640 Brakes

Danny Prosser · Jan 5, 2018

Good morning my friends. I'm working on my tractors this winter fixing them up for spring and got a question. My 640 started making a grinding noise on the right rear and I figured it was something broke. Well I pulled the wheel and drum but everything looks ok. The brakes don't work real well though. When I push the brake pedal down it only spreads the adjusting side of the brake shoes a little even though they are adjusted out tight with the drum on put don't work well. However when I pull up on the pedal they move quite a bit. I noticed that the pedal shaft wobbles in the end that go's into the rear end. Is that where my problem lies? And how would one go about repairing that? I thought about pulling it out and trying to put a bushing or sleeve on it. Anybody ever have this problem and how did you fix it? I'm fixing this one up to keep my sickle mower mounted on for cutting around my pond and ditches and would like the brakes working good. Thanks for any replies or suggestions.

showcrop · Jan 5, 2018

Having a good range of movement when you lift the pedal but little when you step on it makes it sound like that brake is normally running right against the drum. Are your springs all in place?

Danny Prosser · Jan 5, 2018

Yes sir they are. I'm wondering if I need to replace them thou. Would weak springs cause that problem? also that pedal is lower than the other one. Thanks for your reply.

riveroadrat · Jan 5, 2018

I think you lose a lot of pedal action when that bushing is worn. Its usually the left brake, as thats easiest to mash when braking. I havent done any of those yet but if you are already in there I dont think they are that hard to do. The old bushing might be the hardest part. I have taken them out by using a one-ended hacksaw. They are easier to control if you break the blade in half, fine tooth is best I think.

Dollar Bill · Jan 6, 2018

When I push the brake pedal down it only spreads the adjusting side of the brake shoes a little even though they are adjusted out tight with the drum on put don't work well. However when I pull up on the pedal they move quite a bit. I noticed that the pedal shaft wobbles in the end that go's into the rear end. Is that where my problem lies?

A weak or stretched brake return spring can cause one pedal to be lower. Worn brake shaft/bushing will cause the pivot point to shift downward but it would really need to be worn for a drastic difference in pedal height. Rusted/stuck pins will also defeat the brake return spring.

In addition to the brake shaft bushing being worn, I have seen the ball on the end of the brake shaft worn/rusted away.

To remove the bushing: Drive a sharpened drift punch between the bushing and casting to collapse the bushing and pull it out with a pair of vice grips.

Worn brake shaft ball: Build up the ball on the end with a MIG welder and grind it to tolerance.

[b:9e7401d62a]"grinding noise on the right rear"[/b:9e7401d62a] could be the shoe dragging on the drum as Showcrop implied.

[b:9e7401d62a]"When I push the brake pedal down it only spreads the adjusting side of the brake shoes a little"[/b:9e7401d62a] If I understand correctly, you are seeing only 1 brake shoe move when you depress the brake pedal - I'm having difficulty understanding how this can happen. Have you pulled the brake drum off the other side to compare?

showcrop · Jan 6, 2018

(quoted from post at 04:12:55 01/06/18)

When I push the brake pedal down it only spreads the adjusting side of the brake shoes a little even though they are adjusted out tight with the drum on put don't work well. However when I pull up on the pedal they move quite a bit. I noticed that the pedal shaft wobbles in the end that go's into the rear end. Is that where my problem lies?

Click to expand...

A weak or stretched brake return spring can cause one pedal to be lower. Worn brake shaft/bushing will cause the pivot point to shift downward but it would really need to be worn for a drastic difference in pedal height. Rusted/stuck pins will also defeat the brake return spring.

In addition to the brake shaft bushing being worn, I have seen the ball on the end of the brake shaft worn/rusted away.

To remove the bushing: Drive a sharpened drift punch between the bushing and casting to collapse the bushing and pull it out with a pair of vice grips.

Worn brake shaft ball: Build up the ball on the end with a MIG welder and grind it to tolerance.

[b:e124dfe86b]"grinding noise on the right rear"[/b:e124dfe86b] could be the shoe dragging on the drum as Showcrop implied.

[b:e124dfe86b]"When I push the brake pedal down it only spreads the adjusting side of the brake shoes a little"[/b:e124dfe86b] If I understand correctly, you are seeing only 1 brake shoe move when you depress the brake pedal - I'm having difficulty understanding how this can happen. Have you pulled the brake drum off the other side to compare?

Another thing that I just remembered is that the springs are not the same side to side. I don't remember exactly how, you will need to check the parts pages.

640 Brakes

Danny Prosser

Member

showcrop

Well-known Member

Danny Prosser

Member

riveroadrat

Well-known Member

Dollar Bill

Member

showcrop

Well-known Member

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