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Old 05-18-2017, 08:08 AM   #301
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Originally Posted by EastCoastCB View Post
Right on, man. Keep up the good work!
I want you to drive my bus next time you're out this way. Just to compare.
sure thing! i want to drive that bus... you can test your modulator easily as find now from the driver seat..

get on flat ground
accelerate at very light throttle let it shift to second gear.. keep light throttle and let it upshift to 3rd...

now punch it and see if you can feel a definite downshift to 2nd and then a few MPH later you should feel a solid shift back to 3rd.

if you never get that downshift when you punch it soon after a light throttle upshift then that electric modulator is bad..

running with a bad modulator as it turns out shifts the transmission at full load with low line pressure.. resulting in extra heat.. and eventually burns up the transmission..

people tell me since my 545 doesnt yet slip that most likely I just need to replace the internal and external filters and id get some more life out of it.. that the clutch material from shifting like it has been most likely has clogged the pan filter...

something easy to check.. so yours will last!..

that electric modulator isnt cheap, before i junk my old trans I'll pull my new one off and give it to you so you can stuff it in a drawer in case you ever need one..
-Christopher
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Old 05-18-2017, 10:56 AM   #302
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Originally Posted by cadillackid View Post
that electric modulator isnt cheap, before i junk my old trans I'll pull my new one off and give it to you so you can stuff it in a drawer in case you ever need one..
I have heard of some people having electronic modulator problems going with a cable operated replacement. Basically its a retrofitted cable kit that attaches to the electronic throttle pedal and runs down to a new cable actuated modulator mounted where the old electronic one was...

I've actually read about a lawsuit that was buried by out of court settlement back in '99 that proved that allison knew that an on/off electronic modulator on a tranny designed to use a variable input cable operated modulator would destroy the tranny eventually. Allison Service Information Letter 21-TR-02 details this kit and issue...

Heres some pics of somebody who did it with an electronic CAT engine and a 545 trans.
https://www.flickr.com/photos/272657...57626289148399

-edit- it would seem that a shop up in Columbus, OH did the work
W.W. Williams in Columbus at (800) 336-6651
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Old 05-18-2017, 12:13 PM   #303
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Yeah ww Williams is now just a thermoking dealer. I read the same account of it on line the other day .

The issue with the electric modulator is it's not progressive, true modulation regulates lone pressure progressively , the electric is just on or off.
The cable is progressive similar to the old vacuum modulators on the gassers.
The issue came about on the electronic engines, namely the 3126 cat, the t444e, and the dt466E which have no throttle cable and iust an electric engine pedal. Allisons solution was an electric solenoid connected to the ECM. The ECM had a piss poor algorithm of turning on or off that solenoid which caused people to complain the trans hunted up and down constantly and would wear out the clutches prematurely.

The relay would go bad or the modulator itself and no one would really know because your trans would still work fine. Or seem to but under full load you are shifting under low pressure which makes for "slidey" shifts that are heating up the clutches and wearing them much faster than should be.. ever since I've had my bus it's never kicked down I didn't know why... now I do, it's all a learning experience and sharing of info is what I like to do so others can not have the same issues I did.
Christopher
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Old 05-18-2017, 12:31 PM   #304
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That's interesting. About a year ago there was extensive discussion on manually downshifting on hills, because some people's transmissions weren't downshifting on hills. Sounds like the same issue(s).
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Old 05-18-2017, 01:27 PM   #305
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That's interesting. About a year ago there was extensive discussion on manually downshifting on hills, because some people's transmissions weren't downshifting on hills. Sounds like the same issue(s).
part of it is that you cant downshift a transmission after a certain speed.. but yeah they should have some sort of kickdown..

the shift points of an AT545 are adjustable if you take the pan down, there are 3 shift point adjusters for the main shifts... I forget what the ratio of normal to modulated shift is supposed to be... it relates to output shaft speed not vehicle speed.. I dont know how much.. as wit ha 545 you cant tell from your tach because of the torque converter spin..
those valve body "solenoids.. {there are fluid mechanical solenoids, not electrical}" shift based on line pressures applied at ceertain points i nthe valve body... shaft speeds play a big part in what pressure is where..

the AT545 appears to be a pretty easy transmission to rebuild if you do nuke one and want to rebuild it yourself.. in fact its mainly just the clutch packs that go and a lot of cleaning of parts.. esp if it just gets tired..

one of the reasons for downshifting a transmission on hills.. esp an AT545 is that the larger the differential between torque converter input to torque converter output, the more power thats lost and more heat thats made.. if you leave a 545 oin 4th gear and you are punched and slowing down.. esp down to near where it had shifted to 4th you are heating up your fluid very quickly... plus you are lowering your engine RPM from the load.. as you lower your engine RPM you are lowering the internal Line pressure of the transmission which reduces the abilities of the clutch packs to hold in position... so the triple whammy of over-lugging an AT545...

1. torque converter spin wastes power and makes a ton of heat creates hot fluid
2. Hot fluid and reduced engine RPMs result in burnt fluid and low line pressure
3. low line pressures can result in clutch pack slippage which burns up the clutches, fluid, and bye bye transmission..

why is the modulator important? because it applies higher line pressure at various points in the transmission assuming high engine load.. wiothout that modulator if 1,2 or 3 have occured above it can be multiplied and burn it up.

somehow once again I hijacked a thread to talk technical...
OOPS!!!

-Christopher
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Old 05-18-2017, 02:46 PM   #306
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It's ok, CBs got a 545 too.
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Old 05-18-2017, 02:50 PM   #307
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I know and I want his to last! no one should ever nuke a transmission esp for a stupid reason that can be prevented.. let my "lack of knowledge" become someone else "gain of knowledge"...

for myself I kind of lookout for these things to happen as I put a ton of miles comparatively on my busses so im likely exposed to a lot of conditions others may not be.. theres only a few members here that are currently running their busses all over creation and back right now.. most are still in the buold stages.. and anything learned that can keep others from incurring breakdowns or expensive repairs is a win..
-Christopher
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Old 05-18-2017, 04:43 PM   #308
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Absolutely, and the information is appreciated. If I've perceivably given any other indication, it was not intended as such.

Meanwhile we fantasize about better transmissions, not unlike yourself. In your case with more road miles a better transmission is called for.

Considering the cost of the 545, economically it's the way to go for me. Relatively inexpensive to replace and found everywhere. The freewheeling characteristic at highway speeds is annoying but manageable. At low speeds in the mountains I seem to feel some resistance from the engine on downhill stretches. Once I changed my transmission fluid my 545 began downshifting much better.

I complain, because I'd like to have a 3060 with 6th unlocked. I'm not sure this 5.9 could take advantage of the gearing. I once again subscribe to the kiss theory. Keep it stock.
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Old 05-18-2017, 04:55 PM   #309
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So far my 545 seems GREAT, for the most part. For what it is, anyhow.
It downshifts fine, and the fluid looked brand new last I checked.
I just wana get my bus running REALLY cool. I'd love to upgrade to a 2000 series trans. But I may as well buy a rusty runner and rob it for parts. That'll have to wait. Painting this beast is gonna set me back a grand.
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Old 05-18-2017, 04:59 PM   #310
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the 545 isnt as bad transmission in my book.. ive logged wehatever 22 or 23k miles in the last 12 months between the 2 busses on 545s..

the red bus is more or less a toy for me and so it gets tinkered with and upgraded.. i fully believe the only reason im having any issue with my 545 is that myself and who knows how long at the school before me it was run with the bad modulator.. unless a driver specifically complained that they no longer had "kickdown" it never gets discovered.. because you go 1-2-3-4 just like normal.. heck i didnt know.. I knew i didnt have kickdown but thought "well it has this electronic doodad and not a cable anymore so it must act different than my other bus". im going to make a video with the modulator unplugged vs plugged in (i cant hurt the transmission any more than it is).. to show people how it should act vs not act.

-Christopher
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