Alternative parking/emergency brake?

Mr4btTahoe · 11-13-2019, 02:25 PM

Hey alls..

Looking for ideas. Will be swapping the transmission out of my IH 3800/Ward bus in the near future.

Plans are to go with an MT643. Problem is the AT545 that is currently in the bus has a driveline mounted parking brake and the 643 does not.

The 643 was offered with a driveline brake but it was a rare option. Not sure that the 545 brake will swap over and don't have the 643 here yet to compare.

So.. what are other options?

The bus has 4 wheel disc brakes.. all hydraulic. Has a Spicer N175 rear axle.

Haven't found any caliper options that have a mechanical parking brake built in.

I thought about using a line lock of sorts for exiting the bus to chock the wheels... but I really dont know about not having a mechanical brake of some form. Don't get me wrong... I know at speed, that little drum would go up in smoke in an emergency situation pretty quickly... and the 643 is capable of engine braking so that would greatly help get it slowed down in an emergency... but IDK.

Ideas?

PNW_Steve · 11-13-2019, 02:38 PM

The best that I can come up with is to suggest that you look at an Allison 2000 series with the parking pawl instead of the 643.

You would have a 5 speed OD transmission or a 6 speed double OD transmission depending on year and programming.

Good luck.

Mr4btTahoe · 11-13-2019, 02:55 PM

Quote:

Originally Posted by PNW_Steve

The best that I can come up with is to suggest that you look at an Allison 2000 series with the parking pawl instead of the 643.

You would have a 5 speed OD transmission or a 6 speed double OD transmission depending on year and programming.

Good luck.

Would love to but it's cost prohibitive. If I could find something complete so I wouldn't have to track down controllers, harnesses, etc.. for a reasonable price, it'd certainly be an option.

Diverdude0075 · 10-15-2020, 06:03 PM

Quote:

Originally Posted by Mr4btTahoe

Would love to but it's cost prohibitive. If I could find something complete so I wouldn't have to track down controllers, harnesses, etc.. for a reasonable price, it'd certainly be an option.

What did you end up doing? I found a good deal on a Allison 2000, no drum though like my AT545. Just go without an emergency brake.

CHEESE_WAGON · 10-15-2020, 06:04 PM

Wheel chocks. Simple, inexpensive. Not the most convenient solution, but it's safer than going without it. Also, I would not trust a parking pawl to hold an 18,000-lb bus on a slope.

cadillackid · 10-15-2020, 06:24 PM

Quote:

Originally Posted by CHEESE_WAGON

Wheel chocks. Simple, inexpensive. Not the most convenient solution, but it's safer than going without it. Also, I would not trust a parking pawl to hold an 18,000-lb bus on a slope.

its not a parking PAWL. its an actual parking brake.. a drum on the back of the transmission with a lever inside.. he absolutely cannot go without it unless his bus has air brajkes with spring. you cant even park at a gas station without the bus tryiong to roll forward.. there is no 'P' on a bus..

agreed that wheels should always be chocked if parked on any type of incline (or anytime for that matter).. however that brake is necessary to even exit the bus!!

cadillackid · 10-15-2020, 06:28 PM

by the weay though allison does rate their parking Pawls at 30,000 lbs (15,000 for the gen 1). i forget the slope they rate them but its pretty impressive.. and to see one torn apart they are MASSIVE.

the parking pawl feature is only available on the 1000's and the 2000MH (motor home) series.. however it can be retrofitted into the opther model 2000s..

I had the 30,000 lb Pawl installed in the 1000 i swapped into my bus.. ive never replaced my shifter with the 'P' shifter I bought so I havent used the feature but it is there..

CHEESE_WAGON · 10-15-2020, 06:34 PM

I don't care what they're rated at. Look up the rollaway Fords and you'll see why.

cadillackid · 10-15-2020, 06:36 PM

Quote:

Originally Posted by CHEESE_WAGON

I don't care what they're rated at. Look up the rollaway Fords and you'll see why.

notice i said ive never installed the shifter for the park pawl.. I agree not to rely on a parking pawl to hold a vehicle esp a loaded one on any kind of incline..

and chocking the wheels is best paractice anywhere you go!

Mr4btTahoe · 06-08-2021, 09:06 AM

Still haven't tracked down a parking brake setup for my 643. When I get around to swapping it in, I will likely just setup a hydraulic parking brake (similar to line locks) that can be activated just to chock the wheels and then deactivated. It certainly wouldn't be relied on but should hold the bus no problem while I place chocks.

Should work well enough and will be pretty inexpensive to setup. I need to replace the brake lines at the master cylinder anyways so I'll likely add the solenoid when I do it.

cadillackid · 06-08-2021, 09:21 AM

have you tried some of the lesser known places like Dartco or WW williams? maybe at least get the right part number? Meritor made a lot of this stuff. maybe even someplace like Weller truck parts..

I was looking at some of the parts for the one thats on my Superior and the part numbers came back to meritor.. granted that one is on an AT545 but shows that meritor made some of these for the allisons

Mr4btTahoe · 06-08-2021, 09:34 AM

Quote:

Originally Posted by cadillackid

have you tried some of the lesser known places like Dartco or WW williams? maybe at least get the right part number? Meritor made a lot of this stuff. maybe even someplace like Weller truck parts..

I was looking at some of the parts for the one thats on my Superior and the part numbers came back to meritor.. granted that one is on an AT545 but shows that meritor made some of these for the allisons

I've found references to Dartco but no part numbers and no replacement parts. Apparently it's a super rare option most common on large motor homes.

I've been searching off and on with no luck. I've even tossed around the idea of swapping rear diffs as I've seen several big trucks with driveline mounted brakes. I've got options either way... but would be cool to find a factory 643 brake setup.

cadillackid · 06-08-2021, 10:01 AM

true.. prpobably 95% of anything heavy enough to have had a 643 was likely air brakes..I dont know if a parking brake option is available for a 3060 or not and if so would the bolt pattern be similar

rossvtaylor · 06-08-2021, 10:09 AM

MR4btTahoe's idea of a hydraulic line lock is certainly reasonable. Aircraft have exactly this. Our Mooney had a pull knob, which is just a valve, in the hydraulic brake line...so you'll press on the brake pedals to apply brake pressure then pull the knob to lock that pressure in the system. It was just used during short stops (fueling) or while putting in chocks.

cadillackid · 06-08-2021, 12:06 PM

the line lock I had on my 79 camaro did me well at the track for a long time till I started making 650 horsies. then I went to a trans brake... Line lock held my motor back pretty well.

with the hydrassist system you can get some really good brake line pressures built up.

Mr4btTahoe · 06-08-2021, 01:31 PM

My only concern going with a hydraulic parking brake is not having a mechanical backup in case of hydraulic failure. 30k lbs cruising at 65 and no brakes doesn't sound like fun. Don't get me wrong... its highly unlikely on a maintained system... but stuff happens.

I've got a few feelers out for the correct parking brake assembly. We'll see what happens.

The 3060 and 1000, 2000, etc. were offered with a parking brake but I'm not sure if the bolt pattern would be the same or close enough to make work. Those parts aren't cheap either so would hate to just buy for testing.

Mr4btTahoe · 06-08-2021, 02:39 PM

Just got word back and found a complete parking brake setup with drive flange. Only suck part is the price. They want $650 for it.

Not sure if its worth the price or if I should keep looking. I mean... I did get an amazing price on the reman transmission... so its not like I'd be in it total for a whole lot.. but paying more for a parking brake than I paid for a transmission hurts.

Lol

Ronnie · 06-08-2021, 06:09 PM

I would get it. Sometimes the right parts cost a bit, but so worth not messing around with anything makeshift.

s2mikon · 06-08-2021, 06:44 PM

Here is the Federal requirements for parking brakes.
49 CFR SEC. 393.41 PARKING BRAKE SYSTEM.
§ 393.41*Parking brake system.
(a)*Hydraulic-braked vehicles manufactured on or after September 2, 1983.*Each*truck*and*bus(other than a school bus) with a*GVWR*of 4,536 kg (10,000 pounds) or less which is subject to this part and school*buses*with a*GVWR*greater than 4,536 kg (10,000 pounds) shall be equipped with a parking brake system*as required by FMVSS No. 571.105 (S5.2) in effect at the time of manufacture. The parking*brake*shall be capable of holding the vehicle or combination of vehicles stationary under any condition of loading in which it is found on a public road (free of ice and snow). Hydraulic-braked vehicles which were not subject to the parking*brake*requirements of FMVSS No. 571.105 (S5.2) must be equipped with a*parking brake system*that meets the requirements of*paragraph (c)*of this section.
(b)*Air-braked power units manufactured on or after March 1, 1975, and air-braked trailers manufactured on or after January 1, 1975.*Each air-braked*bus,*truck*and*truck tractor*manufactured on and after March 1, 1975, and each air-braked*trailer*except an*agricultural commodity trailer,converter dolly,*heavy hauler trailer*or*pulpwood trailer, shall be equipped with a*parking brake systemas required by FMVSS No. 121 (S5.6) in effect at the time of manufacture. The parking*brake*shall be capable of holding the vehicle or combination of vehicles stationary under any condition of loading in which it is found on a public road (free of ice and snow). An*agricultural commodity trailer, heavy hauler or*pulpwood trailer*shall carry sufficient chocking*blocks*to prevent movement when parked.
(c)*Vehicles not subject to FMVSS Nos. 105 and 121 on the date of manufacture.
(1)*Each singly driven*motor vehicle*not subject to parking*brake*requirements of FMVSS Nos. 105 or 121 at the time of manufacturer, and every combination of*motor vehicles*must be equipped with aparking brake system*adequate to hold the vehicle or combination on any grade on which it is operated, under any condition of loading in which it is found on a public road (free of ice and snow).
(2)*The*parking brake system*shall, at all times, be capable of being applied by either the*driver's muscular effort or by spring action. If other energy is used to apply the parking*brake, there must be an accumulation of that energy isolated from any common source and used exclusively for the operation of the parking*brake.
Exception:*This paragraph shall not be applicable to air-applied, mechanically-held*parking brake systems*which meet the parking*brake*requirements of FMVSS No. 121 (S5.6).
(3)*The*parking brake system*shall be held in the applied position by energy other than fluid pressure, air pressure, or electric energy. The*parking brake system*shall not be capable of being released unless adequate energy is available to immediately reapply the parking*brake*with the required effectiveness.
Read section 3. Don't do some thing half-ass that might get someone killed or injured.

mmoore6856 · 06-08-2021, 07:53 PM

(3)*The*parking brake system*shall be held in the applied position by energy other than fluid pressure, air pressure, or electric energy. The*parking brake system*shall not be capable of being released unless adequate energy is available to immediately reapply the parking*brake*with the required effectiveness.
Read section 3. Don't do some thing half-ass that might get someone killed or injured.[/QUOTE]

this means that those hydraulic locks are not a legal park brake. i had one on a wrecker i drove years ago and they do fail at the worst moment

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