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Discussion Starter #21
Next chore:
My Allison MT643 needs to be serviced. I hope i can either get a new external filter based on the numbers on the filter. The truck is 29 years old with 31,000 miles. No telling whether it has ever been serviced. The spotty info I can find on Allison is mostly not specific to MT643.
They say some were shipped with 15W-40 engine oil, others Dexron III, and newer ones get synthetic. All can run on synthetic, but a thorough wash down is needed. You don't want synthetic mixed with fossil based oil.
Is the suction screen in the sump the only internal filter? Does it need to be changed, or just washed?
 

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Discussion Starter #22
Next discovery:
The fire truck application included an electrically controlled set of valves to lock the transmission in 1:1 ratio high gear for fire pump duty. I have no use for it. I'd like to remove it. A power source from the control on the dash triggers valves. Two hoses run from the transmission. I'm not sure whether I should connect these two tappings on the transmission with one hose, or plug them both.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Do you have the original "circuit" or plumbing route? When not in use through the hydraulic pump, did the fluid have a different way to go, meaning there is always flow through these lines? If that's the case, then I would connect the 2 ports...

Sounds like you've got quite the project.
 

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Discussion Starter #24
I'll get a picture. Much of the wiring got cut when the fire body was removed. The pump operator's station was on the side of the truck behind the driver's door. There are a couple components mounted at rear of the transmission. Two hoses to the transmission, three wires, one of which goes to the dash.
Wild guess: The hoses provide pressure oil from one place in the transmission, the other is the lockup hydraulic cylinder at the torque converter.
I'll explore further to see if the valves are open or closed when not pumping.
The 1500 GPM fire pump used a gear set powered by the driveshaft to choose pump, or rear axle. I think the transmission chose its own gear based on power needed both driving & pumping. Either case you put the transmission in drive, controlled throttle from three different places.
 

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Discussion Starter #25
I've been driving it as my daily driver, fuel gauge still above half. It runs well, I love the roar......but I hadn't factored windows down. It is loud! I'm thinking where I can add a muffler. The Allison is as my son describes; drive it like you stole it. Start up, I wait ten seconds for it to shift to second. By the transition to third, it snaps my neck. I'm Marty McFly when it goes to fourth. Wow!
As I see it, all the power & torque happen at 2000 RPM. I expected a turbo to be different. 65 MPH is at 2500 RPM. I believe the rare trips to interstate highway will be acceptable. Meanwhile, I climb mountains faster than ever before!
 

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Discussion Starter #26
My first GM Medium duty came to me second hand with a previously unused 30,000 LB pintle, rated at 10,000 tongue weight.
Aside from that I have no information about towing capacity. The boys once towed a fully loaded 20 Ton Eager Beaver without wrecking, that without brakes.

I tow a 23,000? GTWR trailer fully loaded with a backhoe successfully.

Pickups have a tow rating. Do these medium duty trucks have a tow rating?
 

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Discussion Starter #27
I took it to a new to me inspection station Wednesday. The place I've always gone announced a not yet certain date, they are closing. The owner's son just died age 22, I guess drug overdose, but don't know facts.

Anyway, new place came out with a long list of reasons to fail me. One wiper didn't wipe clean, one headlight has condensation inside, U bolts don't have exposed thread beyond the nut, triangles not secured to floor, fire extinguishers not secured, brake cans look rusty, one front tire doesn't roll freely, it scuffs a bit for 1/4 revolution parking brake valve seeps air when parking brake is disengaged.

Today I bought all the mentioned parts except front brake drums. They are only in stock in California. $600 each plus shipping & tax. I can't see a problem with the old.

Oh, a new U joint is loose.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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So grateful for no inspections...my truck would never pass.
 

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Discussion Starter #29
I'm getting discouraged!
Among the long list of flaws the inspection garage failed me for, my rear u bolts aren't long enough.
The spring shop I bought new springs, hangers, etc, etc from said "tough SHI*!"
I found a new supplier, bought $180. in new U bolts.
I figured I could jack up the frame where the tires were just touching the ground & change U bolts one at a time.
As I back off the nuts on the first U bolt a few turns, they do not free up. There is significant tension on them still. I don't want to lose my head. How is this done?
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Well, you're dangling the weight of the axle, so can you take that stress off the bolts with another set of blocks? Independently support the axle and the frame to put it in a static, no-load condition.

And they may NOT loosen up by design. That would be one of those things you don't want to shake loose...and no one will ever check if until they fail.
 

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Discussion Starter #31
Not dangling the axle, It's still sitting on the ground. I've changed springs before, but never in a truck this heavy. I'm going to turn this chore over to a professional. I can see it going wrong.
 

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Discussion Starter #32
I texted Rico. It is not easy to call Rico. I vented I'm getting older each day. I doubt I'll live to see a sticker on the windshield. He took over. He texted to say truck is ready. New development; left low beam is newly out. He has an appointment tomorrow @ 7:00 AM. He will deliver it for inspection. He will answer for any faults.

I'm feeling hopefull!
 

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That's awesome Bill! Be sure to post lots of pics of your progress!
 
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