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Old 01-06-2017, 11:42 PM   #1
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12v fuel plate & Allison AT545

I'm in need some opinions, I'm repowering my Bookie & got a 1994 160hp Cummins & Allison at545 from a BlueBird flatnose. Technically, the Allison is only rated for 235hp & 455 ft/lbs torque. I want to turn the engine up with a fuel plate, 3k governor springs, boost elbow & guages. I've never messed with an auto behind the Cummins, how much power could I really throw at it? I'd hope for 300hp & 650 ft/lbs torque. Will this be possible without smoking that trans??
I love my #10 fuel plate in my 98 ram 5 SP, but seems like it would be underpowered with the smaller 160 injector put on the 94 industrial engine. Would a #8 or 6 be to hot let me know what you think. Thanks!
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Old 01-06-2017, 11:49 PM   #2
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Accidentally double posted. Mods, please delete.
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Old 01-07-2017, 06:56 AM   #3
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the 545 very well may have issues with that klind of horsepower.. esp since you are likely wanting to run that cummins at low RPM.. the 545 doesnt reach full line pressure till above 2000 RPM.. and with No lockup converter its not something I would use in a repowering scenerio. unless its just temporary till the wallet can afford a better option...

that said I had an old Gasser Bluebird bus with a 454 chevy and a 545... I dont know my exact HP on that 454 but I did build it up a bit.. intake / cam / valve springs / 4 bbl carb.. so im guessing I was north of 300 HP in that and didnt blow up the tranny.. but it was also a short bus so maybe the fact the bus got up to speed quick saved the transmission...

I have 2 busses now with AT545s and they are fine but definitely like to let the engine rev up, so im not sure that even without power a 545 is a good fit for a Cummins that you may build to run lower RPMs..

if you could get yourself a 1000 or 2000 series im thinking you'd have much better luck.. plus gain overdrive and a lockup converter..

-Christopher
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Old 01-07-2017, 07:31 AM   #4
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what he said.

i have a 190 hp cummins 12v. and i've ruled out any mods with the exception of sliding the fuel plate forward. that alone should put me at the limit of the AT545.

imo new governor springs would be the death of my old cummins.

just curious, but what does a 160hp repower cost? i see new around $10k just for the motor.
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Old 01-07-2017, 07:51 AM   #5
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Turf,
I purchased the 94 BlueBird for $2300. I expect to spend about $1000 in Upgrades/gaskets, replace killer Dow pin, etc.
I think the 3k governor springs will be a big improvement for the the Allison behind it to build line pressure. Stock, a Cummins defuels between 22-2400rpm. I think the 4000 springs would be a bit much though.
Random thought.....My build is a 74 international bookmobile. It currently has an international 345 gas with an Allison of some sort behind it. Any idea what model Allison it would be & if it's stouter than the 545, would it bolt behind the Cummins without an adapter kit? Heck, maybe the trans out of the 94 BlueBird isn't even a 545, would that be the common one in a 72 passenger flat nose? It seems strong & shifts well. I was told thats what it was, but don't know enough about autos to identify myself. Are there marks on the housing to identify?
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Old 01-07-2017, 08:46 AM   #6
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There should be a data plate on the driver's side of the transmission case. It will have the model and serial number on it.

IMHO the AT540 transmission is a great transmission for what it is. But for longevity 210 HP is pretty much the top end for them. Any more than that you will be living on borrowed time.

The AT540 used behind an IHC SV345 will look basically the same on the outside to the AT540 used behind a Cummins 5.9L. The difference is on the inside. It will have totally different governor settings that will cause the transmission to shift at different points. It will also have a different kind of throttle modulator because the gas engine uses vacuum and the diesel doesn't.

Your '74 could possibly have an MT640 transmission. Like the AT540 behind a gas engine it will have different governor settings and throttle modulator as well.

It has been so long that I don't recall what sort of bell housings the different transmissions use. IIRC, the IHC gas engines had an SAE I or II pattern that is the same as the Cummins 5.9L. IIRC the 5.9L came with different patterns and could be had with either a I or a II.
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Old 01-07-2017, 08:47 AM   #7
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Look on the right side of the tranny for the data plate.Can you explain these 3k springs? Very interesting reading.
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Old 01-07-2017, 08:47 AM   #8
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there a thread on here that shows the differece between the at545 and mt643. those are the 2 most commonly found transmissions on the older ones. if its a 5.9 i'd almost expect the AT545, if its and 8.3L its probably the mt643.

http://www.skoolie.net/forums/f33/ho...pecs-1641.html

the at 545 gets a bad rap. its a work horse. we are just close to the hp limit of it.the more you can do to take care of it, the better it treats you. i added an oil cooler to mine and the result was like adding a turbo charger.... it just ran better.

modding a bus and modding the ram truck are 2 different bears. imo, turning the screw up much with the at545 transission would kill it.

i pull a trailer with my bus, and it does it just fine. I'm in colorado so my trips are pretty much just hill climbs.

the governor springs swap is the most cost effective way to get more top speed. but when i'm in the bus, towing, i'm 24K lbs. and getting that mess going much faster than the 70ish it can will get you into trouble quick. for the 5 years of ownership, I got used to going a bit slower. i'm not the slowest on the road, i can still pass a jeep if its towing something.

if you want more power, you should started with it. get an 8.3cummins with the mt643. thats cheaper than beefing up a 5.9. most mechanics will decline modding a diesel, just for the shortened longevity of the engine. these are things we got to do at home. so its an at your own risk, from a shop.

a year ago i played with the idea of swapping up to an mt 643. but its not a straight swap. its a different bolt pattern, its a bit longer, but if you have the ability to do it, its possible. the thing that scared me away from the swap was top speed. it wasn't going to change with a trans swap. swapping a 4 speed for a 4 speed with the same final drive ratio doesn't gain any speed. the cost/benefit isn't there for me.

maybe the 3k springs wouldn't be to hard on it. i'd like to see you do it first!

there are not to many threads of diesel bus mods. one by a guy named lapeer - i think he slid the fuel plate and was happy. that's the only thread i know of. i was really surprised by the improvement from my oil cooler.

i have a high mileage cummins, 300K+, and it got that way just the way it is.
fwiw
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Old 01-07-2017, 11:35 AM   #9
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Versatile,
The 3k/4k governor springs will increase the rpm which the pump begins to defuel. A stock pump starts loosing fuel(power) around 2200-2400rpm. To gain top end power, changing the spring will allow for greater fuel at high rpms. The higher you go though, the more twitchy the throttle is. It can add a lot of performance, without adding much power, it just makes top end power more usable.
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Old 01-07-2017, 11:48 AM   #10
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IMHO at 300 hp you'll be driving over your trans internals the minute you hit a long hill and put your foot into it. At the very least you're going to need a big trans cooler, TranSynd, and a fair bit of luck to survive.

I'm also not sure what you can really do with the extra 800 rpm. The only time you can use it will be in top gear unless you change the shift points. In a MT653 this can be done by dropping the pan and twiddling the springs on the shift valves, but to my knowledge the 545 does not have this ability. Its "programmed" with an oriface plate instead.

You're also going to want a different torque converter. A torque converter that works fine at 170 hp is likely to be mush at 300 hp. I dont think you could stick enough converter into a 545 to really make it work right. That would be a good question for Allison.

I'd consider a swap to a 653 or something else made from more metal. With 300 hp you could definitely benefit from something with an overdrive!

Whatever you do, please post your mischief. I'd like to eaveswatch this and learn from it.
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