4l80e build; output solenoid A and B issues

A forum for discussing applications and implementations of the MegaShift transmission controller code for the GPIO from B&G. This can control up to 8-speeds and 6 shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, and full data logging of all inputs and outputs (among many other abilities). A TransStim to test your completed board is also available.
Orion1800
Posts: 9
Joined: Sun Oct 16, 2016 4:16 pm

Re: 4l80e build; output solenoid A and B issues

Post by Orion1800 » Mon Jun 12, 2017 12:04 pm

I got a chance to do some more digging over the weekend. I have confirmed that the transmission is not able to get into first gear. I did this by wiring up the transmission solenoids A and B to toggle switches. I turned them on/off as per sequence in each gear. I successfully have gears 2, 3, and 4 when shifting manually.

This leads me to believe there’s something internally wrong with the trans, either in the valve body or the bands/clutches. Solenoid A is used in both 1st and 4th gear. So by default, if I am getting 4th gear, then solenoid A is working. I know that the trans has shifted into 1st in the past, so maybe something has failed since, or a passageway is clogged. Either way, I can confirm the Megashift is not the culprit for my lack of 1st gear.

That said, I reviewed the solenoid outputs (SOLST) from a previous data log and it looks like the solenoid states align with the current gear. That is not necessarily something I am questioning. My still outstanding question, is why the Megashift does not seem to be shifting per shift table. And therefore, what factors are causing the shifts? I have attached my tune for reference to the previously uploaded datalog.
Attachments
CurrentTune.msq
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Rukavina
Posts: 47
Joined: Fri Aug 15, 2014 7:58 pm

Re: 4l80e build; output solenoid A and B issues

Post by Rukavina » Tue Jun 13, 2017 11:39 am

so not that I am a genius with this.... I am slowly learning this on my own. I looked at your current tune and one you posted a year or so ago. at least you are on the newest firmware. other than minor differences with your setup and mine I didn't notice anything out of the ordinary. I looked at all switch inputs and outputs. they are correct. one difference is on my tps by rpm table I have it bypassed for now while I dial things in. ie.... raw tps values carry across all rpm ranges. so for the 100% tps bin I have 100 in all rpm ranges. same for 75%,50% 25% etc. that puts the tpsxload dot on your shift table where it is. it had confused me when I was first doing this why my shifts were not where I expected them to be. I will adjust this table at some point but I have left it bypassed for awhile now while I work on other things. also when I built a second trans controller I was testing my outputs before I put load to it and my test lamp was telling me I was in 1st,2nd,3rd and 4th but I wasn't hearing it do the 1-2 shifts, up or down. and I have "paddle shifters" setup so I could command 1st or 2nd. well I put it on the ground for the heck of it and with weight on it I could hear 1-2 and 2-1 working. put it back on stands and could not hear it. so before you spend a million rebuilding your trans - as long as you know your outputs are working right I would drive it.... gently.

Orion1800
Posts: 9
Joined: Sun Oct 16, 2016 4:16 pm

Re: 4l80e build; output solenoid A and B issues

Post by Orion1800 » Tue Jun 13, 2017 2:20 pm

Thanks for the super quick response. I went back though my datalogs and noticed that my PC% control on this current tune was lower than when I knew I was in first gear on that previous tune. So I upped the table range to bring the bring up the PC% at lower throttle openings. I also noticed I had the PWM period set for the earlier trans, so I adjusted that. I am going to try again ‘on the bench’ and see if the increased line pressure and PWM period enables 1st.

I agree that there’s only so much you can do ‘on the bench’. I’ll probably take it for a spin soon, I am confident enough that everything is working to the point that it won’t leave me stranded. My issue is that I live on a hill, on a busy street, by a freeway on-ramp. So there are no ‘safe’ roads to test out a combo. When I leave my driveway I need to be damn confident that I can cruise the mile or so before the nearest empty side road. At least I can test for first right in my driveway.

I’ll also adjust the TPS/load table to be 1:1 on the TPS signal. I noticed the same thing on my datalog, where the load was significantly different from the raw TPS. I think the TPS/load table is a great tool to really refine the shifts, but definitely for testing purposes I’ll bypass it.

Rukavina
Posts: 47
Joined: Fri Aug 15, 2014 7:58 pm

Re: 4l80e build; output solenoid A and B issues

Post by Rukavina » Tue Jun 13, 2017 10:33 pm

I would take 20 min and hook up manual shift buttons. I used a 3 position return to center toggle and a on/off switch for mine but anything will work. If you have any problems like a honkey vss signal you can shift thru gears to get you home.....
And it's fun as he'll too :lol:

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