Downshifting pointers needed

[Pocket]

Originally Posted by GTS

What transmission are you running? Could it be the way the hard parts are set up in the transmission? Orifice size for the TC lockup, valve body set up etc?

I got it figured out a while back. It wasn't a transmission issue (I'm running a BTS), it was simply tuning. I had some pressures that were higher than stock, and on the 4-3 downshift it would slam hard. Knocked down the pressures, increased the delay slightly, and afterwards I could barely feel it.

Funny part is, after all that effort, I don't even use the downshifting anymore. My shift strategy is very close to stock now. Before I had a problem with too much fuel at lower RPM's, so my shift strategy was designed to keep the RPM's up. Now I don't have the fueling problem, so I don't care about lower RPM's as much. Besides, with the amount of fueling I'm throwing at lower RPM's and lower throttle position, it takes quite a bit of throttle movement just to get the fueling up. At that point, the PCM is already commanding a downshift. So then my RPM's catch up, I don't get a lugging engine, I don't get black smoke, and my fueling kicks in at that point.

Problem solved on my end, and the truck drives and shifts like a dream. I can always tell if my tuning and shifting is spot on when my wife comments about how well it drives.

[907DAVE]

Originally Posted by Pocket

Before I had a problem with too much fuel at lower RPM's, so my shift strategy was designed to keep the RPM's up. Now I don't have the fueling problem, so I don't care about lower RPM's as much. Besides, with the amount of fueling I'm throwing at lower RPM's and lower throttle position, it takes quite a bit of throttle movement just to get the fueling up. At that point, the PCM is already commanding a downshift. So then my RPM's catch up, I don't get a lugging engine, I don't get black smoke, and my fueling kicks in at that point.

Very nice Curtis!

That actually took me quite a bit of time to get dialed in........in all situations.

[GTS]

Cool. Glad to hear you got it resolved and a bit on how you did it. Just curius what gearing and tire size are you running? I'm kind of looking to do what you did as my gearing is very tall so a light roll in results in black smoke before it'll down shift. I'm thinking of dialing in the fuel to start ramping up at the rpm that actually starts seeing some decent boost. Which with my gearing is a bit higher in the speed range. I'm looking to do this especially in my DD tunes where I don't care so much about power as I do no smoke and mileage.

[Pocket]

Originally Posted by 907dave

Very nice Curtis!

That actually took me quite a bit of time to get dialed in........in all situations.

You saw some of my earlier versions a few months back. Since then I've really been dialing it in nicely.

Last week I had a chance to try my newest configurations in the mountains. As a test, I switched back and forth between my tuning and stock. My tunes ran slightly lower EGT's while climbing a mountain pass, and were quieter. Even in stock form I could hear a slight timing rattle. In my tunes, there is no rattle.

Smoke is nearly identical between stock and my tunes while driving up a mountain pass at 10K feet. I'm stoked that it's working. Shifting worked exactly as I wanted it to also.

Next step is taking in for dyno runs and emissions testing. I want a 350 hp tune on stock sticks that passes emissions.

[Pocket]

Originally Posted by GTS

Cool. Glad to hear you got it resolved and a bit on how you did it. Just curius what gearing and tire size are you running?

I'm running 36" tires with 4.30 gears. It's almost identical to stock in regards to speed vs. RPM's.

My truck came stock with 265/75r16's and 3.73's. In stock form, my truck would see 2000 RPM's at 70 mph. With my current setup, I see 2000 RPM's at 69 mph, so it's very close.

Originally Posted by GTS

I'm kind of looking to do what you did as my gearing is very tall so a light roll in results in black smoke before it'll down shift. I'm thinking of dialing in the fuel to start ramping up at the rpm that actually starts seeing some decent boost. Which with my gearing is a bit higher in the speed range. I'm looking to do this especially in my DD tunes where I don't care so much about power as I do no smoke and mileage.

Well, I did the opposite of what you are planning. Only because I struggled with the exact same thing for a long time, and finally took a different approach. For me, it's not the tires or gearing, it's the altitude. So it made my learning curve pretty tough to figure out fueling, smoke control, egt's, etc.

If you want, I can shoot you an email with some screen shots. I see you posted your email addy in the other thread. Would you be ok with me shooting you a message? I'd be glad to help you out.

[GTS]

At this point in time I'll accept any help I can get! I've been messing with the software for a few days now but haven't really done much as far as putting a tune together. More just moving things around and familiarizing myself with how it all works. Thanks so much for your input and willingness to help!

[Pocket]

You have mail!

[GTS]

Thank you so much you guys for your e-mails. I've been spending WAY to much time on this stuff lately! I'm just so excited to get going on this tuning! I'm looking over your guys' e-mail now though I REALLY need to be getting to bed! It's almost 2:00 in the morning and I need to get up around 7!

[2006nytro]

ok got a question didnt see a need to start a new thread. when tuneing a trans whats the main things you use to adjust it.

is it rpm vs speed? i would think thats most of it? and is it you set a sertan shift point how does the trans know to shift difrent say at WOT,or just creeping up speed slow? is it a calculation the pcm makes?

[907DAVE]

Shifting is determined by comparing APP (pedal position) and MPH.

So basically the harder you press the go pedal - the longer it will take to shift. When you are WOT, it will shift at a preset maximum RPM - which you can change.

If you want to adjust the quickness/firmness of a shift there is a whole slew of different ways to do it.