4L60E won't shift 2-3 when flooring it
 

Whats up everyone I was wondering I'm having problems with my 4L60E in my 98 trans am when step on the gas peddle more then half or most of the way it will shift no problem but then when I'm punching it all the way down 1-2 shifts great then when it goes to shifting 2-3 it redlines and won't shift sometimes I let off the gas for a few seconds and then punch it again and it shifts 2-3. Does anyone know what the problem could be. The transmission Supposedly has a shift Kit and a tune from what the guy says that I bought it from 4 months ago. I know when driving the car regularly it's shifts perfect no problems and driving it on the freeway shifts perfect no problems. Could someone please help thanks.

The tune is the easiest thing to check. May have to back the values down. Possibly the infamous 3/4 clutches taking a dump also. Very common 4l60 issue.

-Brian

sounds just like mine when the 3-4 clutch pack went out.

Yes, if the problem suddenly arises, it it nearly always a worn out 3/4 clutch.
However, if it arises after installing a different converter, it is often a tune issue; this is one reason a "tune" is needed after installing a high stall converter.

I had this 2-3 shift problem for the longest time. Maybe rare I'm not sure, but my problem turned out to be due to a clogged CAT. There's a trick I heard for testing for a clogged CAT - start up your car and stick your hand at the end of the tailpipe. If it's not blowing very hard (sort of like hot breath) then something is probably blocking your exhaust flow. I had a bad clogged cat. Ended up just straight piping and getting money for the cat. $150. Good luck 👍🏻

How would I go about checking the tune? Or am I going to need a tune shop? And I forgot to mention that when the car gets in the red on 2-3 it hits the rev limiter bouncing back and forth. It seems like it's only happening at wide open throttle with the pedal all the way down

I would start by smelling the fluid. If it smells burnt, it's time to pull the pan and check there for clutch debris. If it smells good, you may have hope. Tunes don't change over time like mentioned previously. If the car was working fine and now isn't, you have something mechanical going on.

-Brian

this sounds like a scenario I haven't experienced myself but seen in posts on here where a combination of not having the car in OD uses more fluid capacity and or low fluid level , a lot of people slightly overfill and leave car in od to help with this problem.

But theres a couple guys with way more trans knowledge than me in this thread already just throwing it out there because sometimes simple things can get overlooked.

You are correct that overfilling by 1/2 quart has helped many people reduce slippage during shifts. I will try to remember to include that in my future posts.

Just encountered the same issue, anyone in Detroit/Southeast MI area suggest someone to investigate the tune.