It should be mentioned that on our trucks (as with many cars) reverse is a very deep gear. On the E4OD transmission, reverse is 2.16:1, which means that it's got only slightly less torque to the ground than it does in first. Add in the fact that most drum brakes are less effective going against reverse than forward and the fact that you're inputting 450lb/ft into the system (way more than the gas truck can do) and you're looking at your explanation, assuming you have the typical worn (not worn out, just worn) drum brake assembly.

Further, FMVSS 105 subsection 5.2.1 does not apply to trucks. Trucks are not passenger cars; the reg says passenger cars and school buses only. There is also the fact that FMVSS in this case only applies to the vehicles as they are when new, not when they're almost 20 years old.

All that said, I would check to make sure your brakes are *properly* adjusted - both the parking brake cables and the actual brake shoe adjusters out back. The truck's parking brake should hold at idle (defined as ~700rpm) on most any angle you are likely to encounter. If you press the throttle, all bets are off - but it *should* be holding at idle. The star wheel automatic adjusters do sometimes need help, though.

 

I did have an auto trans parked on a hill once where I couldn't get it out of park due to the load on the pawl (I had not used the e.brake). we got a few people behind the truck and pushed it up hill to take the load off the pawl so someone could shift it.

 

"should hold"
Here in flat farmland country, the "e-brake" is rarely used, even on manual trans vehicles. 90% of the trucks I have used the PARKING BRAKE on, had siezed up cables from minimal to no use, so they wouldn't fully release when desired.

My local mechanic freaks out when he hears the term e-brake, or emergency brake, because this is absolutely not what its intended purpose is.

When they are worn out, I have seen a difference in the 3" shoes vs. the 2.5" ones. I don't know if it is only the HD models that have the 3'' shoes, but even when mine are worn/ out of adjustment, they will still hold my truck on a <5% grade forward and reverse.

I like the Yahoo answers explanation, because this describes exactly how the friction is applied directionally.

When drums and shoes are both replaced, and properly adjusted, they can hold a lot more than a static load, but once they start to wear, forget about anything but a static load in reverse.

 

My local mechanic freaks out when he hears the term e-brake, or emergency brake, because this is absolutely not what its intended purpose is...

he can freak out to his hearts content, but in the event that ones brake pedal sinks to the floor with no stopping effort, one is much more likely to reach for the parking/emergency brake than the windshield wiper switch.

 

Agreed. It is and EMERGENCY BRAKE, in case of an EMERGENCY when the hydraulic brakes go out

 

when a brake line goes, i reach for the shifter and downshift.
i have never had a working parking brake i could trust on any vehicle i have ever owned, except for the trans mounted driveshaft brake on my 88 F-superduty.

 

The park brake should hold forward and reverse. If it doesn't hold reverse, then it just needs to be adjusted.

I adjust mine by holding the release handle out and cycle the park brake lever rapidly until I feel resistance about halfway in the travel. Depending on how out of adjustment it is, it may take a while. Doing this works the self adjuster without having to get any tools out or get under the car. I think sometimes the self adjuster just doesn't work like it is supposed to under normal use.

The Yahoo answers explanation talks about a dual cylinder drum brake. When was the last time anyone has seen one of those? If the drum brake has one cylinder like our pickups do, then there is always going to be a shoe that tries to wedge itself into the drum no matter what direction it is rotating.

 

Thanks, I see what I did there. Would make a difference, wouldn't it.

Update on my situation.

I haven't had a chance to get the truck back in the shop. Just to busy at the moment.

But I did have to loosen up my rear brakes. I adjusted them tight and got the ebrake to hold. But the rear brakes actually tightened up.
I guess the auto adjusters tightened them up. I back down my driveway.

Anyway I am back to a poor ebrake. I am super busy. My wife and daughter do the 4 H thing. And our county fair starts this weekend. So I am going crazy getting campers, trailers and trucks ready to start moving in Thursday.

As soon as I can I will get it in and work on that front cable.

Thanks,
Joe W

 

[QUOTE=joey2fords;14499326

he can freak out to his hearts content, but in the event that ones brake pedal sinks to the floor with no stopping effort, one is much more likely to reach for the parking/emergency brake than the windshield wiper switch.[/QUOTE]

I like that last line.

 

Hi all,

I finally got time to work on the ebrake.

I went with the stretched cable theory from 1990 F350.

Since my two rear cables are fresh. I figured my ft. or middle cable was the problem.

I cut the cable and installed a turnbuckle and some clamps.

After a few tries I got it to work good. Much better than before. And with out over tightening my rear drum brakes.

I am going to pick up a bigger turnbuckle and look at making that a permanent repair.

Thanks for all the help!

Joe W

 

[QUOTE=weskan;14500680]The park brake should hold forward and reverse. If it doesn't hold reverse, then it just needs to be adjusted.

I adjust mine by holding the release handle out and cycle the park brake lever rapidly until I feel resistance about halfway in the travel. Depending on how out of adjustment it is, it may take a while. Doing this works the self adjuster without having to get any tools out or get under the car. I think sometimes the self adjuster just doesn't work like it is supposed to under normal use.




I will have to try that method.

I forgot all about that. Saves the fun of crawling under the truck with the screwdriver.

 

I've replaced plenty in my shop............common issue across brands, models............

 

I have replaced some front cables before, but they were usually rusted or trashed in some way or another. Rear cables always freeze up from the salt etc. So I have replaced many of those.
But this is the first time I can remember of running into this.
I knew the ebrake should hold like my other cars and trucks have always done.
And now it does.

That's why I love places like this.

Learn something new every day.

Thanks again.

Joe W.