Nick mack rd686s

Please can I have advice on my Jake brake. My engine is a EM6 285 and the Jake brakes do not work, I think someone has tried to by pass something as I have 1 blue wire come straight from the switch to the cylinder head and the other wire comes from a switch on the fuel pump to the cylinder head. I tried putting some wires that I found behind the dash back on the Jake brake and it worked but we I tried the accelerator and the Jake brake was still working and the engine cut out. Even with the engine on tick over the Jake brake was still working trying to cut the engine. Does any one have a diagram and a parts list so I can make sure there is nothing missing.

Please can some one tell me what this is on my and truck and what it was used for

It even has an air operated passenger window

Depends, up hill start 1st. Down hill start 2nd. On the flat 1st. Mine has a 4 spicer auxiliary gear box so under load I would start 2nd in auxiliary and 1st in direct then move up to 3rd in auxiliary then change into direct drive (3rd auxiliary) in 3rd drive. Then move up in as standard drive 4th,5th. The only problem I have is down shifting the auxiliary gear box down , I can not do it. It is impossible?

I would definitely say he is doing damage, this is a maxitorque gear box and combination with a maxidyne engine there should be no need use 2nd low as the engine and gear box best used at 1009 - 1700 rpm. The reason why the gear box has only 5 direct and 1 low is because it can handle low revs under load. If the truck needed more gears you can fit a 4 spicer box making it a 3 stick.

Thanks for everyone replying to the post

The black frame is for a Crain that is not fitted yet but I’m going to put it on soon. The truck used to move houses for a living and it used the Crain for lifting the beams. It has 3 winches on the back as well. The truck is difficult to drive as it has 3 gear boxes, did any other Mack’s have 3 gear boxes

Thanks for the reply, that makes sense. There is a switch on top of the dash, is has normal driving and then rain and snow.

Hi people, just a quick question. My Mack in the photo has an air intake vent on top of the bonnet, my Mack has a maxidyne engine with a tip turbine water cooled. Was all Mack r models fitted with this engine and why is there only some Mack trucks with an air vent on top of the bonnet, is it because my truck came from Canada? any information would be good, I want to learn as much as I can about my truck.