I've recently bought a 95 GMC Yukon with a BJYL PCM $0D bin and I've been doing a bit of driving and data logging.
One of the annoying charaterristics the truck has is to hold onto 4th gear as I moderatly accelerate from 40 MPH to 60 MPH up an onramp. The engine is lugging and goes better if I manually change from "D" to "3" as it goes up the onramp, is there something I can change in TunerPro that will make the trans downshift from 4th to 3rd sooner as the MAP and throttle position go up?
Change TPS to enable kickdown mode to about 80% and Change TPS to disable kickdown mode to 70-75%. Moving them down more will cause it to downshift even earlier.
-1999 Hugger Orange SS, LS2 402 T56, 9 inch Ford 3.90 gears, Tuned with HP Tuners
-2002 Cavalier, Tuned with HP Tuners
-1994 Full Size Blazer ,383 TBI 4L60E, 4.10's, Tuned with Tunerpro RT (Where it all began)
There should be a shift table using speed vs %TPS. Modify it to change the shifting.
What I have done before. Manually select each gear and then use 5% to 10% TPS increments and determine the steady speed the truck drives for each throttle position. Take that data and add about 5% to the TPS values and use it to create the upshift curve. Add about 10% to the %TPS values and use it to create the downshift curve.
Example
30% TPS in 2nd gear = 40mph.
Enter 40mph @ 35% TPS for the 2-3 up shift.
Enter 40mph @ 40% TPS for the 3-2 down shift.
If you are driving 40mph in 2nd and over 35% TPS you are accelerating so stay in 2nd. If you are driving 40mph in 3rd and press the throttle over 40% then downshift to 2nd and accelerate. If you are driving 40mph in 2nd and let off under 35% TPS then you're going a steady speed so shift to 3rd.
Once you start the above, you might find you "pull back" the curves to be less than the 5% spreads to get even more response or "push out" to get less response.
You could also download some stock LT1 Corvette and Camaro bins. Compare the transmission shift points to yours. The old LT1 Corvettes had some pretty aggressive transmission shift points. Even more aggressive than the LS1 Vettes did.
-1999 Hugger Orange SS, LS2 402 T56, 9 inch Ford 3.90 gears, Tuned with HP Tuners
-2002 Cavalier, Tuned with HP Tuners
-1994 Full Size Blazer ,383 TBI 4L60E, 4.10's, Tuned with Tunerpro RT (Where it all began)
Thanks for the reply's, you've given me some things to have a look and hopefully try out over the weekend. Any idea what the shift table might be called in TunerPro, I had a quick look but couldn't find anything that looked quite right?
I also had a look at Bluecat transmission software but I couldn't find a tutorial that showed me how to use it, I'm guessing it's a quicker way to modify the shift table.
Bluecat is very straight forward. Hover over the parameters and it has an explination of what it does. Been using it for a few years here.Originally Posted by Kitch
Hi Fast, is there somewhere I can find some good starting values to input into Torque converter table for my 1995 Yukon and can you recommend a good tutorial on how to best use the Bluecat trans table generator?
Are the tables that I've shown the best ones to adjust in TunerPro?
96lt4c4, are these the kickdown scalars you were referring to?
I had a feeling I'd previously adjusted the kickdown TPS% on my 1994 G20 van's modified BDTZ.bin and the "TPS to Enable Kickdown Mode" was set to 64.8% and the "TPS to Disable Kickdown Mode" was set to 60.2%.
The big table on the left is the one I'm referring to. Plot that table in another program that displays each column as a line because the way Tunerpro displays it will likely be useless.
Here is the table I started with and what I ended with. See how I made the new curves roll up quickly and kept the up and down shift curves fairly close to each other.
The big stupid jumps at the ends of the stock curves cause the transmission to "stick" in the same gear until you go wide open and then it will downshift but if you lift at all it up shifts again. My curves will start downshift as the throttle opens more and more.
As for the TCC, you do a similar thing. Figure out what %TPS at each speed in the range you want it locked and then set values a little higher in the lock and unlock tables.
Attachment 10655Attachment 10656
The pictures really helped show how it works, I can see how the modified curve @ 60MPH would downshift from 4-3 at about 57% TPS. I manually plotted my stock curve and it looks like it would need 73% TPS for the 4-3 downshift.
Yes Sir!
-1999 Hugger Orange SS, LS2 402 T56, 9 inch Ford 3.90 gears, Tuned with HP Tuners
-2002 Cavalier, Tuned with HP Tuners
-1994 Full Size Blazer ,383 TBI 4L60E, 4.10's, Tuned with Tunerpro RT (Where it all began)
And I didn't get too aggressive with that 4-3 curve compared to the lower gears. I mostly left it like it was.
One thing you do have to watch with a truck is getting too aggressive because if you load it then it either won't want to upshift or keep dropping back a gear any time you touch the throttle.
I would also recommend to make the kickdown table speeds the same as the main shift table. So, if you set the kickdown to 80% TPS make the speeds the same as the main table at 80% TPS.
I've been manually plotting some new shift tables to try out but I don't want to change anything until I find the TCC lock and unlock tables, there seem to be a lot of parameters with TCC in them which ones need adjusting after the "upshift/Downshift MPH vs TPS " table has been changed?
If I raise the upshift RPM table values from 4000RPM to 4400RPM do I need to manually recalculate and raise the MPH values in the upshift MPH and downshift MPH tables, as the MPH values appear to have stayed the same?
Last edited by Kitch; 06-25-2016 at 02:06 PM.
The PCM should wait until both the rpm and mph tables are satisfied before it will up shift. So, no you don't have to change the upshift mph to match the shift speed due to the higher rpm.
I try to make it a lower than the shift speed due to rpm as well as the same as the main table. Make life easy by making the main table flat from your kickdown up to 100 %TPS.
The TCC doesn't have to be adjusted at the same time, but you'll likely want to adjust it. There should be some %TPS vs speed tables with values for 2-4 gear that you adjust.
Posting Permissions
Reply With Quote
Bookmarks