Understanding 4L60E operation / tuning

[weinerschizel]

I build a 4L60E and 6.0L Gen 3 LS. For all intensive purposes the 4L60E should behave as stock. It's mostly stock with a few upgraded internals / Sonnax goodies, top shelf clutches, onlything out of spec would be a 2600 stall converter. This is all in my 2001 Chevy Tahoe

I'm having issue with torque loss.

I suspect this is a result of the transmission not holding gear. I'm trying to determine if it's a result of something not tuned properly or a issue with my build. I need to know better how the transmission PIDs work in conjunction with gear changes and holding gears. I assume line pressure observed via Pressure Control Solenoid, PCS PIDs, is reduced during gear changes and then left at maximum pressure, 0% duty cycle, to hold the gear?


My Trans Current Gear PID shows the transmission not locking the gear

My PCS is all over the map even when I think I'm not commanding a gear change. I don't know why it does that. I see the Trans Current Gear PID jumping in and out it's current gear. That cannot be normal operation?

I've attached log file along with corresponding tune I ran.

Here's a screen capture of what I'm trying to figure out

[kevin87turbot]

Your transmission tune is stock. It's not causing the transmission to fall out of gear. The PCS variation in the datalog is normal.

Start with the basics. With the vehicle at operating temp, check fluid level. I typically run that model 1/2-3/4 qt over full.
Check the fluid for cleanliness. If it's bright red/pink, that's great. If it's dark or discolored, then you need to dig further into the trans. I typically check to see if they pass the "smell test." If it has damaged clutches, then the fluid will have a very bad sulfer-like odor.

I've seen a couple of cracked filters that had similar symptoms to yours. Maybe you'll get lucky and it'll be something that simple.

[dhoagland]

Are you really on/off your throttle like this Chart is showing?
This is the worst part of your log, but the signal is pretty "jumpy" most of the way through..

[weinerschizel]

Yeah, I wasn't managing my throttle well. I was pumping it too fast. I went and logged new data and the transmission behaves mostly fine. I logged 30 minutes in two files and only had one torque loss event and no gear fluctuations as in previously shared log file.

My torque loss event was upon ramping up throttle to ~50% with 2nd gear selected on column / shifter. It didn't change gears though. It held the gear. I'm not sure why the torque cut out in 2nd gear like that. Really weird. I don't think is any issue with my transmission build... something in the computer is commanding it to pull torque. It's not showing up on the torque advance PID either.

Backstory: I have a mildly built up 4L60E, designed to handle more power and last longer. I spec'd & built it myself. It has a Circle D 2600 stall converter. I think stock 2001 CK truck was 1800 stall? The idea is the trans should handle whatever my engine can throw at it. I also built a cammed 6.0L LQ9 and swapped it in place of my 5.3L along with the transmission I built.

I started with the 5.3L baseline tune. I've tuned MAF, VE, and few minor tweaks to engine side. I also pulled out the engine side of torque management, along with traction control per HERE AND the brake torque management.

However, my transmission tune remains the original baseline. I making much more torque now with the 6.0L build than the 5.3L. I need to make some updates to the transmission side. Not really sure where to start. Watched this tutorial HERE. Haven't devised a plan to make changes and log data yet though.

I'm wondering if I have some quirks where the trans tune doesn't match up with my new build.

[weinerschizel]

I think I need to start by asking. Where should I start with tuning my 4L60E? I've some basic understanding of the engine side and got MAF & VE somewhat dialed in. I'd like to update my transmission tune now.

I drive my truck slow, off-road, and on highway. I'm aiming for good fuel economy as well. One concern I have is the TCC not locking up when I'm off road.

[kingtal0n]

I recommend start by learning how 700R4 operates using TV cable then extrapolate that knowledge to electronic control

[weinerschizel]

@kingtal0n... good idea. I'll study up on the manual control system. I did use BlueCat to establish a baseline.

My main concern right now is 1 to 2 shift is HARSH. 2 to 3 is a bit better.

I put in a boost valve, corvette servo, and Sonnax Pinless accumulators. It seems the new build is making much better use of pressure than stock setup.

All my changes are in performance pattern. I assume I can access that via the tow haul button on my truck?

I dialed back 1->2 and 2->3 upshift pressures by 19%. Didn't notice a difference.

Here's a video of what I did

[weinerschizel]

I have made a great deal of progress. Have a new trans tune baseline. It's not perfect, I'm still sorting out what I call a torque gap at low RPM on 1 to 2 upshift. I realize I setup BlueCat wrong so this could be the culprit. I specified all the Torque Converter settings incorrectly.

I now have Blue Cat setup as follows:
bluecat Shift Settings.jpg
Bluecat TCC Settings.jpg

I'm populating the performance shift patern now. However, I cannot for the life of me find the "TCC WOT Table"??

bluecat tcc.jpg

Baseline before proposed changes above. Where I'm observing what I call gap in torque on the normal shift pattern from 1->2 shift at low RPM / torque.

05 BASELINE.hpt

[village_idiot]

On your year model, there is no per say "TCC WOT". Go Transmission > Torque Converter > Apply/Release > Normal/Cruise/Hot/Performance

I usually max those tables out above 75% TPS

In the later years, there is a TCC WOT table that uses the parameters you're trying to export from the Bluecat software, but it's not in yours.

[weinerschizel]

On your year model, there is no per say "TCC WOT". Go Transmission > Torque Converter > Apply/Release > Normal/Cruise/Hot/Performance

I usually max those tables out above 75% TPS

In the later years, there is a TCC WOT table that uses the parameters you're trying to export from the Bluecat software, but it's not in yours.

Thanks man! I'll check the TCC WOT tables.

Question 1: It's a long shot but anybody know what may cause a torque gap / clunk?

The torque from output is higher than the torque from the input at low RPM / shift is too slow or something. Tried playing with shift timing, pressure, etc no effect. This seems to be more frequent on the normal shift pattern. Tune is linked two posts above.

Question 2: at higher throttle positions it breaks the tires during shift.

Not sure if this is bad? If I put the throttle down it shifts CRAZY fast and chirps the tires. I assume that's the torque multiplication of the torque converter before lockup? I mitigated some by increasing torque management's timing pull. However, what else might I do?

[Tranzman]

I'm a retired transmission builder myself, I'm here to learn about tuning for my own LS swap. This post caught my eye...
What shift are you talking about? 1-2, 2-3 or 3-4?
Because you built your own transmission, what is the 2-4 band clearance?
What is the 3-4 clutch clearance?
I've heard the Sonnax pinless accumulators cause a firm shift.
Did you use a shift kit of any kind? what are your shift orifice sizes?

[weinerschizel]

I'm a retired transmission builder myself, I'm here to learn about tuning for my own LS swap. This post caught my eye...
What shift are you talking about? 1-2, 2-3 or 3-4?
Because you built your own transmission, what is the 2-4 band clearance?
What is the 3-4 clutch clearance?
I've heard the Sonnax pinless accumulators cause a firm shift.
Did you use a shift kit of any kind? what are your shift orifice sizes?

Upshift from first to second gear while at low torque / low RPM... My guess is output torque is higher than input. It creates a odd clunk. Now that I think of this... it may not be my transmission at all. Maybe I have a bit much gear lash on my rear end. I just thought of that...

I don't recall how I measured band clearance. I didn't have the tool but was within spec / good.

Not sure what the clerance on the 3-4 clutch pack is. I had a builder redo the drum. I built it up, only to find out the input shaft was leaking. At that point I sent it to somebody to put in a sonnax reinforcement sleeve, better 3/4 clutches, and seal the input shaft. I didn't have a press / the jig to do those things.

My build of materials otherwise (Note: I forewent what I labeled stage two upgrades)
https://docs.google.com/spreadsheets...it?usp=sharing

Shif

No shift kit... Just Sonnax goodies such as pin less accumulators. I actually bought some TransGo stuff but upon looking at instructions and quality of materials I threw it away and went with Sonnax. Glad I did. I got LOTS of bunk from people saying I had to use a shift kit. That the transmission will never shift fast or firm enough. The transmission shifts REALLY fast and firm... so firm I had to dial back the torque quite a bit on 1st to 2nd, and 2nd to 3rd. I can feel the 3rd to 4th but have enough momentum that it's not so abrupt. Bit of a long story, but started with a bit of added Torque management but mainly lower pressures. Then it wouldn't hold 2nd gear on a hill climb so I went back to stock pressures and only played with torque management.

Orfice size, I have that written down somewhere not sure off the top of my head. I had followed the transgo instructions.

[Tranzman]

Very good choices on the parts list. Excellent choice on the 4L79 drum by Mason Smith of K&N transmission. Lines 16 & 59 elude to a shift kit though. Was this an actual build list or suggestions?
Did you opt for the Sonnax HD 2-3 shift valve?
How about the Sonnax HD 4th servo?
I've been building since 1977 & performance for the last 10 years. I used to feel the same way as the "Other Builder", but since have had to change my mind. I have used countless TransGo box SK's and 2-3 kits with excellent results. The factory doesn't have performance in mind. I also measure every build for band clearance & 3-4 pack clearance, No special tool.

The band clearance has a lot to do with the 1-2 shift speed/timing.
The 1-2 orifice size has a lot to do with it as well, but it is a tricky combo. Too large of a hole for a crisp 1-2 at low speed can make it harsh at more than 1/2 throttle. To small and it's a slow shift, add a large band clearance...

The .500 boost valve has a OE light throttle pressure, but has a more progressive pressure curve. Meaning it will still only create 100psi of line at low throttle. At higher throttle you will get a boosted pressure 25-50psi more than normal.
Have you put a gauge on the transmission itself to see pressures? Harbor Freight has a gauge set for $40


JMHO, If they are built for the set up, they don't need a lot of tuning.

[weinerschizel]

Very good choices on the parts list. Excellent choice on the 4L79 drum by Mason Smith of K&N transmission. Lines 16 & 59 elude to a shift kit though. Was this an actual build list or suggestions?
Did you opt for the Sonnax HD 2-3 shift valve?
How about the Sonnax HD 4th servo?
I've been building since 1977 & performance for the last 10 years. I used to feel the same way as the "Other Builder", but since have had to change my mind. I have used countless TransGo box SK's and 2-3 kits with excellent results. The factory doesn't have performance in mind. I also measure every build for band clearance & 3-4 pack clearance, No special tool.

The band clearance has a lot to do with the 1-2 shift speed/timing.
The 1-2 orifice size has a lot to do with it as well, but it is a tricky combo. Too large of a hole for a crisp 1-2 at low speed can make it harsh at more than 1/2 throttle. To small and it's a slow shift, add a large band clearance...

The .500 boost valve has a OE light throttle pressure, but has a more progressive pressure curve. Meaning it will still only create 100psi of line at low throttle. At higher throttle you will get a boosted pressure 25-50psi more than normal.
Have you put a gauge on the transmission itself to see pressures? Harbor Freight has a gauge set for $40


JMHO, If they are built for the set up, they don't need a lot of tuning.

I haven't probed line pressure.

I bought a bunch of TransGo parts but wasn't happy with quality of them. I decided to not use them.

after thinking this through I may have too much gear lash, my issue may actually be the rear end. I only have issue when wheel torque (from coasting) exceeds transmission output.

I didn't change any of the valves. It is a stock valve body. I did tear down, and clean it up though.

I installed three pin les's sonnax servo pistons. And corvette servo. I did not use the Sonnax HD servo.

[Tranzman]

Personally I would put a gauge on it. At least that will tell if it is or isn't physical pressure related.
Is this the transmission build from LS1Tech?
You can check band clearance from the outside by using a prybar against the servo cover. You should be able the only fit a 1/8"-3/16" drill bit between the snap ring & the cover. If you push it all the way in, the driveshaft will only turn one direction & lock the other. Keep in mind one way is more difficult to turn, because it is turning the gear-train/reverse drum inside the band. The band when applied holds the drum.
Your right it could be gear lash...

[weinerschizel]

Yup I have a build thread from LS1tech. I think you posted in it?

Sweet trick to check band clerance. I did not do that. However I did somehow measure servo movement to take up slack on drum. That seems pretty exacting.

Would be cool to get a pressure gauge someday and check pressure.