I swapped in a 4l80e out of a 2001 Silverado 2500 into my 2003 Suburban 1500 2wd about 3 months ago. 4l80e was from marketplace with 30 day warranty and seller claimed it had 140k but no way to verify. Trans is completely stock with stock converter, I tuned it with hp tuners and did a segment swap with a 2003 express van, I made very minimal changes from the stock express van tune. It’s been working fine till last week. I was towing my 16ft trailer empty and the trans got hot, shifted to 3rd and slowed down and it cooled back down and did fine the rest of the way. The next day it had hard shifts but no codes. Now today it had hard shifts again and threw code P0894. I’m guessing the trans getting hot was the converter slipping and the code is from the converter slipping. I have not datalogged to see what it is showing but can to verify. My question is I really don’t have the funds for a full rebuild, I just spent $900 to buy it, plus everything else I needed for the swap. What are the thoughts on just putting in a new converter? I’ve been reading and it seems pretty common for the later model stock converters to fail like this.

 

While yes you will need to replace the converter and at the very least install one of these https://www.sonnax.com/parts/2025-tc...ator-valve-kit. I honestly would never spend the time of effort to do either on a 140k mile trans. To much likleyhood other things need to be addresed by that time.

 

I would first confirm that you have good fluid flow through the trans cooler, that the trans (hard) lines are not kinked, etc.

 

I’ve been driving around data logging with ho tuners and can’t get it to set the code again but I did observe this. Looks like it’s calling for lockup and tcc pwm is 99.2% but converter is not locked. It will eventually lock and slip is virtually zero once locked. Am I right in assuming that it should be locked here?

 

It could be something as simple as the torque converter lockup oring on the input shaft. Any time i have done a transmission removal (for an engine rear main seal, for example), i replace that oring. It's only a few dollars.

I've never had issues with that code on vehicles however. Check charm.li to see what the troubleshooting procedures are necessary to diagnose. It's a free website.

Also, do you have an external transmission cooler? I swapped a 4L80e on my 99 Silverado, which did not have an external cooler. I haven't really done any heavy towing with it, but want to say tge transmission runs a tad higher temperature than my 06 Suburban 2500 that has the external cooler from the factory.

 

It does have the factory external cooler.

I pulled the pan today to take a look for clutch material and replace the TCC solenoid and unfortunately there was quite a bit of clutch material mixed with metal. Something is slipping so looks like a rebuild will be necessary.