crazyshuffle

I have a 1965 mustang fastback with auto transmission, and when I drive it sometimes it will not shift to second gear and I can feel the heat from inside the car.The motor isn't running hot. I usually slow way down and then try it again. Most of the time it works fine, this happens maybe one out of four times. I've checked the transmission fluid and its fine. No leaks either. Any suggestions?

TexasAxMan

Vacuum modulator.

crazyshuffle

Is the Vacuum modulator under the hood or beneath the car on the transmission?

Genxer

I agree, the modulator is a good place to start. Cheap enough and not hard to change out. Those things do fail from time to time.

It's on the transmission. It's been years so I can't remember location but you can probably google it.

Boogie's_AutoRama

Yes vacuum modulator.

But since the problem is intermittent it may be a leaking vacuum line.

crazyshuffle

It looks like I might just have an Overheating problem because when I drove it last the radiator leaked out way too much. I checked all the lines and it just leaked out of the overflow after driving. What's wierd is I have a electric fan that suppose to cool the motor? But like I posted before when I was having trouble shifting to 2nd gear I could feel the heat and it usally shifts after I baby it a while. I just got a new thermostat and flushed my radiator out a year ago,but it looks to be an original so I might have to upgrade to a New stock looking radiator. Any suggestions?

bebo

The first thing to do is to get an expansion tank for the radiator overflow. When you heat the coolant it expands and has to go somewhere so it eventually over-powers the radiator cap and goes out the overflow. An expansion tank will solve that problem assumong your car is not actually overheating. The "hot" smell is from the coolant spraying on the engine as you drive the car.
The vacuum modulator is located on the lower rear of the transmission on the passenger side. There should be a vacuum line attached to it and to the intake manifold, which is the vacuum source, so you should see the line which makes it easy to find the vacuum modulater. If, after replacing the vacuum modulator valve (very easy 5-minute job), the transmission still won't shift properly you should take it to a reputable transmission shop.