Lack of performance solved. I think.

[Randee of the Redwoods]

Or maybe at least I found the reason behind it. Pulling into my apt complex parking lot today after work(yes, I had to go out in the snow), the battery light flickered a couple times. What's the first think you think: alternator? That's what I thought. Not happy, but the first thing to come to mind. Ran for codes. 85, 68. 68-Transmission component slipping. Freakin' great. Just what I needed to hear. 85-Undefined ratio error. 68 I understand. My bank account won't, but I do. But the code 85 I don't understand. Ratio? The only ratio I know of is the axle ratio and they are as they came equipped from the factory. I would like some help interpreting that code 85, and maybe what may cause the 68, please. The only thing I can think of is 2 sensors watching the tranny input and output. During slippage they would not match a predetermined table, so the "undefined ratio error" code. Hey, I'm just taking a shot in the dark. Opinions please. Donations please, also.

[patrick m.]

Randee, i believe you hit the nail on the head.
that code will set when computer thinks the tranny is in....say third gear (because the solenoid told it so), but the speed sensor is telling the computer that the output shaft speed is out of range with input rpm.
doesnt sound good :(

[rjschoolcraft]

Exactly right! Clutches are slipping and the input speed to output speed ratio is not right for the gear range selected.

[tom.mcinerney]

I know nothing bout trannies, but have cured cold weather slippage with fluid/filter change in 350 and 400s.

[Randee of the Redwoods]

Fluid and filter were changed less than 2 weeks after the truck was originally delivered a few months ago. Fluid was on the verge of turning orange, color was reddish-orange leaning towards the reddish side. Whatever is going on must have happened recently as the other umpteen billion times I checked for codes, these never came up. Maybe it just took this long for the stress of the hills I drive on everyday to sink in and cause damage. For me, driving to work is uphill, both ways. Seriously.

[DmaxMaverick]

Sounds like the Trans-X wore off. Old used car dealer's trick.

If the tranny starts to slip, add some Trans-X and sell it. They will usually straighten up for a few thousand miles if caught early enough.

Trans-X (if enough is added) will lighten the color of normal Dexron III and give it a slight "solvent" feel (less slippery).

The auto's answer to saw dust.

[Randee of the Redwoods]

I'ma gonna keep driving it. I ain't selling for nothing. Too much into it plus I really do like the truck. I'll foot the tranny rebuild as it was originally planned for in the budged. The headgaskets were not planned for, therefore, the tranny money is now gone. I can still cover it, but it's the extra expense I was hoping to avoid. If the headgasket had not have been bad, the remaining money from the water pump fix would have rebuilt the tranny. So much for the best laid plans.............
And don't mention selling any more. Although a nice shiny new mule would be nice, I can't afford it, I have too much in this one, AND, I can't let go of a truck that my buddy comlimented while I followed him to his dad's house. "Randy," he said. "That truck looks bad as **** in my rear view mirror!"

[whatnot]

It might be worth checking with the dealer to see what they would charge to fix it.
I had the transmission in my 93 rebuilt at the chevy dealer for $1000. (it is a 4l60E though)

[GMCfourX4]

To anyone who knows more about 4L80Es than I do... could a voltage problem cause these error codes??? I would first check to see why the alternator light came on, by going through the routine electrical connection checks and ground checks. I would sort out any electrical problems before I spent money on something that an electrical part says is bad.

-Chris

[Randee of the Redwoods]

The electrical problem? After a dipping voltmeter on a trip home, I ended up at the auto parts store having both batteries checked. Swapping in and out in the sleet and snow only ****ed me off more. Verdict? One bad battery and $70 for a new one. Two days, no flickering battery light. I'm with you on the electrical faults possibly causing invalid error codes which is why I have decided to drive the truck a few days first before checking for codes again. I don't know if these are the type that will self clear or not but I'll find out next week some time.
I have a pretty good idea that I may have caused the one battery to go bad. It just took this cold weather to finally expose it. The old one was a Walmart 950/770. The new one is an Autocraft Titanium 963/770. The lady told me it should be ok since the cca's matched. Better than shelling out another $70 to replace a bettery that wasn't bad. I was a bit leary about running mismatched batteries, but I'll give this a whirl as they are so close.

[Shaun091382]

I just had my 4L80E recently rebuilt in my truck a few mnths ago...it had light towing and minimal maintenance to it and lasted roughly then 330,000km's it cost me around $1850CDN to have it rebuilt and it was rebuild in 1 day..clutches were slipping and putting the truck constantly into limp mode plan on regularly maintaining now as I am current owner hoping to get similar mileage out of it again.

[kowsoc]

I think the "shorting" battery could definitely cause error codes. The batteries produced now do not last like years ago. I've had a few problems that a bad battery(s) have caused.
I build computers on the side and I've seen problems that are caused by flakey power supplies. The computer in your truck is probably not much different...slight change or interuption in power and the PCM is confused. Battery connections are also important.

[damork]

Randee of the Redwoods
Don't rule out those speed sensors being dirty on the tips or a weak 12V source to your tranny.

I added a relay then spliced power into the main 12V line to the transmission as it is known the ignition switch contacts can start to cause strange issues with the transmission. Some companies sell these relay kits, but it is so easy to make and I think it cost me only $10 - wire, relay and all. More of a job to install it than anything, but it still wasn't bad.