Stumped on 76 Datsun 620 Trans

[CW240Z]

I bought a 76 Datsun 620 last summer that had been sitting for a few years untouched. I got the truck running but could not get it in gear to drive, so I went through the clutch/transmission of the 620 trying to figure out what was wrong. I replaced the clutch master cylinder, slave cylinder, and installed a new clutch kit. After bleeding the system out it still would not go in gear. It's odd because when its running and I try to change gears the trans won't grind or make a sound. Its as if I'm hitting a wall and there's no gear there. Is there something I'm missing or is my problem deeper in the trans?

Chase

[Zed Head]

Do you mean the shift lever won't move in to the proper position when the engine is running? Will it go in to gear when the engine's not running? Can you start it in first gear and drive it? Make sure you're pointed the right way and have some room to go in case the clutch doesn't work.

[CW240Z]

When the truck is not running I can shift through the gears easily with and without the clutch engaged. Its only when it is running that I can't get it into gear. The weird thing is that the truck won't grind or take off it I start it in gear.

Chase

[Zed Head]

If the truck won't take off when started "in gear" then it must not really be in gear, or there's a broken shaft in the transmission or the drive shaft is not connected. The shift lever moves a shift rods which moves a shift fork which moves a synchro coupling sleeve over the dog gears of the gear being selected. Shift forks have been known to break. If the behavior of the shift lever changes when the engine is running it seems like there must be something wrong inside the transmission.

You said it's like hitting a wall. Do you mean the shift lever doesn't move as far, like it's hitting something, when the engine is running?

Just trying to clarify. If you can get the shift lever in to position but nothing happens when the engine is turning, the odds point to something broken inside, not the clutch. You might drain the fluid and look for pieces.

[CW240Z]

You said it's like hitting a wall. Do you mean the shift lever doesn't move as far, like it's hitting something, when the engine is running?

Yes. When it runs I can't engage a gear.

I had the trans completely out when I was doing the clutch job and changed the fluid in the process. There weren't any signs of broken components or pieces of metal in the fluid. The drive shaft is properly connected as well. My problems so far don't seem to be related to the recent clutch job. I'm thinking that it is an internal problem as well. Most likely I'll find a 5 speed to replace it. Thanks for the input!

Chase

[zKars]

One more test. Car off, put it in first gear, foot off of the clutch. Can you push the truck? If not, then put your foot on the clutch. Can you (someone else, your foot is busy) push the truck now?

This test will determine if you are getting clutch release with the pedal. If it does in fact release, then you should be able to shift with the engine running too.

It sounds like you are are not getting the clutch to release with the pedal. I assume you see movement of the release arm at the clutch slave when you push the clutch in? About 3/4 inch or so? If you do, then you have the wrong release being sleeve in there, and clutch is never releasing. May have come to that way, or the pivot ball in there is busted.

Just some more clues. Good luck!

[olzed]

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