Don't give up the fight. We're all pulling for you.Originally Posted by boba
Don't give up the fight. We're all pulling for you.
Hiya's
Have you tried the BAMM memcal? It's 3.73 vs your 4.10 rear end and probably a few other things. Once you lose scanner data stream, it means the eprom is no longer communicating. Those early 7060 memcals were notorious for pin problems.
-Carl
Thanks for the reply's - both.
@ In-Tech I'm running the BAMM now, It's on a Moates adapter with a custom prom for the trans from Sinister performance.
Honestly I had no idea what I was putting in there when I got it, but it works as well as the AWUM the rig came with, which is also the chip I had in the original ECU when these hicups started.
I didn't know there were pin problems with the memcal's, all I can say is I'm getting the same driveability weirdness with either one.
@MO LS - thanks for the support, I'm trying to get somebody to rocket-freight a DRAC (CBU 16124435 if anyone's interested) to me by Friday. (I need to be gone by Monday next week).
Reason being, I did the jumper re-calibration for tire size on the DRAC I have, and noticed it now "bumps" the speedometer needle at low speed, maybe related - one of the last times I drove it with with the old 7060 PCM the speedo needle flipped over all the way to the right.
My current working theory is that the trans going to neutral at 50~60 mph, the pulsing speedo needle at low speed, and the speedo flipping are all related, and all point to a bad DRAC. Also if the DRAC is passing 12v to an ECU pin that looks for a 5v square wave signal it could be the source of the electrical aneurysm this thing is having now.
I wish I could get an actual circuit board schematic for the DRAC, I'm thinking it may just have a bad diode and it's putting 12 volts to the ECU on the VSS input to the PCM.
I have diodes and a soldering iron.
I could fix that here and be done with this drama!
(sorry if my grammar and context are scrambled this morning, it's early and I'm pretty cranky over this...)
Last edited by boba; 04-10-2024 at 05:00 PM.
First thing is get rid of that adapter and just try the memcal alone, Those are a HUGE failure point regardless of brand. Report back ;)
-Carl
I found and ordered a replacement DRAC, my testing approach today to start with will be to put my scope on both trans output speed and VSS input to see what I get.
Question on ditching the adapter though, you say the BAMM is for a 3.73 gear, so if I remove the adapter it will control the trans, I'll just be getting a different speed input?
I changed back to the original AWUM memcal, still had a MIL & low idle, re-seated the chip but didn't bottom it out in the receiver and it was suddenly all good.
I don't know what to think of this now, except it's going to be hard for me to trust it. I'd do more if I had a work environment where I could, but that isn't the case for me right now.
I should get the DRAC in a few days, I have no idea now if that will change anything.
Wasn't able to get any scope patterns out of the current DRAC today, but that might be my fault - I need some more working time with the scope I have.
Hiya,
I'm not sure if you have internet on your vacation. How's everything going?
-Carl
I'm full time in this thing In-Tech, it sucks to have my house break down on me, but I'm doing the snowbird thing so at least I'm in good weather.
Yes I do have internet (most of the time) I've had to learn to adapt on that like everyone else who does this. It's workable.
Updates since I've posted last - the DRAC module I ordered was a kerfuffle, seller sent the wrong part so I couldn't compare it to the one I had. He does have the correct unit and he's a good guy so if do end up needing the part I'll know where to get it.
I've also had a chance to open up the rest of the wiring harness and can say it's been thoroughly checked out and I haven't found any damage, some discrepancies compared to the schematics but I'm sure that's due to manufacturing changes that GM made during production, and it has been working fine up 'till it didn't.
Long & short is that I'll be putting it in a trans shop ASAP and getting the 4L80 rebuilt.
It's still going into limp mode, even though it's running better - and I don't want to drive 1200 miles back to home base in 2nd gear.
What really bugs me about the whole thing is that when It throws the MIL and goes into limp mode I get a no com with the ECU, can't read a darn thing, no codes or data all.
That and it doesn't store any codes either. This is consistent with both PCM's that I've had in it over the last six weeks and I have no idea why.
I get an MIL and the PCM totally sh*t's the bed. It's frustrating at levels I probably shouldn't try to describe, but you get the picture.
Other symptoms that lead me to suspect the trans are my speedometer needle is now pulsing at low speeds. I don't remember that from any time in the previous five years I've owned this thing.
In looking through some 4L80E rebuild videos I've seen rebuilders point out weak sprag clutches and torque converters along with everything else a manufacturer does to make their stuff just good enough to get through warranty, so my best guess is a failed rear sprag and a cracked drum that may have deformed the output tone ring.
This rig weighs in at a lithe 6 tons and it's got 125k miles so I'm probably due anyway.
I'll put that all on red and take it with me to the transmission shop casino.
'Cause baby needs a new pair of shoes!
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