Autostick Experts Needed; no gears after reverse?

[Redbarnresto]

I’ve got an issue with a ‘74 autostick (which has the Park function) that’s got me wanting to pull my hair out. It shifts through the gears okay (usually) but there seems to be a specific issue with when you select reverse, you then can’t select other gears, as if the clutch is no longer disengaging. Sometimes you can’t even get it out of reverse. Now, why in the wide world of sports selecting reverse causes this issue, I can’t guess. What’s equally weird is that if you put it in park for a few seconds, it’ll usually reset somehow and you can then find your gears. I’m bamboozled by it, so any input would be greatly appreciated. Naturally I’ve cleaned and adjusted the contacts in the shift lever and did all the other checks and adjustments listed in the Bentley, at least to the extent I was able to understand them. I have some questions about that, as the Bentley is surprisingly vague and nondescript.

1) Unless I missed it, the Bentley makes no mention of the neutral safety switch except for that it’s in the electrical diagram. As near as I can tell, when the car is in neutral it first of all completes the starter circuit, obviously, but there’s a secondary function in which it grounds the control valve so that the clutch is always disengaged when the car is in neutral. Is this correct? I’ve done a test and this is what is occurring on this car, at any rate.

2) I’ve tried to adjust the clutch but am very confused by the instructions given. It says to pull the pushrod out from the servo and if the adjustable collar is more than 4mm away from the edge of the bracket, to loosen the lock nut and spin the collar 6.5mm away from it on the eyelet end. Only thing that’s really throwing me here is that this collar is like a tie rod, with reverse threads on the eyelet end. When I thread it away from the locknut I make it longer on both sides, which results in it now being vastly further away on the opposite end than it was to begin with as opposed to closer. I can’t think what I’m missing here. They ostensibly want the gap between the collar and the bracket to be 4mm at the most, not 4mm at the least, yet all you do when following this procedure is make it bigger and bigger. I’ve alternatively followed the instructions from the section describing how to do a preliminary adjustment of the rod and clutch arm, and the results are wildly different. I’m at a loss on what I’m missing and how these two procedures from the same manual can yield such different results.

Okay that’s all for now. I greatly appreciate any input at all.

Dan
_________________
Red Barn Restorations

[Redbarnresto]

Update: I found a couple holes in the servo diaphragm. I’m surprised it worked at all, but they were pretty small holes so I guess that explains the intermittent nature. Still odd that it seemed to work great until I put it in reverse, and I admit I’m a little unsure if I think replacing the diaphragm will actually cure the issue. It certainly isn’t helping things, though, so naturally I’ll start there.

I’m still curious to hear input into my questions if anyone could shine some light on that. Thanks!

Dan
_________________
Red Barn Restorations

[airschooled]

Tell us about this "park function?"
_________________
One-on-one tech help for your vintage Volkswagen:

www.airschooled.com

https://www.patreon.com/airschooled

[Redbarnresto]

[airschooled]

Very cool. Never seen one, and just reading that part of Bentley for the first time…

When you are “stuck” in reverse, does the shifter still allow movement? Or does it feel like you have movement but the transmission is stuck in reverse?

IF your clutch system is perfect, it sounds like a shift interlock pin/spring issue, but that’s really rare unless it was built with issues.

Robbie
_________________
One-on-one tech help for your vintage Volkswagen:

www.airschooled.com

https://www.patreon.com/airschooled

[Redbarnresto]

No the gear lever won’t move, presumably because the clutch isn’t disengaging. Feels just the same as trying to select a gear in a manual without stepping on the clutch pedal.

Dan
_________________
Red Barn Restorations

[sb001]

[Redbarnresto]

I was wondering if you’d chime in, sir, as you seem to be the autostick expert around these parts. Although I’ll share with you one thing which is that the ones with the park function actually use the exact same lock out plate as a manual, as opposed to the unusual one the early autosticks had like you’ve shown (the Bentley makes no mention of this, however, but it’s true).

I ordered a new servo diaphragm and got a shift rod bushing and new coupler as well, for good measure. I agree that it could be related to all that.

I understand how it’s possible to adjust the rod to 4mm if you want but the instructions they give you in the manual make no sense at all. I’d really love for someone to explain it. It says to turn the adjustable sleeve 6.5mm away from the locknut at the eyelet end, which, again, only causes the distance between the sleeve and the servo bracket to grow considerably larger on the servo end. Which is funny, because if you check your work afterwards, you’ll find the sleeve is still greater than 4mm from the bracket, causing you to make the adjustment yet again, with this cycle continuing indefinitely until the sleeve finally falls off because the threads have run out haha. It’s truly a head scratcher and I can’t fathom what they’re on about. Nevermind the fact that the distance between the bracket and the sleeve being 4mm is completely irrelevant, because how long the entire assembly is overall is what matters. In other words, I can remove the eyelet from the clutch arm and thread it in or out of the sleeve on just that end however I please, making a 4mm measurement on the servo end irrelevant overall. They’re presumably assuming it was all set at the factory, and therefore a 4mm measurement would be consistent with assumptions of the overall length, but why assume it hasn’t been altered? Why wouldn’t they just give us a measurement from the bracket to the center of the eyelet to shoot for instead? Again, I’d love to talk to anyone that can really explain this (I’m guessing no one can).

Okay, rant over. I’m just pretty bamboozled by this because it really is the strangest thing I’ve ever seen in the Bentley. All that said, I did adjust to the specs listed in a later section. This being 8.5mm from the beginning of the threads on the servo rod to the beginning of the adjustable sleeve, and 77 to the center of the eyelet.

I’ll let you know how things go when I have the new parts in. I appreciate the input!

Dan
_________________
Red Barn Restorations

[sb001]

I agree that the way the servo rod adjustment is explained is well, just wrong. It specifically states to "barely loosen the adjusting sleeve's locknut" and then "turn the adjuster sleeve 5 to 5-1/2 turns away from the locknut." But because of the reverse threads on that end, you would have to turn the adjuster sleeve to the left instead of the right, which - due to the threads being normal on the diaphragm side - would cause the adjuster sleeve to move farther away from the diaphragm bracket, as you mentioned.

I agree it would have been way easier for them to have just given a distance measurement from bracket to eyelet, especially since it's this measurement that really needs to remain consistent in order to compensate for clutch wear and ensure the arm still travels the correct distance for the clutch to engage.

Anyway, keep us posted on whatever you find out.
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor