What's the difference in an 1228747 & a 1227747 ecm?

I know they are very similar, but how much?

 

Do you mean 1228746 vs 1227747.

As far as I know there is no 1228747

 

http://www.tunercat.com/tnr_desc/do_tc.html

8747 is the H/D 5.7 and 7.4 truck ecm.
It has 1 main VE table, no adder, but other than that, it's really similar to the 7747. The VE doesn't go up very high because the H/D 5.7 made LESS hp than the normal duty 5.7 and the 7.4 wasn't breathing too healthy even in the 454SS.
I've tuned a 454SS that's had 2 engines. I used the 8747 that was original for the original engine but have since gone to the 7747 to keep it tame on the streets. This new fire breather is over 600ft-lbs of torque and still TBI . The only reason for the switch was to have access to all those little things in a tune that make all the difference in the world.
I have one sitting at home collecting dust. Thinking about making it romless.

 

Try a 7060, and you'll then see what a TBI can really do. I say 7060, since I've used it, but probably any of the later P4 series of truck TBIs are as good.

 

Thanks for the replies.
Reason I ask is that I recently purchased an Autoprom and am doing a lot of research before I get started. I find very little info on the 8747 but quite a bit on the 7747.
Grumpy, dowm the road I'll probably convert to a 7060. That ecm was stock in the 91-93 454ss and has 8192 baud & 4l80E control.

 

My G20 is getting a 4L80E down the road as well. I have about killed the current 700r4s clutch packs, very noticeable slip going into 3rd gear when towing a load.

 

I've had the boxes full of suspension parts, a 472 caddie enigne, SVO engine, AL Cleveland Engine, several sets of heads, car, and trailer, and now have 120,000 miles on mine, and the fluid is still cherry red, and smells like new. I spent more time working on the tranny calibration then on the engine.

It's amazing how you can taylor the tranny stuff to your driving style, and loads that you carry.

The only warning I have on the tranny stuff is watch the %TPS to unlock the converter. A full load, into a strong head wind when you're trying to make time, might mean not having the converter lock. And, MPG stinks in that scenario!!.

 

I think the 8747 and 7747 have either different pinouts, or different memcal locations.

 

I bet it would but I haven't had the chance to tune a 454 with a pcm yet, just small blocks. Besides, I had the 7747 and this guy I'm working with is only interested in getting the lowest ET. His shift kit is so hard that it chirps the tires with just the lightest bit of throttle... it's just a crazy truck and I'm hoping he doesn't crash it when it rains. He's lucky if he gets 8mpg average!
On vacation these past 2 weeks I played with the suburban's transmission settings exclusively and was well rewarded. The shifting has been reduced, picked up almost 3mpg average and raised the shifting point at WOT. It was shifting at such a low RPM with the sbc. I know the motor is weak but with a little tweaking my stopwath knocked 1.8 seconds off the 0-60 by delaying the shift from 1-2 . Left the 3-4 and 4-3 stuff alone since it was near perfect (as far as feel). And this was all done without a scanner hooked up. Just a deiverse excel spreadsheet setup for the suburban only. I've got it showing the RPM that the shift occurs instead of MPH... only thing I haven't gotten a good feel for is the downshifting. That stuff is HARD to visualize. I have to keep imagining the truck going up a huge incline which then makes me think more throttle... AAHHHH too much . Next time out I'll have my scanner and we'll work on the timing tables. I'd like to knock a little more time off the 0-60 and keep the gas mileage the same. I've gone and rambled on, sorry. I just got back from vacation and have nothing to do tonight .

 

Could you interchange the PCMs?

I have an extra 7747 but my car is a 8746, it would be sweet to have a back up PCM.