It started doing the 2-3* shift flare when warm and at part throttle. WOT shifts ok. Cold shifts OK. If I just leave it alone and let it flare the 500-ish RPM, will it die a quick death??

Install issue? Wrong fluid? Bad wiring? Any trans guy I call just wants to yank it out and sell me a re-build (at 3k miles). My googling has uncovered several internal possibilities but I'd like to try the simplest thing first and ground jumper wire at the (GM) trans controller trick.Is that an older issue thats been solved? Will it be an issue if I do that unnecessarily?

It's a newly finished project with about 3k miles on it. Bought the connect-and-cruise LS3/4L65e about 2018, and started driving it 2021 for about 3k miles now.

GM tech won't help Its 'out of warranty time-wise' regardless of the low mileage. Ironically I love the connect-and-cruise option for serviceability but the dealer runs and hides when they see a 1974 Dodge van pull in. I've seriously been told "We don't know where to get Dodge parts" JFC, just close your eyes and plug in to the ALDL

Hope thats enough info for the braintrust here to help and THANKS in advance!

*EDIT

 

custom tune?

 

Can you double check that this is not the 2-3 Up-Shift?

 

All stock GM, as delivered in the connect-and-cruise kit.

Ya know... you're right, I'm wrong. I guess can't count to 3. Its the 2-3 shift, I'll edit it.

 

Are there any tests I can perform without a $5K Snap-On computer? I'm technically savvy with normal tools.

Found this:
https://www.transmissiondigest.com/4...hift-now-what/
I'll need to find the circuit in this custom wiring install. Will it act the same if I put it on stands and manually select the gears?

There are a lot of different causes but it seems replacing the EPC solenoid solves it for some people. Hate throwing parts at it but might be worth a guess?

 

Hooking up a 0 to 300psi pressure gauge to the line pressure port of the trans and monitor line pressure during the 2-3 shift would help a lot in determining what is going on with your trans.

 

Cool,thanks! I can do that. What Psi am I looking for?

 

At idle in P,N, D & 3. 70-90 psi Reverse should go to 120-130 M2 & M1 180 plus
At 1500 P,N D & 90-150 Reverse 180-200 M2 & M1 210
While driving it will vary with throttle, but when it shifts you will see a momentary drop in pressure. If you have 150-180psi and it shifts to 3rd and slips, but it didn't in 1st or 2nd. You probably need to have the transmission removed and looked at for 3-4 clutch distress. it is usually caused by improper set up in the tune.

 

Ok, thanks for the specs! No matter how rare I think that would be from a 3k mile, GMPP built, stock OE program, Ill do that and see what I find.
Hopefully I don't find anything, lol.