no drive gear. help!

[aaron7621]

I had a recent post here earlier. I have a 68 mustang with a C4 trans. when the car is cold the transmission will hesitantly go into reverse, but will not go into drive. I have to wait until the car is warmed up before the drive gear will engage, but when the car is hot i have no reverse gear. I recently changed the filter and fluids out and put in a new modulator valve, but still nothing. I checked out the low-reverse servo and it was a little sticky so i replaced it. the car jumps into reverse, but still no drive. any ideas on what is wrong? also the engine makes a "hissing" sound when driving the car, but not when in park. any help is appreciated.
Aaron

[Phillyfanfrombirth]

"hissing" is usually a vacuum leak... any chance that you have or could borrow a vacuum gauge to find out where you are?

Are your fluid lines free of kinks?
How's your shift linkage?
Do you have the lines running to the radiator, or an aftermarket cooler?
Is the transmission vacuum line hooked up to a full time vacuum port?

If you have fluid that isn't being impeded... and you have solid vacuum read out, and the linkage checks out then it starts to sound more of an internal problem...

[aaron7621]

thanks for the reply. I'm sure i can get a vacuum gauge from my dads work.

I have checked the fluid lines and have found no kinks anywheres. For the most part the car is pretty much stock with the exceptions of filters, lines, plugs, and a carb and radiator. the trans cooler lines go into the radiator and no aftermarket part. i know the vacuum port out of the modulator runs right all the way into the manifold via a spliter. i checked the linkage and it's fine.

I'm thinking it's internal just because it takes so long for the car to go into drive. like the seals are hard and soften up with the heat overtime. plus the car feels like it wants to "go" but can't. like something is holding it back.

thanks for the replies. I'll look into checking the vacuum lines for sure next.
-aaron

[Rev]

How long since the tranny has been rebuilt (years and/or miles)? I hate to say it, but it may be time for it. I have to do mine every few years or about 20,000 miles. I do abuse mine with drag strip and G-tech runs as well as a little street racing, but I figure that's what I have mine for. The clutches in my C-4 always wear out and that clogs up the valve body. I take mine out myself, pay to have it rebuilt, and then put it back myself. Costs me about $500 and a fair amount of labor doing it myself in the driveway, but that's the way it works for me.

Rev

[Phillyfanfrombirth]

If you go the rebuild route, do it right... don't opt for a "used" tranny... Pay for the rebuild and get it over with, it will be well worth it.

[aaron7621]

thanks for the replies again.

yeah i'm positive it needs a rebuild. When i got the car everything was original on it and the transmission doesn't look like it's been rebuilt. I have another one in my yard, but that one looks bad. for one the inner downshift lever looks as it has been twisted off (by the way i got that one from my brothers friend). I have no clue how that happend.

the main thing i was looking for in troubleshooting it was to see if it could possibly be replacing something simple such as the modulator valve or putting in new seals rather then clutches or a new pump. whatever it is i know what i have to do now.

Thank you all for helping me out on this. I appreciate it very much.
-Aaron

[Rev]

Doesn't sound like the vacuum modulator. My bet is it's clutches and bands worn out.

Rev