PCM relearning or Trans Probs????

[twintips_17]

So I reprogrammed my truck to stock today to sell my edge and it is acting way differently. I know that’s kind of weird. I know I’m not having the shifts or power of the edge. I’m talking about a weird down shift.....

I will be driving at a constant speed and then let of the gas to coast and after a couple of seconds it drops about 500 rpms and the engine is being used as a brake. I have never seen this before and my other screw doesn't do it and it is stock.

I would bet it is just the PCM relearning itself but something has me scared deep inside. :cry-blow:

Any thoughts.....:help:

[blackfx4ny]

What speed do you notice this at? Or does it happen any time you begin to coast? I have the canned tunes but my torque converter is set to lock up at 40. If I coast down from 42 the converter unlocks at 40 and I notice that sometimes. I do know when it locks I notice a drop of about 3-500 rpm, maybe the unlocking causes the gain in rpm. This is a complete shot in the dark and I am probably way off. I do hope it's something simple though. Problems are never good, especially going into a weekend.

[twintips_17]

What speed do you notice this at? Or does it happen any time you begin to coast? I have the canned tunes but my torque converter is set to lock up at 40. If I coast down from 42 the converter unlocks at 40 and I notice that sometimes. I do know when it locks I notice a drop of about 3-500 rpm, maybe the unlocking causes the gain in rpm. This is a complete shot in the dark and I am probably way off. I do hope it's something simple though. Problems are never good, especially going into a weekend.

It happens at all speeds between 20-65. Everytime the torque converter unlocks it will cuase a jump in rpm's by about 300-500. I drove it a bit tonight and it is not happening as much. But it still does.

[blackfx4ny]

I'll bet you were right in thinking the computer was relearning shift strategies, that sounds right to me. Maybe the Mad Doctor can shed some light on this and we'll both learn more about it.

[Power Hungry]

On deceleration, any time the RPMs drop it is usually a sign the converter is unlocking and allowing the vehicle to coast without feeding back into the engine. If the converter is locked, the RPMs should be higher.

This can be verified on the Gryphon by selecting "COMM GEAR" from the Display Setup and monitoring what the "LOCK" symbol does when the RPMs change.

In any event, I don't think it sounds like a problem. However, keep us posted as to what you find and we can make a better decision once we have a little more information.

[SinCityFX4]

Mine did this with my VMP tunes until I asked Justin to modify the TQ converter...he raised the lockup point for 3rd and 4th. Problem gone...

The TQ converter settings seem to be a very preferential setting....much like the shift firmness...

Do you get requests to alter those settings alot Bill?

[twintips_17]

On deceleration, any time the RPMs drop it is usually a sign the converter is unlocking and allowing the vehicle to coast without feeding back into the engine. If the converter is locked, the RPMs should be higher.

This can be verified on the Gryphon by selecting "COMM GEAR" from the Display Setup and monitoring what the "LOCK" symbol does when the RPMs change.

In any event, I don't think it sounds like a problem. However, keep us posted as to what you find and we can make a better decision once we have a little more information.

Will i be able to moitor this with my 02 when i get my gryphon? I thought that was only an option on the 04+'s???

[Power Hungry]

SC,

I get those requests from time to time and am constantly in search of the "ideal" converter strategies. As you said, it is such a subjective and preferential parameter. What works for you may not be good for someone else.

TT,

:doh: Forgot that you had an 02. Unfortunately, I don't have COMM GEAR in that code. The gear shouldn't be an issue, but I'll have to check and see what is available for monitoring converter lock.

[Jackpine]

So, Twintips, back to your original post and the Mad Doctor's insightful response, it sounds like your torque converter is unlocking when you let up on the gas to coast and the engine is NOT braking you. That's exactly what mine does by the way. I've sort of gotten used to it by now.

If it really bothers you, I imagine Bill can try to tweak your custom tune, when you get it, to minimize this behavior.

- Jack

[twintips_17]

So, Twintips, back to your original post and the Mad Doctor's insightful response, it sounds like your torque converter is unlocking when you let up on the gas to coast and the engine is NOT braking you. That's exactly what mine does by the way. I've sort of gotten used to it by now.

If it really bothers you, I imagine Bill can try to tweak your custom tune, when you get it, to minimize this behavior.

- Jack

Kind of the opposite. The engine is breaking me significantly. I have used jake brakes in the past and it feels real similar to that. It only lasts a couple of seconds then it goes right back to normal. Im guna drive it a bit more today and hopefully i will be able to update.

[Jackpine]

Kind of the opposite. The engine is breaking me significantly. I have used jake brakes in the past and it feels real similar to that. It only lasts a couple of seconds then it goes right back to normal. Im guna drive it a bit more today and hopefully i will be able to update.

This is confusing! It sounds like your torque converter is unlocked before you release the accelerator and then it locks! This is really the only way you'd get significant engine braking in my opinion and the only way you'd get a noticeable "lurch". It seems exactly opposite to what I observe on my truck.

- Jack

[twintips_17]

Well......

I just drove my truck again and i didn't notice it at all. I have put about 55 miles on my truck since i reprogrammed it back to stock.

I have chocked it up to relearning.

I hope i am right......:shrug: