Help, c4 problem with rough idle

[creellimit]

Need help. '73 stock 302 w/ C4: I was driving home last week and Bronco decided it would no longer shift into 3rd. at same moment idle became very rough and will stall if not given gas. I now can shift it into 1st, 2nd and reverse. Drive location with column shifter puts it in 1st and will not shift out of it. Engine still very rough idle. Fluid levels are where they should be.
Are rough idle and tranny issue directly related?
Thanks,
creellimit

 

[wildbill]

I have not had a problem like that but I would look for a vacuum leak as it can mess up the shift of the trand and make a motor run bad. Also make sure it is not a vacuum leak as they will burn valves good luck. Bill %) ;D

 

[SaddleUp]

Sounds like the vacuum line to the modulator came off. Look at the back of the tranny for a small cannister with a vacuum connection. Be sure the vacuum line is plugged in and then check the line all of the way back to the intake to make sure it isn't leaking.

And yes, In this case they both can be related. Both can be problems on there own an unrelated to each other but when they occur at the same time it's a safe bet that they are and that it is the vacuum to the modulator.

 

[Broncobowsher]

If you can safly do so, go under the truck while it is idleing. Pull the vacuum hose off the modulater. Stick you finger on it and check for a strong vacuum. If it is not strong, follow the line up and make sure it hasn't fallen off or split.

Also, if you pull the line off and tranny fluid runs out, the modulator is bad.

I had a friend with an F150 that had a modulator go bad. the fluid ran up the vacuum hose and swelled it. It then fell off and he lost his shifts. Mall security wasn't happy about me fixing it in there parking lot.

 

[creellimit]

Thanks everyone for your help. Problem was a vacuum line that was split.
You guys know your stuff!!