M1008 Brake Capacity??

[LT67]

Just curious what the brake capacity was on the cucv trucks...

I discovered the trailer brakes were not working when I had to haul the tractor n trailer(7500lbs) with the 85 M1008. I maintained my distances in traffic, but I had zero issues getting stopped. To be honest, I was impressed that the M1008 brakes were able to handle that load. The 6.2 diesel going up a long hill was another story

**trailer brakes have now been fixed and are working as they should.

 

[Jeepadict]

Brake capacity is best stated in GVW ratings:
GVWR - gross vehicle weight rating
GCWR - gross combination weight rating

These are the safe LEGAL weight limitations set by the manufacturer when it was built.

Now, being a CUCV owner you're going to find 2 distinct and different ratings for this type of truck: 1) the weight rating the US Govt spec'd for the contract which is what GM stamped on the door and is what is listed in the TM, 2) the rating given to every other K30 in the world built in the same vintage in the same configuration. Legally, you're liability is restricted to the numbers stamped in the door. Real-world safe operating limits are going to be the same as the civvy K30 in the same configuration. You'll see guys from all walks of life bragging about overloading the truck that they're driving whenever they're feeling froggy. YMMV

The noticeable difference is in the towing capacity noted in the TM which some fellas prescribe to like the Bible. Others use the civvy ratings as they are much more applicable to everyday use. GM has a fantastic historical library where a guy could easily find information like this and much more.

Note: any modifications or improvements do not legally change any weight rating for DOT enforcement. You can upgrade the entire truck, but without the approved Vehicle Completion sticker in the door jamb from a certified body builder you are liable for any overweight infraction should an accident occur and God forbid there is a fatality related to the accident things go real bad real fast.

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[MarcusOReallyus]

The noticeable difference is in the towing capacity noted in the TM which some fellas prescribe to like the Bible. Others use the civvy ratings as they are much more applicable to everyday use. GM has a fantastic historical library where a guy could easily find information like this and much more.

Tow ratings are limited by the mounting of the pintle hitch to the bumper assembly. Use a properly frame-mounted trailer hitch and the civvy numbers would apply.

 

[Jeepadict]

Tow ratings are limited by the mounting of the pintle hitch to the bumper assembly. Use a properly frame-mounted trailer hitch and the civvy numbers would apply.

This mindset is one that has boggled my mind for years. The Pintle/Lunette combo is used by the military on the light side for continuity as the heavy towing capacity is required to use a Lunette. The Lunette is used for 10K and up weight even up to class 8 trucks with air brakes ex Lineman trucks. We use a Pintle in the frame mounted hitch on all our trucks on the flightline and they have a 10K weight rating...and the CUCV bumper has more steel and hardware than a frame mounted hitch. I'm not debating your opinion, just stating the things that make my brain twitch.

I use the frame mounted hitch weight ratings for "weight carrying" as my limits on my bumper pintle as the weight distribution rating is a different concept.

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[LT67]

No way I would attempt to attach a dbl axle trailer to the rear bumper... especially with a tractor loaded on it. The 85 M1008 has a stout trailer hitch set up mounted to the frame.

 

[MarcusOReallyus]

This mindset is one that has boggled my mind for years. The Pintle/Lunette combo is used by the military on the light side for continuity as the heavy towing capacity is required to use a Lunette. The Lunette is used for 10K and up weight even up to class 8 trucks with air brakes ex Lineman trucks.

The militarily often has different needs than civilian uses. One thing that drives a lot of decisions is compatibility with other equipment in inventory, and another is compatibility with NATO specs. Another factor is simplicity of inventory. Another factor is less benign - the simple idiocy or outright corruption (or both) that sometimes gets into the specification process. The P-38 Lightning was specifically called an "Interceptor" simply to get around a stupid limitation that had been put in place by some bureaucrats on the weight of the armament that a fighter could carry.

Don't expect to figure out why they do things that seem to make no sense if you don't take these factors into account.

...and the CUCV bumper has more steel and hardware than a frame mounted hitch.

More steel does not automatically equal greater strength. The configuration matters. Where the steel is matters more than how much.

A frame mounted hitch is designed for one thing from the ground up - handling the weight of a trailer.

The CUCV bumper was not. Carrying the weight of a trailer is a secondary function, and it's basically jury-rigged to be able to do that.


The fact that it uses a pintle has nothing to do with its weight- carrying ability.

 

[Jeepadict]

Well, I guess our eyes see different things given different experiences and we can always agree to disagree. The contraption in this pic (below the bumper) makes many folks pop a blood vessel in their forehead when they cry "it wasn't built for that"...no smart guy, it was modified for that use. My favorite thing has always been adaptation or multipurpose use...just because that's what it was originally designed for doesn't mean that's what it's limited to nor what is safe or unsafe.

The weight ratings for the GVW and towing capacity were stipulated by the gov't contract, not by GM engineering design specs as shown by the notable difference mentioned previously. Carrying weight on that bumper has been done on these trucks since they were first introduced in the civilian market, and were reinforced to allow the integration of the 10k lb pintle. The steel bumper on the CUCV is exactly identical to the civvy steel bumper in all respects except for the different holes. Consequently, since the components are structurally sound I'm comfortable carrying the same weight on the pintle as is stated for max weight carrying on a frame mounted hitch.

 

[LT67]

Well, I guess our eyes see different things given different experiences and we can always agree to disagree. The contraption in this pic (below the bumper) makes many folks pop a blood vessel in their forehead when they cry "it wasn't built for that"...no smart guy, it was modified for that use. My favorite thing has always been adaptation or multipurpose use...just because that's what it was originally designed for doesn't mean that's what it's limited to nor what is safe or unsafe.

The weight ratings for the GVW and towing capacity were stipulated by the gov't contract, not by GM engineering design specs as shown by the notable difference mentioned previously. Carrying weight on that bumper has been done on these trucks since they were first introduced in the civilian market, and were reinforced to allow the integration of the 10k lb pintle. The steel bumper on the CUCV is exactly identical to the civvy steel bumper in all respects except for the different holes. Consequently, since the components are structurally sound I'm comfortable carrying the same weight on the pintle as is stated for max weight carrying on a frame mounted hitch.

So I'm not the only one with a GMC badge on a CUCV truck lol

 

[Jeepadict]

So I'm not the only one with a GMC badge on a CUCV truck lol

Full disclosure...not a CUCV, it's my 78 RCLB K25. Plow truck, water haul truck, retired repo truck, do whatever I want because Squarebody trucks will always be badass truck...have a few MVP parts from the CUCV because a Squarebody is a Squarebody and CUCV parts are from badass trucks and those badass parts compliment the 1/4" plate steel reinforced frame and live hydraulics rather nicely I think.

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[MarcusOReallyus]

Well, I guess our eyes see different things given different experiences and we can always agree to disagree.

First you have to get your facts straight.

The weight ratings for the GVW and towing capacity were stipulated by the gov't contract, not by GM engineering design specs

No. GM designed the CUCV bumper to meet the government specs. That's one fact you have wrong.

Carrying weight on that bumper has been done on these trucks since they were first introduced in the civilian market, and were reinforced to allow the integration of the 10k lb pintle.

And there's another fact you have wrong. The 10k pintle is original military equipment. It is there by government specs, engineered by GM for the CUCV. It came off the assembly line that way, as specified, as engineered. It is not a later civilian modification.

The steel bumper on the CUCV is exactly identical to the civvy steel bumper in all respects except for the different holes.

Strike three. Nope. Not even close. It's a very different animal.

In fact, the differences are so great that fitting a civilian trailer hitch to a CUCV has been the subject of a lot of discussion here over the years, precisely because it is very different. Take any standard civvy K30 of those years, and you can easily find a stock civvy trailer hitch that will bolt right up to the truck. No modifications needed. Pick your brand, pick your retailer. Curt, Draw-Tite, whatever. E-trailer.com, U-haul, most of your auto parts stores, Amazon, just about anybody can supply you a hitch that will bolt right up. No fuss, no muss.

No such standard civvy hitch exists for the CUCV. You either have to modify the hitch or the mounting points, usually in a way that compromises the strength of the standard bumper.


Everyone is entitled to his own opinion, or so the saying goes, but you are not entitled to your own facts.

Maybe you have some butchered modified mangled half breed on your truck that has misled you. Given the GMC tailgate, that would not be surprising. Between trucks passing through Reserve outfits, fire departments, and other local government agencies, there certainly have been a lot of modifications done.

But whatever the reason, you are just flat wrong about CUCV bumpers and their pintle hitches.

Read the manual.

 

[LT67]

.. So back to my original question...

Somewhere before I read that the K30 1 ton brakes were rated at 10K lb stopping capacity.

 

[MarcusOReallyus]

.. So back to my original question...

Somewhere before I read that the K30 1 ton brakes were rated at 10K lb stopping capacity.

Hmmm. The -10 says the GVWR for the M1008 is 8800 lb, the M1010 is 9450, the M1028 and M1028A1 are 9400, and the M1031 is 9200. (There's a table on page 27.)

They don't list a GVW that I could find, but on page 96, it says, " FA1008, M1008A1, M1028, M1028A1, M1028A2, and M1028A3, Equipped to tow M101 Series 3/4 ton trailers with maximum towed load of 3100 Ibs. Load on tongue should not exceed 300 Ibs."

So if we assume the vehicle is loaded up and is pulling a loaded trailer (all within stated specs), that's 8800 + 3100 = 11,900 for the M1008, and 12,500 for the M1028.


So sounds like the 10k figure is in the right ballpark. I have to assume there is some safety margin in the stated specs, so maybe the real limit is something like 15,000.

But maybe I'm looking at that wrong. I don't think I've ever seen a brake rating on a vehicle, though.

 

[cucvrus]

Who needs trailer brakes? Just put the load in the cargo bed and drive on. Its got a Cummins.