I currently have PCMforLess tuning on my car with stock shift points. My transmission recently went out and I bought one that came out of a 94 Z28. It was only in for about 2 months before it crapped out. But when it was in and with the same program as before and now with a 3000 TCI lock-up converter, the car wouldn't shift until around 6200 rpms. I spoke to the guy who is rebuilding my tranny this time (not the same as the other) and he said the PCM should be the only thing other than a gear swap based on the mods I told him which are the basic bolt-ons. The tranny that is going back in is my stock one and I'm wondering if the tranny is going to be shifting right. I believe this is the correct forum for this. Thanks in advance for any info.

 

It could depend on alot of variables, the PCM is programmed to shift at certain point for a given combination. If the engine makes for hp than the orginal that the PCM was programmed for, shift points could change...if the Main Line Pressures were changed in the new tranny compared to what they were physically set at in the old tranny, shift points could change.
The computer just instructs the tranny when to open valves and actuators and other electronic parts in the tranny, it may take a few moment for that instructed change to take place. For example, if the Main line pressure, MLP, is lower now in the new tranny, it will take it long to lock the clutches to shift gears, in those few moments longer that it takes, your engine will rev to higher rpms.
When I installed my LT4 in my truck, I left all of the tranny settings the same in the PCM as compared to what they were in the old PCM....the new motor produced alot more hp than the old one, and it would shift at about 5500-6k rpms with it not even floored, although the shift points were set at certain mph/tps settings just as they were originally. In order to compensate, I raised the MLP settings and brought the WOT rpm shift points down, now it shifts fine at around 2500-3500 rpms depending on what TPS is reading, and WOT shifts at 5200rpms.

So if nothing changed in the PCM and the motor was the same, I would guess that the MLP settings were different in the new tranny. The MLP can be adjusted physically inside the tranny, and they can also be controlled in the PCM on LT1/LS1s to a certain extent, raising them too much in the PCM could cause the electronic pressure controller in thetranny to prematurely wear out. I'd saying nothing more than 90-100 or so in the PCM for MLP settings, there a table for MLP vs TPS in the PCM.

 

Thanks man, that was very informative.

 

The transmissions are different between the 94 and 95. The two have different transmission tables to reflect the differences. Using the trans tables for a 94 on a 95 or vice versa is not going to make the transmission last long. That's probably why your 94 trans died in 2 months.

 

There are some physical differences in the 94 and 95 f-body trannies, such as the TCC solenoid is pulsewidth modulated from the PCM to control how hard the TCC is locked on a '95. You'll notice a difference in the # of wires on the tranny wiring harness, a '95 has more. I used a '95 PCM and wiring harness on my truck, which is a '94 with a '94 4L60E tranny. It kept throwing tranny codes, then realizing there was a difference in the # of wires, but the pin outs were the same for the wires that were in common with the original '94 harness, I re-flashed the PCM with a '94 A4 program, and all codes went away. As far as the MLP, shift points and TCC lockup settings, there was no major difference in the '94 and '95 tranny settings in the PCM though, but I had to alter all of them anyway since it was longer in a light f-body vehicle so it didnt shift worth a crap for a heavier vehicle that is geared differently than a f-body.....as far as how long it will last...not sure, its only been in there for about 5k miles but so far so good...I'm sure I'll toast the tranny sooner or later with almost twice the hp it was meant for