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Old 09-06-2018, 09:00 AM   #1
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MT 545 yay or nay?

Hello and thanks for looking....

For example, I have a car with a internet notoriously bad engine. It has served me flawlessly.


The “lowly” MT 545.....is it really that bad?

And why would an activity bus have one?


Thanks....
-Shay
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Old 09-06-2018, 09:11 AM   #2
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MT545 is not a thing.

You probably mean AT545.

AT545 is awesome around town, but it's the worst choice on the highway. I know, I have two of them. It will get you where you're going BUT it's much less efficient at highway speeds and especially on big step hills. Under those conditions its turning horsepower into heat instead of into work, and that heat is what tends to kill them. Adding an extra cooler will go a long way towards keeping that heat under control but it's still going to be losing that power.

The issue is that there are no lock-up gears. You're always on the torque converter, which isn't a big deal around town, gives for a nice smooth ride. But on the highway where you're in the upper range of input RPM it's actively hurting you.

But again, I've put a ton of miles on mine, including every damn mountain area west of the mississippi. It can be done, but you need to be aware of your temps and not be in a hurry.
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Old 09-06-2018, 11:47 AM   #3
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I have this transmission and it's the least desirable tranny on these forums, but it's not a bad transmission in any way. You just need to keep the fluid changed and don't overheat it.
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Old 09-06-2018, 02:08 PM   #4
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I've got a bus with extremely low miles and hours and its on its second 545.
I've had 3 buses with 545's and they're ok for low speeds.
Any amount of interstate or mountain driving drives me crazy with a 545, though.
I've got a shorty with a DT466E and allison 2000 and that' s a GREAT combo. My other bus with the low miles and the 545 was cheap enough that I can upgrade the transmission if I end up deciding it has to go. I'll probably just keep the 545 in it since I don't really need to go much faster than 45mph around here. I'll take the other bus when I need to go highway speeds. OD and lockup are amazing!
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Old 09-16-2018, 09:08 PM   #5
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i used to be a fan of 545s till i nuked 2 of them with just roadtripping across the eastern 2/3 of the country.... now one bus has a 1000 and the other is getting a 643 (almost ready to bolt it up in the next few days)...
-Christopher
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Old 09-16-2018, 11:34 PM   #6
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The 545 was the industry standard for many years. But...times have moved on. Most folks what the things they lack...lockup...OD...more gears...higher torque rating...


They can be made to last but it takes a lot of work and staying on top of things. Like temperature. They do NOT handle heat well at all.
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