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Old 08-04-2013, 08:21 PM   #11
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Re: AT545 and Mountain driving

The lack of lock-up means your transmission can spin freely of crankshaft speed, within the realms of shearing the transmission fluid in the converter. Since the stator in a torque converter can overspeed, but not underspeed there is little resistance to this. But it really doesn't matter because an engine can only provide engine braking through pumping loses and mechanical friction. Since friction is so low it is pumping loses that need to slow an engine down. Without a throttle blade the pumping loses on a diesel engine are pretty limited. Basically, you need a lock-up converter and some means of causing pumping loses like an exhaust brake or a compression brake which releases the compressed air charge before it can do positive work on the piston.

Your transmission is fine. The key is to just slow down and enjoy life at a slower pace. Remember you are driving a bus, not a sports car.

*edit* A transmission cooler is very important on the way UP the hill, but on the way down I wouldn't worry about it. The transmission cooler is in the radiator which means engine coolant temp ultimately controls transmission fluid temp. Since the engine is pumping nothing but cooling air going down hill it is cooling the coolant rather than heating it and should offset any increase in temp from the transmission. Many modern V-8s use the cooling air effect and cylinder deactivation to allow limited power operation despite a complete cooling system failure.
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Old 08-05-2013, 08:50 AM   #12
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Re: AT545 and Mountain driving

thanks all!!!!!

hey, i have another question about the tranny, i think.

part of my issue with it, is a noise that comes on for apparently no reason. i'm guessing it is a cooling fan, but idk. when running down the road, more so when hot than not, a "roar" comes on from the engine, and then switches off a few minutes later. no gear change, speed change,..... just a roar.

i totally thought it was the tranny making the noise. but then i stopped on a hot day with motor on fast idle, and it made the noise again, which was my first inkling that it might not be the tranny (i was stopped).

is this roar related to the trans or is it a cooling switch/fan, or...? any ideas appreciated.
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Old 08-05-2013, 10:05 AM   #13
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Re: AT545 and Mountain driving

probably just cooling fan(engine)

I just came back from running up and down to grandfather mountain, and ran fine using the drive at 2200 rpm attitude, temps good...I did turn on the heaters for a 3 min climb just as precaution (pulling from red light at bottom of a 6% grade)
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Old 08-05-2013, 11:38 AM   #14
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Re: AT545 and Mountain driving

I would say for sure fan. I used to drive a large straight truck and when the fan clutch engaged it was fairly loud. I could actually feel it bog the engine slightly.
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Old 08-05-2013, 12:04 PM   #15
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Re: AT545 and Mountain driving

thanks for the info

that gives me more confidence than the "oh sh*t" look everyone makes when it goes on



now i can say "its suppose to do that"
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Old 08-05-2013, 03:33 PM   #16
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Re: AT545 and Mountain driving

I have a rear engine and can bearly hear it, but I can hear when the fan kicks in. I bet not as loud as you front engine guys.
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Old 08-05-2013, 03:46 PM   #17
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Re: AT545 and Mountain driving

the first gen hummers were really loud...not stealthy
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Old 08-05-2013, 05:42 PM   #18
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Re: AT545 and Mountain driving

fan makes the most sense..... i hope.

i also use to have a straight truck that had an overspeed light.... idk, but that is the only other thing that comes to mind.....antother light i had no idea what it was for.
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Old 08-05-2013, 06:39 PM   #19
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Re: AT545 and Mountain driving

First time I heard the cooling fan on my front Cummins 5.9 engine (former bus) it rather startled me. It was quite loud, but it didn't stay on long -- it was easy to see the temperature needle moving down while that fan ran. Next time you hear the sound, watch that gauge to see whether it drops.
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Old 08-07-2013, 01:02 PM   #20
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Re: AT545 and Mountain driving

Quote:
Originally Posted by turf
no retarder that i know of. i wish it did. what does it look like? maybe it does and i dont know it.

the bus came out of the mountains of arizona.... im a little surprised it does so poorly, but, im a bus now and need to slow down.
a retarder would be hard to miss. there would be a lever on your steering column and some corresponding lights that light up when you move it. when you pull the lever while driving it feels as if you are braking when your not. or maybe you have one and its not hooked up, if there is a BIG wierd magnetic looking coil around your driveshaft somewhere you have one. We just got home from a short camping trip at a high mountain lake about 30 miles from home, we climbed over 3500 feet and today on the way down i didnt have to touch the brakes ONCE, just used the retarder, and mind you, this is a winding, rocky dirt road and the 3500 feet climb happens in about 15 miles, not extremely steep, but long enough and slow enough to make the retarder come in handy.
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