M101A2 violent braking!

[davey8943]

My brother recently picked up an M101A2E1 from Fort Campbell. I hooked it up to pull it a few miles down a normal city street. The trailer was loaded with a few hundred pounds of tree limbs.

As I began to apply normal brake pressure on the towing vehicle, the trailer started to shake violently back and forth. The effect was as if I had attempted a pannic stop with the towing vehicle, then released the pedal suddenly. Except this repeated a number of times (maybe 3?) during one braking event.

If I applied lighter pressure on the brakes of the towing vehicle, the trailer seemed to behave a little better.

The TM doesn't seem to be much help. I think I did a pretty good job of searching old threads, and found no mention of this type of action.

Any ideas on what is going on or how to fix it?

Thanks,
Dave

 

[papakb]

I've found the 101s will do this empty but with some weight in the trailer they usually settle down and run smoothly. If I tow it empty I leave the actuator pin in the coupler and don't have the problem.

Kurt

 

[Nonotagain]

There is supposed to be a small shock asorber mounted to the master cylinder assembly. If the shock is worn out or missing, any time that the tongue of the trailer moves to the rear the brakes will be applied.

Check the condition of the shock. Also, if the trailer has sat for a long period of time the brake shoes and drums will be rusted up causing very grabby brakes.

 

[Unforgiven]

There is supposed to be a small shock asorber mounted to the master cylinder assembly. If the shock is worn out or missing, any time that the tongue of the trailer moves to the rear the brakes will be applied.

Check the condition of the shock. Also, if the trailer has sat for a long period of time the brake shoes and drums will be rusted up causing very grabby brakes.

That's assuming the A2 trailer has surge brakes. As far as I know it's air activated hydraulics.

But, if they are surge brakes then the jerking motion could be do to the orifice constrictor within the master cylinder. If somebody rebuilt the master cylinder & forgot to put the orifice back in, then it would engage/release/engage/release ... especially down hills

 

[Unforgiven]

Nevermind, I thought it was a 105A2

If the 101 has surge brakes then check the orifice in the master cylinder.

 

[davey8943]

My thoughts were exactly along with NoNotAgain... the shock absorber had gone soft.

Then Unforgiven hit the nail on the head. The master cylinder has been recently rebuilt.

So I thought I would try an experiment. I took a different M101A2 trailer (one that brakes as it should), and removed the shock absorber altogether. When I took the trailer around the block, and I wouldn't suggest doing this very far or with much weight in the trailer, the trailer reacted EXACTLY like the one that I was complaining about to start with!

So that confirms, at least in my mind, that the shock absorber is the failed component. Now the question becomes: Where can I get a replacement? I have seen sources for other trailer components (springs, covers, etc), but never this shock absorber!

Any help would be appreciated!

Dave

 

[frodobaggins]

See if you can find any numbers on it and post pics too.

 

[bumble900]

I've found the 101s will do this empty but with some weight in the trailer they usually settle down and run smoothly. If I tow it empty I leave the actuator pin in the coupler and don't have the problem.

Kurt

Can you elaborate on this actuator pin, or post a picture. I don't see any reference to it in the TM or remember it on the A2 that I recently sold.

Thanks
Mike

 

[timntrucks]

yes i might need that part number as i have 3 trailers that have those surge brakes on them

 

[Nonotagain]

yes i might need that part number as i have 3 trailers that have those surge brakes on them

After a search of TM 9-2330-202-14&P, I found the part number and the cage code.

Part number is 1844-2
Cage code is 93072

A quick search of the cage code comes back to Toledo Stamping and Mfg.

A Google search yielded this info.

Toledo Actuators | Balcrank Products Inc. Customer Service 800-747-5300 Fax 800-763-0840

Still uses the same part number, just that you need to shell out $48 per shock.

 

[bumble900]

Hey at least they offer bulk pricing!

 

[davey8943]

NoNotAgain,

Thanks for the link! I did some searching on the NSN number:

2510-01-050-7136

I came up with a website previously posted on SS :

Schutt Industries > HOME

What are the Cage numbers and part numbers? I was under the impression that an NSN was a unique identifier... but what is it really?

Thanks
Dave

 

[Nonotagain]

NoNotAgain,

Thanks for the link! I did some searching on the NSN number:

2510-01-050-7136

I came up with a website previously posted on SS :

Schutt Industries > HOME

What are the Cage numbers and part numbers? I was under the impression that an NSN was a unique identifier... but what is it really?

Thanks
Dave

Cage numbers are unique to a manufacturer. NSN numbers are associated to a part that goes out for bid. The lowest cost wins, or should win, except if the company is minority or woman owned.

Page 297 of the TM is a breakdown of all of the part number listed for the lunette/brake assembly with the manufacturers part number, the NSN number and the cage code.

NSN #2510010507136 Cage code93072 MFG part #1844-2

 

[papakb]

The actuator locking pin is a 3/8" x 4.5" pin that goes thru the front actuator link arm and then thru the body of the coupler. It locks the actuator into a forward position and disables the brake system. It's important to have this pin in place when your backing the trailer up or the brakes will set.



Here's a link to a vendor with the actuator shock:

http://www.toledoactuators.com/product_info.php?cPath=38&products_id=147


Toledo Actuators | Balcrank Products Inc. Customer Service 800-747-5300 Fax 800-763-0840

Kurt

 

[bumble900]

papakb

Does the actuator locking pin go through the hole circled on the attached drawing? It makes sense to me but I don't see any reference to it's use in TM 9-2330-202-14&P.

Am I correct to say that any pin that will fit in the hole will work in locking out the actuator?

Mike

 

[papakb]

Roger that! Whatever goes thru that hole will keep the actuator from moving and setting the brakes on the trailer. Any 3.8" rod will work, a bolt, ball detent pin, or an aircraft quick release pin.

I'm surprised there's no mention of it in the manual. Any time you back the trailer the brakes will set if it isn't in place. Maybe it's time to send Connie Rod a correction letter for PS magazine.

Kurt

 

[bumble900]

Looked again and nothing on an actuator lock out pin, they rely on the shock absorber to prevent braking while backing up

Here is what I found on the Break Actuator:

Section III. PRINCIPLES OF OPERATION

1-16. HYDRAULIC BRAKE SYSTEM.

a. Brakes are applied automatically by the hydraulic brake system when the towing vehicle slows or stops, or when the trailer breaks away from the towing vehicle.

b. The major components of the hydraulic brake system and their functions are as follows:

1. Hydraulic Brake Actuator Assembly. This assembly transmits the braking forces of the towing vehicle to the trailer by inertia. It consists of a drawbar coupler, master cylinder, breakaway chain and lever, and leaf spring.

2. Drawbar Coupler. The drawbar coupler attaches to the towing vehicle and controls the master cylinder. When the towing vehicle goes forward, the drawbar coupler is pulled and the brakes are released. When the towing vehicle slows down, the trailer pushes the drawbar ring into the towing vehicle and applies the brakes.

3. Master Cylinder. The master cylinder changes the mechanical motion of the drawbar coupler and breakaway lever into hydraulic pressure. It has a built-in shock absorber to prevent jerky drawbar coupler movement. The shock absorber prevents hydraulic pressure from building up when the towing vehicle backs up.

4. Breakaway Chain. The breakaway chain is attached to the towing vehicle. If the trailer breaks away from the towing vehicle, the breakaway chain will pull up on the breakaway lever and apply the brakes.

And this is all it says on backing the trailer:

2-14. TOWING INSTRUCTIONS

c. BACKING

CAUTION
Jackknifing when backing may cause damage to hydraulic brake actuator assembly.

1. Always back towing vehicle slowly and gradually.

2. Whenever possible, have an assistant driver or another person act as a ground guide.

3. Adjust all towing vehicle rearview mirrors before backing.

4. When backing, rear of trailer will move in opposite direction in which towing vehicle is turned. When towing vehicle Is turned to the right, rear of trailer will go left. When towing vehicle has turned and backing in a straight line is required, turn towing vehicle in direction trailer is moving. This will slowly bring towing vehicle and trailer Into a straight line.

So once my EUC clears I'll be looking forward to checking it out on my new used 101A2. And I'll be sure to give you the credit when I file the "Recommended Changes To Equipment Technical Publications Form"!

Mike

 

[Unforgiven]

REVERSING SOLENOID VALVES

 

[number9]

My M116 started doing this same thing today on a trip with the kids dirt bikes on it. I had to pick up a semi and drive it about 75 miles for my wires uncle so she followed in the truck with the dirtbikes. We got to the inlaws and she said the trailer was acting fine again. Sure enough when I drove it again the violent braking is gone. I did see that the shaft on the shock was wet so obviously it's leaking but it makes no sense that the symptoms would go away.

....

 

[coyotegray]

My M116 started doing this same thing today on a trip with the kids dirt bikes on it. I had to pick up a semi and drive it about 75 miles for my wires uncle so she followed in the truck with the dirtbikes. We got to the inlaws and she said the trailer was acting fine again. Sure enough when I drove it again the violent braking is gone. I did see that the shaft on the shock was wet so obviously it's leaking but it makes no sense that the symptoms would go away.

....

If you lost enough fluid from the master cylinder it would stop. That may be what you saw..

Andy..