Shift pressure tuning

[athet]

Since my long and wandering post about the 4L60E got me nowhere, I'll ask directly: Is there a way in the V6 HPtuners software to change shift pressure?

It would seem that you can affect it indirectly via the 'shift time' adjustment, but since there's no input speed sensor on the 4L60E (which apparently there is on the 4T65) is there any way to directly affect shift line presure?

I guess I can play with torque management and tell the PCM that there's more torque happening than there is really, but that would make small throttle shifts very harsh.

Another quote: "The 4L60 shift line pressure and
torque management are whatever they are calibrated to be, and the shift
time that results is the shift time - an output, not an input, is what I am
saying here. "

I get what the transmission guys call a 'slide-bump' on the light throttle 1-2 upshift. It goes away completely at more than 12% throttle and the shifts there are crisp but not jerky.

My force motor settings start at 670 and fall from there, so I guess I'll just subtract 9-10% from the first three rows globally and see how it does.

Full throttle shifts are nicely firm, but still not tire chirpingly hard. Could just be that my 90k transmission is tired, also. If I need to rebuild it it'll be to V8 specs + light valving changes.

As ever, yay HPTuners!

-Anton

[rattle]

have you looked at the A4 shift properties page, might want to adjust the upshift pressure modifiers

[athet]

No such thing in the V6 code that I see, just the force motor current properties, which are a global control i.e. they raise the commanded pressure ALL THE TIME when you change them, and the 'desired shift time vs. torque' properties that seem to be a backhanded way of raising the shift pressure.

According to my GM Powertrain buddy, the 4L60E can't have a real shift time control because it doesn't have an input shaft speed sensor to tell it the shift is complete. Apparently just measuring the engine pulldown during the shift isn't accurate enough.

So far, I've raised the Force motor current settings enough that I get nice tire chirping upshifts at more than 30+% throttle, but it still has a bit of a 'slide-bump' 1-2 shift. I guess I'll keep raising the pressure via the force motor settings, but it's kinda wasteful pumping all that heat into the fluid because I'd be running higher line pressure all the time.

Hope I've explained my situation.

-Anton

[guardsman01]

I think to get what you are looking for, you're going to have to adjust both your shift times, and the force motor current tables.....

The force motor current can be translated into an approximate line pressure.....the current and subsequent pressures are listed in the service manual.

The PCM will command higher pressure during acceleration, etc., so to ensure that you get good shifts, you will want to make sure that the line pressure increases quickly when you get on the gas.

I haven't figured out yet how to post shots of the tables, but I've massaged mine so that it's running slightly above stock pressure at normal cruise, and then very quickly increases as the force motor current drops.

I'm writing in a hurry, so sorry if this doesn't make perfect sense right now.

Anyhow, decreasing you shift times will make the shift harder, however......if you still have a stock tranny, I wouldn't advise getting too wild with the pressure or the shift times.

The stock clutches, bands, and fluid are designed to allow slip, and the shift times are long, to make soft shifts.

I can get you a list of the oarts that I've installed in my tranny, and a general idea of how I've programmed it.

John

[athet]

Yeah, I did pretty much what you did. I played with the small throttle pressure until I got it to still have 'garage shift' as GM calls it where it goes into gear gently. THere's an algorithm that looks for the P/N switch to be on, 0% throttle, and idle engine speed, and it EASES the trans into gear. I discovered that more than about 940 in the idle speed line pressure (first column) meant it would BANG into gear. That sorted, it basically does what I want it to now, with crisp but not harsh shifts at moderate throttle, and hard shifts from there.

I have decreased the shift times to .3 or so, and since the shift time is really controlled by the hardware at that point I don't see any faster shifts even at 0.0 with the stock internals. The transmission is definitely tuned for soft and slow clutch/band-killing shifts, because theoretically the customer demands it... Sheesh.

It seems you would know this having changed the internals, but I would imagine the V6 4L60E is built even lighter duty than the V8 model. I doubt my 90k mi trans is in the best of shape, since it doesn't shift super hard even with very high line pressure at WOT.

I kinda wonder if the trans programming is underestimating the actual torque in my case since my jeep weighs fully 1200 lbs less than the original F-body, so if the trans programming uses any kind of delta to compute torque, ie how fast the speed is changing (0-60 now takes 5.3 sec) then it would mess up the calculation.

I'm not helping by not having changed the trans vehicle speed calibration when I put in the 3.55 rear axle. I've fudged the shift speed tables, and with an electronic programmable speedometer I don't have to worry about that, but the PCM still thinks the vehicle's going ~13% faster than it is.

I'd love to hear what you've done to your transmission, as once I've killed this one I'll probably get it rebuilt to V8 truck spec, because it's still only dealing with ~230hp unless I go nuts with a supercharger.

Thanks for sharing your experience, it reinforces my choices. :

-Anton

[coachcrow56]

If you go to Edit---Transmission----A4 Shift Properties----you can adjust Max Line Pressure there----factory setting is 96 on my 2000 GTP.

[97rs4life]

If you go to Edit---Transmission----A4 Shift Properties----you can adjust Max Line Pressure there----factory setting is 96 on my 2000 GTP.

my factory line pressure is 90 for my 97 camaro 3.8l