Anyone have a 4L80E program?

[Taz]

Sorry … Tow Haul mode is “Performance” mode in the tune …


Regards,
Taz

[killerbee]

Isn't it odd, the allison TCM has nearly no temp constraints, accept for TC warmup defeat.

[Taz]

Shift quality or “feel” is the result of the interaction of desired shift times, trans pressures, and torque reduction. A “built” trans will have had hard parts added that will mechanically increase trans pressures - often requiring some compensation in the tune to arrive at a reasonable shift.

You took the time to post your current tune - will try and take a look at it tomorrow (getting late here).


Regards,
Taz

[Taz]

Just getting started here this morning. Reread your post – didn’t realize the tune you posted was that which you are planning to use to address the shifting problems – which has yet to be implemented in the vehicle.

Either post the old tune, or give that one a try - and then report back with changes / continuing issues.


Regards,
Taz

[Chevy366]

Don't know about those FLT things , who are they ? Any way , with a built trans or a TransGo kit it is best to take everything back to stock calibrations to start with , then adjust from there , as Taz stated .

[ScarabEpic22]

Go back to stock TCM tune and work up from there. Trans builders do things like raise line pressures and change the hole size in the separator plate, so a few actually recommend leaving the TCM tune 100% stock (but I disagree and think it can be better with a little tweaking).

[Telco]

Unfortunately the program I was working with is gone due to some computer problems. But, the program I loaded only changed shift speeds, with no changes to line pressure. With the new program there is no change in how it shifts. Shifting is still fine below 50 percent throttle, too harsh over. The source program for the 4L80E came from holdencrazy.com.

FLT is the guys that supplied transmissions to a fellow named Parish who is supposed to be putting 1200HP to the ground through a 4L80E. As I understand it, FLT honed their skills by guaranteeing that they could build a trans that Parish could not tear out, so every time he tore the trans out they rebuilt it and upgraded what he trashed until he could not trash it any more. What I have is a Level 3, which is supposed to be set up to handle towing and 500HP. The converter is a low stall, supposed to be close to stock. I figured if they could handle this guy's truck, mine should be easy for them.

Here's a vid of the truck, and there are many more on youtube.

http://www.youtube.com/watch?v=hOm6H...eature=related

[Chevy366]

Strange a stock .tun should have tamed it a little .

[Taz]

You’re using an older (2000) 4L80E calibration - which did not appear to be “stock”. I updated the Desired Shift Times, Trans Pressures, and Torque Reduction to those from a stock 2003 LQ4 4L80E two wheel drive truck.

The shifts will probably still be too firm, but at least your “base line” values are now stock.


Regards,
Taz

[slow67]

You’re using an older (2000) 4L80E calibration - which did not appear to be “stock”. I updated the Desired Shift Times, Trans Pressures, and Torque Reduction to those from a stock 2003 LQ4 4L80E two wheel drive truck.

The shifts will probably still be too firm, but at least your “base line” values are now stock.


Regards,
Taz

Also, most builders on recommend a stock to as a starting point.....so that you don't break any parts from too harsh of a shift. A bigger feed hole (for each gear) creates more fluid flow from the same pressure, which is better than more pressure to create the same feel. Also a firm, quick shift is desirable....the stock-like slide into the next gear actually creates more wear and tear as the clutches are actually are sliding instead of grabbing. as long as your line pressure is under ~200 psi at WOT, you probably can't make it shift hard enough to hurt the trans.

It looks like a stage 3 is a rebuild with stock hard parts (all the rotating parts, etc) but with improved hydraulics. I'm not sure what the feed hole sizes are, but you can make the shift from 2-3 as hard as you want....it won't hurt the trans. 3-4 you have to be a little more careful, but its still difficult to hurt the transmission.

The weakest part of your transmission is the stock input shaft, these seem to give out around 750hp in a 4000lb car (some more, some less obviously), and then next is the 2.75 low gearset, which is partially responsible your harsh shifting....it is a bigger drop from one gear to the next, so more RPMs are dropped for each shift.