VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 41 Special Deluxe Shifting Problems

Converted the vacuum-assist shift on my 41 Special Deluxe to "manual" shift and am having linkage adjustment problems. Shop manual says nothing about adusting the shift control levers. Searched these forums but can't find anything that's helping.

I'm new to this so I'll just refer to the shift rods (from the steering column to the transmission) as the upper and lower control rods - the upper being closest to the firewall/highest on the column. The lower control rod was the one replaced during the conversion.

The only adjustment I've been making is to the bushing, I believe it's called, of the lower rod. The bushing can travel up and down the rod a ways by screwing it up or down. The problem I'm having is that when I raise the bushing to keep the tang from the upper rod from shipping out when I shift into second, I cannot fully engage 1st or 3rd gear. If I lower the bushing even one or two turns, the tang on the upper rod will slip out of where it fits into the lower rod and will jam up in second gear. The lower rod is also getting in the way of the brake pedal. When it jams in second, I can't push the brake and have to coast to a stop - rather unsafe. I figure I may be able to bend the rod a bit more to keep it away from the brake pedal but that probably won't solve the main problem.

I filled the transmission with 1 1/2 pints 90 weight gear lube - it was bone dry/not even a drop - and that fixed the loud whine in first and second.

The goofy thing is, on some adjustments, I can get through all of the gears just fine for a mile or so and then it will either jam up in second when trying to shift to third, or I am completely unable to shift into first or third depending on the adjustments I've made to the height of the bushing on the lower control rod.

Should I also be adjusting the upper control rod? Or does something need replacing?

It has occurred to me that maybe I installed the conversion control rod to the transmission backwards/flipped? The instructions that came with it from ChevsOfThe40s didn't say much and included a picture that was obviously of the original conversions sold; not the current ones. It also included a nut and bolt with mismatched threads so I'm not all that confident that going by the picture in the instructions was foolproof.

Hi Blake,

I think you need to go back to the manual and follow the directions on page 211 through 213, especially the adjusting of the shift control rod (#4. pg 213). The shift control rod is the smaller rod which is attached to the lever on the interlock. Your new part that replaced the vacuum assist rod attaches to the operating shaft and is the large shaft that sticks out the cover. The attached pictures should help. I'v been tweaking my adjustments for at least 10 years so keep the faith, you can get things to work better depending on the condition of your transmission, motor mounts, transmission mount, etc.

Good luck, Mike

P.S. THIS INFO IS FOR NON VACUUM SHIFT LINKAGE

Now that I re-read #4 on pg 213 it makes more sense. Thanks! I'll give it a shot.

I've replaced the motor mounts and lubed the transmission - as I said, it was bone dry. Probably has a slow leak somewhere so I'm watching for it. I'm betting it's leaking down the torque tube as someone mentioned earlier.

As for the transmission mount, I'd forgotten about that one until you or someone else mentioned it. ChevsOfThe40s are out of stock so I have a rebuild kit coming from eBay.

Still fudging with this.

I'm thinking the tang on the shift control rod should slide into the slot of the larger rod only when shifting into 1st or reverse, and then out when shifting into 2nd or 3rd? Or should the tang always be inside the slot?

OK, after staring at it for a good long while and working it through with a beer, I don't think the tang should ever slip out of where it fits into the control rod. But it always does when I shift into second and then it gets jammed up. If I adjust the swivel to where the tang won't slip out, the shift handle on the steering column is angled down quite a ways and I lose the ability to shift into first (or it pops out of first as soon as I let off the clutch).

I've only been adjusting the control rod to this point, since that's the one I replaced. Now I'm thinking I need to loosen the upper bracket and rotate it clockwise slightly, compensating with the smaller control rod by lowering its pivot. I'm thinking this would allow me to adjust the control rod more to keep the tang in the slot and not have a downward angled shift handle and, hopefully, not have it pop out of first.

Thoughts or dissenting opinions?

I have thoughts and disenting opinions:

a. Thoughts: Gather what you need and restore the shifting backto the vacuum assist.

b. Disenting opinion: You should have done "a" above in the first place.

Best,

Charlie

BRW: What parts do you have or what do you need to fix it back like it is supposed to be?

BTW2: The above is given with the best regards in mind for you best enjoyment of your 41. Is too!

Don't think I haven't thought about that. But the vacuum assist canister is pretty bad. I have no idea how long the previous owner drove it after disconnecting it (guessing 40 or 50 years). The canister is rusty, all the rubber is rotted and crumbling, the linkage is bent, and I can't get any back and forth movement of the piston. I think I'd probably need an entirely new assembly ($$!!).

I know you're a purist, but with the conversion it shifts just fine, effort-wise. Just trying to get it to shift correctly now.

BJ I live in Ames, I have some extra vacuum cylinder parts off my 41 also if you would like to come up sometime my 47 still the vacuum shift and works good.
Denny
My phone is5152311980
PS I will be at Wayne Larson Rollin Thursday night.

Dens, I'll give you a call. Like I've said, I would love it if I could restore the vacuum assist. Have all the linkage. It's just the canister and/or interior parts that are shot.

I am not familiar with the 41 arrangement at the base of the steer column but I am thinking the shaft from the lever should only connect with 1 of the arms at a time but the tang should line up with a groove in both when everything is in nuetral, 1 arm selects 1/rev the other selects 2/3.
Tony

Although it looks like I may be converting her back to vacuum assist (still have original linkage, so may not have to fudge with adjustments much), from what I observed while staring at the linkage and moving it by hand, I think I figured out how it works, which would help with the adjustments.

The control rod (the long one) actually operates all gears, reverse and first through third. When you pull the shift lever on the steering column toward you, the smaller shift rod pushes down, which allows the control rod to select reverse or first. When you let the shift lever go forward, the smaller rod raises and allows the control rod to shift between second and third. This, of course, would require that the tang on the smaller rod to always be engaged with the control rod.

Someone correct me if I'm wrong. I was looking for an explanation like that all over the forums and the web but couldn't find it. If I'm correct, maybe it will help someone else. If I'm wrong, someone correct me so I'm not giving out bogus information.

BJ

I have a '40 and have been back and forth between vacuum and manual several several times. When converting to manual I do the following,
1. disconnect both rods at the levers on the column,
2. make sure the tang is in the middle of the groove (right to left),
3. shift lever in car should now be horizontal or near horizontal,
4. make sure gear shifting lever (large lever) on transmission is in neutral (middle detent) (I've always had to get under the car to do this),
5. adjust the gear shifting rod so that it installs easily into the gear shifting lever,
6. pull the shift control lever rod forward and adjust so that it installs freely into the shift control lever.

You should now be able to shift from gear to gear freely without gnashing of gears. If I had problems and was unable to shift freely it was because the transmission was not in true neutral (sometimes the detent is difficult to find) or I did not have the shifting lever (inside the car) in the horizontal position when in neutral..

Hi Mike,

Thanks for your directions, I seem to be fiddling with my linkage whenever I have the patience (not that often). Your explanation makes a lot of sense. I see no reason that the after market rod should not work well for Blake once he has made the correct adjustments IF THE TRANSMISSION IS IN GOOD CONDITION. I wish to add a couple of pictures to the ones covered in my above post so those not familiar with the vacuum assist and its alternative can see the differences.

Best wishes,
Mike

Mike B., Transmission seems to be in good condition. Before I removed the vacuum assist - which still had the linkage hooked up but the assist canister was disconnected from the vacuum - it shifted fine through all gears though it took a bit of effort and had a high whine in 1st and 2nd. Took care of the whine by putting 90 weight gear lube in - it was bone dry. The problems only began appearing after converting it to manual shift.

Meeting with Dens41 tonight to see what parts he has. Probably going back to vacuum assist but anything's possible at this point. I just want to drive her! I don't mind manual shift - drove old farm trucks and tractors as a kid - but I have to admit I was intrigued by the vacuum assist in the car. Was disappointed to find it disconnected and totally non-functional.

Mike D., I think #2 on your list is where my problems were originating. If the vacuum assist doesn't pan out, I'll definitely go with your instructions.

BJSoder on reading later posts my last suggestion will not work. The selector lockout is inside the gearbox, my suggestion is for the lockout at the base of the column where 1 rod for 1/rev and other rod for 2/3.
Tony

Many thanks to dens41 for providing me with a working vacuum assist! And to Mike B. and Charlie for the parts!

Installed the vacuum assist and the old control rod. Anyone have any idea why I can't shift into reverse or 2nd even after multiple adjustments? I can shift into 1st and 3rd. Notice it's only the "upward" shift gears that are giving me problems.

Had reverse once, made a slight adjustment, lost it again and haven't been able to get it back. Is this all in the adjustments to the control (big) rod or is there something I'm missing?

Hi Blake,

Have you ever taken the cover off the side of the transmission? If you have it is very easy to reinstall it with the yokes in the wrong position causing shifting issues.

Here is an online catalog that will help in your identification of part names. Chevy Old Car Manual Project. Additionally, here are the addresses for illustrations that should help in the Master Parts Catalog Chev. Models 1929 to 1954 specifically the illustrations under 1940-48 Pass. Steering Column Gearshift Mechanism and the 1939-48 Pass. Synchro-Mesh Transmission (Steering Column Gearshift) are helpful with correct part names you can use to explain your problems.

Also please post some pictures of your linkage.

Thanks, Mike

Nope, I've never taken the side of the transmission off. When I removed the old vacuum assist and linkage, I didn't mess with the transmission or linkage at all - just set the old control rod aside. When I installed the new vacuum assist, I re-attached the old control rod without adjustments to see if it would work. No reverse or 1st gear. That's where I'm still at even after multiple adjustments to the swivel.

So, I'm not sure if the next adjustment I need to make is in the control rod or the vacuum assist itself.

Please post pictures of your set up.

Thanks, Mike

P.S. I am a fan of Double Clutching when experiencing problems grinding gears. It took me a few years to get my linkage adjusted well enough so that I could just count to 5 when shifting from 1st to second gear. I know I have an old tired transmission and have begun accumulating parts for a rebuild. I live in a city of 40 thousand where only 3 or 4 roads have speed limits in the 40's. I also have seat belts to help me survive an accident at my local speeds.

Actually got it figured out after crawling under the car and testing my theory that something was preventing the control rod from fully lifting. It was the small clamp for the vacuum line. Every time I raised the control rod, like when shifting into reverse or 2nd, the clamp was catching on the side of the transmission. Took the hose off and rotated the vacuum assist rod and boot 180 degrees. Now she hits reverse and all three gears.

However, even though Dennis bench-tested the vacuum assist canister and it worked perfectly, it's not working now. Would this be caused by the valve link being screwed too far in or too far out on the valve rod? I could try adjusting it by disconnecting the reactionary levers but I don't relish the idea of working under the car with the engine running.

Or, could I just not be getting enough vacuum from the manifold? Wondering about that since my windshield wipers barely work. How would I test that?

BJ first think to check is the vacuum. If you don't have a gauge then put your finger over then end of a hose connected directly to the intake manifold. If the hose falls off your finger it does not have enough vacuum. Of course your best situation is to have a gauge and actually measure the negative pressure at the hose end. Not how long it takes to get to the maximum vacuum. It should be nearly instantaneous.

Chipper, yes, that was what I was going to check next - start the engine and pull the vacuum hose off to feel for suction. Unfortunately, now the starter won't turn the engine over (that's another thread).

As soon as I get the starter going again - or new or rebuild starter - I'll go back to the vacuum test.

Thanks!