There are a lot of bad side effects to this because if you change the tire size or R&P ratio the PSOM has to get reprogrammed to correct the speedo, however that will change the ratio between Output Shaft speed and Vehicle Speed, requiring the EEC-V to be flashed as well.
Thanks for the great INFO. I have just a few more questions.
First how does changing gear raitos effiect the pulses per mile, the tone ring is not changed with the gears or is it?
By taking the signal from the tranny output shaft, I neatly sidestep all of that. Even if I change the tires & gears, the EEC-V will be blissfully unaware and continue to base shifts on the output shaft speed (which is how the governor worked on the the older trannies, like the C6).
Second if you change the tire size or gear raito doesent the change the amout of drive line revlutions per mile?
Now if you measure the speed BEFORE the t-cases then guess what, you don't need the 4X4L signal and you don't need to account for the low range ratio because the computer DOESN'T SEE THE DIFFERENCE! This may take some deep thought for some to comprehend, but the engineering behind this approach is sound and it DOES WORK.
I like this idea.
Yep, the cleanest way is Superchips Custom Programming using their re-flasher. That way there are no extra things plugged into the PCM, it just goes into the internal flash memory just like the stock programming. The problem is cost -- at least $300. Since I don't need to change any other parameters (yet), I've found harware workarounds for the emmission issues. The downstream O2 is fixable with a $40 O2 sensor eliminator. The EGR works fine by changing the plug and using the EVP sensor instead. The EVAP could be solved easily by running a piece of 5/16" hose to the vapor bottle I already installed and is plumbed into the fuel tank vent. I have the new-stype EVAP valve already mounted and plugged in. Another alternative is to connect the EVAP up as an alternative air bypass around the throttle body, kinda like a second ISC/BPA valve. That would likely result in the idle change the EEC-V is looking for. The Misfire Sensor is the trickiest. I was planning on converting to EDIS-8 anyway (I have an "adapter" circuit prototyped that would make EDIS a direct replacement for TFI-IV without requiring a change to the EEC), so that's a good exuse to swap timing covers and install the Crank sensor and reluctor.
Great info please keep us posted if it works. Would you use the coil packs off a newer moduler motor?
Maybe. It would have to generate the 8k PPM signal the PCM wants, or you'd have to run it through a circuit to give you 8k PPM. Some GM cruise control sensors that install inline in the speedo cable are 8k PPM. These are usually found in early 80's GM cars and several Jeeps of that era with factory cruise.
This is the way Ford did it with a pulse generator driven off the speedo out put befor they put the sensor in the rear end.
You mean "F3" don't you? I have a set of those heads in the garage. Came off the the '96 motor that donated its wiring and computer. Will probably look into that as a swap, or a set of the Pro Topline heads that are supposed to be improved versions of the F3 heads.
Sorry my bad your right they are F3s. Tell me more about the Topline heads. Ive never herd of thease are they a factory casting copy or are they a preformance upgrade?
Thanks again for all the great info Leadmic