Shifting problem>>Tuning

I recently swapped a 97 pcm into my 96 Camaro and did a few things. The only thing I change by way of shifting was taking the shift durations down to .2. I was getting a problem of a "double shift" at 2-3 but we worked it out. It shifts fine at any variation of partial throttle, and shifts great at WOT except in the following cases:

When accelerating normally to anything below 20mph, and flooring it at that point, it shifts down quickly and goes through the gears just fine. Now, if you accelerate normally to ~25 -+4-5, and floor it, it down shifts just fine and goes on it's way to 2nd, but when it hits shift point, the acceleration stops, and the engine sounds as if it's bouncing off the rev limiter. If I floor it at ~25, then take my foot off the gas just slightly, it will make the 1>2 shift just fine.

When accelerating normally to ~30- ~35, if you floor it at this point, the engine rpms sound as if it down shifted normally, but the acceleration is very mild for a about a second, and then it grabs and goes off just fine. If I push the pedal just shy of WOT, it down shifts normally.

any ideas?

Anybody??

Post your tune.

I don't have access to it at this time, but it's basically a stock tune with a few codes removed, lowered shift durations and I changed the mph for 1st to 2nd shift to get rid of the double shift I was experiencing.

I'll try to get a copy of the tune and post it up here tomorrow or Sunday.

Did you do anything with the torque management?

Yeah, I disabled it by instructions from another much more experienced tuner. Could I have messed something up in there that caused this?

here is my tune..

http://www.freewebs.com/lookingbacko...oyfeb2dtcs.hpt

Could you post the stock tune? What gear ratio & tires sizes are on the car?

Russ Kemp

A few things I see right off the bat,

Your tune has WAY more torque reduction then a stock 98 V6 tune.

Your tune says you have a 3.42 gear in your rear with 24.9" tires is this true?
If you don't have 3.42's this could be your problem.

You have lower shift pressures than a stock 98 tune.

Russ will see allot more then I do. He writes the guides everyone learns from.

I have 3.42s and 245/50/16 tires that I took .2" off for tire crush.

I used a tune off this site that said it was stock. Could it have been messed up to begin with?

What should the shift pressures be at? That was one of the things I changed but we had a problem and had to redo everything, we might have missed that step.

My tune has more torque reduction than stock? I thought I disabled it?

Try this trans tune out. The F-Body cars use 24.9 as the tire diameter, even though the advertised diameter is actually 25.7". I increased the shift pressure table, note that if you don't have a performance shift button, only the normal shift tables are used. I also set up the torque reduction table, the force motor table, shift speed & TCC lock up speed tables.

You had the traction control tables set up to cut torque at 0 ft lbs torque. I set it up to 400 ft lbs.

I don't know all the differences between the 1996 & 1997 4L60E transmissions, so there may still be some calibration differences.

Russ Kemp

Thank you sir! I will try that one out. I'll have to arrange a meeting with my tuner and I'll get back to you on the results! Thanks again.

This is the stock tune out of my 98. Compare it to what was in your car. You should be good with what Russ sent you.

Thanks again Brain, and Russ for the tune. I finally had a chance to load it in, and it's definitely an improvement and I feel the extra torque through the rpms. But it's not perfect. When I floor it from 20ish now, when it's ready to shift, where it used to bounce of the limiter, it seems to instead hit the limiter and "bounce" down into the next gear. But it does shift, just takes about twice as long as a normal shift and is rough.. Flooring it from a stop is still just fine through all gears. WOT from 30-35 still slips for a good second or two before it grabs 2nd.

ideas?

I would try setting your WOT shift speed to match your part throttle shift speed at 100%. Looks like you might want to copy the part throttle shift and apply to the WOT speeds....just an idea...

Looks like the problem isn't the tune, it's the PCM.. I loaded an entirely stock tune onto the PCM, and it still bounced off the rev limiter before shifting into 3rd if you do WOT from 3rd gear @ ~30. I'll note though, that it doesn't slip into 2nd anymore. Stock 96 pcm has no shifting problems whatsoever.


Unfortunately that means not only buying a new PCM, but another set of credits to unlock the new PCM.

The thing is though, the tune Russ gave me worked better than the others. It would bounce once off the limiter just once, then jam into 3rd, instead of just sitting there bouncing.

When I put the thing in originally, I was getting a double shift type thing, and we solved that with some MPH modification, but it still does this ^^ which I guess you could almost call a double shift. Do you think changing the MPH more might help at all?