VCCA Home Forums TECHNICAL - 1945 AND NEWER 1946-1948 1948 Chevrolet -Vacuum gears versus floor shift

I'll admit I am not a BIG fan of the vacuum gears on my '48 Chevy sedan. I can live with them if I have to but was wondering if there is any advantage to having my car changed over to floor shift and how easy (or difficult) is it to change to a floor shift. Or is it better to leave it the way it is??

I absolutely love the vacuum gear shift on my 1940 coupe. It shifts like a dream.

dtm

mholten,there is a simple conversion kit you can get to by-pass the vacuum canister...Floor shift???..What is wrong with the vacuum shift on your car

My buddies 40 shifts like a dream. My 48 not so much. It works, but not like his. Guess I am a bad boy as I haven't checked any of the measurements on the vacuum unit. Also need to revisit the clutch adjustment. I do have the conversion pieces if I decide to remove the vacuum shift parts.

Keith, I guess we are in the same boat...My shifting is good but actually drops out of second from time to time. Over the years I have just gotten use to it..I have the conversion unit as well

It really can't be changed to a floor shift because the transmission case has no opening on the top.

When I first got mine, I double clutched it from first to second and second to third. I adjusted the clutch and slowed down my shifts and it doesn't grind like it did at first.

My biggest complaint about the vacuum shift is that when I am at a stop and drop it into what I think is first gear...when I let out the clutch and take off it feels like it is really in third gear...no acceleration! To avoid that happening, I have learned to hold the gear shift lever in my hand while also holding the steering wheel with the same hand (right, of course). When I first got the car it had a 70s Nova steering wheel which is much smaller than the original. I know have an original wheel, thank goodness.

Does it need some adjustment, etc.? I guess I'll probably just learn to live with the vacuum gears.

Spend some time adjusting the rods following the shop manual..Adjustment is what it sounds like to me

At a stop, in 3rd gear, move the shift lever to 2nd gear, then back into 1st. See if that helps in finding 1st gear.

Installing an aftermarket floor shift assembly will certainly take away, from the originality of your car, if that is a concern to you.

Another alternative is to find the conversion kit that does away with the vacuum shift but retains the column shifting so it looks original. Watch e-bay and/or post need in the parts wanted section in the VCCA chat site if you want to go that route.

Dick

In my bad shifting days, I put the conversion kit I have on the 48..It s basically a replacement rod that attaches directly to the tranny...Strange to find it really did not change a thing in shifting performance..I removed it and spent the time to adjust both rods correctly

Thank you all for your advice.I will go the adjustment route and hope that helps and will try to double clutching. Originality is a concern of mine...M Holton

I spent some time last summer adjusting the linkage rods on my 1940 and it did help a lot. Before I could`nt shift into 2nd without double clutching ....but still need to double clutch into 3rd . Shifting slowly really helps( the 2nd gear shift is like butter now ) ...Following the service manual is confusing to me ....I did a lot of trial and error and got it shifting much better , but still not like some that love the set up. I believe I have worn tranny syncros..and it`s all a related problem ....Try adjusting the rods one at a time,one turn at a time..one way then the other ...you will see quickly which way helps or makes things worse . Usually 1 turn can completely miss the gear or maybe help ...if it helps try another turn in that direction until you find the sweet spot . I pulled the vacummn shift and went through it and made sure it was right ( process of elimination) The experts probably think I`m nuts ..but it worked for me . Good luck!

If everything is working correctly a 48 with vacuum shift should shift smoothly with no double clutching. It should shift between gears with one finger. Mine does.

The vacuum shift assist has nothing to do with double clutching or gear grinding. If these conditions exist it is an internal transmission problem 95% of the time.
The vacuum shift forcing the shift is hard on the syncronizers. That is why cars with vacuum shift are more common to have the problem.
Transmission dropping out of 2d gear can becaused by the little energizing spring on the 2nd gear.(in the transmission)

I have learned when at a stop. I shift into what I think is 1st gear. I then let out the clutch just a bit and you can tell right away if you are in 1st or third.

I had a 48. The vacuum shift was one of the great features and gave me no troubles in 10 years. Why then did people do floor shift and column conversion? Often it had to do with the cars getting old and the column shift mechanism needing to be overhauled. The cars were usually bought by young guys who simply put in the floor shift, bucket seats and all of that stuff. One of the major problems arose when the cars started to become tired and needed to be push started which you couldn't easily do with the vacuum shift because the motor wasn't running so you couldn't get into gear. I once met up with an old fellow who had worked in the Government Motor Garage and they had a lot of Chevrolets. He said that they had little trouble with them though they did carry a tool that enabled the drivers to engage a gear if say they had a flat battery. I should have asked him more about that. As I said, one of the great features, just get it adjusted right. I agree with Keith's comment about checking that you are in first; it's a fine line.

I have never had to double clutch...Am I 0ne of the lucky ones???

Thank you!

I think we must be chef, but years ago I had a '42 and it worked great also ( until I drove it in blizzard and froze up the shifter.) After it thawed out it was OK!

mholton...Did you try to adjust the rods?It so any improvement?

Chef-Chevy - mine drops out of second on occasion, and will sometimes pop out of third too, yet it otherwise shifts easily and I just shift it back into gear whenever it does drop out. Is this just a linkage adjustment or is it related to the vacuum assist? Although I'm used to it, and consider it a quirk of the car, I'd like to get it working correctly, if possible.

It is my opinion it is vacuum cylinder adjustment

MH,

I don't really know what the problem is here.

I do know that Gene is right when he says that most problems such as slipping out of gear are internal transmission problems.

When the vacuum cylinder is properly adjusted, it is a pleasure to drive a car so equipped. One can change gears so easily. Just a nudge with the finger tips and the gear slips from one gear to the next.

I hope you can get yours properly adjusted so that you no longer have a notion to change it out to a simple lever mechanism and scrap the vacuum device. To do so is to accept defeat. Don't let that adjustment whip you.

Just my opinion.

Charlie