Trans is jerking when on the brakes

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Model T Ford Forum: Forum 2015: Trans is jerking when on the brakes
Top of pagePrevious messageNext messageBottom of page Link to this message  By mike mclean pefferlaw ontario canada on Monday, June 15, 2015 - 08:19 am:

i have a 26 4 door when i am just coming to a stop the car jerks to a stop or going down a hill slow it does it only when going slow have i broke the brake drum or am i down to the rivets on the brake band it had kevlar linning on the bands but they have been on there a while thanks mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kirk Peterson Absaroka County on Monday, June 15, 2015 - 08:56 am:

Mike
I have a very similar issue with a 27 engine/trans. The engine is not in the touring right now. I have yet to fully investigate.
I did find a broken piece of a brake shoe in the trans screen, Maybe?

I have also found the following Post on the Forum a while back:

"We met at Crystal River this winter...hope you're doing well. I've seen how you drive and can state to the others that you know how to drive your car.

My $.02 worth. Having done many bands, I've never taken out bands that were round when compressed, but have always installed bands which were round when compressed (after forming and checking on a scrap drum). I only install bands by pulling the hog's head first, to ensure that the bands aren't re-distorted by working them through the hog's head door.

Now to my point: Many bands have the ears "tipped in" from fatigue/use. They are no longer perpendicular to the casting in the hog's head. Also, many bands are bent "down" at the very ends. I believe that either or both of these conditions together contribute to the leading edge of the band trying to be forced down into the drum with much higher localized pressure than the remaining area of the band. Under moderate braking, the band is set and operates smoothly...when just easing up, only the small area of the very end of the band (leading edge) is still in forced contact with the drum and drive train goes into a brief but violent stick/slip situation. I suspect that a worn u-joint or front drive shaft bushing would likely contribute to this chatter once it starts.

I'd try one or two things: verify that the removable ear is truly vertical/square to the casting (if not, remove and correct), and also consider placing several washers over the brake shaft to effectively extend the length of the hog's head casting boss inside. This will rotate the band's installed position slightly clockwise (when viewed from driver's seat) and reduce the tendency to self-energize when pedal pressure is low."

Hope this helps


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis on Monday, June 15, 2015 - 10:46 am:

The bands get to a point where they self energize. The band grabs the drum and then releases making the shuddering jerking type noise. I sometimes think it's from the band conforming too well to the drum. When the bands gets glazed is when it shows up most.

Check your drum for cracks and if the Kevlar lining isn't worn too bad, you can un-rivet it and flip it over and reuse it. Put it on the reverse drum since that one isn't used much and put the reverse band on the brake.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis on Monday, June 15, 2015 - 10:48 am:

Just noticed the year and obviously swapping bands around with reverse isn't an option...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Johnson on Monday, June 15, 2015 - 11:08 am:

Jerking while braking or just idling down prior to putting in the clutch to slow down the car can be caused by play in the driveline, caused by a worn out U-joint, worn drive shaft bushing, and/or worn ring and pinion, etc.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adam Doleshal on Monday, June 15, 2015 - 11:22 am:

Trans covers that were originally made before the production switch to demountable (quick change) bands don't always have enough clearance inside to clear the lugs on the quick change bands and can cause some odd behaviors. (even though the "book" says you can go ahead and just put quick change bands in an earlier car).

This can happen on any of the bands. On the low speed band, it could very well feel like you describe.

This is something easy to check for; Use a bright flash light and a dental mirror...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adam Doleshal on Monday, June 15, 2015 - 11:29 am:

...And I did see you have a 1926, so it would have originally come from the factory with quick-change bands (if it does currently have a 1926-1927 style engine in it), so what I say about "earlier" engines probably doesn't apply...

But you should still check for the sort of thing that I show in the photo, because I have also seen some machining and casting defects that have caused the same sort of interference.

I have scrapped 3 trans covers in the last five years... 2 because the casting was so far off of the machining that I could not re-machine the shaft holes and 1 because the casting was so thick on one side the cover would not fit on a pan without warping 1 arm, then found out the starter to ring gear clearance was wrong (my guess is they may have known it was machined wrong in the factory because the cover was on a "non-starter" engine).


Top of pagePrevious messageNext messageBottom of page Link to this message  By mike mclean pefferlaw ontario canada on Monday, June 15, 2015 - 09:03 pm:

thank you guys for your thoughts I am going to look in the next few days and I will report back


Top of pagePrevious messageNext messageBottom of page Link to this message  By mike mclean pefferlaw ontario canada on Wednesday, June 17, 2015 - 04:12 pm:

got the band out today the drum is ok no cracks but the Kevlar was all glazed over so going to reline it and see what happen s then thanks for the help mike


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