Help With TM's

[GCecchetto]

Please forgive me if this has been asked before, but I didn't find much from searching the forums. I'm a nube to these trucks, got home last Sunday from driving my 2008 M1078 A1R from Maryland to California. I have a variety of things I need to address before continuing to drive the truck and am hoping you all can lend me some help relative to navigating the TM's. I have the TM's for the truck, but not having any luck figuring out where they hide the torque specs in the TM's. Maybe I just haven't found the correct TM yet. My immediate need are the torque specs for the M8 fasteners in the timing cover plate, the M12 bolts through the timing case for the air compressor, and the bolts in the motor mounts to the block.

Anyway, what I haven't seen is anything that explains the logic of the TM's and how to navigate them and they don't seem to be labeled very well. Seems labeling is all numbers rather than something that tells you what is in the particular TM, like just be a list of the parts in a specific system with their part numbers vs the actual procedure of servicing that particular system. Again, my apologies if this is akin to asking "what's the best motor oil"

 

[GeneralDisorder]

Didn't like my answer eh?

The TM instructions are difficult to decipher because the item numbers and illustrations don't coordinate well.

The TM also provides essentially the same torque chart I suggested (which all originate from the machinists handbook). Here's the chart from the TM itself if you like that better than one of the hundreds that you can call up at will from google images:



The TM pages on the cover removal and installation seem to suggest (again the item numbers and call-outs are crap so I trust my calipers and the bolt grade and a torque chart for this application) 15-25 Ft/lbs for the M8's and 60-90 Ft/lbs for the M12's. BUT YOU NEED TO LOOK AT THE FASTENER's GRADE in case some PVT got a bolt from the bins in the shop supply and it's not rated for the torque required by the spec.

An experienced mechanic will always trust feel first - torque readings can be misread, misprinted, and set wrong on the wrench or the wrench can be broken or out of calibration. Use all your senses and your common sense especially and triple check the fastener size and grade against the torque chart and "feel" what's going on as you tighten. If it feels like it's going elastic or going to strip out - STOP and evaluate the situation before you absolutely wreck your day. Moving too fast is what gets people into bad situations.

 

[GeneralDisorder]

Also worth mentioning that all that stuff is just standard Caterpillar C7 torque values and the TM is just a (lowest bidder) reinterpretation of the Caterpillar manual specifications.

And it goes without saying I think that all the threads need to be clean and undamaged, the bolts all in the proper holes, not bottomed out, and not insufficiently engaging enough threads (1.5x the diameter for iron and steel, 2x for aluminum).

TM's can be a wealth of knowledge. But they are also probably THE WORST written/copied/organized manuals you can imagine. They routinely contradict themselves in various iterations, leave crap completely out, and are at times extremely vague on stuff. Reading them is difficult at times even for those of us that that trained on how to do it. If there is a civilian manual covering the same topic (C7 engine, or Haldex air compressor, or WABCO ABS controller, etc, etc) then it's usually a better option. You are basically playing a written game of telephone with the TM's and hoping the team that transcribed it didn't F it up.

 

[GCecchetto]

Thanks. Just trying to be thorough. Many time I have seen torque specs that call out a torque value that is below the value recommended by size and grade. The bolts I'm dealing with here are all the original CAT grade 10.9 bolts, and yes, I totally understand the "feel" aspect of this. I bought longer grade 10.9 shoulder bolts for the 2 M8's through the AC bracket so I still have the same thread depth in the block. The lower of the two M8's through the bracket is where the oil was coming from. Yes, I know that likely means there is an issue with the timing cover gasket. Hoping to make that a repair for another day.

 

[SCSG-G4]

GCecchetto

The TM numbering system follows a VERY LOGICAL pattern. First two characters stand for Technical Manual, first number stands for the branch of the Army responsible, for trucks and generators it's "9" for Ordnance, the next four digits are the FSC number (Federal Supply Code) 2320 for wheeled vehicles and 2815 for diesel engines follow a similar pattern. The next three digits is a number the corresponds with that particular piece of military equipment within the FSC. Then we get to the nitty gritty, those last two numbers and letters. The -10 means that it is an operator user manual, if the number starts with a '2' it is designed for first echelon support (IE the motor pool), if it's a '3' it is for a depot facility and so forth, 5 being factory. The second digit will be either be a zero if it only is for that level or a higher number (usually 4 or 5) meaning it is for all levels above the first number. A suffix of -P means it is a parts manual, and there are other suffixes when the manual is spread out over multiple volumes. So a -24P is a parts manual for levels 2, 3, and 4, while a -35P is parts for levels 3 to 5.
Separate from the manual numbering system is a "Distribution Code", meaning who gets to see that manual. All of the manuals on this site are Distribution "A" - available to all, including the Russians, the Chinese, etc. Higher levels on the distribution codes become more restrictive, some to the extent that the item manufacturer cannot see the military manuals on what they built. Thus, we DO NOT have all the manuals you might need or want. Hope this is slightly clearer than mud!

 

[GeneralDisorder]

This has recalled to my mind a torque "unfortunate mishap" occurrence to which I was party.

While "training" in the rebuild process of a rotary screw compressor "air end" assembly, we came to about an M8 socket head cap screw with a very specific torque value as it was THE bolt that held the tapered locking mechanism of the air-end's drive pinion gear shaft lock. I believe the prescribed torque was 22 Ft/lbs. The torque wrench supplied by my employer was procured from the tool crib and with my supervisor looking over my shoulder I tightened the bolt - the wrench did not click. I stated that the wrench had not clicked and I was sure that I had exceeded the prescribed torque. My supervisor inspected the torque wrench and noted that it was set correctly. He put a socket extension in the bench vice and that's when we realized the torque wrench (Snap-On) was broken internally - it would click in both directions and not spring back. OOPS!

So we procured a different torque wrench and tested it. Then removed the bolt and my supervisor visually inspected it for any deformation or stretch and then said "looks ok" and we installed and torqued it.

Several weeks later I was called into the service managers office. This air end with my name on the rebuild paperwork had gone into service in a facility in California and had run for about 24 hours then spit the drive pinion gear into the bull gear assembly and the whole machine seized and caused about $50,000 in damage and downtime, What saved my job is that *I* didn't make the call to reuse that bolt and my supervisor backed up my report that I deferred to his judgment and that I had done everything absolutely perfectly including asking if we should replace that bolt. Fortunately we both kept our jobs that day.