4L80E, Tuning Help

[Buick Motorsports]

Hey Guys,



Got reacquainted with a fellow gearhead tonight. He tells me that he's put a 4L80E in the car. He cannot get the tune right and there seems to be no one here who can help him and the TCI help line didn't pan out for him( I didn't ask for the details.

I told him that I would ask the collective knowledge of Lateral-g for help.

Here is the specs:

1956 Chevy
502 (500 - 550hp @ crank ) naturally aspirated
4:56 gears
4L80E is stock gearing, the tranny shop put in a "stage 2 shift kit"
TCI computer and harness

All he wants is a factory tune that will behave predictably. Here are 2 symptoms of the tune:

- when he gets on the throttle, the trans will not shift unless he lifts the throttle.

- when he is rolling @ 5 - 8 mph, and he ratchets down to first gear, the car almost comes to a complete stop. He says it feels like its going to throw him through the window.

Those are the basics, hope that you Guys can maybe give us a hand.

Thanks.

[Jake's Performance]

Sounds like he has something off a bit on the tune for the WOT upshift but tell him to very carefully inspect the shift linkage/adjustment.

A 4L80E with the extra detent, using the normally supplied shifter lever on the trans, has the lever pulled back at such an extreme angle that shifting from 1-2 can be problematic. The cable is no longer pushing on the lever in the center of it's arc, it's pushing on it near the end and it makes for an almost straight line, so most of the force is going straight and not moving the lever.

Also ANY slop in the linkage creates problems. I've had to weld the pieces together that are normally bolted so they would have zero slop.

The valve body kit (if they used TransGo) has you restrict the feed to the low band. Many builders omit this step. Admittedly the method looks archaic but it does prevent harsh 2-1 shift.

I wouldn't shift it manually to low gear under decel until stopped.

[oestek]

It also sounds like his throttle position sensor may be off if it wants to shift when he lifts.

[Steve Chryssos]

All he wants is a factory tune that will behave predictably. Here are 2 symptoms of the tune:

- when he gets on the throttle, the trans will not shift unless he lifts the throttle.

Shift timing is based on TPS position and VSS reading unless the TPS is at 100% WOT. Then shift time is based on RPM. First rule of any TCU calibration is to make sure that the TPS is fully calibrated. The calibration process varies slightly depending on whether the TCU is Gen 1 or Gen 2 (PCS). Please clarify if the TCU has a silver cast aluminum case (gen 1) or a red case (gen 2).
As for VSS, it uses tailshaft speed, final drive ratio and rear tire diameter to calculate vehicle speed. Again, the proper values must be entered into the setup
Max rpm for WOT should be set at least 500 rpm less than the engine's redline. This allows some time, as a function of rpm, for the shift to complete. A soft transmission or loose converter will exaggerate the shift time delay at WOT.

- when he is rolling @ 5 - 8 mph, and he ratchets down to first gear, the car almost comes to a complete stop. He says it feels like its going to throw him through the window.

Jake's feedback is spot on since there really are no shifters available for the 4L80E. Most are intended for 700's and 4L60E's. Typically, the end user has difficulty achieving full Park or full 1st gear. If your buddy never had a problem reaching Park, then he needs to adjust in that direction. The computer doesn't have much influence here other than a wacked out TPS reading that is applying too much line pressure at a low throttle angle.

If all this sounds like rocket science, have your buddy call me and I'll do my best to set him straight on the tuning. We no longer support TCI products except for pre-existing customers, but it sounds like he really needs some support. Tuning is actually very easy.

[critter]

I sure hope I qualify as "pre-existing".

[Buick Motorsports]

Thanks to all!

Steve, I will find out which unit he has. Thanks very much.

[Buick Motorsports]

Steve, it is the Gen 2 (red case). any additional info you can give us on calibration is so greatly appreciated. BTW, when I was talking to him last night, the Shrifter came up. He may be a client in the future, his eyebrows went high up when I said paddle shifting.

Thanks again.

Shift timing is based on TPS position and VSS reading unless the TPS is at 100% WOT. Then shift time is based on RPM. First rule of any TCU calibration is to make sure that the TPS is fully calibrated. The calibration process varies slightly depending on whether the TCU is Gen 1 or Gen 2 (PCS). Please clarify if the TCU has a silver cast aluminum case (gen 1) or a red case (gen 2).
As for VSS, it uses tailshaft speed, final drive ratio and rear tire diameter to calculate vehicle speed. Again, the proper values must be entered into the setup
Max rpm for WOT should be set at least 500 rpm less than the engine's redline. This allows some time, as a function of rpm, for the shift to complete. A soft transmission or loose converter will exaggerate the shift time delay at WOT.



Jake's feedback is spot on since there really are no shifters available for the 4L80E. Most are intended for 700's and 4L60E's. Typically, the end user has difficulty achieving full Park or full 1st gear. If your buddy never had a problem reaching Park, then he needs to adjust in that direction. The computer doesn't have much influence here other than a wacked out TPS reading that is applying too much line pressure at a low throttle angle.

If all this sounds like rocket science, have your buddy call me and I'll do my best to set him straight on the tuning. We no longer support TCI products except for pre-existing customers, but it sounds like he really needs some support. Tuning is actually very easy.

[Steve Chryssos]

That is a PCS based controller. Ask your buddy to give me a call, or he can try PCS directly at (804) 752-6025. (VA)

[KEISLER]

Hey Guys,

Got reacquainted with a fellow gearhead tonight. He tells me that he's put a 4L80E in the car. He cannot get the tune right and there seems to be no one here who can help him and the TCI help line didn't pan out for him( I didn't ask for the details. <SNIP>

Jason,
Using the TCI software, run a datalog while driving the car through all gears, upshift and down shift. Then send me the .TLG datalog, and we'll look at it. We should be able to help you.

We don't use the TCI product or software or transmission, but the controller hardware is the same, and we should be able to give you support.

We sell hundreds of these electronic hydramatics annually, both with and without paddleshifter, and we can resolve most problems by phone or email. And I know the guys at TCI, and can get you to the right person there if we can't quickly help.

Shafi Keisler

[Steve Chryssos]

We took care of that last week, Shafi.

[Larry Callahan]

I think it's time to close this one down at least for a bit.