Any 6l80 experts around?

[67Steven]

Thanks for the help.

I ran the truck up to Wong's Performance in Vancouver yesterday since he is a GM Corvette guru. The truck drove great 34 miles up there, not a hint of trouble.

He used a Tech2 and found 2 codes: Lost comms with CAN/BUS and ABS controller, nothing else. Apparently these were set up in my tune as 'throw a code, but not a CEL'. He removed them and updated my tune- then we ran it on the dyno. All the shift tables looked correct and it shifted where it was supposed to according to the scanner. No problems at all, ran up and down gears, the transmission was within 1 mph of the dyno and the Tech2. Got the engine temps up to 250 degrees and no problems, (other than a leaking radiator cap I discovered) We figured the codes might have been the culprit, so I drove home.

On the way , it occurred again. Engine really chugged to keep going until I could pull over. I am beginning to think it is occurring when the transmission has to shift up and down repeatedly- winding road the first few times, and stop and go traffic yesterday. I did notice that it held second gear instead of shifting to first at low speeds a couple of times. Since I had to get home, I reset the pigtail and drove the rest of the way home.

One additional item. When I pulled over, I was at a slight incline. I put it in park and hopped out to pull the plug. After a second or two, the truck rolled back to rest on the park pawl- almost like the transmission 'released' itself.

If it was the tune, why would it not act this way from the start? It drives awesome first thing in the morning- could heat be a cause of this? Should I run the trans through a dedicated remote cooler and not through the radiator?

Steven

[Hart_Rod]

Originally Posted by 67Steven

Thanks for the help.

I ran the truck up to Wong's Performance in Vancouver yesterday since he is a GM Corvette guru. The truck drove great 34 miles up there, not a hint of trouble.

He used a Tech2 and found 2 codes: Lost comms with CAN/BUS and ABS controller, nothing else. Apparently these were set up in my tune as 'throw a code, but not a CEL'. He removed them and updated my tune- then we ran it on the dyno. All the shift tables looked correct and it shifted where it was supposed to according to the scanner. No problems at all, ran up and down gears, the transmission was within 1 mph of the dyno and the Tech2. Got the engine temps up to 250 degrees and no problems, (other than a leaking radiator cap I discovered) We figured the codes might have been the culprit, so I drove home.

On the way , it occurred again. Engine really chugged to keep going until I could pull over. I am beginning to think it is occurring when the transmission has to shift up and down repeatedly- winding road the first few times, and stop and go traffic yesterday. I did notice that it held second gear instead of shifting to first at low speeds a couple of times. Since I had to get home, I reset the pigtail and drove the rest of the way home.

One additional item. When I pulled over, I was at a slight incline. I put it in park and hopped out to pull the plug. After a second or two, the truck rolled back to rest on the park pawl- almost like the transmission 'released' itself.

If it was the tune, why would it not act this way from the start? It drives awesome first thing in the morning- could heat be a cause of this? Should I run the trans through a dedicated remote cooler and not through the radiator?

Steven

Interesting. I think there is probably something in the tune causing the problem, but I would double check your shift linkage to make sure you are getting it in gear correctly. Next, what tranny temps are you seeing? When they were s scanning it at the shop they should have been able to see this. You really need to have a scanner connected and data log when this situation occurs. One more thing, before u reset the tranny, do u check for codes?

Can u email me.a copy of the tune?

[67Steven]

Originally Posted by Hart_Rod

Interesting. I think there is probably something in the tune causing the problem, but I would double check your shift linkage to make sure you are getting it in gear correctly. Next, what tranny temps are you seeing? When they were s scanning it at the shop they should have been able to see this. You really need to have a scanner connected and data log when this situation occurs. One more thing, before u reset the tranny, do u check for codes?

Can u email me.a copy of the tune?

Shifter works okay, it uses the detents on the trans for location. I don't remember checking the trans temps, at that point it didn't occur to me that might be a problem, and Thomas the tuner was watching the scanner as I ran up and down the gears. Engine temps are usually 180-230 degrees driving.

Yeah, unfortunately I know I need to have a scanner connected. I need to find someone willing to drive around for an hour or so to see if it acts up as my poor, little scanner does nothing for live data for transmissions.

I did check for codes the last time and I had nothing pending or active, clear slate and no CEL.

I wonder if I had another 'stock' tune put on the transmission and drove it like that for a while to see if repeats- would it be worth it?

I will call the tuner tomorrow and see if he will email the tune to me and I will send it down to you.

Thanks for all the help!

[Bigdav160]

Your symptoms sound like a pressure solenoid that is leaking. It will cause a tie up. In a OE tune it would cause a code and default to limp in mode.

My buddy at the dealer says he puts a lot of valve bodies in the 6l80's. I know you didn't want to hear that.

[67Steven]

Well, I'd rather know the cause and deal with it than to go on like it is, $$ or not!

Actually $$$ or not, heh.

[BR3W CITY]

250 degress is really warm...I prefer not to let my engine get there if I can avoid it.

What are your trans temps?

The problem with doing it on a dyno is that you can only load the engine so much, and not really under real world circumstances. If your issue is only under a certain load condition, you may not pinpoint it on a dyno.

If the shift timing is set really slow, the delay for a downshift will be longer than the actual amount of time your in that position. Lots of tip-in and pulling off in twisties will do this. Gas, gas, breaaak, gas, brake....back n forth. If the trans is set to a super long delay, or an awkward lockup/release, you'll never make it to the right gear at the right time. This can be adjusted, but lots of tuners don't mess with the finer tranny settings (since most don't rebuild transmissions lol).

IMO you need to get a road-test to actually show a tuner whats happening. Corvette's have a much more complicated traction control/tq management system than any swap car, so there may some things that the tuner isn't comfortable messing with. Changing abuse protection settings and lockup release is something that does make some tuners uncomfortable.

[67Steven]

Originally Posted by BR3W CITY

250 degress is really warm...I prefer not to let my engine get there if I can avoid it.

What are your trans temps?

The problem with doing it on a dyno is that you can only load the engine so much, and not really under real world circumstances. If your issue is only under a certain load condition, you may not pinpoint it on a dyno.

If the shift timing is set really slow, the delay for a downshift will be longer than the actual amount of time your in that position. Lots of tip-in and pulling off in twisties will do this. Gas, gas, breaaak, gas, brake....back n forth. If the trans is set to a super long delay, or an awkward lockup/release, you'll never make it to the right gear at the right time. This can be adjusted, but lots of tuners don't mess with the finer tranny settings (since most don't rebuild transmissions lol).

IMO you need to get a road-test to actually show a tuner whats happening. Corvette's have a much more complicated traction control/tq management system than any swap car, so there may some things that the tuner isn't comfortable messing with. Changing abuse protection settings and lockup release is something that does make some tuners uncomfortable.

Well, it sounds as though I need to invest in a trans temp gauge. I will order one tonight probably. 250* was sitting on the dyno with a semi- worthless fan running on it, it never gets that high driving.

What you describe gas-brake-gas, etc. is exactly the types of driving I have done to experience the binding. It does feel that I am 'confusing' the trans when I drive this way. Open road and higher gears seems to be no problem.

Sometimes I need to come to a complete stop to get it to shift into first or it will try to start in 2nd or higher and bog the engine for a second before down shifting and taking off. This condition is not always, but occurs every now and then, never first trip out for the day, though.

The tuner I went to is about the if not the only tuner around that even knows what a 6L80 is. He does more than just 'vettes, he has dyno tuned quite a few LS swaps before, mostly Landcruisers as I understand it.

I hope I can talk him out of a copy of the tune on the truck to forward it on up the food chain.

[BR3W CITY]

Ok, I mentioned the 'vette thing, just since some folks that "specialize" also ignore other stuff lol.

When he put it on the dyno, were you able to go part-throttle at all and try to replicate the problem? Depending on the guy, he should be able to sit in the passenger seat with hpt and his laptop, and watch your gear shifts /line pressure vs throttle % to see whats actually happening.

[clinebarger]

Some TCM OS's will do a 2nd gear start in certain conditions, The Supercharged CTS-V does this. 2nd gear ratio is 2.36...Not much different than the 1st gear ratio on a TH400/TH350.
From the description of the symptoms, Sound like it's taking of in 3rd (3rd default mode)

"If the transmission is in 1st, 2nd or 3rd gear during a transmission electrical component failure, the transmission will default to 3rd gear. All solenoids will default to their normal state. If the torque converter clutch was applied, it will release."

Fifth Gear Default

"If the transmission is in 4th, 5th or 6th gear during a transmission electrical component failure, the transmission will default to 5th gear. All solenoids will default to their normal state. If the torque converter clutch was applied, it will release. The transmission will stay in 5th gear default range until the ignition has been turned off or transmission shifted to reverse. When the vehicle is restarted, and shifted back into drive, the transmission will then operate in the 3rd gear default range"

Originally Posted by 67Steven

He used a Tech2 and found 2 codes: Lost comms with CAN/BUS and ABS controller, nothing else.

I'm interested in the CAN/BUS code, Do you know the code number?
•DTC U0100 in the TCM will cause the transmission to go into default gears.

Do Not discount what Bigdav160 said, A leaky Variable Bleed PC Solenoid can cause very weird $hit to happen, Including Tie-Up's (binding) & Default modes.

Clutch to Clutch transmission are a whole other world compared to the 4 speed "E" transmissions, And need to be tuned accordingly. From what I have seen "Tuners" do more harm to these than good.

[Hart_Rod]

Steven - did you get any further with this?

[67Steven]

Originally Posted by BR3W CITY

Ok, I mentioned the 'vette thing, just since some folks that "specialize" also ignore other stuff lol.

When he put it on the dyno, were you able to go part-throttle at all and try to replicate the problem? Depending on the guy, he should be able to sit in the passenger seat with hpt and his laptop, and watch your gear shifts /line pressure vs throttle % to see whats actually happening.

Yeah, we sat on the dyno for around 40 minutes, and it did not occur. We went up and down through the gears a bunch. Sometimes slow, sometimes fast, and a few times just to third and back down. He watched the gear selection, pressures, everything that could cause the issue, and he said all looked good.

Originally Posted by clinebarger

Some TCM OS's will do a 2nd gear start in certain conditions, The Supercharged CTS-V does this. 2nd gear ratio is 2.36...Not much different than the 1st gear ratio on a TH400/TH350.
From the description of the symptoms, Sound like it's taking of in 3rd (3rd default mode)

"If the transmission is in 1st, 2nd or 3rd gear during a transmission electrical component failure, the transmission will default to 3rd gear. All solenoids will default to their normal state. If the torque converter clutch was applied, it will release."

Fifth Gear Default

"If the transmission is in 4th, 5th or 6th gear during a transmission electrical component failure, the transmission will default to 5th gear. All solenoids will default to their normal state. If the torque converter clutch was applied, it will release. The transmission will stay in 5th gear default range until the ignition has been turned off or transmission shifted to reverse. When the vehicle is restarted, and shifted back into drive, the transmission will then operate in the 3rd gear default range"



I'm interested in the CAN/BUS code, Do you know the code number?
•DTC U0100 in the TCM will cause the transmission to go into default gears.

Do Not discount what Bigdav160 said, A leaky Variable Bleed PC Solenoid can cause very weird $hit to happen, Including Tie-Up's (binding) & Default modes.

Clutch to Clutch transmission are a whole other world compared to the 4 speed "E" transmissions, And need to be tuned accordingly. From what I have seen "Tuners" do more harm to these than good.

Sorry, I do not remember the code number for the CAN/BUS fault. I tried to use my scanner for a history, but it shows nothing.

When I first got the truck running, I had a CEL for "Solenoid 'E' range or sticking" The transmission started in 3rd and I drove approximately 600 feet and parked it. The next time I started, the code had cleared itself. That has been the only TCM code other than 'lost communications' I have found on my little scanner.

What it is doing now, does NOT feel like the third gear default start and run, it really feels like the brakes are being applied.

If I don't come to a complete stop, the truck will sometimes stay in second gear, but not always. The more I read on these transmissions, the more I am inclined to believe it is a tune issue. I think the stop/go/stop in the lower gears 'confuses' the tune in the TCM -for lack of a better term.

Originally Posted by Hart_Rod

Steven - did you get any further with this?

No, I have been swamped at work. I did change the trans fluid and filter, and it was nice and red and clean, nothing in the pan or on the magnet.

I have made the decision to purchase HP tuners so I can share my tune and maybe have someone smarter than me say "Here's your problem right there..." It will be nice to make changes at home and not pay someone $100 a whack to change the tune, or $1000 just to diagnose it like one local shop wanted.


Thanks again for all the help you guys are giving me, I appreciate it greatly!

[67Steven]

Whoops, Double tap.

[clinebarger]

Originally Posted by 67Steven

Yeah, we sat on the dyno for around 40 minutes, and it did not occur. We went up and down through the gears a bunch. Sometimes slow, sometimes fast, and a few times just to third and back down. He watched the gear selection, pressures, everything that could cause the issue, and he said all looked good.





Sorry, I do not remember the code number for the CAN/BUS fault. I tried to use my scanner for a history, but it shows nothing.

When I first got the truck running, I had a CEL for "Solenoid 'E' range or sticking" The transmission started in 3rd and I drove approximately 600 feet and parked it. The next time I started, the code had cleared itself. That has been the only TCM code other than 'lost communications' I have found on my little scanner.

What it is doing now, does NOT feel like the third gear default start and run, it really feels like the brakes are being applied.

If I don't come to a complete stop, the truck will sometimes stay in second gear, but not always. The more I read on these transmissions, the more I am inclined to believe it is a tune issue. I think the stop/go/stop in the lower gears 'confuses' the tune in the TCM -for lack of a better term.

It may well be tuning. "It feel like the brakes are on" Sounds like a bind over the internet, But could be the lack of "Overrunning" when you let off the gas pedal, The TCM locked in Tow/Haul mode will do that?

[67Steven]

Originally Posted by clinebarger

It may well be tuning. "It feel like the brakes are on" Sounds like a bind over the internet, But could be the lack of "Overrunning" when you let off the gas pedal, The TCM locked in Tow/Haul mode will do that?

You know, I wondered about the tow/haul mode, I know it has different shift tables, could the TCM in any way convert to tow/haul mode without driver input?

[clinebarger]

Originally Posted by 67Steven

You know, I wondered about the tow/haul mode, I know it has different shift tables, could the TCM in any way convert to tow/haul mode without driver input?

The tuner could have pasted the Tow/haul table over the normal table?
This is speculating of course.

[Chvy2NV]

Subd. I know I'll be needing this later

[67Steven]

Okay, I suppose I should update this thread, albeit with an embarrassing reason.

The whole time I have been saying it feels like the brakes are being applied, well that is exactly what is happening as I discovered today.

I have been driving it around trying to get it to act up again now that I have HP tuners and can actually have real data to problem solve. It occured near home, but this time I popped it in neutral, and still had the dragging feel. So I gimped it home, jacked up the front axle and both tires were locked up. Shut the truck off and a second or two later it released.

So, correlation does not equal causation! It has probably been just enough time when I unplug the transmission to ease off the brakes, and so I assumed it was transmission issues. What an idiot I have been.

Now I need to figure out why my front axle wants to keep the brakes engaged.

Thanks for all the ideas and help, I really do appreciate it!

Off to start a new thread.

[Hart_Rod]

Originally Posted by 67Steven

Okay, I suppose I should update this thread, albeit with an embarrassing reason.

The whole time I have been saying it feels like the brakes are being applied, well that is exactly what is happening as I discovered today.

I have been driving it around trying to get it to act up again now that I have HP tuners and can actually have real data to problem solve. It occured near home, but this time I popped it in neutral, and still had the dragging feel. So I gimped it home, jacked up the front axle and both tires were locked up. Shut the truck off and a second or two later it released.

So, correlation does not equal causation! It has probably been just enough time when I unplug the transmission to ease off the brakes, and so I assumed it was transmission issues. What an idiot I have been.

Now I need to figure out why my front axle wants to keep the brakes engaged.

Thanks for all the ideas and help, I really do appreciate it!

Off to start a new thread.

It happens to all of us! It's real easy to talk yourself into a diagnosis, especially with something unknown such as these new transmissions. As far as the brakes, a friend of mine had a similar situation going. We finally diagnosed his problem to the push rod from the brake pedal to the master cylinder being adjusted out too long. We shortened the rod, problem fixed.

[67Steven]

Originally Posted by Hart_Rod

It happens to all of us! It's real easy to talk yourself into a diagnosis, especially with something unknown such as these new transmissions. As far as the brakes, a friend of mine had a similar situation going. We finally diagnosed his problem to the push rod from the brake pedal to the master cylinder being adjusted out too long. We shortened the rod, problem fixed.

I just got done checking that very issue, and I have it shortened, as well as cleaning and re-lubing the front calipers. I hope this does the trick!