wacatak

ive replaced the O-rings once but it blows the top one out in the same spot every time so I figured it was wore out.

Im needing a new shifter knob for my 12 spd maxitorque anyone know where I can get a new one besides through Mack. Thanks

it has 2 tags that say mack reman, but i cant find anything to tell which one it is. Is there anything i should be looking for?

ive got a 1991 688 with the e7 400. I was wondering what it takes to turn the pump up on this truck. If anyone has any information it would be appreciated. Thanks

mack said that i had to buy the whole shifter so i located 2 new orings but it didnt correct the problem. So the shifter may be the next step. All the info is appreciated. Thanks

I just replaced the o-rings mack said that they just sell the whole selector switch. When it spits it out in 5 min I can put it back in and run awhile then it will do it again at some point just an intermitent problem. Wheres the pressure regulator your talking about? thanks

im looking for some information I have a 12spd maxitorque and in the selector switch on the shifter knob it keeps blowing the top o-ring out. Any ideas what would cause this problem? I already replaced the o-rings. Thanks

i have a 1991 688 dump truck with a 400hp and 12spd, ive just had the truck for about a yr and dont use it eveyday. My issue is i can shift the truck fine running through the gears but when it comes time to shift down ill shift from 5 h to 5L it wants to grind for a bit going in. Im looking for any advice or info that would be helpful. Thanks

well hooked it to another trailer and the truck is fine so now time to disect the trailer.

ok thanks im going to hook it to a friend of mines trailer that i know there is no problems and see if the truck works with it. ill let you all know how it goes. thanks again for the help

To start hope everyone is having a good Christmas. I have pulled the foot valve apart it was alittle dirty cleaned it all out and put it back together. I charged the truck brakes then the trailer brakes with no trailer hooked up and there was no leak out the exhaust on the foot valve so far so good. I then roll it out of the shop hook it to the trailer and the same problem as before it leaks out the exhaust valve and wont release the trailer brakes. Does anyone have a contact number for someone that has some good knowledge on the air system, Im just trying to wing it but I dont want to start buying parts with out an idea where to start. Thanks again

ok thanks i will give it a try. Thanks again

Ive got a 1991 rd 688 dump truck the brakes on the truck are good and act fine but when i charge the trailer brakes it leaks more air than the truck can make out what looks like a diaphragm on the brake valve. Any ideas on this? Can I take the valve apart to see what the problem is? Thanks

well i got back to work on the truck today and i believe i have fixed it. I traced the lines back to the valve/regulator i dont know the correct name but it is the valve where you can set the pressure, i pulled it apart cleaned it and stetched one of the springs to give it a little more tension and it seems to be working. Let me know your thoughts. Thanks

im going to be away from the truck until the first of the week.Then I will get it in the shop where I can take a look at it to see where the lines are going. So ill post then to see what I have to replace to get it fixed. thanks again

there are two of these tied together one for each side and they both are leaking air, so its possible for both of them to be bad?

yes i have a pic on my phone i just have to try to figure out how to load it on here. The name on the 2 valves is midland ill try to get the pic uploaded.

sorry tag axle. it is air up and down steerable and air brakes. The leak is present with brake on or off. The mack dealer tried to get some info from eaton with no success. Thanks

The 2 valves that are leaking are tied together between the airbags and mounted to the frame. I believe the manufacturer is midland, when i engage the axle they just keep bleeding air. Thanks again

I have a 1991 rd 688 with a eaton drag axle when I engage it the valves coming off the drag axle keep bleeding air. When the truck is at an idle it bleeds out faster than it can maintain. If anyone has any ideas or any info would it would be greatly appriciated. Thanks