Chevrolet Repair: Transmission Work, vacuum modulator, park lever

Question
Can you please tell me how to tighten up the linkage inside a transmission? The transmission will not shift. The truck is a '76 Chevy 1/2 Ton 4x4.

Thank you for your help.
Candy

Answer
Hello Candy,
I assume you have checked the oil level and condition to see if it is burnt smelling.
If it runs in low and reverse, but is just not shifting, I would first check the vacuum modulator and vacuum hose. The modulator is mounted to the right side of the trans case, just above the pan lip.
If it isn't operating, the trans won't shift out of low, or if the hose or modulator is leaking, it may shift out of low, but not to high.

With a spare piece of vacuum hose connected to the modulator, suck on the free end of the hose, and the modulator should not leak.
It runs on full manifold vacuum.

If the modulator and vacuum system are all ok, then there is a shift governor in the transmission that might be sticking or broken. Again, assuming it works in low and reverse. The governor is accessable from outside the transmission, but you may not want to mess with that.
There are also a couple of band adjustments, but again, not necessarily for the inexperienced.

You were indicating shift linkage. All of the linkage is outside the transmission, but if you are moving the lever on the side of the transmission, and don't hear the little clicks of the detent inside the transmission, then removing the pan may be necessary. There is a little pin that moves a spool valve in the valve body. It just fits into a groove in the spool, and directs all the shifting, except for the park lever. But if it shifts into any gear at all, that shouldn't be the problem.
I have never seen that pin just fall out or break, but it is possible.

All this assumes an automatic transmission. If you have a standard, write back.

Van