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Air suspension? Ride height ?

You should be changing your oil then!!!

Bro! So post the model and year of truck and last six of the vin there are guys on here that may be able to help either the vecu wiring set up . I no longer have access to this stuff ! There are a few here that may! I would think there would be voltage down one wire to that switch! And back to ground at the vecu! Does the power show up at the wire at the switch?at the transmission? If so a full 12v or .7

That is the switch the wire I’m not sure! Have you checked for boost leaks black smoke is a good sign! You got fuel! lack of air may be your issue! Air filter new? Check the turbo ! Check thectube at the compressor inlet and at the manifold left side for holes also by pass your air drier temporarily for something to try! They can dump boost as well!

So I need to ask what trans do you have and are there any codes coming up other the the inlet air ? If you have a 18 speed Tran s un plug the low range switch at the rear shift cylinder see if this changes things! If the wiring to this switch has rubbed together anywhere between the switch and the vecu it will de rate the power by 50 percent! This will not throw a code the computer will think this is normal!follow that trouble chart you have posted there if you can locate the two wires to the switch cut or remove them from the vecu plug this way the vecu will never see a closed switch!

Agree totally with this statement ! spring brake is the most common failure with this symptom, there are a few other issues that can happen How ever yours fell in to the most common category ! Thanx for posting the fix!

All good bro ! Took the leaky boom cyl out had it repaired and repaired to the tune of 1600 other than that it’s working out well! Haven’t had much seat time yet been busy with other shit! Thanks for asking! I think after using the 4x4 I can hear a bad u joint in one or both of the for lack of a better term cvc joints bit of clattering on turns! May have to address these at some point apparently there are 2 u joints per side! not to much info on line but haven't searched hard on this yet been too busy with other stuff!

Yup to avoid buying tools pull it stand it up on a wheel rim of the appropriate size or two 6x6 wooden blocks and pop the back cover ! Recommend checking the rear bearings on the main case while you’re there how ever not nessary just a precaution!

Agree with Paul ! If you have the access to an 18 speed fuller( out of a Mack) then that would be an alternative ! That said you will loose all your back up speeds fuller has 2 your 12 speed has 5 ! The problem may involve a broken shift fork or shift rail ! the model of your unit makes for a difficult remove narrow frame ! You could pull the floor plate remove the center shift lid and look at the rails and forks how ever it sounds like the trans has to come out! Can you post a picture of the piece you have found on the drain plug! the only dog clutches in this are on the splitter and you still have hi /low Correct?

Plan A just sayin! It’s a pricey project however! Is what it is!

Nice my favourite! Model bar none for a dump truck !stand up oil change!😂It’s best to pull the transmission hatch if the box controls haven’t been mounted over it you might get lucky most box guys don’t consider that someone may have to pull the transmission some day! The trans can stay in the truck to do the back section but likely have to go to the dealer to have it done! Still check the yoke bolt and fork bolt also answer joes question there that is important too for proper diagnostics!

Cl713 likly has a Cummins in it! Check the rear output yoke for tightness! These were quite an issue behind the Cummins ! If it’s tight remove the top rear shift lid and check the shift fork bolt ! If it’s tight then the back section of the trans may have to com off and neew synchro plates installed!

Ahh I’m a bit out of touch on lumber prices i I just pull up a log and make my own stuff! 2/4 2/10 2x 8 cost about a buck a foot to make including fuel and logging costs! Not wear and tare on the equipment thou! And me!😞

Yup good thought Joe ! That said had this happen many times ! Shit got in the injector on installing of the line just my observation! AC engine particularly bad for this because of all the crap in the way !Replace the injector! Good to go! Cylinder not getting fuel! just sayin!

If you have bad compression I think it would be smoking! Do you have blue white smoke or excessive blo by? if not go with the bad injector theory!

does the engine have an engine brake?

The ground breaker can simply be by passed to get out of a pinch! Also if it does turn out to be the relay ! Make sure you’re given a constant duty relay cole Hersey is a common replacement and they make both and look identical!

i second the relay

yup another smart move in the name of saving a few pounds! At least they could have keyed these, Nope!

Kevin posted this years back sheds some light on the relationship! The mack V8 was molded around the scania V8!

Wow never seen a mid liner in a rd! Seen a fare few scania engines back when scania was associated!

TLC is EVIL!

the bottom oring has been deleted its a not necessary oring the only orings needed are the ones that seal the fuel from getting out of the steel line and the top oring to keep the oil in the engine! I have seen the older injectors used that has 3 oring groves on the return they deleted the bottom oring ! as Joey mentioned the groove half way down the injector is an assembly point!

yup start at the beginning ! the primer getting hard is odd there should be fuel returning to the tank at that point!

The Mack store will give you a blank stair unless you happen to run across a parts man in a wheel chair and hearing aids ! 🤣 Appears to me someone has put in an extra check valve on the fuel return under the stop lever there ? remove that number 6 line fuel should flow when you pump the primer up! The other thing is stick your finger in the hole where the pump came from and feel around in there I have seen this idler gear fall off ! it is held on by a c clip! it runs off the governor drive! I have also seen this gears idler shaft so worn the gear flops around a lot I would usually check this if I have a pump off as you have there! I really sounds to me like you got a restriction on the inlet side from the tank! By what your describing!