Trans swap issues

[Mark T]

that truck might be transphobic

[Joey Mack]

howdy, So have you had any more success?  I know you said the speedo is inop,  I have an app. on my phone called digihud,  its a simple speedometer, with a large display thats easy to read..  I use it during test drives, and when I am calibrating a speedo head...  jojo

[Noble1]

Oh have a bush button but how do I hook up the starter?  It won’t do anything with voltage to the two side posts maybe they just need cleaned up. 
I started it befor with a screwdriver across the two big posts.  

[Joey Mack]

one of those 2 opposing wires should have a red band around it..  thats the pos. from the key..

[Joey Mack]

since it wont crank with the key, you can hook an in-line fuse to a post in the top fuse panel. there should be a row of posts under the cover. use a post the powers up with the key in the run position. run it to the button, then down to the starter post that has the red band on it. you can un hook the original wire and tape the end to protect it, and hook the new starter button wire to the post.. jojo

[Noble1]

I get 3.4 Volta on the 2 opposing terminals. Neither one does anything when I apply 12 volts 

Mia there like a safety switch on the ground to either one as well?   

Edited September 20, 2022 by Noble1

[Joey Mack]

that is odd,  is it possible the celenoid is bad too?  i know you can buy a replacement for about $35.00.  i have replaced them quite a few times.. they dont seem to last as long as the older types, like on a 42 MT starter..  I also see the contacts are dirty. the larger black wire coming from the celenoid should be the signal wire for the starter. volvo uses gray wires as the grounds, black may be 'hot'..  i need to look at one in my  hand to refresh my memory.. i figure that when you power the key signal line, that there would be 12v at that black wire's post.. 

[Noble1]

Your not talking the big post on the bottom or the front?  
I don’t see a red band either.  

[Noble1]

So the the celinoid one side should be ground and the other a hot when you want it to start.  It started before the trans swap but you had to hold the key for 20 seconds before it would crank.  Maybe there is another safety switch on the ground side possibly?    Would be interesting to look at a schematic.  

[Joey Mack]

[doubleclutchinweasel]

Be sure to take Joey's advice with a grain of salt!  Remember, he is still heavily self-medicated!

Sorry, Jo-Jo!  Could not resist pokin' the bear just a little bit!

Hope you're up and back at it soon.  Take care.

[Joey Mack]

yeah i'm gettin there..  Dr. Beam is helping me.  I just fixed a dose of meds, a minute ago..  

[Noble1]

Ok after some more testing with the key on and I put the left side to ground and apply 12 volts to the other side it will crank.  
must be another switch somewhere on the ground.  
so until I find that I in theory could put the left side to a ground and the right side to a keyed power through a push button.  
I will wait until I have help and see if the clutch switch or something else let’s the ground circuit complete before I do the above.  

[Joey Mack]

Dont forget the salt..    

[Mackpro]

The engine ecm controls the ground for that small solinoid on the starter. The engine ecm looks for the start signal from the VECU, which is looking for a neutral signal from the  now missing trans ecu . The VECU can be reflashed from the dealership to a manual trans. Years ago Mack would not this on the 2008 and up trucks but a couple  years ago they said they would. Removing the Auto shifts and Ultra Shifts in the older grey engine trucks was easy to by pass all the wiring . Not so sure on these MP equipped trucks 

[Joey Mack]

I vaguely remember that, MP..  That is why I asked him to try jumping the starter, and then installing a starter button..  Do you think that would cause any de-rate's or other performance issue's..  I know I did this before on a deleted '09 CXU, for a farmer.  He had some MIL's iluminated, but could run the farm truck just fine..  I dont want to give bad advice..   Glad you came in on this...  Jojo

[Mackpro]

I’ll see in the wiring diagrams for a 2012 Auto shift if it’s a simple jumper harness added in like the older CXN and CHN’s 

[Noble1]

I really appreciate the information you guys are giving and look forward to what you find out.  
we just picked up another ch today.  
454 with an 18 spd.  
I will post pictures of our fleet here someday.  

[Joey Mack]

Well You just got a good one.  I'm in!!!

[Mackpro]

This is really a hard one as all the start relays go back to the trans ECM that is no longer there . Somewhere there is a Relay #20 ( Mack doesn’t say where) start enable relay. It doesn’t show up on any of my fuse box diagrams. There is also a relay usually mounted on the outside firewall labeled MEIIR, I was hoping jumping this relay would work but it won’t as it goes back Trans ECM.  The trans ecm powers up 2 relays sorta in line , the hidden relay 20  and the regular start relay #36 that in the fuse box by the clutch pedal. The main goal is to get 12 volts on wire CB28A  at the VECU connector B pin 28. You also have to put 12volts on the CB28B wire at relay 20 which will feed back and engage the regular start relay 36 . Be very careful with relay 36 it can be turned and inserted 90 and it will never start . 

[Joey Mack]

MP, do think the starter button will cause any issues.  I know the '09 that I did, worked fine..  

[Mackpro]

46 minutes ago, Joey Mack said:

MP, do think the starter button will cause any issues.  I know the '09 that I did, worked fine..  

it’s worth a shot. 

[Noble1]

Went our local Mack dealer today is Sioux Falls SD and asked them.  Basically got the run around to just bring it to them and it would take a few days and wire harnesses and engineering services or something.  
 

so today we slap it to set her I jump the starter with a screw driver just to test and we take it for a spin to make sure it won’t derate.  Ran good and didn’t have any problems except for the giant hole in the floor yet.  
 

what if I put 2 push buttons in one for the ground and one for the power wire that way it isn’t hooked up all the time only when it starts?   Or do you think it would hurt have the one terminal grounded all the time.  
 

I will dig around for the relays if I get time.  
but we started combining beans today.  
 

Edited September 22, 2022 by Noble1

[Noble1]

Didn’t have time to dig and find relays.  I just put a push button start switch in.  Unhooked the factory wires and taped them up.  Works like a charm.  
mused a 15 amp momentary switch that was already there and some wiring that was installed before we got it for a PTO that was taken off before as well so I only had to splice a few ft of wire.  
 

haven’t hauled a load yet but she seems way more powerful than with the auto.  

[Joey Mack]

good deal...