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Buss \medium duty truck mechanic around?

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nomoreusmc

nomoreusmc

Meat Mopper
Original poster
Oct 24, 2024
188
238
Sw Missouri
Was wondering if anyone was a bus or medium duty truck mechanic. I have a 95 GMC top kick 7,500 box truck that the emergency brake stopped working. I want to move the truck to put it in it permanent position for the next two years to finish the build and now I have to chalk it because apparently the park prawl in the Allison transmission has broken. I was told that this has the school bus style parking brake but after searching on the Google machine, apparently it's rare enough that I can't find anything about it. Can anyone help?

366 big block Chevy w Alison Penske truck built on a school bus frame. Tia
 
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nomoreusmc said:
Was wondering if anyone was a bus or medium duty truck mechanic. I have a 95 GMC top kick 7,500 box truck that the emergency brake stopped working. I want to move the truck to put it in it permanent position for the next two years to finish the build and now I have to chalk it because apparently the park prawl in the Allison transmission has broken. I was told that this has the school bus style parking brake but after searching on the Google machine, apparently it's rare enough that I can't find anything about it. Can anyone help?

366 big block Chevy w Alison Penske truck built on a school bus frame. Tia
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Certified Diesel Tech here. It should have a big round drum on the back of the transmission that the drive shaft bolts to. That big round drum is the parking brake.

Does your truck have a round park brake handle on the lower left of the driverside kick panel?
 
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nomoreusmc nomoreusmc if you need help. Let me know. I can call you or you can call me if need be.

Also i should have mentioned i am a certified Over The Road Truck Technician. Semi-retired so to say.
 
That's awesome I was really hoping to find someone to help me out. I have built drag cars and raced motorcycles but I don't do much of the work anymore. Just don't have the body so I need someone to talk to so I go in educated when I get someone. I will have to take a peek under the truck but the parking brake is a button on the dash that looks like an air brake. This is electric assist brakes which I've never worked on.

If you want to build a twin cam Harley, we can talk rod ratios and what compression ratio pistons you want. Honda single cam? Yes 4663 Mitsubishi, oh baby! Pre-LS small block Chevy I can talk about that all day long. But I specialize in making things go fast and this just isn't that. To be honest I'm not used to being ignorant when it comes to mechanics. But I just have no experience in this area!
 
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nomoreusmc said:
That's awesome I was really hoping to find someone to help me out. I have built drag cars and raced motorcycles but I don't do much of the work anymore. Just don't have the body so I need someone to talk to so I go in educated when I get someone. I will have to take a peek under the truck but the parking brake is a button on the dash that looks like an air brake. This is electric assist brakes which I've never worked on.

If you want to build a twin cam Harley, we can talk rod ratios and what compression ratio pistons you want. Honda single cam? Yes 4663 Mitsubishi, oh baby! Pre-LS small block Chevy I can talk about that all day long. But I specialize in making things go fast and this just isn't that. To be honest I'm not used to being ignorant when it comes to mechanics. But I just have no experience in this area!
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Ok it might have a Mico type park brake. A electric over hydraulic brake system.

I think that system you held the brake pedal down then pressed the park brake button to lock the brakes. Then you released the brake pedal.

So are you having park brake issues? Or did it break the parking paw off inside the transmission?

Or is this what you are trying to figure out.

PM me. I would like to see a few pics of a couple things & I can offer better advice.

Thanks.
 
If it is the brake system I am thinking of.

It will have a 12volt electric motor bolted to the bottom side of your brake master cylinder at the firewall under the hood.
 
DieselTech said:
Ok it might have a Mico type park brake. A electric over hydraulic brake system.

I think that system you held the brake pedal down then pressed the park brake button to lock the brakes. Then you released the brake pedal.

So are you having park brake issues? Or did it break the parking paw off inside the transmission?

Or is this what you are trying to figure out.

PM me. I would like to see a few pics of a couple things & I can offer better advice.

Thanks.
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I just got clear of what I was doing. Let me get a few pictures and I'll pm you my phone number. Call or text good 👍
 
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What if I have both?

1000004414.jpg

1000004415.jpg

1000004416.jpg
 
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DieselTech said:
Lmao I always turned them down. No fun job. If I remember correctly you still have to loosen the cab mount bolts a bit .

My buddies are big into their duromax trucks.
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You can do it without loosening the cab mounts. It's a job pulling everything out the top, but doable, though, a topside creeper is a must have.
Better have your valve lash set right, cause there are no do overs the way they made the LB7
 
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Thank God it's just a school bus 366 Chevy. Cable unhooked from the solenoid in a metal box under the cab on the driver's side. More to come.
 
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DieselTech said:
Lmao I always turned them down. No fun job. If I remember correctly you still have to loosen the cab mount bolts a bit .

My buddies are big into their duromax trucks.
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I know more about the Duramax LB7 than I ever intended on knowing. My truck was losing antifreeze with no detectable leakage under the truck. Oil on the stick looked clean but the cooling system never built any pressure.

Took it to a shop and they found it had a blown oil cooler. Had them fix that. the cooling system built some pressure after that, but was still losing coolant.

Finally showed as milk on the dipstick, so I knew coolant was mixing with the oil. The shop that replaced the oil cooler said it had to be either head gaskets or the water pump leaking coolant into the crank case.

They wanted something to the tune of $5000 to do head gaskets. Ummmmmm, nope, I did it myself and also replaced the water pump while I had it torn down.

Been fine ever since.
 
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nomoreusmc said:
And for the record, what a weird system for a heavy duty truck, a drum brake bolted in between the transmission and the driveline, really? Actuated by a big solenoid instead of just a lever and a spring....... Who earn their engineering degree with this one?
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I'm still hung up on... small block chevy... God I love them!
Oh I love my two duramaxs as well but the vehicles with small blocks... you could fit in the engine compartment!

Ryan
 
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