Since we have some savvy transmission guys here. I have a 6L90 in my CTS-V and the general consensus on the V forums is that GM sold some of these cars about a quart low on ATF. Guys are adding a 1 - 1.5 quarts into them and eliminating a problem where you hit the rev limiter on wide open throttle shifts, usually the 2/3 shift. My car was doing this too and I added an extra quart. It did stop it almost entirely. Almost. Every once and while it will kiss the rev limiter on a 2/3 shift. I'm wondering if I need another half quart or if I should correct the issue with tuning. Either command or 50rpm sooner shift or set a hair higher redline.
The junkiest automatic transmission ever manufactured?
- Thread starter sloinker
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You need a control!
*With the trans COLD, Engine idling-Trans in park with the vehicle level, Pull the check plug & add ATF 'til it comes out the check plug hole.
*Warm the ATF up to 85°F, While idling in park with the vehicle level, Pull the check plug & allow the excess ATF to drain out.
*Replace the check plug & add 1 quart.
You will now have 1 quart OVER the maximum GM recommended fill. This is what I do on all 6L80E/6L90E units in G8/CTS-V/Camaro/Corvette.
If your car still exhibits the symptoms......
*Connect a Transmission Pressure Gauge & test drive the vehicle. IF the Line Pressure drops off abnormally during the flaring 2-3 shift......Add an additional 1/2 quart.
*If no abnormal pressure drops are observed......Adjust the calibration accordingly.
I don't know if you do your own tuning or not....But I will add this just in case.
*I find it easier to Lower the Shift vs MPH (Full Throttle Shift Speed in MPH) opposed to Shift vs RPM; In fact most of the 6L80E/6L90E's I've tuned Do Not respond to RPM changes.
*I don't recommend upping the rev limiter on LSA engines, No need in beating-up your valve springs & supercharger for no reason.
This is the shift scheduling tab for a 2008 LS3/6L80E Corvette per HP-Tuners, Your CTS-V will be very similar.
I pointed out the three tables on the left that need changed.....
*Shift Pattern A is "Normal" shift speeds
*Shift Pattern B is "Performance" shift speeds
*Normal.....It this calibration, It's the same as Shift Pattern B/Performance.
If yours has "Sport/Competitive" mode....That will be Pattern B, And Normal will be Pattern A, If you have a "Normal" tab....Compare it to A & B, Keep it matched to it's corresponding table!
The top left tap shows the Normal Shift Speeds, Pointed out is the 2-3 shift speeds, Lower BOTH values 5 MPH. Do the same to the A & B tables.
The bottom left tab is Shift vs RPM....Like I said, Never had luck modifying the values here!!!
![[Linked Image]](https://i.imgur.com/ZUwdW40.png "[Linked Image]")
*With the trans COLD, Engine idling-Trans in park with the vehicle level, Pull the check plug & add ATF 'til it comes out the check plug hole.
*Warm the ATF up to 85°F, While idling in park with the vehicle level, Pull the check plug & allow the excess ATF to drain out.
*Replace the check plug & add 1 quart.
You will now have 1 quart OVER the maximum GM recommended fill. This is what I do on all 6L80E/6L90E units in G8/CTS-V/Camaro/Corvette.
If your car still exhibits the symptoms......
*Connect a Transmission Pressure Gauge & test drive the vehicle. IF the Line Pressure drops off abnormally during the flaring 2-3 shift......Add an additional 1/2 quart.
*If no abnormal pressure drops are observed......Adjust the calibration accordingly.
I don't know if you do your own tuning or not....But I will add this just in case.
*I find it easier to Lower the Shift vs MPH (Full Throttle Shift Speed in MPH) opposed to Shift vs RPM; In fact most of the 6L80E/6L90E's I've tuned Do Not respond to RPM changes.
*I don't recommend upping the rev limiter on LSA engines, No need in beating-up your valve springs & supercharger for no reason.
This is the shift scheduling tab for a 2008 LS3/6L80E Corvette per HP-Tuners, Your CTS-V will be very similar.
I pointed out the three tables on the left that need changed.....
*Shift Pattern A is "Normal" shift speeds
*Shift Pattern B is "Performance" shift speeds
*Normal.....It this calibration, It's the same as Shift Pattern B/Performance.
If yours has "Sport/Competitive" mode....That will be Pattern B, And Normal will be Pattern A, If you have a "Normal" tab....Compare it to A & B, Keep it matched to it's corresponding table!
The top left tap shows the Normal Shift Speeds, Pointed out is the 2-3 shift speeds, Lower BOTH values 5 MPH. Do the same to the A & B tables.
The bottom left tab is Shift vs RPM....Like I said, Never had luck modifying the values here!!!
I mean't the RIGHT tabs in the last couple sentences.....
Clinebarger great info, thank you. I do have HP Tuners and SCT software. I also have a good friend in the GM performance tuning business but he doesn't like to do trans tuning. For what it's worth, he is very leery about raising the rev limiters on the LSA engine without a spring upgrade. He wouldn't lift mine even 100rpm, he works on ALOT of LSA equipped cars.
I don't blame him. GM has a history of equipping their engines with valve springs that are adequate. Go forever within their expected parameters. Outside of them? Sucks.
I remember when we bought a replacement industrial GM V8 for one of my forklifts it contained a warning to "install appropriate racing valve springs for constant high speed operation such as shredders or the like". The most interesting part of that was imagining what kind of shredder uses a GM V8 for its powerplant.
I remember when we bought a replacement industrial GM V8 for one of my forklifts it contained a warning to "install appropriate racing valve springs for constant high speed operation such as shredders or the like". The most interesting part of that was imagining what kind of shredder uses a GM V8 for its powerplant.
Mr. Bonestripper
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Originally Posted by supton
I generally think Toyota (Aisin?) has something against the concept of convertor lockup--they are quick to unlock and push too tall of a gear. I can repeatedly get lower rpm in my truck by commanding downshifting on a hill. It'll push 6th unlocked rather than 5th locked. I'm guessing it's to prevent wear and tear on the trans, but it just grates on my nerves. My Camry it turns out is the same way; in 3rd gear it won't lock up until some high rpm, and is very quick to unlock even still (if I'm heavy on the throttle and have OD locked out).
Oh well. I just live with it. They seem to be long lived, so I just put up with it, and worry about other things in life. Around town I just lock out gears if I think it best.
All you have to do is turn overdrive off and it will lock up 3rd gear or 5th gear......
I generally think Toyota (Aisin?) has something against the concept of convertor lockup--they are quick to unlock and push too tall of a gear. I can repeatedly get lower rpm in my truck by commanding downshifting on a hill. It'll push 6th unlocked rather than 5th locked. I'm guessing it's to prevent wear and tear on the trans, but it just grates on my nerves. My Camry it turns out is the same way; in 3rd gear it won't lock up until some high rpm, and is very quick to unlock even still (if I'm heavy on the throttle and have OD locked out).
Oh well. I just live with it. They seem to be long lived, so I just put up with it, and worry about other things in life. Around town I just lock out gears if I think it best.
All you have to do is turn overdrive off and it will lock up 3rd gear or 5th gear......
Originally Posted by Jmoney7269
Originally Posted by supton
I generally think Toyota (Aisin?) has something against the concept of convertor lockup--they are quick to unlock and push too tall of a gear. I can repeatedly get lower rpm in my truck by commanding downshifting on a hill. It'll push 6th unlocked rather than 5th locked. I'm guessing it's to prevent wear and tear on the trans, but it just grates on my nerves. My Camry it turns out is the same way; in 3rd gear it won't lock up until some high rpm, and is very quick to unlock even still (if I'm heavy on the throttle and have OD locked out).
Oh well. I just live with it. They seem to be long lived, so I just put up with it, and worry about other things in life. Around town I just lock out gears if I think it best.
All you have to do is turn overdrive off and it will lock up 3rd gear or 5th gear......
That's what I do.
Although to specific, this transmission won't lock up in 1, 2, 3. Only 4, 5, 6 (4 is direct, 5 and 6 are OD). Don't know why but that's how it's programmed.
Originally Posted by supton
I generally think Toyota (Aisin?) has something against the concept of convertor lockup--they are quick to unlock and push too tall of a gear. I can repeatedly get lower rpm in my truck by commanding downshifting on a hill. It'll push 6th unlocked rather than 5th locked. I'm guessing it's to prevent wear and tear on the trans, but it just grates on my nerves. My Camry it turns out is the same way; in 3rd gear it won't lock up until some high rpm, and is very quick to unlock even still (if I'm heavy on the throttle and have OD locked out).
Oh well. I just live with it. They seem to be long lived, so I just put up with it, and worry about other things in life. Around town I just lock out gears if I think it best.
All you have to do is turn overdrive off and it will lock up 3rd gear or 5th gear......
That's what I do.
Although to specific, this transmission won't lock up in 1, 2, 3. Only 4, 5, 6 (4 is direct, 5 and 6 are OD). Don't know why but that's how it's programmed.
Originally Posted by Gasbuggy
Clinebarger great info, thank you. I do have HP Tuners and SCT software. I also have a good friend in the GM performance tuning business but he doesn't like to do trans tuning. For what it's worth, he is very leery about raising the rev limiters on the LSA engine without a spring upgrade. He wouldn't lift mine even 100rpm, he works on ALOT of LSA equipped cars.
I too have noticed tuners don't like modifying trans tables, The main reason being.......
Hydraulic Actuation takes time, Just because the unit has Electric Solenoids doesn't mean they're able to control clutch packs like an On/Off switch.
Tuning-in "Lead Time" goes all the way back to the infancy of electronic transmissions, Which was actually learned/perfected when transmissions were 100% Hydraulic.....It's just MUCH easier with electronic transmissions!!
Lets use a TH400 as an example.....
A guy is bracket racing his '70 Chevelle, Has a pretty hot N/A big block & it shifts automatically at 6,400/1-2...6,200/2-3. He wants more power & installs a 200 shot of Nitrous.
Now the car hits the 6,600 rev limiter on the 1-2 shift & shifts 2-3 a few 100 RPM later than it did. Naturally....If you built his transmission, He will call & say somethings wrong with it!
Explain to him that his car is now accelerating faster than it did when using his new toy, A few Governor tweaks later.....It's back shifting at 6,400/6,200 WITH the nitrous, But WILL now shift early without the power-adder.
Being in this situation before.....You save the Springs & Weights & Clone the original N/A Governor for him to swap out when he's street driving.
**You will probably make $4.00 an hour through this ordeal & the customer is still unhappy because he has to jack up the car & swap Governors.
Clinebarger great info, thank you. I do have HP Tuners and SCT software. I also have a good friend in the GM performance tuning business but he doesn't like to do trans tuning. For what it's worth, he is very leery about raising the rev limiters on the LSA engine without a spring upgrade. He wouldn't lift mine even 100rpm, he works on ALOT of LSA equipped cars.
I too have noticed tuners don't like modifying trans tables, The main reason being.......
Hydraulic Actuation takes time, Just because the unit has Electric Solenoids doesn't mean they're able to control clutch packs like an On/Off switch.
Tuning-in "Lead Time" goes all the way back to the infancy of electronic transmissions, Which was actually learned/perfected when transmissions were 100% Hydraulic.....It's just MUCH easier with electronic transmissions!!
Lets use a TH400 as an example.....
A guy is bracket racing his '70 Chevelle, Has a pretty hot N/A big block & it shifts automatically at 6,400/1-2...6,200/2-3. He wants more power & installs a 200 shot of Nitrous.
Now the car hits the 6,600 rev limiter on the 1-2 shift & shifts 2-3 a few 100 RPM later than it did. Naturally....If you built his transmission, He will call & say somethings wrong with it!
Explain to him that his car is now accelerating faster than it did when using his new toy, A few Governor tweaks later.....It's back shifting at 6,400/6,200 WITH the nitrous, But WILL now shift early without the power-adder.
Being in this situation before.....You save the Springs & Weights & Clone the original N/A Governor for him to swap out when he's street driving.
**You will probably make $4.00 an hour through this ordeal & the customer is still unhappy because he has to jack up the car & swap Governors.
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