djslcs

Here are the facts:

Trans has a fresh rebuild on it from century, and their tune.

converter has been back to PI TWICE first for a restall second to be checked due to it pushing the car at idle in drive (i have to hold the brakes hard,if it doesn't kill it bogs the car down)

- tcm is brand new, and has been reflashed.
- PI claims " all is well in converter" clearances etc are ok. I just don't get it. once the car is moving it drives fine, shifts fine, but when your sitting there at idle, it not only feels like your locked up ( we verified lockup is working with tech2, and the slip comes up properly ) but it bucks when your starting to move. Precision swears that this thing should not budge at idle in gear. But it does. I made sure the flow thru the cooler was sufficient. It was not blocked by any means. I don't know what else to try. I cannot get my hands on a stock converter for a 08 c6 a6, and i REFUSE to throw more money at this thing. I spent $450.00 on a TCM plus a little more to install, and that fixed NOTHING.

SO, has anyone heard of anything like this? What does this issue sound like to you guys?

mrvedit

Update: Oops, I didn't see that you had a 6L80E, thought you had a 4L60E.

This is almost identical to this recent thread:
https://ls1tech.com/forums/automatic...p-r-n-d-3.html

A bad and dragging lockup clutch in the converter is the first concern, but since the converter was replaced, I'm confident it is a problem in the trans. Something in the TCC fluid circuit is not right. That thread will give you ideas of what to test, especially if you are willing to drop the pan and experiment a bit.

aknovaman

iTrader: (7)

Seen a similar problem on a '07 burb 5.3L 60e swap we did on a Jeep. I had to adjust the PCM decel and idle timing areas and idle air flow areas among a multitude of other tables. Jeep ran perfect including fueling and trans operation; it just wanted to shove you through the intersection at stoplighs.

poorhousenext

Where are you located?

I have a never used stock 6L80E converter that came with trans when I did 6L80E/LS7 build in a 66 Vette. I replaced it with a Yank converter instead of using it.

bbond105

Did the problem start when the rebuilt trans was installed or was the problem there before the trans was rebuilt? You didn’t state when the problem first started.

mrvedit

Oops, I didn't see that you had a 6L80E, thought you had a 4L60E.
Still, I think the principals are the same - the TCC is partially applied.

djslcs

I basically bought the car with a box of parts. It did not have this issue before. When tuning he adjusted all kinds of stuff but it didn't fix it, it kept the car from dying. The car worked properly before the Trans and converter were gone thru. It basically stalls the car when cold and is tight when it's idling in drive. Once your moving, it is perfect but it is literally like a standard when your at idle in drive. I am located in Slidell, La..

bbond105

I would try calling Century for tech support. I don’t think the torque converter is causing this. I don’t have any experience with this trans so I don’t think I will be able to be much help. I did look at a parts brake down and there is a big difference from a 4L60E.

poorhousenext

Hoping you were a little closer makes it easier for loaning parts.

Question: Did you do install, and have problem from get go, no trans tuning or did you do install and then take car directly to have it tuned. I'm not all up on how 6L80 works, but someone who tries to tune an A6 like they do an A4 can really screw up trans. The trans to engine comunication is critical.

Might try PM
ing member here, TrueBlueGTO. He's done a lot of 6L80E swaps in different veheicles, he might have seen your kind of problem before.

djslcs

It worked before the change with the same tuning etc. Nothing changed cept the stall speed and a rebuild on the trans

djslcs

Does this sound like an overly tight/ broken converter? I really don't want to waste any more money in vain. If anyone would be willing to lend me a converter id be glad to pay for shipping and return it promptly upon my reinstall and findings.

Dark SS

iTrader: (6)

6L80's do some strange stuff with big (4k+) stall converters. I've personally seen 2 vettes (1 was mine) with yank 3600's work flawlessly and 1 with a yank 4k have nothing but issues.

djslcs

well I'm glad that I'm not the only one i just need to find a loaner for the time being for my process of elimination.

bbond105

I have a stock 4L60E LS 300mm converter you can try if it will work with your trans. I don't know if it will interchange or not. Hopefully someone who knows will chime in. I’m only 45 min from Slidell.

djslcs

Hey man,

I tried the stockers from some 4ls from some c5s and camaros. The problem is the bolt pattern is different, vettes generally have the same bolt pattn, but the snout id is smaller on the 4Ls than the 6Ls. Thanks for the offer though. I do appreciate it

Circle-D

iTrader: (21)

Have you done any data logging to see what TCC slip is showing when you drop it in gear? I might help some, not sure. In park/neutral the TCC slip should be close to zero, no resistance on the input shaft. When you drop into gear the TCC slip should match the crank RPM. Basically the input shaft is stopped when the FWD clutches are applied. Not sure if that will really show anything though.

I doubt it is a tune issue, family certain you can not even turn on lock up in first gear through the tune. My guess is a hydraulic issue, could be trans or converter. Sadly not much advice for you.

Chris

mrvedit

While the 4L60e and 4L80e have valve bodies with numerous valves and springs, the 6L80e has a valve body consisting mostly of PWM solenoids. The function of the old valves and springs is all done by software controlling the solenoids. Hence the software and tuning are much more critical.

Since the OP says the tune was not changed, but the trans had just been rebuilt, a problem with the rebuild is also suspect. Personally I would first reference the 5th-Gen Camaro and related forums to see if anyone there had a quick answer or suggestion. If nothing there, I would remove the valve body and replace the gaskets to rule out any cross leaks. Of course trying a different converter is also a good plan to make sure it doesn't have a defective and dragging lockup clutch.

djslcs

Thanks guys for all the insight. The guy above on here is gonna be kind enough to mail me a stock converter for me to try and I'm gonna diag that way. It will only cost a little shopping, so I'll know, inadvertently if the converter is the issue. If it doesn't fix it then it's on to plan b, having the Trans gone thru. I'll post my results. He said he can't ship for a week or so, but I've got other things getting done, so I can wait. Just need to put known good parts in to test

poorhousenext

Finally found my never ran stock 6L80E converter this morning. But before we possibly waste your money on shipping converter back and forth, got some questions that need to be addressed.

What did you use for a converter before going with PI converter in car now?

Do you know which basic 6L80 tune was installed in old internal TCM, an was the same base program loaded in the New TCM installed or replaced with another tune?

Did the car with the box of parts in it you bought come with a 58 Reluctor LS engine and 6L80E, or is this a conversion to 6L80E. Not all ECMs are compatable with 6L80E. What model ECM are you using?

Quote on wire harness builder's website.

Quotes on 6L80e Transmission Builder's website.

#6L80Upper. 6L80 Upper Valve Body Assembly. This is the upper portion of the two piece valve body in the 6L80E. These are new AC Delco Valve bodies, not remanufactured. Complete VIN Required when ordering.

What rear end ratio does car have and what is approx weight of car? 6L80E has a Granny geared 1st gear (4.02) while 2nd (2.36) is also like a 1st gear ratio used in 4sp/5sp manual trans.

I just swaped out 2008 LS7 engine over to a stock 2014 LS3 and had to retune throttle shift paramatures, but with new LS3 ECM goes in limp mode anytime you go wide open throttle. Drives and shift goods as long as you drive noraml. Seems late model throttle bodys can be a problem, so we are pulling the throttle body off the LS7 to see if that fixes the problem. I'll be using a different trans in car LS7 is going in so maybe Throttle body want be a problem with it and it's ECM.

djslcs

The Trans was tuned by century, the new tcm was flashed by a gm tech, it was the correct reluctor wheel as it was an ls3 that went back in, the car runs drives and shifts fine I just firmly believe that there is an issue with the converter with how it lugs the motor down in drive @ idle.