VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Vacuum Shift

After I recently did the brake job on the 41 coupe, got the tool and adjusted the vacuum shift before I put it back on. I had it adjusted so that shifting the control back and forth the piston slide in and out smoothly and as strong, smoothly and quickly in both directions.

After reinstalling it I found that the shift lever didn't want to stay in the reverse or second gear positions. There was a definite tendency to slowly slip out of gear.

I took the vacuum shifter off and, using a longer vacuum line, went through the process of adjusting it again. As I took it off I put a piece of wire coat hanger in where the pin is so that it wouldn't turn. Same as what I had done when I had installed it. Now, again, Inserting the tool, I readjusted the by turning the control one half turn each way. Slow out faster in and visa-versa. It operated just as the maintenance manual said it was supposed to and just the same as I had installed it. In other words, I put it back just the way I took it out and used the piece of coat hanger to hold the adjustment in place so that there was no way it could turn while installing the pin. No change. Same as before.

I didn't mess with the transmission shifting levers while doing the brake job.

Question: Anyone have any idea what is the matter here? (Before the brake job it operated just as it was supposed to.)

When being adjusted the port to the chassis was open. When installed back on the car and hooked up the port was connected to the filter on the chassis. That's the only difference. The port to the chassis was hooked up before the brake job.)

As much as I'm always harping about the excellent vacuum shifter mechanism and encouraging its use, this mystery is both troubling and embarrassing. Is too!

I can't figure out what in the world is wrong.

Any advice would be appreciated.

Thanks,

Charlie

Maybe just maybe it is constipated.

When was the last time you gave it a good dose of jack oil to lubricate its innards.

Even though it is appears to be working correctly, it may be losing some of its holding power?

Just a thought.

Good luck!!

Russel,

Now that was a real good thought. I have never oiled the innerds of it. I'll try it. It makes sense to me.

Thanks for the response,

Best,

Charlie

READ YOUR SHOPMANUAL FOR LUBRICATION OF THE CYLINDER, IT IS NOT LUBRICATED WITH OIL BUT WITH SHOCK ABSORBER FLUID.

Do not know what todays equivalent is????

Maybe something like https://shop.advanceautoparts.com/p...8uswZTc4wxoCwNwQAvD_BwE&gclsrc=aw.ds

Or search "vacuum pump oil" on Google.

Here is a thread from way back in 2008 on the AACA, same question.
https://forums.aaca.org/topic/121206-bendix-brake-booster/

Russell,

Not to worry. I have plenty of GM shock absorber fluid.

Gene,

Thanks for the "heads up."

It is really hot here these days. My stinkin' garage is not air conditioned and fans won't quite do the job. Even lighter knots are crawling into the shade. I'll wait until WX conditions are a bit better... say below 90 degrees or so.

I'll let every one know how it turns out.

Best,

Charlie