1980 4 speed manual. First gear pops out into neutral when going downhill on a steep bumpy driveway or going across a very bumpy gravel parking lot with potholes. The only other time it pops out is when I shift down from 2nd to first at high rpm. Other than that, it is fine.

Some background. I inherit this car so I don't know how it behaved before, so when I got it , it was not even running. As part of the process to get it in decent shape again, 4 months ago I removed tranny to replace clutch and components. Not sure if the oil had ever been changed (it was super nasty), and so I flushed and cleaned the tranny with kerosene while I had it somewhat apart. I did not take apart the driveline, just pulled off the housing to get access to shift rods and be able to clean more thoroughly. Finished the clutch job, put it back together, put regular 75-90w gear oil in it from the parts store. Finished the other work on the car and now I started to drive it, learning that first gear pops out.

The gear shifter is a little sloppy. I took it off and am in the process of "building it up again" with JB weld on the wore out parts, namely the metal ball that goes into the cup, and the groove, which is also worn to be a bit loose. I'll put new bushings and plastic cup in it as well.

I noticed that the motor and transmission shimmies from left to right, not a vibration, but more of an oscillation. I have read that worn motor mounts can cause this problem of popping out of gear, and I wonder if this movement of the tranny/engine is a symptom of a worn motor/tranny mount.

Last, I wonder if I should use a different oil in the tranny that would fix this problem. I'm not a big believer in "remedy in a bottle", but I am willing to try it if I don't have to take the tranny off again!

I am interested in your thoughts. Please help.

Thanks!

 

Whatever you put in there, don't add anything that attacks brass synchros. I just use the Lucas synthetic 75-90W. Given all the slop in your shifter, maybe fixing the cup and ball will address the pop-out.

 

And replacing the front engine mounts is simple and easy. If the engine has room to move due to failed mounts, it could be causing the shift lever to hit one of the rubber boots in just the right spot to pop it out of 1st gear. Using quality transmission gear oil is recommended, as well - the synchro aren't unknown for being particularly strong, so shift smoothly and deliberately. Not sure why you'd be downshifting into 1st gear at high speed, though - don't get in the habit of doing that.

 

Typically you are likely seeing a worn collar and the only fix is rebuilding the transmission and installing new synchronizers (for good measure) and collars. The teeth in the collar can wear, causing the selected gear to become disengaged as it cannot keep it engaged in higher torque situations.

 

Guys, thanks for all the feedback. I am hoping that I can get away without have to tear off tranny again in the near future. But it is what it is. I'll try the easy options first. I talked to the previous owner (my cousin) and he said it did not pop out of first gear before. So I am thinking that the flushing of the tranny when I had it apart really loosened things up, and then with new oil, perhaps allowed those worn synchros and teeth to be so well lubricated that it now pops out. Tranny removal is likely inevitable, but I am hopeful that one of these fixes with buy a few years.

Please take look at the two videos and tell me if you think that this is excessive motor/tranny movement. Note that the wheels are raised and the car in in 1rst gear. I pushing on and off the accelerator: https://photos.app.goo.gl/t8KLV65LgrxUX1j5A
https://photos.app.goo.gl/LrShgAR6TU8y1CQ87

 

Watched both videos and they don't look alarming to me. Just my .02 and I'm not a proper mechanic.

 

One more observation: With the car on jacks, when in neutral and running, the output shaft (and therefore the rear wheel) turns some when I push on the accelerator. Now, it is not a high degree, I can hold the wheel with my hand, but it does turn.

Any thoughts on that?

 

Typical and to be expected. Even with the trans in neutral, the gear lash generates a tiny amount if torque that then finds its way out to the rear axle. Normally, you'd never notice this, as the car would be sitting on the ground and more difficult to move. In this example, the rotational torque gets translated into heat: which you'll also never notice because the trans is a collection of big chunks of heatsink.

 

Thanks for the explanation on that.
I'm headed out for around 10 days. I got a jug of Redline 90 wt gear oil on order and will give that that a shot when I return. I did also fix up the linkage via bushing and some wore-out metal on the shifter, but have not tried it. I'll report back in a couple of weeks. Its a long shot, but its worth a shot before tearing the tranny off again.

 

I finally got the Redline 90 wt oil. Took a long time to ship. Also added some Lucas oil as well. I noticed that the gear oil that I drained out, which only had about 30 miles on it and 4 months, was pretty nasty already even though I cleaned the tranny with kerosene before I put that oil into it 4 months ago when it was apart and sitting on my bench.

Anyhow, I don't know if it was the oil change or tightening up the linkage as previously described, but it mostly fixed the problem. I also tightened up the nuts at the tranny cross-mount. I only got it to pop out of first gear once, trying to do it on purpose. Perhaps it was all three changes, but I'll never know because I did them at the same time and quite frankly I'm just happy that it works!

thanks for all of the input that you provided.