C4 with no 3rd gear

[66Sprint6]

Was pullin out of Autozone today, punched it to get into traffic and when the tranny shifted into 2nd, it barked the tires. I thought "wow, that was cool" the I realized the RPM's were gettin a bit high and realized it wasnt shifting into 3rd. I then came to a stop, and went at it again, except this time, it wouldnt shift from 1st to 2nd. I bumped the shifter forward and it shifted REAL crisply into 2nd but still no third. Any ideas guys? I want to do the T5 swap so this tranny messin up is a blessing, but not this soon, I dont have the money to do the swap yet. What should i look into that might be causing this?
Matt

 

[Anonymous]

when my transmission wasn't shifting from 2nd to 3rd, the vacuum line from the engine to the tranny had come loose.

 

[Anonymous]

3 things come to mind:

1. Low tranny fluid (or very old).
2. Plugged filter in the tranny pan, causing low pressure at higher RPM.
3. Loss of control in the vacuum modulator, which can come from an open or leaking vacuum line to the trans or a hole in the diaphragm inside of the modulator itself. This latter item can be tested by pulling the vacuum line off at the modulator, then check for oil. If there's red fluid, there's a hole in the modulator's diaphragm & it needs to be replaced.

 

[Anonymous]

Had that exact same problem. Mine was the vacuum line from the engine to the transmission had crumbled due to old age. Glad it was a cheap fix and not a rebuild.

 

[Anonymous]

I had the same problem as well and like the others it was a vacum line from the tranny had come loose.

 

[66Sprint6]

You know, I figured it was that, but funny thing is, the day before, a rubber plug on one of my new carbs unused vacuum plugs came off and the car wouldnt start, took me 15 minutes to realize it wasnt there. Ill take a look at it when I get home. I really enjoyed how it drove tho, it was like a manual with no clutch and shiften REALLY crisply, it was awesome. Oh well, real dumb question, what side of the motor should the vacuum line be and where does it hook up? (in case it is completely gone)
Matt

 

[Anonymous]

There should be a steel line coming up from the left side of the motor looking at it from the front of the car. I doubt it's missing, but if it is, the vac. modulator is on the tranny at the back? of where the pan is. Kind of looks like a distributor vac. advance. There is rubber hose on both ends of the steel line, check it all, it can rot or just come off.