MT647 swap into MC-5C blog update - electrics

[bevans6]

So I am now on the slippery slope to actually finishing this marathon, and today's topic was electrical conversion.  The Spicer 4 speed has two major electrical connections to it, the reverse solenoid and the reverse light switch.  The MT 647 also has two electrical connections, the neutral switch and the reverse light switch, so I plan to reuse the transmission wiring loom with the fancy connector at the electrical box.  This also nets me a switched feed to the rear electrical bay, the wiring that runs from the reverse dash switch to the old reverse solenoid.  I will tie those wires off with a label so I can reuse the - maybe to activate a rear docking light, or something.

The reverse light switch is straight forward, it just grounds the reverse light circuit.  I'll just re-terminate those wires with appropriate connectors.

The neutral switch connection is also straight forward, it's just grounds the coil of the neutral relay.  The neutral relay is a different matter - first off, I don't have one, and second off, it has to be wired to control both the fast idle circuit (no fast idle in gear, pretty important) and the starter  switch circuit - no starting in gear.  In my case, my bus came with the optional engine stop relay, which stops the engine if an over-heat is detected.  All of the overheat/oil pressure switch sensors on my engine are disconnected (the gauge senders are still operational), so the relay is just sitting there, and happily it is the same model relay as the factory neutral relay, so the switch is a natural.  I'll just un-wire the engine stop stuff, install a jumper or two, disconnect another couple of jumpers and voila, neutral relay.  Easier said than done, it's a tight little electrical bay and the wires are stuffed in pretty well, so I have created a step-by-step job list of what to take off, what to move, and what to add.

Brian

[luvrbus]

Check your new shift tower it may have the neutral start switch already there,you know about the special 0.090 aluminum washer you use when mounting the switch on the transmission ?  

[Lin]

Somehow this is sounding a lot more complicated than mine.  My shift tower had a neutral safety switch, but we did not use it.  The transmission came with a neutral switch on it, so I just wired it inline with the starter. It is a much shorter wire run that way and easily accessible.  If I am remembering correctly, I think that there was a reverse light switch in the shift tower also, and we did use that.

[bevans6]

The shifter comes in a couple of different varieties, I ordered the one with no switches.  My neutral switch came new in a bag with a washer, so I presume it's correct but I will go and check.  It seems to work fine.  I thought about "hacking" the neutral switch for the starter but decided to go the relay route because I have fast idle.  I need to ensure that fast idle only works in neutral, as well as only starting in neutral.  Plus I had the relay no longer doing anything.  The other thing is I prefer the idea of the switches working when the transmission thinks it's in neutral or reverse, not the shifter thinking it's put the transmission into neutral or reverse.  Hopefully a good choice.

Brian

[luvrbus]

Shift towers come in different versions because not all 5,6 and 700 series Allison's have ports for backup lights and a neutral switch both work good ,Lins is really not a hack job it's done that way by many that I have came across   

[bevans6]

I meant "hacking" in the software modern sense of just using a work-around, not in the old-school sense of "hacked about with a hammer or an axe"    No offense meant!

[bevans6]

|Is it better practice to terminal the switch grounds locally on the transmission case, or pull them back through the cable/plug into the panel?  I can think of reasons to do either...

Thanks, Brian

[luvrbus]

Either way is fine but I ground everything to case even the Stone/Bennett or lockup valves not has hard for me to chase a bad ground that way

[bevans6]

I agree with you, so I will ground to the case.  Simplifies the wiring anyway.  BTW I sent you a long delayed postal money order on Monday, sorry for the delay.  Hopefully it covers shipping both this time, and the time it got returned from customs a few years ago.

Brian

[daddysgirl]

The shifter comes in a couple of different varieties, I ordered the one with no switches.  My neutral switch came new in a bag with a washer, so I presume it's correct but I will go and check.  It seems to work fine.  I thought about "hacking" the neutral switch for the starter but decided to go the relay route because I have fast idle.  I need to ensure that fast idle only works in neutral, as well as only starting in neutral.  Plus I had the relay no longer doing anything.  The other thing is I prefer the idea of the switches working when the transmission thinks it's in neutral or reverse, not the shifter thinking it's put the transmission into neutral or reverse.  Hopefully a good choice.

Brian

I have a love/hate view of Neutral safety switches, but there are some that are grounded by removing the washer (in my book anyway). Mine is/was hacked to the starter...until I replace the starter (new 40 sitting in the garage) and finish the wiring to the relay. But not in this heat...the pavement is too hot to walk on with bare feet.

[luvrbus]

I agree with you, so I will ground to the case.  Simplifies the wiring anyway.  BTW I sent you a long delayed postal money order on Monday, sorry for the delay.  Hopefully it covers shipping both this time, and the time it got returned from customs a few years ago.

Brian

No problem I never worry about you paying lol our exchange rate  sucks for you and I feel bad about that  

[bevans6]

Just make sure you take it to the bank and cash the damn thing - it's not a personal check so the Post Office already has my money!     I would die an unhappy man if I thought they had more of my money than they needed to.  Ha!