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The Shop Truck

1971 Chevy C20 with a custom flat bed.
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folkenheath said:
Go look at your shift charts and make sure the downshift for that gear doesn't overlap the upshift from the gear below.

There needs to be a decent gap on every one, also, I go back and make sure the shift charts end up right at or below the WOT setting, so there is no discerpancy.

For example, here is one of my regal shift parameters...

The WOT shift..


is what makes the black lines on the shift charts...always make sure they coincide so you don't have differences. Also, check that the gray lines and the colored lines don't overlap, that will cause issues, you can make the gaps bigger, but not smaller. You can also see the red shift lines end up at or just below the black WOT lines approaching 100% throttle.



Unless you purposely don't want it to shift, as I don't want it to shift to 4th at WOT, so I make it so it doesn't. I would have to change that if I ever did a 1/2 mile or something, but it can go 165 MPH in 3rd so I'm good for the quarter with my 3.60 gears. Anyway, just some examples.
Click to expand...
Thank you for the examples and explanation. I just made a quick change at the track and screwed up something like what you're saying. I'll dig into it more when I'm at home with my big screen.
There are two other things I need to figure out as well. On my last hit, I left at 3200 RPM and it left softer than when I launched at 3K, so I'm not sure what's up with that. It also seemed like my burnouts weren't as good after the first 3 days. I'm not sure if I hurt the torque converter (2500RPM stall) or what. I don't have a trans brake so I'm just foot braking with the 2 step.
The other issue I had was #6 running cool. As soon as it's making power #6 cools down ~200F lower than the rest.
1787753875260.png
I swapped the coil thinking the spark was going out, but it didn't fix it. The plug itself looks good.
 
r3dd0g said:
Thank you for the examples and explanation. I just made a quick change at the track and screwed up something like what you're saying. I'll dig into it more when I'm at home with my big screen.
There are two other things I need to figure out as well. On my last hit, I left at 3200 RPM and it left softer than when I launched at 3K, so I'm not sure what's up with that. It also seemed like my burnouts weren't as good after the first 3 days. I'm not sure if I hurt the torque converter (2500RPM stall) or what. I don't have a trans brake so I'm just foot braking with the 2 step.
The other issue I had was #6 running cool. As soon as it's making power #6 cools down ~200F lower than the rest.
View attachment 533943
I swapped the coil thinking the spark was going out, but it didn't fix it. The plug itself looks good.
Click to expand...

Swap the injector and/or the temp sensor and see if it moves with one of those. If you swap them both at the same time makes sure it's to different cylinders and you know which one went where.

Also, because the 4L80E has a turbine speed sensor, you can tell if the clutches are slipping and how much the converter is slipping. I actually even made "math channels" that calculated converter slip and the gear ratio based on the RPM vs turbine speed and the turbine speed vs output speed. You have to do a little math to convert RPM to speed but it works well because you can look at that channel at a glance and see if the clutches are holding and your actual converter slip in the other channel. That allows you to check the converter lockup too. The only time that will be off is when it goes into OD because the turbine speed is after the OD gearset, so then it's off by 25% but it still works.
 
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I finally got some time to dig into my datalogs and was comparing my quickest time to my last time when I noticed something. Then I went back and looked at all my logs from last week. Since I put the party pulley on it's been doing a 1-3 shift, every single one of my passes was 1st to 3rd, when I lowered the WOT shift point for 1-2 it made it shift back into 2nd. The truck should have been faster/quicker, which is awesome, but it sucks that I didn't notice until now.
This is the quickest run at Northern (dashed lines) vs my last pass at Mid Michigan. I compared it to the last run down at firebird and it didn't do it then when I was limited to 11psi.
1787949813185.png
 
I'm going to have to talk to someone smarter than me on this. It appears that there is a preset delay to prevent a double shift like this, at the lower power level that was sufficient to prevent the double shift, but with the higher power it's taking longer to actually get into 2nd. On the dashed lines you can see that it actually grabbed second and RPM was dropping, then it shifted to 3rd. When I lowered the WOT shift point for 1-2 the RPM is still on the way up when it shifts to 3rd.
On the dashed line it does the 2-3 shift exactly .75 seconds after the 1-2 shift, the solid line does the 1-2 at the WOT 1-2 shift point and the 2-3 at the WOT 2-3 shift point, which is over that .75 seconds. I checked the one other log I had (day zero) and it was also a .75 second delay. I need to be able to modify this delay to give the transmission time to complete the shift, but it doesn't appear that it's a setting I can change.

@folkenheath any ideas? I have some other people I can ask, but I won't get an answer until next week.
 
I could look at your tune file to look for why but I am at the river and don't have my laptop, I was on the slalom ski earlier this morning.

There is usually a delay between when it calls for the shift to when it actually shifts, this is how long it takes the transmission to actually shift, but I don't think it's 3/4 of a second. I can't look at my logs to confirm until Monday. You can see this better with the math channels I made. Also, have you tried the overlay feature to follow the data log on the tune?

What do your 1-2 and 2-3 shift speed tables look like? Can you screen shot them here?

Do you have any advanced tables running?
 
I watched a vid on the 8hp recently and it was talking about the different trans shift speeds
And I do think it said 4l80e (that what this is?) was between .4-.6 sec.

My WOT shift is set 400 or 500 below my rev limit because of that.
 
Enjoy your weekend. I was just wondering if you knew a quick answer to the issue I think I'm seeing. I can send you my log files and tune if you want to see them, but I think I just wasn't wording my question properly so I'll try to explain better.
I believe this is the page that is causing the shift to happen, not any of the TPS vs Speed graphs.
1788019816501.png
This is before I adjusted the 1-2 shift point so it would shift by 6500, it wasn't completing the shift until 7K with the smallest pulley on with it set to 6300RPM. This is a snip from the datalog from this run, it shows when the 1-2 and 2-3 shifts are commanded. I have the crosshairs set on the 1-2 shift point and the RPM shows 6310, right at the WOT setpoint. .75 seconds later, the RPM is still over the 2-3 shift point (6700RPM in this case) and the Dominator tells it to shift into 3rd. I have 2 different logs that show this same behavior, grabbing second, then shifting to 3rd before it pulls the engine down in 2nd. When I lowered the shift point to 5800, it shifted into 3rd while the RPM was still climbing.
What I'm trying to figure out is what tells the dominator to not instantly shift into 3rd as soon as it hits 6350RPM, because that happens every time. It seems to me like there is a .75 second hold on the next shift, but I don't know how to adjust that timing to prevent the 2-3 shift.

1788020127921.png
 
folkenheath said:
I could look at your tune file to look for why but I am at the river and don't have my laptop, I was on the slalom ski earlier this morning.

There is usually a delay between when it calls for the shift to when it actually shifts, this is how long it takes the transmission to actually shift, but I don't think it's 3/4 of a second. I can't look at my logs to confirm until Monday. You can see this better with the math channels I made. Also, have you tried the overlay feature to follow the data log on the tune?

What do your 1-2 and 2-3 shift speed tables look like? Can you screen shot them here?

Do you have any advanced tables running?
Click to expand...
If it wasn't clear in my last post, get to this when you can, no rush. The truck drives fine and there isn't another test and tune session for a couple weeks.

I also saw the same info Shady saw .4-.6 seconds, but mine is taking longer than that at the higher power levels. I did do the overlay feature and looked at the shift settings, that is why it dropped back into second after I adjusted the WOT shift point, but not why it's shifting into 3rd before it completes the 1-2 shift. These are my shift graphs.
1788020686643.png
1788020710073.png
I just wanted to add that it did the 2-3 shift at 65mph, well below the 100mph setpoint.
 
I see, it seems as though your converter is loose enough and/or your trans is shifting slow enough or slipping enough that the computer commands third based on max RPM alone.

I don't recall a way to change the minimum time between WOT shifts off the top of my head, I can double check that on Monday.

I would first do my math channels to confirm if the the trans is slipping.

If it is then that needs to be fixed.

If it isn't and the converter is just that loose with that much power, then you can either change the converter, or not shift based on RPM. Let me explain.

You see where your red line is over your black line on the 1-2? You should fix that.

Also, to fix the 2-3 shift, you could move WOT shift to like 8 grand, or something above the rev limiter like you have 4th gear. Then it will revert back to shifting by speed, and use the speed at 100% throttle and ignore the RPM. Then you can tune the speed it shifts to be done by the RPM you want.

Also, do you have a triple disc lockup converter? If so you can lockup at a certain speed after the 3rd gear shift to get more speed through the traps.

That's what I can think of without having the software in front of me. I can probably give you a better answer Monday.
 
Thanks, I was leaning toward something in the trans not being happy with that amount of power. Gearstar rated it for 1400hp, but I'm not sure if that was crank or wheel. I was also noticing that the launches were getting weaker throughout the week, I'm hoping a new converter gets me fixed up.
 
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