Hey guys new to the forum.

I have a 2004 chevy colorado that was ls swapped with a rebuilt lq9 and rebuilt 4l60e by a reputable shop. All the wiring was done by current performance and everything works as should except one issue that nobody can seem to figure out.

The issue is as follows. Truck will drive great all day on side streets, no issues shifting at all. When you get on the highway everything seems fine until you drive at least 6 miles. At this point if you need to slow down or take your foot off the gas, once you get back in the gas the truck will drop out of OD and go into third. Then in order to knock it back into OD you have to accelerate to at least 74mph. This process will repeat every time i have to slow down or come off the gas. Now when getting off the highway it will wind out all the shifts from first and you have to give it throttle in order to shift. Then for no reason it will start to work fine and shift completely normal. Also, if you shut off the truck and restart it the issue goes away.

The builder believes it is a computer/tune issue and not mechanical as he rebuilt the trans. He tried a new tune and swapping out the TCM but neither have worked, he is at a loss. Current performance even sent the logs to a tuning school and they were unable to provide any answers. He says it goes into a “WOT” mode when it acts up but is unsure of the reason

if anybody has any ideas or recommendations i would greatly appreciate it, thanks.

 

Transmission Fluid Temperature issue?

 

Nope, trans never gets above 200. Plus i can drive on side streets with no issues, only comes up on the highway.

 

Post a log and the tune file.
Yes I know the tuning school looked at it...but if you had it figured out, you wouldn't be here.
Maybe somebody will pick something up that they weren't looking for

 

I agree.

And I find that MaroonMonsterLS1 to have taught himself and learned about GM transmissions in a very short time and very thoroughly.
He could have just become another DIY builder like many of you...
But he did not stop there... he committed to learning all that he could (pretty much all the information that exist) and has more or less mastered the Hydraulic, mechanical, and electrical engineering that is involved.

I do NOT think I have ever said anything about it...
But, I seriously applaud you Grady!
I wish more people had the interest and intelligence to pursue the GM transmissions as you have.

And on top of it all... you made a business out of it!
You remind me of myself about 10 years younger!
Congrats! I hope you both enjoy and succeed in the business.

 

I will try to get it sent to me, thanks

 

Here are the files i was sent, i can’t see them as I don’t have hp tuners software....

 

It does drop out of 4th shortly after Trans Shift Mode changes from Performance to WOT. But I don't put a lot of stock in HPT Scanner PID's until they can be verified with a Tech 2.

I would like to see the tune (ECM & TCM).

 

yeah thats what ive been told that it goes into a WOT mode but unsure of the reason, i will see if i can get the tune

 

Well, I'm pretty sure I can see the WHY to your problem. Just like Cline noted
The trans mode does indeed show performance WOT.

However...are you sure the issue is that it drops into 3rd?
Looking at the logs...it looks like it stays in 4th, just kicks out of Lockup?
During all of the occasions when it looks like you slow down then speed back up, the commanded gear never changes from 4th. So, If it is indeed dropping into 3rd...it doesn't appear as though the computer is commanding it to be done.


Post the tune file if you have it.
Also...is there any segment swapping or anything like that going on with this setup?

 

When it goes into this mode if you manually downshift into 3rd from drive there is no change in RPM leading me to believe it is downshifting into 3rd.

As far as the segment swapping, I'm not 100% sure. The computer and wiring system was done by current performance and is specifically designed for this swap, using an e40 pcm and TCM from a trailblazer or SSR in order for everything to communicate with the Colorado's electronics

 

Well, in both the logs you posted, I don't see anywhere that you slow down, computer commands 3rd, then you follow that right up with acceleration to 74mph as described.
I see slowing down then speeding back up, but the commanded gear is never 3rd.
Until the end of both logs it shows 3rd as commanded, but I don't see you accelerate back to 74, so it doesn't really match the described issues.

I mean, realistically the 60e, for 4th gear, is pretty simple. You could drill and tap the servo cover and watch pressure from only that location and see what 4th gear oil is doing.
You never mentioned...have you gotten a line pressure reading when any of this happens?

 

The logs were done by the guy who did the swap after I described the issues so I can’t say what he did when he was logging it. Im just describing whats been happened in my experience

I haven’t done a line pressure reading and I don’t believe he did either but not 100%

 

Who did the tuning? Was it current?
Can you post a tune file?

 

I believe the base tune was done by current and the builder did the final tune. He is going to try to send me the tune file but he had a power outage and isn’t sure if it got wiped.

I think I'm going to invest in a HPT MPVI2 to make this easier

 

Purchased the MVI2 and pulled the tune and also did a fresh data log starting from a stop then proceeding onto the highway

 

You need to configure the Scanner.....We can't see any trans data the way it's configured!!

The first issue I see is.....You have no ISS sensor or at least it's disabled in the tune. The T42 TCM depends on the ISS to calculate converter slip values.

The fact that you can "reset" the shifting behavior by shutting the vehicle off tells me that the TCM is in a default strategy because a diagnostic test failed, Simply "turning stuff off in the tune/calibration" doesn't always cut it.

I'd like to see the TCC Slip RPM PID in a rational state, The first logs you posted showed irrational TCC Slip Rpm values BUT as I already stated.....I take HPT scanner/log values with a grain of salt 'til they can be verified with a Tech 2 or even a Snap-on scanner.

I don't want to send you down the wrong rabbit hole here, But I've personally had issues running T42 TCM's without a ISS if it was originally calibrated for one. Sure....There was a few E40/T42 vehicles without a ISS, Like a 2005 V8 Trailblazer, 2005/2006 GTO, & 2005/2006 SSR which were low production compared to the millions of E38/T42 GMT900's made.

When I build a bench 4L60E for a swap.....I ask what controller they're going to run, If it's a T42, I build a ISS 4L60E Period, Like I said.....GM made millions of them.
May I ask why you're running a E40/T42? A LQ9/4L60E is classic P59 PCM territory for a swap.

 

First time using the scanner, i will go back and figure that out. As far as the ISS i will look into that.

the reason for the e40 is because that is what current performance uses in these swaps in order for everything to work correctly for the colorado.

 

I configured the scanner for the transmission and took two data logs that show the issue real well. In the first log near the end you can see the command gear go from 4th to 3rd after letting off the throttle. Then I accelerate to 74/75 and it goes back to 4th. I repeated this 3 times.

The second log is on the side streets and you can see how it winds out the shifts and the 2/3 wont shift until around 40mph and it will not shift into 4th.

 

I had a 700r4 one time tht wouldnt go into OD until around 80mph. When trans was cold it shifted good at first but once warm it took pushing it pretty hard to get OD gear. Ended up being a bur inside the 4th servo hanging it up. Cleaned up bur and reinstalled, trans shifted great!

Not saying thts your issue but its a thought. I personally havnt looked over the logs. Dont have access to my laptop. Maybe later I'll look them over as well