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TrailblazerSS
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Discussion Starter #1
Some time ago I sheared my output shaft on the 4l70, it was the only stock part left in the transmission. I decided I would go with a stronger transmission altogether, and after reading about someone on here who had supposedly perfected the swap I figured I would try and tackle the task myself. After gathering all of the pinouts, diagrams, and other info from here and other forums there was still something that plagued me with the wiring. I did not want to buy the entire kit that was previously made and I am stubborn, I wanted to see if I could get the wiring harness by itself and get some pointers on a few things. I figured I had purchased some stuff from TBMsport before, so I tried and did not end up with much help as I believe they are no longer in business.

Well as much as I would love to make some money, I would rather see information I put in work for to be put to good use by other people. For those who are interested in putting a 6l90 into a TBSS, here you go!!! From what I have found and been able to verify, you have to have an '08-'09 RWD TBSS for it to be an easy swap. Here is what I did:

I found a 6l90 and dipstick out of a '13 2wd 2500 HD for (2000$) and found an adapter for the transmission line ports that converts it to -6AN for (50$) so that I could easily run two trans coolers from PCM of NC for (500$) and I put a Trans Temp sender in-line. I was able to convert my 3200 stall from the 4l70 to the 6l90 for (400$) and the only modification done to the transmission crossmember was notching out the center channel for the stock transmission mount stud to where it is the same distance back as the other two studs that have threads of them. After getting all of this together and in the truck I had to address the driveline situation, and the driveline shop in town told me that with the measurements I took it looks as if I can simply buy a slip yoke for the 6l90 and a conversion u-joint for (150$). 1350 to 1410 neapco and a 1410 slip yoke got the job done and I did not even have to cut the driveline!
 

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TrailblazerSS
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Discussion Starter #3
As far as the harness the only confusing part for me was the GMLAN wires. There is three sets coming out of the t43 in the 6l90, one pair is 120 ohm supplied. Pin 10&11 in the t43 are the only ones you need to hook up. They tie together with the two sets that are at the t42, so you unpin the two sets from the t42 and hook them up to the one set from the t43. Everything else is pretty straight forward. I haven’t started it yet, however this seems to be waaay too easy!

I will be getting it done this week and my tuner is eager for me to let him play with it!


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Good job, that's exactly how I have mine. Only issue I have is I cant get the speedo to work.

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I read somewhere that in 08 everything including the guages operates off of the can network so I have been contemplating tying my speedo in.

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'08 Silver TBSS
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Interested in seeing the results of this as well!
 

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TrailblazerSS
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Discussion Starter #9
If I get it figured out... I’ll never tell


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My speedo works fine. I've put some more info below.

HPTuners Details:
I've used 08 and 09 TBSS ECM program. Running 09 right now. I've run an 08 Sierra TCM program, 07 Corvette TCM program, and 2008 Yukon Denali TCM program.
I have excel spreadsheets with info about a handful of potential OS and segment IDs vs make, model, and year, but can't attach an excel sheet to this post.
The Yukon and Corvette both have the same TCM OS which allows segment swaps. I swapped the transmission and diagnostic segments from the Corvette and use the OS and system segments from the Yukon when I was troubleshooting my TUTD problems (it was a wiring issue, not a programming issue). My current configuration allows TUTD and works with the dash gear indicator, but isn't perfect. I've heard that some TCM OS can display the gear in the dash display and the PRND321 indicator works. My PRND works perfectly, but below that the correlation isn't correct and in some shifter positions the gear indicator disappears. One day, I'll likely reprogram the TCM with different OS trying to fine one that works best, but right now, mine works well enough. It shifts and drives great.
Corvette TCM program by itself caused communication issues and other funky behavior. Some of the corvette segments cause communication issues when swapped.
100381


IMO, the CTS-V shift points and torque converter are perfect (when adjusted based on our gearing and tires).

This may help with the speedometer issues.
Transmission>General>Output speed sensor: fitted
Speedo settings below (I'm running 295/40R20 tires and 3.42 gears).
100375


One TCM wire needs to be wired directly to the e67. I believe it's the internal transmission PNP signal and it goes to pin 46 on X3 (grey) of the ECM.

Be careful with the PRNDL. If it's not installed correctly, your car won't start. The PRNDL switch must be correct to allow the car to start, shift, and run. Keep it in park. I bought a new one because my factory one spun freely and wasn't in the right position. The replacement had a plug which fixed it in park.
Pins 1 and 12 of the sensor must have continuity to allow the car to start. This connection is continuous when the sensor is in Park and Neutral.
Pins 9 and 11 of the sensor must have continuity to trigger the Park Interlock. This connection is continuous only when the sensor is in Park.
100373

100374


I bought AN adapters for the 6L80E cooler, but didn't use them due to header and driveshaft clearance. I used the 2009-2013 CTS-V transmission cooler lines instead. They are almost plug and play and required no modifications. I only had to make a mount from a simple piece of bent steel (virtually anybody could make something similar). I welded a bolt onto it, but this is not required. These lines do not connect to the factory cooler, but can be connected directly to the PCMofNC brake duct transmission cooler. The included PCMofNC lines are a bit long, but can easily be remade to the proper length by disassembling the AN fittings and shortening the hose. I have heard reports that the PCMofNC cooler isn’t big enough to be used alone unless it includes their fan kit. I also tried Camaro 6L80E lines because they looked close online, but they did not fit.

Tim
 

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Hey guys, on a 08 as far as the mount, all you have to do if I remember correctly is flip the aluminum piece over and around and it bolts right back in.

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My speedo works fine. I've put some more info below.

HPTuners Details:
I've used 08 and 09 TBSS ECM program. Running 09 right now. I've run an 08 Sierra TCM program, 07 Corvette TCM program, and 2008 Yukon Denali TCM program.
I have excel spreadsheets with info about a handful of potential OS and segment IDs vs make, model, and year, but can't attach an excel sheet to this post.
The Yukon and Corvette both have the same TCM OS which allows segment swaps. I swapped the transmission and diagnostic segments from the Corvette and use the OS and system segments from the Yukon when I was troubleshooting my TUTD problems (it was a wiring issue, not a programming issue). My current configuration allows TUTD and works with the dash gear indicator, but isn't perfect. I've heard that some TCM OS can display the gear in the dash display and the PRND321 indicator works. My PRND works perfectly, but below that the correlation isn't correct and in some shifter positions the gear indicator disappears. One day, I'll likely reprogram the TCM with different OS trying to fine one that works best, but right now, mine works well enough. It shifts and drives great.
Corvette TCM program by itself caused communication issues and other funky behavior. Some of the corvette segments cause communication issues when swapped.
View attachment 100381

IMO, the CTS-V shift points and torque converter are perfect (when adjusted based on our gearing and tires).

This may help with the speedometer issues.
Transmission>General>Output speed sensor: fitted
Speedo settings below (I'm running 295/40R20 tires and 3.42 gears).
View attachment 100375

One TCM wire needs to be wired directly to the e67. I believe it's the internal transmission PNP signal and it goes to pin 46 on X3 (grey) of the ECM.

Be careful with the PRNDL. If it's not installed correctly, your car won't start. The PRNDL switch must be correct to allow the car to start, shift, and run. Keep it in park. I bought a new one because my factory one spun freely and wasn't in the right position. The replacement had a plug which fixed it in park.
Pins 1 and 12 of the sensor must have continuity to allow the car to start. This connection is continuous when the sensor is in Park and Neutral.
Pins 9 and 11 of the sensor must have continuity to trigger the Park Interlock. This connection is continuous only when the sensor is in Park.
View attachment 100373
View attachment 100374

I bought AN adapters for the 6L80E cooler, but didn't use them due to header and driveshaft clearance. I used the 2009-2013 CTS-V transmission cooler lines instead. They are almost plug and play and required no modifications. I only had to make a mount from a simple piece of bent steel (virtually anybody could make something similar). I welded a bolt onto it, but this is not required. These lines do not connect to the factory cooler, but can be connected directly to the PCMofNC brake duct transmission cooler. The included PCMofNC lines are a bit long, but can easily be remade to the proper length by disassembling the AN fittings and shortening the hose. I have heard reports that the PCMofNC cooler isn’t big enough to be used alone unless it includes their fan kit. I also tried Camaro 6L80E lines because they looked close online, but they did not fit.

Tim
Its alot to absorb for my weak brain but I know the solution I need is in there. Thank you very much for volunteering the info.

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TrailblazerSS
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Discussion Starter #14
Ha, we dont need you anyway because Tim G stepped up. Lol

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If there is one thing we know for sure... it’s that Tim has got us covered!


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All I know is I love my car so much more with this setup. The old one sucked, the original factory 4spd tune was horrible.

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TrailblazerSS
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Discussion Starter #18
How many of you resplined your built 4l70 stalls


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How many of you resplined your built 4l70 stalls


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I have a bolt together converter from tci set at 3000 for now because my car just keeps evolving and I can see at some point it wont be on the street anymore.

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Discussion Starter #20
Hey guys, on a 08 as far as the mount, all you have to do if I remember correctly is flip the aluminum piece over and around and it bolts right back in.

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My 08 I turned that around and had to knock the center slot back even with the others


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