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M11/12 Front band adjustment question

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george w View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Topic: M11/12 Front band adjustment question
    Posted: May/03/2021 at 10:04pm
The TSM calls for 1/4" clearance adjustment. What's the down side to reducing this clearance ? What if the adjustment was set to half that or less ? This seems to be a very loose spec. that allows for a slower engagement and some slippage as a result.
Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: May/04/2021 at 9:12am
An old article states that IF you replaces the old clutch band material with the newer higher co-efficient of friction material with the better grove pattern, the clearance should be reduced to 3/16".
Further to this it states that the newer material provides better oil/heat dissipation, less slippage, more contact area.
All promoting better performance and longer transmission life.
So IF you have replaced the bands since the mid 70's, you should have the upgraded material and the clearance should be reduced from the TSM specification. The newer band material started to be used at about the same time AMC started using the 727.
   
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: May/05/2021 at 6:47am
Without enough clearance there will be more drag (the band is closer to the drum in some areas than others -- it's not concentrically spaced when off) and more heat generated. You might be able to reduce it some due to wear, but I'd be careful about it. If you have a trans temp gauge you can record a temp measurement now, adjust the band a bit tighter (maybe down to 3/16") and see how much the temp goes up on a long drive. If not much you should be okay.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: May/05/2021 at 8:27am
I don't have a trans temp gauge but I did take a chance a set the band adjustment to 1/4 inch and then turned the adjustment screw in another 1/4 turn. I took the car for a couple of local drives and so far the shifting results are to my liking.
This adjustment setting also came with the change over from the F-O-M valve body to the SC valve body. The SC valve body came from a 69 so with it came some of the detail improvements that AMC/BW made when they went to SC. Downshifts from 3 to 2 or from 2 to 1 seem more responsive at part throttle and you can now get kickdown from 2 to 1 or 3 to 1 up to about 25 mph. Upshifts also seems a bit quicker and more positive. Interestingly I did not have to make any adjustments to the vacuum modulator setting. Shift points are spot on.
Having said that I did "adjust up" the vacuum modulator pressure setting over the factory settings years ago. I did this both with the 67 Ambassador and my 69 AMX and have never regretted it. I always felt the pressure settings, and as a result the upshift points, were too low and were specified for comfort and economy rather than to optimize performance, shift firmness and ultimately the life of the transmission's friction materials.
Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: May/05/2021 at 5:46pm
All the adjustments are more for economy and comfort than anything else. 1/4 turn tighter shouldn't be enough to make a lot of difference in wear, and if it improves the shifting so much the better!
Frank Swygert
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