MackTech

Could be a secondary leak

I could also be the spring brake inversion valve (I think they used the Bendix SR7 valve back then in Granites, nowadays they use the Wabco IR2 valve) there could be problems there or with any of the lines connected. On the SR7 there typically was a supply line from the secondary to a check valve on the SR7, a trigger line from the firewall, a balance line from the service relay, and delivery lines to the spring brakes. There might have been one other line that went to the front secondary brake circuit as well.

Data is vehicle specific, I would double check the connections at the ECU to make sure there are no bent pins.

You can actually tell by looking at the wires for the switch connector you're thinking of using. Look at the wires and look for an F before a number. There will be other letters and numbers.but look for something like F65

You can get a "service cab" from the Mack Customer Adaptation Center in Macungie.

Not trying to be a smartass, but did you pull out the pin that keeps the spring brake off?

Does your truck have traction control? If so the traction control valve could be bad.

Fuse for the ECU might be blown

Just the tube from the oil pan, is just like an airline. Push the retainer towards the oil pan and pull the tube out.

You always have the Allison 4700 option too! It's a 7 speed (deep reduction first gear & a very deep reduction R1 -17:1 ratio)

"Jack" Mack is a GU MP-8 with an MP-10 turbo which puts out 800 hp with 2800 ft/lbs of torque. Unfortunately it's not a production engine. It's a one off made as a "show" truck. I'm wondering why Mack doesn't offer it. If an MP-8 can do 800 hp, there's no telling how much can be squeezed out of an MP-10. Though the torque curve is pretty much from 0-2,800 but with that kind of power, why the hell not.!

A solo clutch does self adjust after you initially set it

Could have wiring problem on your trailer, causing it to backfeed, which is tripping the ECU. Has it ever worked without that problem when hooked up?

There is a turbo from an MP-10 on it and it's on a regular standard GU frame. There is unique programming in it as well. The pickup bed is still a ways away yet.

It is a one of a kind being made for the plant. It is a GU712, all wheel drive, MP-8, 800 hp, 2800 lbs. of torque, and is having a custom pickup bed installed.