Running L99 on road course: water temp effects on shift points ???

[Zombie killer]

It seems to me that my L99 will prevent a early paddle downshift and will also make the transmission automatically up shift slightly earlier after the water temp gets higher. I can live with the downshifting delay, but the stupid early upshift before the peak rpm hits and I paddle up shift is annoying. It doesn't do this strange behavior unless I run hard and the water temp rises. I have watched the transmission temp gauge and it doesn't get hot but the moment the engine temp gets higher (magic temp seems to be 230) the rpm range that the transmission shifts at will change. I run in manual mode and no nannies. Just curious if anybody else experiences this or maybe knows for sure if this is a parameter of the computer system or if maybe I need to add better cooling to the transmission.

[zfrederick]

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[Wasted Youth]

Not sure if you got an answer, but I've experienced this as well on a road course (gotta try and get a fast lap in early!!!), and it's normal behavior for the 6L80.

Just like the engine, there are safe parameters for the trans as well, and the 'Hot' tables in the TCM lower the Shift RPM & Shift Speeds when deemed necessary. Obviously even if you're in TUTD, this will happen on its own.

Keep in mind, if you are getting your trans hot enough to use the Hot tables, you're cutting down the life of your ATF significantly, and should plan on replacing it accordingly.

If you plan on doing a lot of road course work, a dedicated trans cooler is recommended...

[hammdo]

I personally run 100% distilled and 2 bottles of water wetter in mine for the summer. I do road race mine and have a ton of coolers (I'm FI and on corn). I also have the biggest trans cooler B&M offers. I'm not at the experience level you are, but did a lot to get her ready...

-Don

[Zombie killer]

Originally Posted by Wasted Youth

Not sure if you got an answer, but I've experienced this as well on a road course (gotta try and get a fast lap in early!!!), and it's normal behavior for the 6L80.

Just like the engine, there are safe parameters for the trans as well, and the 'Hot' tables in the TCM lower the Shift RPM & Shift Speeds when deemed necessary. Obviously even if you're in TUTD, this will happen on its own.

Keep in mind, if you are getting your trans hot enough to use the Hot tables, you're cutting down the life of your ATF significantly, and should plan on replacing it accordingly.

If you plan on doing a lot of road course work, a dedicated trans cooler is recommended...

I agree on all points made. I have already purchased the replacement transmission fluid but it seems that no auto parts stores can even get the filter and gasket kit. Heck even both local Chevy Dealer parts counter have to order the filter as they don't keep it in stock. It seems I have some weird transmission that parts must come from a remote island in the South Pacific. Lol.

I was thinking of adding fluid capacity but my car sits pretty low now that I would be a nervous wreck of knocking the bottom out of the transmission pan if it ended up straddling a high center object like a radius curbing on the course. I guess I will need to begin the research into the best transmission cooler that is out there. Any suggestions ?

[Zombie killer]

Originally Posted by hammdo

I personally run 100% distilled and 2 bottles of water wetter in mine for the summer. I do road race mine and have a ton of coolers (I'm FI and on corn). I also have the biggest trans cooler B&M offers. I'm not at the experience level you are, but did a lot to get her ready...

-Don

I have never had this problem before so it has me wondering which parameters are the cause of the problem. Is it water temp or transmission temp driven, that seems to be my loss for answers. I plan on data logging the next time and see what I can capture to help figure this out but not sure my SCT can capture the trans data to show what temps it is reaching. I have recently modified the rear Diff to the 3.91 gear set and curious if this new gear set would make the transmission generate more heat from the higher rpms and the more aggressive Torque.

[hammdo]

RPM increase is about 300 around 70 mph so that could be the difference -- I had 3.91s in mine too. Had to go to 3.45s for FI. I logged all my temps when I made changes. I can see what it was, but,I believe I went to a bigger radiator before my first track day. Higher RPMs will get the heat up. Did you upgrade the radiator? Don't recall if you said you did...


I have the B&M pan and I'm lowered too, no problems. I also added the Jannetty dip stick tube to make it easier to fill, and the bigger trans filter to improve flow capacity ...

-Don

[Wasted Youth]

When it happened to me, both my trans & engine temps were high, and I just assumed your trans temps were high too.

The TCM has modes for when the trans is hot, but there's also a Hot Engine mode in the Full Throttle tables. After re-reading your post, and if your trans temps are in-fact normal, & not high, what 'might' be happening is the TCM is seeing the engine is hot/getting hot, and reducing the Shift RPM to protect the engine. I say 'might' because that makes sense intuitively, but I have no direct knowledge on how the TCM actually uses those modes.

As for adding capacity, if the pan is taller than OEM, I'd pass. I couldn't avoid a rock in a local canyon that put a fist-sized dent in my OEM pan; a taller pan would have very likely ripped open.

I have no recommendations for coolers as I've never researched them...


Good luck...

[Zombie killer]

The photo was taken as I was coming hot off the track on the the exit road during one of my runs where the transmission shifts were off. The highest water temp reading was at 230 F. The gauges in the 4 pod show higher temps than normal but while on track I could only glance down and make sure they were not nearing the "red line" limits. I wonder if the high temp tables you are referring to are below the temps as shown in my gauge pod photo. I may reach out to Steve at RDP and see what he knows since he did the tune on my transmission.

[Synner]

I would suggest a radiator and trans cooler upgrade. At a water temp of 230 your tune is cutting timing if set up safely. The trans fluid is also higher than I would want for longevity of both the trans and fluid change intervals. My flexalite has never exceeded 212 even in 95 degree heat. I just changed out my trans cooler to a bigger one since I was still getting 220's and I want it lower so I'm not sure what it will be at until next month when I test it out.

[havelegs]

230? Wow that's hot. Mine in 100+ degree stop and go won't go over 207.

[Wasted Youth]

Zombie killer, thanks for the Rod Stewart moment... [wonders if anyone will make the reference]

Yeah, those temps are high enough for the TCM to look after the trans. You should look into oil & trans coolers if you're going to be doing more track days...

[MJanowich]

Originally Posted by Zombie killer

It seems to me that my L99 will prevent a early paddle downshift and will also make the transmission automatically up shift slightly earlier after the water temp gets higher. I can live with the downshifting delay, but the stupid early upshift before the peak rpm hits and I paddle up shift is annoying. It doesn't do this strange behavior unless I run hard and the water temp rises. I have watched the transmission temp gauge and it doesn't get hot but the moment the engine temp gets higher (magic temp seems to be 230) the rpm range that the transmission shifts at will change. I run in manual mode and no nannies. Just curious if anybody else experiences this or maybe knows for sure if this is a parameter of the computer system or if maybe I need to add better cooling to the transmission.

I just ran a track day at Summit Point Shenandoah and at middle of my last 2 sessions, I could tell the car was shifting earlier, not downshifting when it should and generally felt like it was not as powerful as earlier in the day. I didn't look at the temp readings or have any data logging going.

I'm not exactly sure what to do at this point. I don't want to install a transmission cooler only to find that the engine temp is the bigger issue, or vice versa. Maybe just do nothing? How much do coolers run and what's the labor time going to look like if I have a shop install it?

[Synner]

I would suggest trying awareness of your vehicle and gauges. Then you know what to buy and won't drive your vehicle until it explodes.