Torque Converter Code - 741

[chambie]

Hello,
I have a 97 k3500 Dually 4x4 6.5l This past week i had the tranny flushed at Quick Lube. The following day i hooked my horse trailer on, and set off on a 3.5 hr trip. About 3 hrs in.... the truck stopped shifting to OD. SES light came on. After arriving at the show, i hooked my scanner up and read a PO 741 code.
Torque Converter Circuit Perf/Stuck. Is this something i can take care of myself... or do i need to take it to the shop and have it looked at. I cleared the code. The truck sat for 3 days until the return trip home, and i didn't get the code again. Any help is greatly appreciated.
Lindsay

[Bnave95]

Take it back to Quick Lube first and and have then deal with it. Be strong and firm to the point. Was this done with a filter change? They may need to use there insurance.
Many years ago I had them do a Rear Diff. Lube change, not knowing they did not R&R the rear cover. They also did not know it had a clutch style locker. The locker had tore it self apart. They used the wrong grade of lube and did not use the locker addtive.
There insurance paid the $1300 Bill.

[Robyn]

What may have happened during the flush is that some crap got disturbed and stuck a valve.

I would do as mentioned and go back to the lube shop. If it does it again then your gonna have to deal with it.

Did they use a flushing machine that circulates the oil to flush the converter??

The 4L80 has been known to have sticky valve issues.

The trouble with these is that it may not do it again or it may do it tomorrow.

The 4L80 has an aluminum valve body with steel valves.
It takes very little crud floating through the system to cause issues.

Back in tech school the one thing that was an absolute sin of sins was to get caught using a red shop rag when working in an auto tranny.

One little lint string can jam a valve and cause more grief than anyone needs

When the tranny is flushed any buildup of crud in the converter can be dislodged and depending on how they flush the unit it can end up where is should not.

On these units I drop the pan and clean all the crud and sludge out then replace the filter. The next thing is to fill the pan with fresh oil and then run the rig with the return line from the cooler plumbed into a can and keep pouring fresh fluid through the thing until the return comes clean and bright red.

Doing this will eliminate any junk from getting dumped back into the system.

On a rig with a lot of miles, installing a return line oil filter is a great idea as it filters out the crud that can become suspended in the oil.

The converter is contantly churning up small amounts of metal particles due the blading flexing in the turbine and pump assemblies.

If these are furnace welded then the issue is much less to nil.

The converter clutch also produces small amounts of crud. Any and all crud that is circulated through the coolers can and will deposit this stuff into little nooks and crannies as it circulates through. During a "Flush" the fresh oil can cut the junk loose and send it into the system.

Good luck

Robyn










w

[chambie]

Thanks for the info. When they did the flush, they didn't drop the pan or change the filter. The hooked into the lines in front of the passenger side battery. I assume this is a cooler line ? They said that they push the old out with the new, and stop when it returns clean fluid. My gut instinct told me that that wasn't the best way to go about it, but i'm not sure. I assumed it would flush alot of junk places that it didn't need to be. I asked if they replaced the filter when they did it and was told that the solvent that they use loosens the varnish and cleans the filter. That was when i had my doubts.

From the invoice they filled it with Mercon/Dex111... Is that the proper fluid to use ? i'm pulling a 35 ' 3 horse full living quarters trailer and really don't need the aggrevation of mechanical breakdowns. I am planning on uprgading to a 3.5" exhaust soon, and was wondering about the transgo upgrade. What does that do ? And is there something else i should look at doing.

The trailer weighs around 9000# empty with a GVW of 14k

Thanks in advance,
Lindsay