4L60 to 4L80 transmission issue on 2007 Silverado with 6.0L

Having an issue with getting my speedometer to read on the HP Tuners scan. Swapped a 4L60 to 4L80. Got the conversion harness and trying to go into do a scan and have the MPH show 0. Transmission shifts like crap. Is there an option in Transmission in General to select 4L80? All I see is Auto or Manual in that tab. If we use the old 4L80E TCM that was flashed supposedly by a company online, it will show 0mph. If we plug in the new TCM we just received that is not flashed yet, it will show MPH. What is the issue?

I have attached the tune files to hopefully see if anyone can help understand what is going on or what to do.


Thank you.

What 'conversion harness'? Did it not come with instructions? Does it have relays in it, or is it just a pin-to-pin adapter?

The adapter harness method and dedicated 80E OS method are mutually exclusive - the harness is meant to use the original stock 60E OS, and the 80E OS can't be used with the adapter harness.

It is the ICT Billet 60E to 80E harness.

https://www.ictbillet.com/transmissi...7-lq4-5-3.html

One thing you might need to be aware of doing segment swaps on any kind of T42: https://forum.hptuners.com/showthrea...-misidentified

That file with the 80E OS has the weird 'diagnostic' (actually 'Transmission') segment in it (24238958), I think you should be using the '07 Suburban TCM, the one with 24238957. Same base OS but that one segment is different. And who knows what else is different under the visible parts. At least I think that's what I would try at this point.

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Originally Posted by Rare87GT

Having an issue with getting my speedometer to read on the HP Tuners scan. Swapped a 4L60 to 4L80. Got the conversion harness and trying to go into do a scan and have the MPH show 0. Transmission shifts like crap. Is there an option in Transmission in General to select 4L80? All I see is Auto or Manual in that tab. If we use the old 4L80E TCM that was flashed supposedly by a company online, it will show 0mph. If we plug in the new TCM we just received that is not flashed yet, it will show MPH. What is the issue?

I have attached the tune files to hopefully see if anyone can help understand what is going on or what to do.


Thank you.

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There is normally no issues "writing entire" transmission calibration to a T42. If you can find a OEM setup that matches yours as much as possible you should be able to dump in a T42 4l80 calibration and get going with that. I would think you should be able to find a 07 with a 4l80 in the repository.

Does anyone have the right TCM to use? I did a write entire on the TCM that was supposedly flashed for the 4L80. What should I use? A 4L60 transmission TCM off a 07 Suburban?

I'm just confused how one tune can show the mph on the scanner and then one can't? One will flash the 0700 code but then the other won't but won't show mph. What gives? Speedometer on dash works, but if there is no speed to be met this transmission will never shift right.

I'm helping a buddy out do all this on his truck, but I can't figure out why I can't get a reading and the truck won't shift right.

Your 80E tune file has the TCM segments of 24235341/24233118/24238958/24233116. That's the 'magic' one used for the GMT360s, it originally came from a '07 Yukon. The '07 Suburban has segments of 24235341/24233118/24238957/24233116.

Attachment 133314

blindsquirrel - The transmission in this truck is a 06 Chevy Express Van. Does that make a difference?

No.

How did you settle on that Yukon OS (or whatever it was that has the same segments)? The Suburban is the closest match I have, but surely there were '07 Silverado non-Classics built with the 80E, right? None in the repository though.

I didn't settle on the Yukon OS. The OS should be for a 07 Silverado. Is it not? The TCM was just sent a new one that is only for the 4L60 but was not programmed for the 4L80 I believe. I'm so confused at this point. I didn't think something so simple could be so hard.

Why would one TCM program show mph and one would not? I guess I'm baffled how that can be possible to do that and then show the Transmission code errors.

Also is there specific positioning to the ISS and OSS as long as they are plugging the hole?

All T42s are the same hardware, all years, FWD or RWD or 4x4, 4cyl or V6 or V8. The programming is what makes one work different than another.

I don't have a Silverado (non-Classic) 4L80E file to look at. Or I would have posted it. If the Silverado 80E calibration has the same 24238958 segment as the Yukon example, they you should keep what you've got.

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Originally Posted by Rare87GT

Why would one TCM program show mph and one would not? I guess I'm baffled how that can be possible to do that and then show the Transmission code errors.

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Some ECM/TCM OS combos can't talk to each other.. In that case you get no speedo.. or its maxed at 158 mph

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Originally Posted by Alvin

Some ECM/TCM OS combos can't talk to each other.. In that case you get no speedo.. or its maxed at 158 mph

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That's my issue. How do I figure out which one is the happy one to use? If I use the one that works for the speedo, then I get the 0700 error code. If I get rid of the error code with the other flash, then it won't read speedo on HP tuners scan. The truck speedo itself works no matter what. I don't want to keep using up credits spending $100 to find out which one works or which one doesn't. That's my next issue lol.

The breakpoint is mid-2009, you have a 2007 ECM OS and a 2007 TCM OS. Not your issue here.