength and durability.

I suppose a better explanation for the C3 would be that it isn't as DURABLE as a C4 is.

The C3 was modified into the A4LD four-speed by adding an overdrive gear, which the C3 lacked. This transmission was introduced with the 1985 Bronco II and Ranger, again with four- and six-cylinder engines only. It was replaced by the 4R44E and 4R55E in 1995.

This was the first Ford automatic to use an EEC-controlled torque converter lock-up clutch. Electronic shift control for the 3-4 shift was later added, another first, though other gears remained hydraulic.

Applications:

1985–1990 Ford Bronco II
1987–1993 Ford Mustang (when equipped with the 2.3 I4)
1987–1988 Ford Thunderbird (when equipped with the 2.3 I4)
1985–1994 Ford Ranger
1985–1995 Ford Aerostar
1990–1994 Ford Sierra
1991–1994 Ford Explorer
1991–1994 Mazda Navajo
1994–2002 Mazda B-Series
1985–1989 Merkur Scorpio

I have one in "Marvin" the station wagon. Had to shorten the drive shaft.

FrankBoss