mechohaulic

checking the wires in all pictures no matter what style plug, they all should still be ground wires meaning none have positive voltage. picture having a sender with two terminals would still be just grounds. newer "updated" unit could be made cheaper eliminating second terminal putting chassis ground wire on one of the mounting screws. one version had a spade terminal on the sender housing also. picture of '79 basically a push on plug having one wire from plug to sender ground other wire going into harness would go to gauge

now if the first and last picture represent uber drivers;;I'm call for uber right now. LOL can even call Uber #2 having those headlights ; won't matter if it's dark out.

what's your plan ; alum wheels or inner flat silver with outer lip painted same as truck (green)?

there's those two dreaded words :::"updated and plastic". purposely stated explanation given was based on old school way before the update and plastic became common. old school didn't need modules/ resistor/ computers and others. Things worked fine TOO.

both wires were ground wires which is why original post stated the two wires checked out as ground. one wire (black ) would be a common ground going to sender mounting. second wire (red) is also a ground but going to the fuel gauge independent of chassis ground. it regulates the ground circuit going to gauge. the "hot "live wire is connected to gauge in dash cluster. sorry for confusion.

don't forget there was a common fix for a fuel tank gauge== it is called a clean stick behind the seat. also very accurate.

the reason for separate ground on the sender is because of the rubber straps which will cause the tank to loose "common " truck ground IN MANY CASES. the center post on old school electronics was technically a ground wire to gauge. in days of gas driven units it wasn't always the best idea to have a live 6/12 volt power to a gas/diesel tank. think of a scale model choo choo train in a house. as the operator turns the control =basically a rotating reostat switch the choo choo goes faster and faster and faster;; still with me?? now as the fuel in the tank of a truck lowers the floating sender lowers also. this causes the center post on sender to have lower ground voltage. lower ground to the gauge causes the needle to read lower. if your headlights have a bad ground don't the light get dimmer????? using a meter on the head light with bad ground, will you not get a lower then 12 volt read out??? the fuel gauge gets a lower ground reading causing it to fluctuate. I did say earlier it was a short version using improper technology. what do you expect from an ole man explaining old school electronics.

both wires should be a ground circuit . positive feed will be at the gauge . ground in == ground out to gauge. as the fuel float in tank raises and lowers the rheostat inside on the sender changes "continuity"= short version with wrong terminology, 12-volt ground (black wire) going in/ on sender may be 8 volts out sender (red wire) resulting in gauge not fully grounded and show half tank. taking the red wire to frame providing it does NOT have power and does show as a ground the fuel gauge should jump to full. KEEP IN MIND THIS IS OLD SCHOOL system!! can NOT say it's the same on all this modern computer stuff. I'm trying to put two added brake lights on my 2021 jeep gladiator and I find out it has to be calibrated at the computer. 3 simple tiny wires . checking system having rs light off with my lawn tractor battery ; think two wires touched. now there are only 3 of 4 led lights working on right side and the dash keeps telling me signal light out. point is staying on topic todays electronics are all screwed up.

not sure of this "pete" fellow you speak of LMAO!! I will admit a large car of another brand when set up properly is a nice-looking unit. good two-tone color scheme/ enough chrome to look parade like without over kill /flat top sleeper and decent wheelbase along with few other goodies. for over highway work not as much hauling dirt products. think large car pulling alum flat deck looks fantastic.

had to rewatch the video after reading it is a 600 ton trailer ;; then reread part where the trailer in move video was not the ORIGINAL 600 tonner. didn't seem as one pictured was 600 ton capacity; it's still a HD trailer.

before the save the eco of the world got started; it's interesting and enjoyable to see the old pictures of trucks and compare the many differences. flat fronts/ heavy steel bumpers and heck of a lot more. take a C50/60 (random pick to stay on topic ) . completely disassemble into two piles = one of steel other pile of the plastic:: now take a compatible/ similar truck of today and do the same = one pile steel other pile plastic,, think there will be a noticeable difference?? LOL. plastic hood , engine parts/ enough computer wiring to build 3 or more C50/60's. wiring harnesses.

from what I see in the way of "super truckers" in CT with their blacked out windows/ front visor covering window / and the 100 + extra lights ; not to mention the reckless high speed driving (I said not to mention ); coffee and donut bet on the style vehicle they own ::on the ground/blacked out windows, most time if you can see in as it passes you at twice highway speed , you don't see the driver cause its laying almost in rear seat location. they must want same feeling behind their "car" as the large car .

fortunately there is a BIG difference between the "super truckers" with their 12 inch window blockers and a REAL trucking fleet such as the red /white hood dump truck hauling fleet as seen in the picture. visors on that fleet are practical and useful.

any updated pictures of the DM ?? exhaust stack vertical or horizontal? can't see in picture. noticed all the fleet has sun visors. company standard issue?

there's one few miles from me in CT. don't know a thing about it. has a 15=20 ft box on back , looks to be sitting for ?????? yrs . don't know exact model , never saw any activity in or out of house . wasn't aware the C series had such interest.

west coast always was a large car area ; sadly the large car "migrated " east. now the remaining fleet delivery units are different versions of the large cars; just smaller. they all basically look the same = I don't pay attention to brands much. back in good days when a Monfort of Colorado large car with it's bold yellow/ orange paint thundered through : all stopped in awe ( I did any ways ).

forgot all about trailways used to exist .one of many companies bought out to eliminate competition.

based on "days of old" the factory would not run trailer air system on a unit UNLESS it was part of a large all the same order. red valve / 7 way wires would be factory installed. trailer air may have been on the order sheet, not necessary being installed at factory;; it's the selling dealer responsibility to complete along with dump body install ;; bringing in the third party (body shop) involved with the sell/set up. point is as prementioned, no picture no accurate answer possible.

another post which could be answered correctly IF it was accompanied with photos. trailer air set up by factory brand new ??? body shop installing dump installed air to trailer glad hands ??? no offence to author of post :: a few more specifics would be greatly appreciated.

all you can do is hope it's a positive for the working folk. todays brass sit in their fancy offices with one goal in mind :: how can I make more money. always thought competition was good for people. trend for yrs around here was company eliminates competition with buying them out.

in the day the trucking industry was a regional thing . Mack "owned" the east coast with the competitive brand out west. reason for Mack attempting a foot hold with Mack westerns. todays world Volvo did unfortunate job of running Mack into the ground. no longer a regional territory country. the B-81's/ DM's / superliners are replaced with shiny / large cars hauling dirt.

how fortunate the world is to have those with a big check book to save important parts of history for us poor folk to see. can only hope the truck / trailer stay together. trailer not saved someone will make a couple of bucks at the scrap yard with no concerns of history. not as if there were a fleet of those units ;; only 3 !

In it's day the FDNY super pumper was another feat of engineering. yrs back i spent a week in Allentown (Mack) FD training course. the super pumper was part of a "set". along with the super pumper was it's mate a super tender. don't remember specs (along with much more) today. heard yrs back of a separation, don't know if it was the pumper separated or the pumper and tender separated.

sure hope he comes back with follow up answers

7 pin wire connection I would assume you are referring to a light plug socket. ? is it mounted or tied behind crossmember ? reason asking is to determine how far factory trailer set up you have. are there capped off air lines or an air valve near light plug or along frame ? ? don't think on that new a truck they even use a trolly valve any more . can you access behind the dash to see the red knob checking for capped line . seeing /knowing what you have is a strong determinization of how it is connected. tractor/ trailer protection valve needed?? glad hands or quick connectors for trailer air there or needed ??