Propshaft Parking Brake?

[koolky]

I was looking up info about my 4 speed manual (SM465) and found the option J76. Its been bugging for a few day now, i want ot know what it looks like, or how it works. as far as i can tell it mounts in the same spot as a PTO would...

[Longhorn Man]

it's a drum that mounts on the front of the drive shaft on the back of the tranny and has shoes in it like a drub brake. (PTO would be on the side of the tranny) Personally, i've never liked the drive shaft mounted brake, not nearly as good as a real brake that goes to the wheels.

[koolky]

So if a truck has got this brake on the tranny, does it still have the normal rear brakes? Also, is the brake connected to the hydralic brake system or is it conected to the E brake?

[El Jay]

Originally Posted by koolky

So if a truck has got this brake on the tranny, does it still have the normal rear brakes? Also, is the brake connected to the hydralic brake system or is it conected to the E brake?

The E brake is a drum on the drive line, just behind the tranny. The braking material is on a band that goes around the exterior of the drum. When you set the E brake, a cable pulls the band down tight (supposedly) around the drum.
This style was really popular on Mopars for quite some time. Maybe they still are, I don't know.

Like Longhorn, I've never been a fan of them.

I almost had a friend die because of such an E brake. He had a Dodge motor home and was going to replace the u-joints, or carrier bearing; something under there.
I don't know what he was thinking at the time, and neither did he.
He pulled up into his driveway and set the E brake, and forgot to chock the wheels.
Then he climbed underneath to drop the drive line. As soon as he was disconnected from the 3rd member, the motor home started to roll backwards down the driveway and across his midsection, causing horrific damage to several internal organs. He laid there for a couple of hours before a neighbor wondered, "Why is Mike's motor home parked in the middle of the court?" and walked up to take a look.

I only told this tale because we all have to think ahead about what we are doing so nobody gets hurt.

[Dusty_case]

aah\
hh7\hy grrr sorry my cat is on something would that be harder on the tranny and driveline?

[El Jay]

Originally Posted by Dusty_case

aah
hh7hy grrr sorry my cat is on something would that be harder on the tranny and driveline?

I shouldn't think so.
Normally, when the E-brake is set, the vehicle is stopped/parked.
All this type of E brake does is stop the drive shaft from turning, thereby preventing the rear end from turning.

[special-K]

I like them.They work great.You just have to remember to maintain them.The rear shoe e-brakes get maintained when rear brakes do.It`s unavoidable.These are what is used on heavier trucks up to where air brakes are used.It`s a heavier duty design and I`d like this set-up on my trucks when they get rear discs.They use a disc brake design in more recent models.

[Longhorn Man]

actually, they'll use this on med duty trucks that don't have air brakes. On an air brake system, the natural relaxed position for the shoes is against the drums. To pull them away, you add air, to apply the brake, you remove the air.
On many lighter med duty trucks, they'll have a hyd pump that assists you in normal hyd type brakes... much like a hydroboost, but a much larger scale.
I don't like them becouse they suck as an emergency brake, and I have personally been in situations where they hardly slowed me down when I needed to stop and lost hyd pressure. Tow truck drivers (who NEVER want to put the drive shaft back in) will drop off a truck, pull the parking brake handle, and walk away, and the truck will be chocked by a pebble in the parking lot... and start to move with the slightest urge.
I just feel is a half ass way of making an e-brake/P brake.

[El Jay]

On an air brake system, the natural relaxed position for the shoes is against the drums. To pull them away, you add air, to apply the brake, you remove the air.

Longhorn,
To lessen confusion, it should be noted that this is only for the parking brake.
The service brakes are air to apply.
You know, I know it, every other Cl. A, B driver on the board knows it, but it could be confusing to others.

This is certainly not a criticism of you.
You seem to teach me something every day, whether you realize it, or not.

Enjoy the rest of your day.

El Jay

[Longhorn Man]

And you are absolutly right. Thanks for adding to that.
I don't always finish typing the complete thought.

[special-K]

Yeah,that`s what I was saying.The prop shaft park brake is used "up to" heavier trucks with air brakes.As in,this is the system used on trucks heavier than ours and lighter than HDs...Medium Duty.We all agree.I can see that this system may not be so good as an emergency stop brake.
Those disc-style park brakes wouldn`t be much to stop a truck either.I never tryed,but they are minimal just holding a truck from my limited experience.

[LONGHAIR]

I always dis-liked them because they are "stopping" the drive-line waaay to far from the wheels themselves. There are just too many parts that can fail. Everything from the axles, spider gears, u-joints, etc. have to take the load...asuming there is one, as stated earlier. LOL

Lots of Jeeps had them back-in-the-day

[El Jay]

Originally Posted by LONGHAIR

I always dis-liked them because they are "stopping" the drive-line waaay to far from the wheels themselves. There are just too many parts that can fail. Everything from the axles, spider gears, u-joints, etc. have to take the load...asuming there is one, as stated earlier. LOL

Lots of Jeeps had them back-in-the-day

A most excellent point.
If anything "down stream" of the band brake self destructs; u-joint, axle, whatever, it's like paraphrasing the old Tom Petty song. "We're free, free rollin'"

I'm not hijacking the thread, but I want to share a short anecdote with Longhorn.
I call this Divine Intervention.
An acquaintance of mine (NOT ME! I just drive 'em & break 'em), was working on a brake pod. For whatever reason he had a brain fart & forgot to cage the spring. (He's only worked on this stuff for eons) I have no idea why nobody was killed, or even injured when he loosened the band on the brake pod.
Just one of them things where things could have/should have gotten real ugly...real fast!

I guess I'm just trying to say that even though many of us have worked on stuff for years and years, we can't afford to get complacent.
If we do, we'll get bit in the butt, if we're lucky.
If we're not not lucky, things could very well be disastrous.

[Longhorn Man]

Jay, up here, they rust out and the spring can let go with no warning. I know what you are saying, i can see that happen, and you are absolutly right... he IS lucky no one got hurt.

[El Jay]

Originally Posted by Longhorn Man

Jay, up here, they rust out and the spring can let go with no warning. I know what you are saying, i can see that happen, and you are absolutly right... he IS lucky no one got hurt.

I ain't particularly religious, but I'll stick with my original assessment of Divine Intervention.

I certainly have a grip on the rust in your area. I grew up in western PA, the nearest "big" town was Youngstown.
Got a cuz in the Cleveburg area that I talk to a minimum of once a week.

Have a good week.

El Jay