Trans Tune Review: No 3rd gear on WOT

[SLEEPYDUB]

I would like to have my tune reviewed to ensure the tune is not what is causing this issue. I believe it is a mechanical problem in the trans. Customers transmission builder believes its a problem in the tune. We have agreed to have the tune reviewed to see if I have missed something that would cause this issue. Transmission was just recently rebuilt and completely gone through. See list below.

Tune file and log attached
GTO Tune 3.hpt
WOT Log Trans Slip.hpl

Symptoms:
Normal driving the transmission shifts fine, all the way through the gears. Under WOT acceleration it chirps on the 1-2 shift, but on the 2-3 shift it slips and will not grab the gear. Let the rpm drop back down and try to continue in 3rd, and it just acts like it's in neutral. Slow down and let it down shift to second, and then back up to 3rd at partial throttle and it does OK. It's only on high load in 3rd. If I command 3rd gear and floor it, trans slips.

2006 GTO LS2
Texas Speed Cam
228/232 0.600/0.600 112
Dual Valve Springs
Longtube Headers no cats
Stock TB
Has an upgraded filter, stock MAF
4L65
3200 Circle D Stall Converter
Trans was rebuilt using some upgraded components.
Trans has heavier pressure reg spring, 9 3-4 frictions, corvette servo, HD load release spring, larger hole size in seperate plate, stronger 1-2 accumulator, etc.

Please review the trans tuning and tell me if there is a problem with it that could cause such a condition.
Thank you

[Ben Charles]

Just looked at it for you, Tune looks really good. Commanded .85 lambda, 26 degrees of timing and commanding over 400lbs of Tq around peak tq. The Tq tells the computer how much pressure to give the trans.. MAF looks dialed in fairly close based off Fuel trims, so that is covered which also give us feedback on proper Tq for the trans.

Since the trans is JUST BUILT, I would 100% say its in the build and NOT the tune, reason be is shift time just little lower then stock, Pressure just little higher then stock (both of which would give a faster shift, which is a good thing.)
Tq management is Skewed but on a build like this, should NOT be a problem. IF it was a Boost build, wouldn't be a bad thing to leave a little more in it on the Shifts.
Converter settings a solid, locks up the Tq converter in 4th gear only and doesnt allow the TCC to slip much at all (Good thing, doesn't build heat in the trans)
Wouldn't be a bad idea to get a trans cooler. I would say another problem with the build is look how quick the trans heats up, goes from 15x to basically 190 on a short log with Literally just one WOT, should not get that hot..

Has the fluid level been verified?? I did the math with the factory gears and tire height and looks like the shift points are on target (IF anything a little low, but if hitting rev limiter, whoever tuned it did the right thing by lowering MPH since that is what the computer sees first.

Hope my analyze helped

[SLEEPYDUB]

Thanks for the reply Ben, very informative.
Anyone else have any opinions on the tune?

[kingtal0n]

Are you logging force motor current? Command trans pressure at WOT?

Near wot, the commanded current should be very low, say 88mV or 112mV closer to 0mV.

Are you watching hydraulic pressure of the transmission? Anytime a fresh transmission is installed into a performance vehicle you SHOULD/MUST Attach a 0-300psi gauge and ensure the transmission internal pressure is high enough at WOT to protect the trans.

1. Review commanded force motor current
2. Review internal transmission pressure using diagnostic port on side of trans


It really narrows down the issue when you can see a full commanded pressure, complemented with internal trans pressure. If you get a slip in that situation you know for sure it is something inside the transmission, wrong, pretty much