2006 Chevy Express 3500 having shifting problems

ClubWagon

Observer
Hello everyone! Ok I want to see if anyone has some ideas about what might be going on with my van. Sorry it's kind of a long post but I just wanted to put as my details out there as possible. I've got a few ideas but I would like to hear what others out there might think. I have a 2006 Chevy Express 3500. 6.0 liter V8 4l80e trans about 108k miles. It's a 100% kid hauler and grocery getter. No towing and no heavy hauling. I leave the big jobs to my E350. It started out being an off and on issue with with the trans shifting hard from 1st to 2nd and 2nd to 3rd. What I mean by being off and on I mean in a 15 mile drive it might do it maybe twice a couple times a month. Usually right in the middle of the drive so after everything had warmed up. Then a week or two would go by and it would drive perfect. Sometimes almost a month would go by and there would be no issues what so ever. When it would shift hard it would throw a trans component slipping code a PO894. I could clear it out with my scanner and it would stay off. Then in September we went on a week long 1200 mile trip. Just Indiana to Wisconsin and back so all flat no real big hills to speak of. I had no issues at all until the last day about 200 miles from home. Check engine light came on with the slipping code again PO894 and shift solenoid "a" stuck on PO752. It shifted hard in every gear unless I put it in tow haul mode and it shifted fine with the codes cleared. Out of tow haul mode codes came back and shifted hard again. So I stuck kept it in tow haul mode the rest of the drive home and it seemed okay. Then I kid you not the week after we got back it drove perfect out of tow haul mode and never had anymore codes. I knew something had to be wrong I was beginning to think it was electrical issue since it was so erratic. I decided to change the trans fluid and filter the next weekend. It was the dirtiest trans fluid I've ever seen. I mean it was almost black it was so dark but it smelled like regular fluid. As far as I could tell it was the first time it was changed. After that it got a lot better and did great for the last month or so. Now this week it started something new. Almost every time I put it in reverse the engine seems to become strained and dies especially on a slight incline. It was horrible yesterday I could barely get it parked in my drive way and it was showing 3 trouble codes. Trans component slipping code PO894, shift solenoid A stuck on PO752, And shift solenoid B stuck on PO757. It was also showing one module code. BO951 the description says headlamps on indicator circuit. Which it was night so the headlights were on. So that brings me to today. The damn thing is driving perfect! No codes no problems no hard shifts Nothing! Goes into reverse fine. Literally nothing showing any freaking problems. It keeps making me think there has to be something electrical going on. It's driving me crazy. So any one have any thoughts or ideas? I'm open to any and all suggestions. Thanks!!!
 

Len.Barron

Observer
I didn't see where you are so not sure if rust/heavy corrosion of a wire harness ground would be a possibility, your symptoms sure sound like it could be something like that.
look up the electrical harness drawings and see where the all the ground connections for both the engine and the transmission harness are then clean and reinstall them.
outside of that it may be the internal trans harness or a failing solenoid/servo valve.
 

bbbthreat

Member
We had a similar issue in a 2015 Chevy 2500HD pickup with a 6L90E transmission. It would miss shifts or shift hard, but did so sporadically, with 2-3 gear having the most problems. Ended up being a worn spot in the wiring harness that was causing a grounding issue. 4L80E trannies are known for their electrical gremlins.
 

ClubWagon

Observer
Thanks for the replies! That's the direction I keep thinking too. Something electrical. When I changed the fluid what wiring I could see internally in the trans looked okay I didn't see anything rubbed or anything. I think Len's idea of checking grounds for corrosion is a good place to check too. I've seen plenty of corroded connections cause some crazy problems. Hopefully if the weather is good tomorrow I can get outside and try to look over the harness and connections. Does anyone know what the inside of the solenoids look like? I'm sure I could probably google it but didn't know if it was possible or common if they could get mechanically stuck open or closed or just not seal properly. I know on the equipment that I maintain at work some of the refrigeration solenoid valves can do some erratic things when the valve body gets worn by either sticking open/closed or just not sealing completely. I know it's two completely different worlds I'm just referring to the structure of the solenoid valve itself. I'm in no way trying to compare the workings of a transmission to a refrigeration system. LOL!
 

ClubWagon

Observer
Well I have a verdict on my transmission. After checking over all the wiring and finding out the fluid looked like crap again already I finally just took it to a local transmission shop in town. Reverse band is shot and also has a cracked piston that's bleeding off pressure. Guy quoted me $2300 out the door for a full rebuild with updated/upgraded parts with 1 year 12k Mile warranty on parts and labor. Sound like a good deal? Or should I just go find a used transmission and sell the dumb thing? I have been looking for the last 6 months at E350s to replace this van anyway. I was planning on waiting until around tax time anyway to have some extra cash. So what would you do?
 

GHI

Adventurer
Ouch, at least you know what the problem is now. If it were me I would fix it proper and hold on to it, but you said you were already looking at E350's. I have a 2011 and promised myself I would keep it forever. I haven't had any issues with it yet though.
 

Len.Barron

Observer
$2300 is actually pretty reasonable if it includes removal/install and a new torque converter (I'd replace the cooler as well or make sure he flushes the crap out of it).
 

ClubWagon

Observer
Well $2300 later with a complete rebuild, new torque converter, transmission cooler and lines it's shifting better than ever. The shop I took it to did a really great job. I'm still looking to probably replace it though. Just not sure with what. I'm more leaning towards a 2010 or newer E350 but my wife really likes the way the Express drives. So I may look into a 2011 or newer Express. Then it would have the updated dash and a 6 spd transmission. I think that's about the only differences compared to my current 2006. I guess one good thing about needing a vehicle that seats at least 10 is it cuts down on how many types of vehicles you need to look at. The worst part is only about 20% of the them are NOT white!
 

Len.Barron

Observer
2011-up 15 passenger Duramax van would be a nice fit for you...6L90e trans is a big step up from the 4L80e and the mpg/power increase with the Duramax would really show up when you've got 10 passengers and gear loaded up...it is damn near impossible to find one that isn't white..
 

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