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Acts 2:38-39
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Discussion Starter #1
So, I am mulling over transmission options. The 545RFE actually isn't all that bad, but I'd like first a little lower since I have a 4.7L. So, the 66RFE has a 3.23 compared to the 545's 3.00 and the top gears are .625 and .67 respectively. It seems the cases are the same as well. The gears would let me run a shorter tire, like 275/55s or even something on 17s. And still keep the same highway gearing. Since the 66RFE was bolted up to 5.7Ls in the 2500s, I figure it will bolt up to my 4.7. The things I wonder about are the electronic controls...
I have not looked at a 2500 manual to see what all is involved. If it won't work, I may stick with the auto or look at a stick. Not really interested in a new $40k pickup truck.
Thanks in advance.
 

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Red Trucker
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It may actually bolt in, but what you fail to realize...the "FE" part of "RFE" (Fully Electronic) lol. The RFE is capable of a calculated like 15 fwd speeds and 3 reverse (give or take), all controlled by programming. The minute you plug it into your truck, it'll become a 545, since your PCM will be the governing computer.
 

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Discussion Starter #3
That wouldn't be so good. I have heard the 545RFE is capable of more than the speeds it currently has; but I cannot seem to find information on that. Any idea where that may be posted?
So, it follows if the correct relays or solenoids were energized or de-energized like these 2500s with 66RFEs, then the 545 should use those 66 gears?

Mmmm, 3 reverse gears. That could be entertaining!
 

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Red Trucker
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That wouldn't be so good. I have heard the 545RFE is capable of more than the speeds it currently has; but I cannot seem to find information on that. Any idea where that may be posted?
So, it follows if the correct relays or solenoids were energized or de-energized like these 2500s with 66RFEs, then the 545 should use those 66 gears?

Mmmm, 3 reverse gears. That could be entertaining!
Someone on a forum calculated it out years ago. It was turned into a 6sp for a while by placing 2 prime in between 2nd and 3rd (but only accessible by autostick/manual shifting).

You're missing the point. The 66RFE is a 4th gen transmission option, meaning it is controlled by that specific controller. You cannot reprogram your PCM (which is specifically programmed for your 4.7 and 545RFE) to magically unlock extra gears (or people would've done this YEARS ago). Conversely you cannot use the 4th gen PCM in your 3rd gen. So I'll say it again, the minute you plug it in to your truck, it WILL become a 545 because that is the computer controlling it. The only way possible around this would be a standalone controller and you'd have to figure out how to integrate it into your truck so everything worked correctly and there were no CEL's, etc. It would be easier to retrofit an 8HP70 to it.
 

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Discussion Starter #5
I see what you are saying. I figured I could cut/splice some wiring and force it to change the shifting sequence.

I looked up 8HP70s; used they aren't too bad on price. Even found a new one for about $2k. I thought that it would need a separate TCM, but according to this forum thread, the TCM is integrated inside the 8HP70: https://www.**************/archive/index.php/t-165247.html This is at r a m f o r u m s . c o m/archive/index.php/t-165247.html in case the link gets deleted when I post my reply.

Although, I'd still need bits from inside for the control knob and such.

Might be just as easy to stuff a G238 in; I already did all the math on that...
 

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Red Trucker
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I see what you are saying. I figured I could cut/splice some wiring and force it to change the shifting sequence.

I looked up 8HP70s; used they aren't too bad on price. Even found a new one for about $2k. I thought that it would need a separate TCM, but according to this forum thread, the TCM is integrated inside the 8HP70: https://www.**************/archive/index.php/t-165247.html This is at r a m f o r u m s . c o m/archive/index.php/t-165247.html in case the link gets deleted when I post my reply.

Although, I'd still need bits from inside for the control knob and such.

Might be just as easy to stuff a G238 in; I already did all the math on that...
Correct, TCM is inside the ZF trans. I talked to the guy that figured out how to do it, harness is $1000 (since the TCM is inside the trans it requires a special harness with it's own OBD port to access/program it), transmissions can be had as low as $600 that I've seen, custom driveshaft; the bitch is it has to use the car style floor shifter. This isn't a big deal for me as I've converted mine to floor shift already. Once installed, just some parameters tuning set by HP tuners and off ya go.
 
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