C6 stuck in low.

[volitone]

My 68 f100 sat for a few weeks while I rebuilt the top end. When I got it ready for a test run the shifter on the column felt odd as in it smoothly moved from P to 1 like it wasn't actually shifting.

Underneath the truck I looked at the linkage and it looks to be working fine however, the shift lever on the transmission will move up and down and feels that it is not doing anything inside.

Also there is ATF all along the bottom of the c6. I did add some ATF bringing it to the proper level hoping that would help solve the problem, but it didn't change anything.

I drove it around the block, and it stayed in its lowest gear. It will not go into park, or reverse via the shifter on the column or shift lever on transmission.

How do I proceed in diagnosing, and repairing this issue?

Thanks in advance for any help.

[BobbyFord]

The lever suddenly feeling like it's not moving anything inside the transmission is odd. Generally things don't fall off from sitting for a while. Do you have park?
My first thought is a stuck governor. However, check the vacuum modulator line at the intake. If you have a hand vac pump, apply vacuum at the intake end if the line and see if it holds vacuum. If the vac line is intact, pull the pan and cycle the shift lever to make sure nothing has fallen off inside the case. If everything looks ok inside the case and the lever is moving the selector shaft inside the valve body, remove the driveshaft from the transmission and remove the extension housing, remove the governor and check to see that the pistons inside the governor are free and moving.

[guhfluh]

Yup, check the linkage on the trans, and make sure it is connected to the shaft correctly and the shaft is turning. If it is moving and attached to the linkage correctly, you'll have to drop the pan and check the other side. Unless the rooster comb fell off, you should still feel the detents when the shift lever moves, therefore it sounds like it's not moving. If it moves in and out of the trans, it may be able to come off the comb and shift valve, so it sounds like the shift lever on the VB may have just come loose. I'm not knowledgeable on C4's, but that's general auto trans info.

[volitone]

Nope...I don't have park...strange huh?

Thank you for the two replies. I feel like I now have a starting point.

[BobbyFord]

Nope...I don't have park...strange huh?

Thank you for the two replies. I feel like I now have a starting point.

No park definitely sounds like a linkage issue. Possibly the large nut holding the selector shaft to the case has come loose.