Advice on reducing shift firmness under low tps

[JustinSEO]

I just did a rebuild on trans on my Z28 (94) and also put a near stock lockup converter in it as my high stall converter clutch gave out.

The car is much tighter now, and I notice a very harsh 1-2 shift. I am wondering how much you guys generally step down pressure (-5 -10 -50).

I will have a gauge on it while doing this to verify the minimum line pressure is met while 1-2 happens. I don't want to beat the crap out of my new sunshell and hard parts; and chirp tires while trying to pull off from a stop light.

Hope to get some insight from someone, thanks! I will likely try taking 10% out first and see what i get. Just don't want to decrease pressure and hopefully even with the shift kit it's possible to decrease firmness without burning up clutches.

[lionelhutz]

First off, you have to understand that the main line pressure table only picks a value from 0-96. It is not line pressure. The 0-96 value is used to look up the force motor current and that current sets the line pressure.

EEHack has the ability to vary the internal 0-96 "psi" value. You could use this to map the real pressure vs 0-96 "psi". Then, you can adjust the main line pressure table and you'll know exactly how much you're changing the real line pressure.

You can also check the shift times and could make them a bit longer, especially if they are zero. I wouldn't go much past about 0.3.

[JustinSEO]

Yeah I have been researching how the 4l60e works and how the computer controls it for quite a while. I understand the force motor reference and also have used the EE Hack duty cycle slider on the precious trans during troubleshooting.

Will the adaptive shift times being increased really make a huge difference in firmness if there is already a shift kit installed in this trans? It was never this firm with a loose converter but now when I have to take a turn it almost feels like I'm being pushed off the road when I hit 2nd.

[lionelhutz]

I'd try to get the pressure close to begin with.

[JustinSEO]

Thanks, my pressure is in spec as to what my parts supplier recommended but I just need to soften 1-2 and 2-3 a small amount.

Ill consider and research some more as I go, thanks for advice and if anyone else has experience in trans tables give me a reply.

[donf]

I had a very firm shift 1-2, but when I rebuilt my 1995 4l60e a few months ago I just returned the 1-2 accumulator to stock as it was a towing application. This took away all of the harshness 1-2, even with a Corvette servo, tighter band clearance and .082 feed hole. If your 1-2 accumulator spring setup is not stock, I would look there first, before other changes. My 1-2 accumulator was actually set up like a 94 with the reversed position, reversing the piston like the 95 and later and putting the factory springs back in helped a lot. New separator plates are not that expensive either if your feed holes are too big.