Shift harshness

[jhkm12345]

I'm running a 4l80e trans run through a microsquirt trans control unit. I have an ms3x gold box running the engine and talking to the trans control via CAN bus.

My problem is that I have a severe 1-2 shift. I adjusted line pressure positions in the tune, but don't get substantial changes in feel.
What sort of line pressure curves are you guys using that you've found to be comfortable without being sloppy?

[Raymond_B]

I think that's your engine controller tune, can you post the trans controller?

[jhkm12345]

DUH...

[Raymond_B]

I don't have mine running yet, but I do not see why turning it down a bit from the default settings would hurt. You might also try to datalog while taking a drive and make sure what's in the shift curve is actually what's commanded.

In addition you could turn off "common" line pressure and tune per gear, but I'd try dialing it back a bit 1st.

[nathaninwa]

My 4l80e has fixed line pressure I was able to use the retard function to calm down wot shift harshness. Still working on it, but it was getting better last year

[jhkm12345]

interesting. fixed line pressure by design or for some performance gain modification?

I was under the impression that all 4l80e's had a pressure control solenoid

[nathaninwa]

It has a Jakes Performace D3 tranny brake. I asked about the line control and they said they had to many people ruin trannys by not knowing how to tune it right, so they fixed any mods they provide with a th400 fixed pressure control. I can add back they said, but user beware

[jhkm12345]

For anyone who cares to hear the result of my efforts, I have it shifting smoothly now by way of extremely low line pressure percentages and different curves applied to each individual gear position.

with a mechanical line pressure gauge hooked to the 4l80e, I went into test mode in gear and moved the percentages around...
I found that for percentages between 60 and 100 there was next to zero impact on the true line pressure PSI.
In fact, I didn't see any real impact to line pressure until I got down in the teens.

In order to make the 1-2 shift smooth at 30% throttle or less, it needs to be set at 8% line pressure. 10 is too much. 12 will snap your head off your shoulders and bark the tires. 7% is a lazy slipping shift, destined to burn up a gearbox.

Odd to say the least, but the car has been smooth, comfortable and successful for about 1000 miles now.
The application is a 1963 Jaguar MK10 sedan with complete 6 liter v12 driveline from a 1995 jaguar xjs sport. engine, trans, suspension, steering, brakes,etc.
I have a suspicion that the 4l80e in an xjs is NOT the same internally as a chevy truck, so please use this information with care on a standard GM gearbox.

[linuxman51]

I messed with that a bit on my 4L80 as well, I ended up setting the shift tables so that my car starts off in 2nd gear for tps < ~15% or so.

[kikkegek]

For anyone who cares to hear the result of my efforts, I have it shifting smoothly now by way of extremely low line pressure percentages and different curves applied to each individual gear position.

with a mechanical line pressure gauge hooked to the 4l80e, I went into test mode in gear and moved the percentages around...
I found that for percentages between 60 and 100 there was next to zero impact on the true line pressure PSI.
In fact, I didn't see any real impact to line pressure until I got down in the teens.

In order to make the 1-2 shift smooth at 30% throttle or less, it needs to be set at 8% line pressure. 10 is too much. 12 will snap your head off your shoulders and bark the tires. 7% is a lazy slipping shift, destined to burn up a gearbox.

Odd to say the least, but the car has been smooth, comfortable and successful for about 1000 miles now.
The application is a 1963 Jaguar MK10 sedan with complete 6 liter v12 driveline from a 1995 jaguar xjs sport. engine, trans, suspension, steering, brakes,etc.
I have a suspicion that the 4l80e in an xjs is NOT the same internally as a chevy truck, so please use this information with care on a standard GM gearbox.

nice! I am glad I found this thread searching thjrough this forum.

I have just finished installing a 4L80E and Microsquirt in my 77 GMC C15 Suburban and have also noticed the harse shifts in allmost all gears, unless apply allmost no load. As soon as I apply even a little load the shifts become pretty hard.

link to my car is in my signature

The lowest linepressure I now have set is 12%. still harse.

could you share you MSQ, so I can take a look at your settings?

[jamies]

Ive setup a 4l80e a while ago, just checked the settings min line pressure for any gear is 50%. Sol freq is 590hz.
Might be worth checking or trying the different solenoid frequency to see if you get more adjustment range

[kikkegek]

Ive setup a 4l80e a while ago, just checked the settings min line pressure for any gear is 50%. Sol freq is 590hz.
Might be worth checking or trying the different solenoid frequency to see if you get more adjustment range

thanks man. I read somewhere that sol frequency was 292 for early modela and 590 Hz for alter models. They apparently changed it around 1994.

Ill hook up a 400 psi gauge and check the actual line pressure, just to be sure

This what I found oline:

The case conenctor plug that was prone to leaking changed from 92-93. The force motor AKA PCS that controls the line pressure changed from 93 to 94. It went from a 292.5HZ(cycles per second) to a 614HZ(cycles per second) and eliminated the cleaning cycle every 10 seconds that was used on the previous 91-93 force motor. Also a new spacer plate was used for 94 and the torque signal compensator valve in the accumualtor housing was eliminated. In order to use the older style force motor and accumualtor housing you have to swap valave bodies I have been told(have not tried this myself to verify it, but many have done this swap and had issues until they either changed PROM's or valve bodies). One can use the new style trans and force motor with a PROM update to eliminate the cleaning cycle and change the force motor cycles per second. If one uses a new style trans with an old PROM the force motor will likely live a short life at the different HZ, and you will have a pressure spike every 10 seconds when it commands a cleaning cycle. And if it happens to shift during said cleaning cycle you could get one funky shift with the pressure fluctuation. ON EDIT(in case somebody in the future references this thread) The valve body difference comes into play if you put a 94+ trans into a 93- truck you either have to use the 91-93 valve body, OR open up the 94+ valve body and drill out the seperator plate as well as swap force motors to make it work. So yes there is a difference, but it is in the seperator plate and passages drilled or not drilled. Otherwise you have to use the new style PROM that eliminates the cleaning pulse every 10 seconds.

[kikkegek]

check out my topic on the force motor.

I seem to have solved this issue for my 4L80E with a simple diode mod:

http://www.msextra.com/forums/viewtopic ... 6&start=20