M101a2... brake...slam...skid...slam...skid

[Rustyshackelford]

Hi
I have an m101a2 that I tow with my m1009. I haven’t done much work on it so I haven’t spent much time in this section of the forum so I’d like to ask about my problem with the surge brake. When braking it skids and slams back into the truck over and over until I stop. Is this something that needs to be adjusted or is it the sign of a bad part?

 

[Evil Dr. Porkchop]

The shock absorber in the hitch is likely no good.

 

[Rustyshackelford]

Thanks for the quick reply. Is there a thread discussing where to find these and how to replace them? Or can you tell me here in this thread?

 

[Evil Dr. Porkchop]

The part number is 1844-2. Not the cheapest nowadays. They're very straightforward to change, I'm sure another thread will tell you better than me typing it out. Just have to remove a few fasteners, not difficult at all. If you can grab the lunette and move it back and forth without any real resistance then the shock is bad.

 

[Tinstar]

Croft trailer has the least expensive shock.
Its an OEM one from Hydro-Act.
https://www.crofttrailer.com/1844-2-hydro-act-actuator-damper-shock/

Agree on what others are saying.
Your shock has failed.
You can insert a 3/8”x4” grade 8 bolt in the brake lockout hole so you can still use the trailer.

 

[two.fiveM35]

Or you can put a grade 5 bolt thru the hole that locks out the brake mechanism

 

[BLK HMMWV]

I was going to suggest the bolt trick as well.
BH

 

[Tinstar]

Or you can put a grade 5 bolt thru the hole that locks out the brake mechanism

Grade 5 isn’t strong enough if trailers heavy.
Others have done that and it bent the bolt.
Making removal a total nightmare.
Several threads about it.

 

[two.fiveM35]

Grade 5 isn’t strong enough if trailers heavy.
Others have done that and it bent the bolt.
Making removal a total nightmare.
Several threads about it.

I was under the impression that grade 5 had a stronger shire streangth than grade 8, and 8 was stronger in the other direction.

 

[Engineer 1SG]

It is a common misconception that a grade 8 bolt is brittle and that a grade 5 bolt has better sheer strength. The tensile strength of a bolt is its strength when being pulled, while its sheer strength is its strength while being stressed across its diameter. The sheer strength of a bolt is typically 60% of its tensile strength, therefore it stands to reason that any bolt with a greater tensile strength will have a similarly greater sheer strength.

As for grade 8 being more brittle, a grade 5 bolt will fail under both tensile and sheer applications at levels far below an identically sized grade 8 bolt would ever fail due to "brittleness."

To quote from the linked document (an excellent discussion of bolt strength), "Typically, fasteners are not brittle below 180 ksi ultimate tensile strength. Grade 5’s have an ultimate tensile strength of 120 ksi and a grade 8 fastener has an ultimate tensile strength of 150 ksi. This is why brittle is a relative term."

See the linked article for more details: https://www.rockcrawler.com/2003/04/fasteners-making-the-grade-a-technical-discussion/

 

[Tinstar]

It’s for overall hardness of the steel is my understanding.
Its heat treated differently.
The shear strength is improved along with the tensile strength.

Grade 10 isn’t usually carried by the box stores but that’s a bit overkill anyway.

 

[Rustyshackelford]

Thank you. Where is the lockout hole?

 

[Rustyshackelford]

Also, when off roading do you find it better to use the surgebrake or to lock it out?

 

[Tinstar]

The hole just forward of my lockout pin.

Thank you. Where is the lockout hole?

 

[bigbe5678]

Nice Setup Thanks for the picture

 

[Tinstar]

Also, when off roading do you find it better to use the surgebrake or to lock it out?

Off roading or 4 wheeling?
I’ve read it’s mostly personal preference on whether to disable them or not.


If the trailer is loaded at all and you try to back up an incline, the brakes will activate.
Always carry a pin or bolt to lock them out.

Dexter makes a surge brake unit called FreeBack.
Works normally and when backing up a loaded trailer it does not lock the brakes.
I have it installed on one trailer. It works.
Easy swap.

 

[Engineer 1SG]

Back when I was in the Army, we used to have to tow MEP-012A generators that weighed 25,000 lbs that had surge brakes. More than once the generator trailer tongue was bent out of shape when someone tried to back up the trailer without using the lockout pin.

 

[Tinstar]

Dexter FreeBack brakes.
Easy swap and hassle free.
Biggest pain was putting trailer on jacks.

Dexter makes great stuff and is the OEM Military supplier for some of the M101A2/3 parts.

 

[Tinstar]

Back when I was in the Army, we used to have to tow MEP-012A generators that weighed 25,000 lbs that had surge brakes. More than once the generator trailer tongue was bent out of shape when someone tried to back up the trailer without using the lockout pin.

I’ve read here on SS of guys doing that backing up their driveway, not knowing the brakes needed to be locked out.
Some even kept trying until parts broke.

 

[juanprado]

I triple yes the shock as that is exactly how my m101 was after I picked it up from red river and made a side trip to hot springs. It was not happy at all in the land of hills.

I would also suggest ordering the nylon bushings for the links as I found 2 bad ones when I disassembled.