Suspension bolts

[RMS]

I'd rather replace bolts than repair frame damage.

I hear ya.....and frame damage is what I got from running gr8s on the lower fender mount( its always the first thing to touch ) so what is the best choice for fasteners in such areas ?

(stock bolt soft, stretches before damaging. becomes floppy over time during "regular service". galling fine thread pia to re&re )

(gr8 just stronger than frame and appliances. Items stay secured over time. nominal galling

gr12.9 / fedalloy supper high torque capability, brittle, they make a big bang when they let go.... is it more likely to sheer before damaging frame ?

[isaac_alaska]

Chuck a grade 8 in the lathe and put a shear point in it. Jut like a snowblower shear pin. Won't stretch, but still breaks before the frame bends. How deep to cut into it is a question for someone else... Or I could simulate it in solidworks

[MSeriesRebuild]

Neither bolt or frame damage should be an issue! Grade 8 bolts are fine in these components; now the question remains, why are you getting damage, well my guess is like before, components tweaked, a twist where no twist should be, wear in some critical areas that cause things to operate in a stressful situation instead of in perfect alignment as they should, etc. If you are stressing your truck to the point of the bolts pulling the holes in the frame, well, that amounts to abuse of the components as they are currently set up. Apparently the truck is too "light duty" in the frame area for your application. I'd venture to say, (based on the info you have given), you need to get in the shop with your rig, tear it down to the point you can access the frame area. You need to get everything in proper alignment, then reinforce these frame areas in the correct fashion so that stress is relieved. A number of ways this can be done, but is different in every application depending on any individual situation. Its up to you to assess the problem areas you find upon a detailed inspection, then take the appropriate steps to correct each of them. You may want to consider a double frame like was used on the civilian power wagons, this will likely be a big improvement in your application, and it doesn't affect the needed amount of frame flex all that much. This is all I can say, not being able to see what you have going on and details of your application, so obviously my knowledge concerning your individual situation is very limited; a shot in the dark, but I think I would consider double frame rails as a first option in your situation.

Getting back to pin wear, breakage, nuts coming off, etc., this was likely a bad pin. Why was the pin bad?? You need to know this, there are vendors out there, some whom are highly regarded that think it is fine to repro these (and other components) with no regard to the actual integrity of the part. Many times repros are import parts, vendor actually has no clue as to what (parts are made from, quality control or the lack thereof in the manufacturing process) he is marketing until problems like you have had start to show up. Then what do they do when problems are realized? I hate to say this, but it is true, some will keep right on selling them after they know about possible defect issues, be careful where you buy, FORCE vendors to disclose info about their goods, if an explanation sounds a little off, (like they are not telling the whole story) likely they are not, I've learned to spot this; they have learned that they will get blow back if we find out they sell us inferior goods. Purchase wisely from reputable vendors, this starts by learning which ones are reputable, I'm here to tell you, all ARE NOT. Simply put, some repro pins are not made from correct steel, are not heat treated correctly, among other issues. You need to check what you have here. Spring pins are carrying the load; pins that strip, stretch, and break are simply #1, not good pins, #2, issues exist with your frame and spring alignment that will break any pin you install. You have issues that need immediate attention to see what is going on before you end up in an accident as a result. My suggestion to you is this; DON'T PRESS YOUR LUCK; get to the bottom of these issues now, or we could be reading about damage to you as a person instead of your truck; I would hate to see that.

[Elwood]

I'd rather replace bolts than repair frame damage.

I hear ya.....and frame damage is what I got from running gr8s on the lower fender mount( its always the first thing to touch ) so what is the best choice for fasteners in such areas ?

(stock bolt soft, stretches before damaging. becomes floppy over time during "regular service". galling fine thread pia to re&re )

(gr8 just stronger than frame and appliances. Items stay secured over time. nominal galling

gr12.9 / fedalloy supper high torque capability, brittle, they make a big bang when they let go.... is it more likely to sheer before damaging frame ?

Am I correct in assuming that at least some of the problem is caused by hitting obstructions with the brackets and/or running boards when going off road?

Maybe I'm missing something, but why not change out the OEM fine thread bolts that hold the bracket to the frame for some grade 5 coarse thread bolts? I know the military was fond of fine thread, but coarse thread would be stronger and less likely to gall in this application?

And I'll second Charles' observation about the variance among vendors. There are a couple that I will buy from only as a last resort, and then I end up having to inspect everything very closely and send back an unacceptably high percentage of items.

[MSeriesRebuild]

I'd rather replace bolts than repair frame damage.

I hear ya.....and frame damage is what I got from running gr8s on the lower fender mount( its always the first thing to touch ) so what is the best choice for fasteners in such areas ?

(stock bolt soft, stretches before damaging. becomes floppy over time during "regular service". galling fine thread pia to re&re )

(gr8 just stronger than frame and appliances. Items stay secured over time. nominal galling

gr12.9 / fedalloy supper high torque capability, brittle, they make a big bang when they let go.... is it more likely to sheer before damaging frame ?

Am I correct in assuming that at least some of the problem is caused by hitting obstructions with the brackets and/or running boards when going off road?

Maybe I'm missing something, but why not change out the OEM fine thread bolts that hold the bracket to the frame for some grade 5 coarse thread bolts? I know the military was fond of fine thread, but coarse thread would be stronger and less likely to gall in this application?

And I'll second Charles' observation about the variance among vendors. There are a couple that I will buy from only as a last resort, and then I end up having to inspect everything very closely and send back an unacceptably high percentage of items.

Personally I like grade 8 fine thread fasteners best. Standard torque used for those is higher than recommended for course threads and we have had great results. We use grade 8 fasteners almost exclusively in our builds; we don't stock any other grades in our bins with the exception of small machine screws, and a few sizes of grade 9 fasteners (the strongest commercial grade fasteners available) for some special application stuff. It is the standard with us to use course threads in cast or aluminum housings only. Reason here is fine threads will pull out of cast or aluminum, thus are a poor choice in these applications. A good example there is the front axle knuckle joints on Dana 60 axles used on an M715. They originally used fine threads in cast; we have found a multitude of these stripped over the years, we typically oversize the bolt holes and tap in course threads, which corrects the issue.

[RMS]

why are you getting damage

Am I correct in assuming that at least some of the problem is caused by hitting obstructions with the brackets and/or running boards when going off road?

yes sir

All my damage and every broken part is due to off roading. my truck pulls trailers it doesn't ride on them.

it spends most of its time in places like this :

on roads no better than this:









I am nice and gentle with the mighty m37 I dont take it out jumping like I do the car

Getting back to pin wear, breakage, nuts coming off,

never broken a spring pin....well I did but it was the center pin...lower leaf broke, chunk fell out, u bolts went lose, axle shifted and sheared pin.

why not change out the OEM fine thread bolts that hold the bracket to the frame for some grade 5 coarse thread bolts?

I think I will the next time they need replacing

back to suspension bolts:

it is a good Idea when servicing the spring bushings to inspect the center bolt in the leaf pack. a rusting center bolt can cause leaf damage as it rusts it starts to swell and jack.

[MSeriesRebuild]

It is time wasted talking about this any further; unless you build your frame and suspension to a state capable of handling the kind of off road abuse your pictures suggest you are putting your truck through, you may as well just expect tweaking, stretching, breaking, crazy wear patterns, and a host of other issues to numerous to mention. A stock M37 suspension and frame is of great design and quality, however it is simply not built to take this sort of treatment without issue.

[RMS]

you may as well just expect tweaking, stretching, breaking, crazy wear patterns, and a host of other issues to numerous to mention

I do expect such things and thats why I ask. I would rather have a sacrificial part (a fuse-able link if you will) that will fail rather than cause major frame or component damage. for example I don't run the two lowest bolts on the rear fenders. I found I don't incur box damage if a tree or rock grabs the fender

[RMS]

DON'T PRESS YOUR LUCK; get to the bottom of these issues now, or we could be reading about damage to you as a person instead of your truck; I would hate to see that.

I appreciate the sentiment Charles

I feel the need to state that every time before the truck heads off road a complete nut and bolt inspection takes place. fluids are checked, brakes are adjusted as well as the points.
once the off road excursion is complete the truck gets cleaned, every surface gets touched by rag or brush. then everything is inspected again with a wrench on every bolt, greased, nipples cleaned, drain plugs pulled to check for water contamination. fluids replaced or topped up if needed. sheet metal straitened then some paint on any needed areas.

I may use my m37 and sometimes abuse it, but every job gets done, nothing is left to chance. I'm not the only one on the road.

[Elwood]

Charles is right, a ball hone is really only used for applying a desired surface finish, and is not suitable for removing any appreciable amount of material. We use them all the time on Nikasil engine cylinders as a "deglazing" tool. On a soft metal like these bushings I would expect them to load up right away and act more like a smearing tool than a reaming tool.

Curious as to the usefulness of a flex hone on soft bronze bushings, I decided to try one on the Pitman shaft bushings that I recently replaced on an M37 steering box. After pressing in the new bushings (and using some Loctite 609 bearing mount compound, since the right bushing was more of a push fit than a press fit in the steering box casting - I guess Gemmer's quality control was a bit off that day), I first rough sized the bushings using a Critchley adjustable reamer. These things are a bit tricky to use, as they can't take off too much in one pass, and you have to sneak up on the final dimension without going over. But as the length of the blades is longer than the combined length of the two bushings (apx. 3"), and since I had a pilot for this particular reamer (a No. 29: 1-1/8" to 1-1/4" range), I could true up the bores on the two bushings before finish sizing them with the flex hone. After measuring the replacement Pitman shaft, I was shooting for a final clearance of between 0.002" and 0.004". I used the reamer to get to a clearance of 0.001", and then started with the flex hone. Surprisingly, it had no trouble removing another 0.001" in short order, giving me a consistent final dimension on both bushings at the tight end of the range. Plus, the finish has a nice crosshatch. The flex hone balls didn't appear to be loading up with bronze, and I had to be careful not to run it for too long, and go oversize.


Critchley No. 29 adjustable reamer with pilot


Flex hone BC114320AO 1-1/4" with flex hone oil


Finished bushings


Finished bushings