Stuck 3720 Parking Brake

[orlo]

All:

The crappy parking brake they put on the 3x20 cabs finally stuck on me.
(Crappy compared to the open 3x20's) It either doesn't hold or doesn't release. I took off the knob and pushed it in as far as I could after unjoining the brake pedals to put a lot of force on it. It's not letting go this time (It always eventually let go before). I tried everything from inside - It's pouring out so I'm not crawling underneath now, but I'm hoping there is just an exposed linkage I can tinker with.

Has anybody had it stick this bad and know where the linkage is? Also has anyone made any improvements to this sorry excuse for a parking brake/release to improve it?

Thanks,

 

[radman1]

I haven't had any issues with the brake on my 3720 cab. Did you set the brake really tight and now it is having issues? Mine releases easily but I tend to only set it enough to hold the tractor. My guess is the linkage is bent or messed up enough that it won't release. When I set mine, I can feel a racheting-like mechanism. It most likely is not disengaging this mechanism rather than anything major within the brake system.

 

[Nuru]

I haven't had any issues with the brake on my 3720 cab. Did you set the brake really tight and now it is having issues? Mine releases easily but I tend to only set it enough to hold the tractor. My guess is the linkage is bent or messed up enough that it won't release. When I set mine, I can feel a racheting-like mechanism. It most likely is not disengaging this mechanism rather than anything major within the brake system.

No issues here, mine works fine and holds the tractor, even on my sloped driveway while it is running.

 

[sunnyside360]

Ditto -- no problems here with the 3720 cab parking brake. Always works without any trouble. Let us know what you find.

 

[orlo]

Fixed it. I've attached the diagram for the parking brake so others can see. I know my dealer has had other customers with this issue as I had complained to him that it was hard to release (Probably due to my problem before it got this bad) - I think now I know why.

The end of the cable (via you pushing it) is what releases the parking brake 'pawl' with all the teeth on it. All that keeps that cable from slipping through is a little double bend in it. No different than a throttle cable on a lawn mower that is push/pull.

---------|____ (kind of like that).

What had happened to mine is that the end slipped through so that pushing it did nothing - it just slid the cable through the pawl instead of pushing it open to disengage it. I'm sure it's been this way for a while as it's always been a pain to release and I'd have to try several times so I'm sure it had slipped through, just not as much. Also, the cable (A single, non stranded piece) was bent in a curve also which I'm sure contributed to it and is probably what let it slip through in the first place.

What I'm sure happened is that I pushed it BEFORE stomping on the pedal (or stomping on it hard enough) to release it and probably pushed it through or bent it. I know it's been this way for a while (maybe always) since the brake knob never came out much when pulled (it couldn't since most of it had slipped through.

Now it sticks way out and I can release it easily.

I still am not impressed with this but now it works and I can probably prevent it from happening again. What I think they should have is a heavy spring that pulls the pawl back as soon as you press the brake pedal and release the pawl/right brake engagement - So you'd pull a 'pull only' cable to engage and lock the pawl (Would lock when you release the brake and mesh them) and you wouldn't even have to push to release it.

To get at it was a little bit of a pain, it's buried under the firewall (in the bubble near your feet) so you have to reach way under (I have a loader on also) but you can do it. I used needle nose vice grips to put it back in place, then I bent back the cable so I hope it won't slip through again.

I guess the lesson learned here is not to push that too hard.

 

[orlo]

Parking Brake Diagram

 

[radman1]

Glad you got it fixed. I agree, the heavy spring to disengage it seems like a better idea. Older tractors had brakes like that to release them. It may be a liability issue to make it with a self-releasing spring. It amazes how complicated the current brake diagram system is designed.

 

[sunnyside360]

Excellent news. One hates to have problems but it seems less painful when you can fix it without having to buy any new parts -- not to mention the dealer did not have to transport it to his shop.
Many thanks for sharing your experience.