Downshifting pointers needed

***907DAVE*** · #1 Wed, May 12th, 2010, 12:23 AM

I am experiencing a similar issue with my 4-3 downshift, I was going to try and tackle this issue when I get the emulator. I feel you pain when trying to fine tune things with no real progress.

Not trying to sound to dumb here........have you tried backing down the 4-3 shift pressure?

Pocket · #2 Wed, May 12th, 2010, 09:29 AM

Quote:

Originally Posted by 907dave

I am experiencing a similar issue with my 4-3 downshift, I was going to try and tackle this issue when I get the emulator. I feel you pain when trying to fine tune things with no real progress.

Not trying to sound to dumb here........have you tried backing down the 4-3 shift pressure?

I could try that. It's set at whatever stock is.

***907DAVE*** · #3 Wed, May 12th, 2010, 12:00 PM

Another thing worth trying is the parameter Downshift Slope into 3rd.

I do not know what this will do but might be worth a shot.

GTS · #4 Mon, December 13th, 2010, 01:05 PM

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?

Pocket · #5 Tue, December 14th, 2010, 12:41 PM

Quote:

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*** · #6 Tue, December 14th, 2010, 01:06 PM

Quote:

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 · #7 Tue, December 14th, 2010, 03:04 PM

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 · #8 Tue, December 14th, 2010, 07:31 PM

Quote:

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.