2015 SS auto trans drops out of overdrive

[mxdude]

Hi,

I have a 2015 SS automatic trans. I can be driving down the highway just cruising around 70, and some times my transmission will drop out of overdrive randomly. Then if I come to a complete stop, it shifts from 1st to 2nd fine, but will not shift to 3rd until rpm is at 3k and it will not shift into 6th (overdrive).
If I stop, and shut the car off for about 30 seconds and restart it. Things work fine again. Any ideas on what might be going on? I believe the transmission is the 6L80. Any advice is greatly appreciated.

[InFiD3ViL]

Yea its a 6l80e. How does it manually shift if you use the paddles? Any issues that way? Is the car on stock tune still?

Have you checked trans fluid level and condition? It's a bit of a pita if you didn't install a dipstick, but not too bad at all.

[ariZona28]

I'm no auto trans expert by any means but a bit more info may get you some positive responses. How many miles on vehicle? Any mods? Fluid level OK? Any leaks? Last time trans was maintained (filter and fluid change)? Is car a daily driver, race car or somewhere in between? How is shift performance when shifting in manual mode with paddles? Will it stay in 6?

Just saw INFID3VILS post so you can see great minds think alike LOL!

[mxdude]

Thank you for the responses so far. The car has 65K miles on it. I had some mods done to the shifting with an HP tuner, but since this started happening, I had the transmission settings set back to stock. It shifts perfectly fine until that happens. When it does happen and I try to use the paddle shifts, it says shift not allowed. I just bought a filter, seal and fluid to change the fluid, but have not done so yet. There's no dipstick for the fluid so I don't know the level or condition of it until I change it. Also, it's a daily driver. When it runs normal, the auto and manual shift work fine. When it shifts out of overdrive (Acts up), the manual will not allow it to go to overdrive. I hope that helps.

[Aqua Blue RS/SS]

I would get a jre transmission dipstick for it since your going to be changing the fluid anyway. That’s about the best I can add at this point until you change the fluid, sounds to me like a rebuild could be in order if you’ve already returned it to the OE tranny tune. Have you been able to pull any transmission related dtc’s? I’d be real curious to see what the fluid and filter look like.

[mxdude]

Thanks for the feedback. I did get a code once of P0741. I reset it, and have not seen that code again, but it still drops out of overdrive at random. I can just be cruising around and it happens and I wasn't even getting on it. It doesn't do it all the time, so it's hard to trouble shoot.

[xstuntman]

Low trans fluid level gets you low line pressure, lots of down shifts, and I've read a lot about GM sending these cars out two quarts low. Add in no factory dipstick and its surprising it hasn't been a bigger issue.

[mxdude]

Thanks for your feedback. I ordered a jre transmissiion dipstick kit. It's 79.95, not bad but they also get you for 2 day shipping with no other optiion which is another 17.78 but I figure it's a good investment. I will provide feeback after installing it. The JRE (Janetty Racing) website has a video on it. Looks pretty simple to install, just pop out factory plug, install grommet provided in kit, install tub and bolt provided bracket to transmission housing. I'll give it a go. Maybe my fluid is low? I want to change it any way. My buddy is going to help me, he recommends flushing the system completely to get dirty fluid out of torque converter etc. He said to get 12 quarts of fluid because just changing the recommended 4 quarts is all you will get out of the pan. It will not get all the fluid out and then you are just dialuting the existing fluid.

[ariZona28]

XSTUNTMAN brought up a good point about fluid level. While you're waiting for the stick to show up here is the factory (Chilton Manual) "fill to spill" method to check the fluid level. If you're going to change it anyhow it would be nice to check it 1st to see if it is indeed low.

[xstuntman]

No flush. Just drop the pan and iirc it's like six quarts you get out. It's also a great time to install a drain valve (7 or 8 bucks) while the pans dropped. Between the dipstick and drain it makes for a happy trans.

[mxdude]

Thanks for the pictures Arizona28 and also for your feedback xstuntman.

[Aqua Blue RS/SS]

Do not flush it. If your really worried about do a few drain and fills over a couple hundred mile span. I’ve seen flushes kill more than a few transmissions.

[InFiD3ViL]

Originally Posted by Aqua Blue RS/SS

Do not flush it. If your really worried about do a few drain and fills over a couple hundred mile span. I’ve seen flushes kill more than a few transmissions.

I agree, especially when it's already acting up.

Based on your code and how its fine sometimes and doesn't feel like it's actually slipping, I'm thinking maybe something related to the harness/electrical for the TCC solenoid or the TCM itself.

Maybe get under the car and check external harness and connectors for the trans. Unfortunately with the TCM being internal to the 6L80, you may be heading to a trans shop if there are actual TCC solenoid/TCM issues. Maybe you can get lucky and find some frayed external wiring.

[mxdude]

Thanks for the feedback Aqua Blue SS/RS and InFiD3ViL