The Stovebolt Site Forums The Shop Area General Truck Talk Shifting a crashbox

Gentlemen,

I recently started yard driving my project for shakedown runs and hope you all can give me some guidance. First off, I am not a truck driver so operating a non-synchronized transmission is a "new" frontier. I have read past threads about the process of double clutching as well as watched some videos for tractor trailer training. The process is straight forward enough, but implementing the process has been challenging. I have yet to make a perfectly grind free shift during my approximately 2 miles of driving experience. I think most of my issue is due to "reprogramming error" on my part by default I try to drive it like a sychro transmission. It is kind of like driving a right hand drive manual transmissioned vehicle...you know the process, but some things are in the "wrong" place.

Also on the same theme of teaching an old dog new tricks is the process of starting a cold engine with the stomp starter. I am hard wired to think that the right foot is always responsible for the throttle. This is tough when one needs to feather the accelerator to get the engine to fire while cranking simultaneously. I been doing this with both feet, but I noticed sometimes I have inadvertently feather the starter instead. Not a good idea.

Any nuggets of information from the sages would be greatly appreciated as the grinding hurts me more than the truck. I realize that proficiency comes through experience, I am just trying to speed up the learning curve.

Thanks in advance.

BTW, once I have gotten the old gal moving under her own power, all I want to do is drive around but there is still much to do before the truck is street legal. These old trucks are awesome fun!

Paul

Paul,
I will assume that you already know the basic process of shifting this type of transmission, since you state you have read past threads. So let me emphasize what I think is the most important aspect of the process, and that is the importance of matching the engine rpm with what it will be when you put the transmission in the next gear. You can do the clutch thing correctly, but if you over rev (or under rev)the engine, you will get clashing of the gears as you attempt to slide the shifter into the next gear.

Regarding a cold start, you should use the throttle cable to get a bit more gas into the carb. Even the owner's manual recommends pulling the throttle cable out a bit on a cold start.

When I first got my '42 I began looking for a three speed synchromesh tranny to replace the crashbox but now I am proficient enough, and I enjoy the challenge, that I feel it is part of the charm of driving the truck.

Kent

First of all, stomp starter operation is a "heel and toe" process. Push the starter pedal with the toe of your right foot, and work the throttle if necessary with your heel. If you're having to manipulate the throttle, you're either not using enough choke for a cold start or the engine isn't tuned right. With a properly-tuned engine and a good carburetor, a cold start should go like this - - - -ignition on, pull choke knob out fully, push start pedal until the engine fires, push choke in partway until the engine runs smoothly. It should not be necessary to do a Jose' Greco dance on the pedals! Automatic chokes and/or electronic fuel injectors have made cold starts pretty much idiot-proof!

On the shifting, slow down your motion on the shift lever. The gears have to have time to equalize speed as the clutch is disengaged and the shifter moves to the next gear. It's possible to ease the shifter close to the next gear position and "feel" when the tooth speed equalizes. Most grinding shifts are caused by rushing the effort to get into the next gear. On a downshift, things get a little more complicated, but let's stick to upshifts for now. Have fun!
Jerry

Jerry,

Thanks for the coaching. I don't have the accelerator pedal on yet, just the linkage ball end so that explains much of the heel-toe starting issue. You are dead right about the choke issue, as I have not operated a carbureted engine in probably over 25 years and even then they were with automatic chokes.

I also suspect you are right about the speed I am attempting to shift. I feel I am treating it too much like a modern manual transmission.

I love all of the human involvement to run an antique vehicle. In the day, you HAD to know and feel the machine in order to properly drive and operate. Now vehicles are so "push a button and go" in nature, the computer makes all of the decisions and actions for you.

I will incorporate your suggestions this afternoon.

Paul

All good advice but what they don't mention is time. It takes time to learn a non-synchro transmission. Two miles is not nearly enough. It is an acquired art. And even when you have learned it, don't expect every shift to be grind free and flawless.

Put in a gas pedal before you try driving. A big part of learning is coordinating the throttle and shift. And don't grab the shifter like you were going to have to force it into gear. I slide her into gear with 3 fingers when it feels right. Many of the old timers used just 2 fingers. But we all grind a gear every once in a while. I have been around non synchronized boxes for 60 years. I never heard the term "crashbox" until I got on this forum.

Slow and steady. When you shift think that you are making 2 moves instead of one, shift to neutral and then to next gear.

One more suggestion; if you're shifting the 4-speed from 1st to 2nd, there is a huge difference in speed between those gears. The engine will rev quite high in 1st in order to get a smooth shift to 2nd. I will often forget this when taking off with my '46. After you have driven several hundred miles, it will be quite natural.

As mentioned, take it slowly, and don't rush it. It may take twice as long to make that shift as it would in a synchronized tranny. Once you get the hang of it, it will come naturally. And, like was mentioned above, it will take more than a couple miles to get it figured out.
Good luck! Keep us posted.

Gentlemen,

I made another attempt at starting and shifting my 41.

Unfortunately I did not read the many replies before my excursion, but will use the information next time. I did install a gas pedal and that made all of the difference in starting the truck using the heal-toe method. Using the starting sequence recommended by Jerry was spot on, thanks!

As for shifting through the gears, I tried going a little slower and less forceful, and it seems to have worked well. The process of depressing the clutch-shift to neutral/clutch shift to next gear is just sort of alien to me and I suppose it will take a little time to reprogram. It is like learning a new dance step. It is funny that I can jump from my newer automatic CVT car to my work truck 5 speed to my tractor hydrostat and never consciously think about how to shift any of them. I just need to add driving a non-synchronized gear box into my mental tool box.

I ran through all of the gears once without a single gear clash one time an thought I had down, only to miss 3rd gear on the next try. Practice, practice, practice. I found that shifting going downhill is much easier than uphill. I even started working on downshifting, but the quick timing needed to keep up RPM's is tough if climbing a hill.

Overall, there was a dramatic improvement but I would not claim proficiency yet. Is that a shameless justification to drive around in ones old truck project or what? I really need to get this project completed so it is inspected and highway legal, but just needed the morale boost of actually driving the truck versus just working on it for the last two years. So much to do, so little time...

Thanks for all of the great information, I appreciate your guidance.

Paul

The experienced crashbox drivers actually shift 'em without using the clutch, but that's a lesson for another day! The clutch is only used for starting and stopping- - - -all the shifts are made by easing up on the throttle and slipping the shifter in and out of position while there's no load on the gears. Try it with two transmissions in tandem- - - -5 speeds in one and 3 in the other! Two shifters to play with, and sometimes it's necessary to have both hands off the steering wheel! We learned not to make any shifts at all in a low-speed turn.
Jerry

The man that taught me to drive trucks told me about a '52 Ford F7 the local fire department had was the most miserable shifting truck he ever drove. He said that the clutch had to be used. Wish I could remember how it was done. He drove from the early 1930's until 2007 when he passed away. He would use the clutch to downshift the 2 speed rear at times. Now even many of the big trucks come with automatics. It won't be long and the "art" of shifting will be a thing of the past.

Darn now I will have to take the 41 for another "test drive"!

Getting better, will try out all of the suggestions. "light touch" and "feel" seem to be reoccurring words.

Thanks again for the input.

and practice, practice, practice!

I'd like to throw in another one for you. My first was a 59 Ford line truck for the telephone co. Straight 5 sp with no syc at all. Then later in life how about a 2 stick Mack. I find that you mostly have to listen to your engine and make sure you ease it in an out of gear, don't force it. If you just ease in towards your up shift it will suck itself in for you. I've been driving trucks of all kinds since before I got out of the Navy in 72 and once you learn to be patient you'll be ok.Larry

I like the idea of driving the truck like it was built. It's part of the fun. I've gotten pretty good at normal driving, but downshifting is still hit or miss... mostly miss though.

Last year I had trouble with the truck stalling due to a plugged idle jet, and trying to restart the truck by popping the clutch was a disaster. Not being able to rev the stalled engine made getting the thing into gear a very grinding experience. Sure don't want to try that again!

I am making progress. Unfortunately just when I think I have gotten the process down I miss a shift, especially 2nd to 3rd. I tend to think that I forget it is not synchronized and began shifting as if it was a synchronized transmission. Still not second nature. Downshifts are a challenge especially when climbing steep hills. Can't wait to get the old girl tagged so I can "practice" farther from the farm.

I also noticed that it is often difficult to shift into first gear (when stopped) unless I first shift into 3rd gear. It seems as though it is a shifting fork/rail issue. Is this normal? I did not rebuild the 4 speed, as it looked real clean inside without any measurable lateral play in the bearings/shafts. Undoubtedly the man that used the transmission before me was an experienced double clutch driver.

For myself these old girls were not made for speed. Do not expect to race off the line, just sit back and enjoy the ride and the shifting will become natural. As one post said just use the finger method, clutch move to nuetral ,release clutch, engage clutch, slip in. And enjoy the ride and don't for get to wave to everyone.
Proud owner of 1945 stock GMC.