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Old 01-01-2016, 11:57 AM   #11
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Engine: Cummins 4BT
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Mine is an SAE 3 that was bolted directly to a Cummins 4BT. Same pattern as a 6BT. I never ran it but was told prior to purchase it was fully functional as was the engine I bought with it. It also has a driveline park brake attached.
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Old 01-01-2016, 04:10 PM   #12
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Engine: 5.9 Cummins, Allison 545
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dangit! looks like im going to houston

my bus has 300k miles on it...... the engine seems strong, but that trans gives me night mares.
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Old 01-01-2016, 04:19 PM   #13
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You want to try for a trans that was behind a similar engine if not the same. They have shift patterns tailored to engine rpms.
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Old 01-01-2016, 04:24 PM   #14
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hmmm, ..... edjumacate me

this is over my pay grade

thanks for all the kind replies!!
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Old 01-01-2016, 06:47 PM   #15
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Engine: DT466 Trans: MT643
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There are some 5.9s with MT643s behind them. That would be an upgrade
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Old 01-01-2016, 09:41 PM   #16
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Quote:
Originally Posted by turf View Post
hmmm, ..... edjumacate me

this is over my pay grade

thanks for all the kind replies!!
Different engines have different power bands. Here is a definition that
probably explains it better than I can. An AT545 from behind a 4 cylinder diesel probably shifts at a higher rpm than a 6 cylinder. An Allison shop can probably make adjustments. I don't know if I can do better than that. Anyone else want to chime in?


https://en.wikipedia.org/wiki/Power_band
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Old 01-01-2016, 10:53 PM   #17
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Engine: 8.3 Cummins
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I've read using a C-3 oil in them gives them better performance. C-3 hydraulic oil or 5W20 or 5W30 engine oil, which is C-3 rated as well.

They're pretty bombproof trannys. But you need to like to coast to a stop with them.
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Old 01-02-2016, 12:47 AM   #18
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If you have an AT540 series transmission it would be best to replace it with a like transmission.

If you shop around you should be able to get one installed for less than $3.5K. Good rebuilts that are built for your specific engine and application are available for under $2K.

A transmission that was behind a 5.9 is not going to have the same valving and governors as a transmission that was behind a 7.3.

While a good Allison tech might be able to swap stuff out to make it work it is a lot easier and cost effective to get what you need at the beginning.

Swapping up to an MT640 series would be a big step up but the costs would be considerably higher since you wouldn't have a core to swap so you would be purchasing the transmission outright.

The same would hold with going to any of the newer WT series transmissions.

Personally I don't understand the angst about the AT540 series transmissions. I agree they don't hold back going down hills and not having a lock up makes them a little less fuel efficient. But at the same time I have seen them go well over 200K miles in 11-12 row conventional or TC2000 buses.
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Old 01-02-2016, 09:46 AM   #19
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AT54_s are TH400s on steroids. Open one up and there's a TH looking at you (almost).

There are 100s of thousands, of ATs running around in trash trucks, skoolies and every large rental truck I've used. Basic, sturdy power delivery.

I used to run a long bobtail from Sun Valley CA to Vegas with one behind a DT466 many times. Most of our line trucks at (now) AT&T had them. (I retired in '94 so don't know what they have now)

I mine will downshift from 4th at 55, 3rd at 32 and 2nd at about 24. Not a lot of engine braking but enough that I utilize it often.

The best...perhaps not but they work hard.

YMMV....... Mine does
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Old 01-02-2016, 09:08 PM   #20
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i agree, your mileage may vary.

this AT545 has 310,000 miles on the clock, slips, overheats, makes noises you never want to hear, has the fragrance of burnt oil, but has kept on going.

after all the inputs..... i dont think i'd have a problem with a rebuilt 545. i think thats smart money.

however, fixing it doesnt address any of the shortcomings of the setup.

if money were no object, i'd go for the mt643, plus a new ring gear in the differential.
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