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Old 08-24-2014, 03:31 PM   #1
Mart
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Default Does your clutch release properly? One test method.

I wrote a few words for Henry Hopper following his problem with gear grating. I thought I'd put them here because the description of clutch release is universal and may be of use or interest to anyone.

Not going smoothly into 1st is nothing to do with double declutching (also called double clutching).

There is no synchro in 1st, so if the gears are turning you will hear a gentle (hopefully) grating as the meshing of the gears slows and stops the one that is turning. The teeth have pointy edges so they contact first and once the speed matches, the chisel points aid in the sliding engagement, which if they were turning, actually means turning one backwards very slightly.

Imagine the scenario. The box is in neutral, clutch engaged (foot off pedal). The lights change, you press down the clutch pedal and try and select 1st. Imagine it all in slow motion. the clutch plate what diameter clutch??? That maybe a factor), input shaft, counter shaft and 2nd gear were only moments before, spinning around at engine idle speed. You slide the first gear slider towards the 1st gear part on the cluster. The slider is stationary, connected to the output shaft and the wheels. You slide it straight into the 1st gear on the counter shaft. Only when the rotating parts have dissipated all their inertia and stopped will it engage.

So the advice to count to 10 and then engage is probably good. Idle speed is worth taking into consideration, could it be lowered slightly? Are you using an 11" clutch? That would have a greater inertia than a 9", and a 10" would be in between.

The one big elephant in the room is the clutch. Does it actually disengage? When you push the pedal down does the disc really fully release? If you think it does, how do you know?

I'll tell you how to test it, but it takes skill and a little nerve.

Start 'er up and let the engine idle. You need a gear that does not have synchro. On an early Ford 1st will do. On something else you may have to use reverse. (Even then some modern boxes have synchro on reverse)

So, as I say start er up and idle in neutral with clutch engaged. Using both hands to avoid unwanted movement, slowly move the gear lever towards 1st. Grit your teeth. As the gear teeth start to clash hold the lever still and maintain the gentle clashing of the teeth. Press the pedal slowly down through it's travel and stop when you hear the gear clashing stop. Holding your foot still, reselect neutral and turn your attention to your foot. Stroke the pedal to the floor and make a judgement on how much travel there is after the clutch releases before you touch the floor.

Now, in an ideal scenario, the grating stops cleanly at about 2/3rds stroke and there is plenty of travel left before you touch the floor.

If the grating never actually stops you do not have a clean release of the clutch. This may be due to insufficient travel on a non stock hotrod linkage or if a stocker a sticky or grease impregnated clutch plate.

To explain the select 2nd then 1st scenario, it does work, I remember doing it on my Mini when I first could drive. I could select first while rolling backwards which you couldn't normally do.

So, as in the scenario at the start of this thesis, everything is spinning merrily, except the 1st/ reverse slider, and the 2nd/3rd synchro sleeve which is stationary, anchored to the output shaft. This time, you push the clutch pedal down and immediately select 2nd. The 2nd gear synchro slows down and stops the spinning parts (including the clutch plate) and before you actually fully engage 2nd, you instead select 1st, which goes straight in because nothing is turning.

Viola!

So, if you are experiencing gear clashing, first of all do the clutch release test and if it is fully releasing cleanly, check your idle speed and then do a count to ten and try it. If it works, try nine, then eight until you find a time delay that suits your car. If you are caught unawares at a traffic light, momentarily select 2nd before taking 1st and that will get the job done.

Hope someone finds this helpful.

Mart.
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Old 08-24-2014, 04:02 PM   #2
tamnalan
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Default Re: Does your clutch release properly? One test method.

I'll vouch for the "2nd then 1st" scenario. I use it at stoplights fairly frequently in my '43 jeep.
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Old 08-25-2014, 05:13 PM   #3
dp1743
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Default Re: Does your clutch release properly? One test method.

Excuse me for butting-in, but I have to tell you... A good friend of mine, when I first bought my 40' suggested using the 2'nd to first method. I've done so every time and never had a gear clash problem.
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Old 08-25-2014, 09:50 PM   #4
Jay in Mass
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Default Re: Does your clutch release properly? One test method.

Quote:
Originally Posted by dp1743 View Post
Excuse me for butting-in, but I have to tell you... A good friend of mine, when I first bought my 40' suggested using the 2'nd to first method. I've done so every time and never had a gear clash problem.
Funny that you should happen to mention that about putting it into second before going into first. That's what I was taught to do in 1956 when I was learning to drive in a 49 Ford. I still do it today and never get gear clash going into first. It does stop the gears from spinning.
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