Well the 4l80e segment swap finally got done on my friends 1500. He killed 3 "built" 4l60e's after we put a procharger on the 6.0. A local shop is tuning the truck and everything appears fine as far as wiring (speartech swap harness) shifter position, ect.

Problem is the 4l80 starts in 3rd gear when you put it in drive. Once they had the truck on the dyno it was DOWNSHIFTING as the speed INCREASED. No one around here seems to have any idea what specifically would cause this. The trans was shipped to him from the midwest (we both live in wilmington NC) so having the original builder look at the tranny is not an option. When the tranny was shifting it was smooth and solid. So i believe that the internals are o.k. Any insight would be great, his truck has been down a long time while he saved for the 4l80e and this has really taken the wind out of his sails. I have researched and talked to many people but I haven't managed to get anywhere as far as a solution other than pull the tranny and have it rebuilt again.

Thanks for any advice you guy's can provide.

 

Who did the segment swap? Do you have the tune you could post?

 

lol, that really sucks ***, but is kinda funny.

Ive heard they do some really crazy stuff after a bad segment swap

 

IIRC its shift solenoid B that works exactly opposite of shift solenoid B on the 4L60E. In my case, OBD1 TBI there is a shift solenoid state table that had to be corrected. Once that was done everything was copacetic. IIRC the shift pattern otherwise was 3 - 2 - 1 - 4.

 

National speed in Wilmington worked with an outside tuner in va to do the segment swap. HP tuners could not do the segment swap on his pcm. His truck is 99 z71 and his OS was not compatible with your standard 2500 6.0 4l80e file (even another 99 evidently). Problem was he needed a custom 2 bar OS which led to all sorts of headaches. So the general thought here is it is the tune from what I am gathering? I was assured this was not the case but I am now starting to doubt that.

 

Considering (at least on an OBS) there are no wiring changes to the shift solenoids needed, yes I would say the problem lies in the tuning. For what its worth you can take a normally closed 5 terminal relay and invert the shift solenoid B signal and make it work. I actually drove mine for a couple three months lately before finally figuring out the shift solenoid table state.

 

oldred95

I will ask the tuner about the shift state table and see what he says. Hopefully this will simply be a "duh" moment with an easy fix. It would be great to hear all it took was a simple switch of a table.

Thanks for the help.

 

did you repin your harness or use a speartech adapter?

 

Well its whats causing your problem but its not just as simple as a table. To do it correctly the entire segment should be used from a 4L80E program. In my case that didn't and couldn't happen with the code I'm running. A 4L80E can be made to work just fine off the 4L60E code but this is in a compromised situation where you don't have options. Ideally you want the correct segment for said transmission.

 

You can run a 4l80e perfectly off a 4l60e tune. It requires some wiring changes, and in a way it's superior to an 80e segment swap because the converter can be commanded not to unlock in 4th when you let off the gas.