8L90E I want a crisp shift. Seems to drag between gears

[HellKnightHicks]

2018 GMC Denali Crew Cab
Super Charger
92mm Solar TB
Stainless works full exhaust.

Maybe im old school but I awlays really liked the crisp shift in the 4L60E Transmissions. I could make them snappy.

I tuned my buddies 15 with 6l80E and was able to get his shifts crisp but not brutal. I cant seem to figure out how to do that with my truck.

Its either just how this transmission shifts or I just dont know how to tune them.

I fixed some of it by changing the minimum timing table.

I've upped my max pressure to 1000KPA

Haven't touched the shift inertia tables as I'm not sure I understand them. Higher number faster shift?

I had read that people were having issues with setting the shift timings to low so I looked at several tunes and put the shortest stock shift times I could find.

35 -Current Tune.hpt

Any advise would be appreciated.

Thanks

[HellKnightHicks]

Upping the upshift shift inertia seems to have brightened up the shifts quite a bit. I think ill be able to get the shift feel im looking for from this table.
In case anyone else was looking for the same information

[HellKnightHicks]

Witht his Controller it seems that we can add pressure offset but not direclty adjust the base pressure values.

So Im adding some pressure with the pressure offsets now.

[Joshinator99]

Your max pressure is half of where it should be. TCC Apply Pressure Ramp is way too conservative. I'd suggest TCC Desired Slip to zero across the board too. Just my humble opinion, of course.

[lucas287]

Your max pressure is half of where it should be. TCC Apply Pressure Ramp is way too conservative. I'd suggest TCC Desired Slip to zero across the board too. Just my humble opinion, of course.

Curious what your TCC suggestions have to do with directly making the shifts crisp?

I never had luck with the inertia tables. I left all the pressures alone too. I've only changed the shift timing tables, up and downshift, modifying the areas that feel slow by about 10% quicker at a time. The big results are in the Shift Torque Factor Adder Modifier tables.

Here's how I have mine set up:

Adder.JPG

Adder Modifier.JPG

[lucas287]

^ These changes alone will bark the tires on the 1-2, 2-3 shift at WOT. That's crisp enough for me. At light throttle it feels stock but quicker.

I like to monitor the TQ MGMT spark at higher throttle inputs and try to keep the timing advance slightly positive.

[JR2010]

^^ How does react during downshifts with those settings?

[lucas287]

^^ How does react during downshifts with those settings?

Feels normal, nothing weird or clunky about it. In fact, I haven't touched anything on the downshift side. Upon looking at my latest tune a bit more, I actually left the downshift times completely alone. I feel like they are intentionally slow on the multiple gear downshifts to prevent damage. Plus, if I'm romping around I don't leave it in D. I'll limit it to 5th or 6th to prevent having to go from 8th to 3rd/4th (the shifts that take FOREVER)

You can get more downshift response/aggressiveness by modifying Shift Scheduling --> Part Throttle Shift --> Normal: Downshift.

[JR2010]

I ask because I get the occasional bump from the back when coming down the offramp. Almost like its hanging then downshifts hard enough to feel like someone rear ended me. Doesn't happen all the time but it is annoying.

[lucas287]

I ask because I get the occasional bump from the back when coming down the offramp. Almost like its hanging then downshifts hard enough to feel like someone rear ended me. Doesn't happen all the time but it is annoying.

Do you have your shift scheduling modified? I ended leaving mine alone because it would act goofy every now and then. Instead I just keep my TCC unlocked unlocked until 6th gear.

[JR2010]

Haven't touched it. I was going to adjust the MAF first since I changed out the factory exhaust for a Borla system and have an AFE drop in filter. Figure its moving a little more air which could affect the shifting somewhat.
I've messed with the shift torque factor multiplier by itself but did not mess with the table.
Have not messed with the TCC tables but noticed that the 4th release is set at 6.2137 all across the table. That does not seem correct when I compare to a 2018 it has that same value only in the 0% column and then set at 15.5342 across the row.
Don't know why its done that way or if that may be part of the issue.

[lucas287]

A lot of the 8 speed driveability issues can be contributed to the awful tcc tables. Just try setting 1-5th gear at 318 all the way across for lock and unlock. Then make 6,7,8 all lock 1 mph above the part throttle shift mph. (You need to have several tables open at the same time).

I get 6th gear and lockup by 30 MPH. It's perfect for me because slow speed traffic and around town is much smoother. But city cruising is still unaffected.

Might be easiest for me to just post my tune and you can try what you want lol I'll do that tomorrow when I'm back on my laptop

[lucas287]

You can even reference the C7 corvette lockup tables and apply the same logic. Not sure what GM was thinking with these trucks.

[JR2010]

Here is my current tune. All stock but with AFM/DOD disabled, MAF x 1.05.

[lucas287]

Knock yourself out! The engine side is pretty much stock on mine as well. But this will show you what I've done to the trans settings.

2016 Silverado 6.2 Tune # 50 (Stock DD and stock DFCO).hpt

[JR2010]

Thanks, will take a look at it.

[lucas287]

Side question - does your GMPP Borla exhaust have the valve built in? I know it's technically there for AFM (which I, generally, don't like and disable) but I actually notice some low speed torque loss any time I bolt the flapper valve open.

[JR2010]

It does, but I left it alone, haven't really noticed any loss. The system has a nice rumble to it when you get on it but is quiet going down the highway. If you decide on one be sure to get a new clamp to connect it to your existing y-pipe. Also, soak the bolt in Mouse Milk or something to release the rust and not strip it out. I spent more time getting that off than doing the rest of the system.

[str8dum1]

table 15440 isnt available for the 2018 8l90 trans

[cmitchell17]

table 15440 isnt available for the 2018 8l90 trans

Email support and tell them to add it to your OS, its on my 17 8L90 Camaro T87A OS.

I tried trying to take out some torque reduction by setting the torque adder tables to all 1, then removing a small percentage by using negatives like you did, but it never seemed to do anything for me. However, I tried it again with close to your values, so far it might feel a little better but that might be placebo, the logs are still showing the timing dip past -12 degrees on the WOT shifts so its still taking out the same amount of torque reduction it did before.