How smooth should tranmission drums be?

dumb person

dumb person

Well-known member
So i believe my transmission slips, new bands, new cams on the peddles, the drums may be too smooth. Do i need to make them rougher? Is it possible for them to have worn too smooth?

The people of your world would be horrified to think of someone putting a stainless steel wire brush on the drums while the engine was running but it appears to be the only option available to me.
 
hello
you may only need to adj the clutch
kevin
1923 model t roadster p/u
1930 model a tudor
 

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The drums should be smooth. If they are ruff it would be like taking sand paper to the linings. Type mtfca; clutch adjustment in your search box and you will get a lot of hits on the subject.
 
i did think about adjusting the clutch but high gear & neutral work well. Only low and reverse are a problem.
 
hello
then you will need to adj the bands more. the reverse has to be done from under the trans cover and the low band can be done from the out side the trans on the rt side. don't go to tight adj and ck may take a cople of times and if to tight then lossen a little
kevin
 
OK you have me confused. You say new bands and then that you have no adjustment left. With new band linings you should have lots of adjustment. DO NOT scratch the drums!! they must be smooth. Please explain.
 
Could be the band lining is now glazed up and won't hold on the drums. If run too loose or not enough foot pedal push to really hold low and reverse bands against the drums,, so that they 'lock up' and make the planet gears do the trans work, then the spinning action of the drum will glaze the new linings. Probably the brake lining is still good because it is used sparingly and with enough foot pedal pressure on and off.

Or could be the new linings were installed with bumps or gaps, the lining has to be fitted correctly, bumps and gaps will wear first, leaving the lining away from the drum.

Or the bands are standing proud of the drums, that can happen if the bands are sprung, as when installed thru the transmission opening time and time again, bending them out of shape. Before install of the linings, the band "ears" should be only 3"-4" apart, and the band a concentric clean circle to mate with the drum.
 
Several things can cause this problem.

First, make sure the pedals are not contacting the floor boards. The last several sets of new reproduction floor boards I have used had the slots cut short in the front. I typically have to add 1" forward on them.

Second, over time the pedals get bent forward. When that happens you don't get full travel, and it throws off all the adjustments. You may have to remove the pedals and re shape them.

The drums grab the bands best when they are perfectly smooth, which gives maximum contact area. On the other hand some machinists will cut the diameter of the drums on a lathe in order to make the drum perfectly smooth. This reduces the diameter of the drum, which causes you to lose adjustment. It often leads to cracked drums too, particularly when Kevlar bands are used with machined too thin drums.
 
Whatever you do, don't roughen up the drums ! With new bands you should certainly have all kinds of adjustment left ??
Wayne
 
There is a cam on the bottom of the brake and reverse pedal. The reverse usually does not wear much because of little use, but the brake cam on the pedal can wear to the point that it does not move the brake band when depressed. The pedal should start pushing the band against the drum after little movement of the pedal. I have seen pedal cams worn to the point that they would almost not move the band at all when the pedal is pressed. There is a second part to the cam which is bolted to the transmission cover and is replaceable. Both halves need to be good to get good braking action and adjustment.
Oh, if you have RHD, there are cams, but in different locations. The low adjustment is inside the transmission and the reverse and brake adjustments are on the outside.
 
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Which linings have you fitted? I used the cheaper option on my 1923 Tourer in 2009 and they lasted one trip. They were just too thin. Change to Kevlar and have done over 5000 miles since and plenty of adjustment left.
 
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