L31/6L80e

[NickTransmissions]

i was hoping to nail this down before i bought a 6l80e. maybe i can find one pulled at a yard and take some measurements.

Why do you want to swap to a 6L80?

Are you planning to have a 6L80 built then install or buy a used one?

 

[97Centurion]

thanks for writing this up. i'm considering this for my tahoe and can't seem to figure out how things worked out with the bellhousing/flywheel/converter combination.

i'm still trying to figure out what works with what so bear with me.

so the short of it as i understand (maybe i'm wrong) is the ls style transmissions including the 4l60e (and 6l80e i think) have a longer pilot on the torque converter (compared to the l31 transmissions) where it centers into the back of the crankshaft. this works on the ls motors because the rear crank flange is shorter. (in both cases the flywheel ends up in the same place relative to the bellhousing flange by using a flat flexplate for the l31 and dished flexplate for the ls) there's a good write up on this here

All about Flexplates, Converters, Transmissions and Spacers - LS1TECH - Camaro and Firebird Forum Discussion

Automatic Transmission - All about Flexplates, Converters, Transmissions and Spacers - When installing a different (non-stock) transmission there is often confusion over what flexplate to use and whether a spacer is needed. When swapping an LS engine into a custom Hotrod, there is even more...

ls1tech.com

on gen1 converters, the pilot extends about 0.25" past the flexplate bolt flanges
on gen3/4 converters, the pilot extends about 0.60" past the bolt flanges

so when using an ls 4l60e or 6l80e behind a gen1 motor l31 i would think the converter pilot would bottom out on the crank flange before the bellhousing touches the back of the block. there are kits for mounting an ls trans behind a gen1 block and they have 0.400" spacers for the bellhousing flange and flexplate to converter flanges.

so why did this not happen in your case? i see there was a lot of clearance between the flexplate/converter bolt flanges, but was there any play where you could move the converter back and forth? i would be worried it is pushing against the back of the crank and would wipe out the thrust bearing or the trans pump...

what am i missing?

attached pics of a 4l80e gen1 converter vs 6l80e converter to show the difference in pilot lengths

Hi there! To partially answer your question, yes, after bolting the 6L to the block, there was (in my case) sufficient spacing between the torque converter and flexplate. My magic numbers were 1/4" minimum and 3/8" maximum - I was somewhere in between. This is with no modification to the torque converter. I'm not very detailed enough to research numbers and specs and basing this swap on those numbers. I wanted to do this with my own findings and trials and wanted to share my journey with the best OBS forum to date. I apologize for my ignorance with the details.

I do encourage the journey if you've the time and spare cash. If more of us do this swap, maybe there will be some more data for anyone else interested. I couldn't find ANYTHING regarding this swap into a GMT400 and it was super frustrating.

P.S. I am still running this transmission and it's still going on strong. I took a short video about about a week ago.

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[Old 96]

Hi there! To partially answer your question, yes, after bolting the 6L to the block, there was (in my case) sufficient spacing between the torque converter and flexplate. My magic numbers were 1/4" minimum and 3/8" maximum - I was somewhere in between. This is with no modification to the torque converter. I'm not very detailed enough to research numbers and specs and basing this swap on those numbers. I wanted to do this with my own findings and trials and wanted to share my journey with the best OBS forum to date. I apologize for my ignorance with the details.

I do encourage the journey if you've the time and spare cash. If more of us do this swap, maybe there will be some more data for anyone else interested. I couldn't find ANYTHING regarding this swap into a GMT400 and it was super frustrating.

P.S. I am still running this transmission and it's still going on strong. I took a short video about about a week ago.

xc_hide_links_from_guests_guests_error_hide_media

I have accumulated everthing to do the swap short of the TCM 2650. Still doing research on getting the speedo to work. Seems us 2wd guys don't have the second vss like the 4wd guys with the tranfer case. Since you lose the vss on the 4l60e we have to rely on output from the TCM 2650 which has output of 2000 ppm vs our vss output of 4000 ppm. Ideally if you can use the low and high side inputs to the ecm, you could correct the speed in the tune. Pin 16 of the TCM 2650 is supposed to be low side output. Just need to figure out high side. BTW, your swap is what inspired and intrigued me. Should be a nice coupled behind my whippled 383

 

[NickTransmissions]

I have accumulated everthing to do the swap short of the TCM 2650. Still doing research on getting the speedo to work. Seems us 2wd guys don't have the second vss like the 4wd guys with the tranfer case. Since you lose the vss on the 4l60e we have to rely on output from the TCM 2650 which has output of 2000 ppm vs our vss output of 4000 ppm. Ideally if you can use the low and high side inputs to the ecm, you could correct the speed in the tune. Pin 16 of the TCM 2650 is supposed to be low side output. Just need to figure out high side. BTW, your swap is what inspired and intrigued me. Should be a nice coupled behind my whippled 383

Are you trying to swap in a 6L80 or a 4L60E? All 6Ls have two speed sensors on the internal trans wiring harness, input and output. The sensors and harness are located on the top side of the VB/TEHCM assembly and face the belly of the case. The ISS reads the cut-outs on the 3-5-R drum while the OSS reads/picks up the rear ring gear housing. Both are hall effect sensors. I would think your TCM would read both, with the rear serving as the VSS.

 

[Old 96]

I was going off memory. It is actually pin 41 of the TCM that is speed output. I am swapping a 6l80e in place of a 4l60e. For reference here is the pinout of the TCM 2650

 

[97Centurion]

I have accumulated everthing to do the swap short of the TCM 2650. Still doing research on getting the speedo to work. Seems us 2wd guys don't have the second vss like the 4wd guys with the tranfer case. Since you lose the vss on the 4l60e we have to rely on output from the TCM 2650 which has output of 2000 ppm vs our vss output of 4000 ppm. Ideally if you can use the low and high side inputs to the ecm, you could correct the speed in the tune. Pin 16 of the TCM 2650 is supposed to be low side output. Just need to figure out high side. BTW, your swap is what inspired and intrigued me. Should be a nice coupled behind my whippled 383

Niiiice!!! That 383 is gonna tear up the road! I'd definitely be stoked to follow your progress! With that 4:1 first, you'd be a rocket from a stop...besides having a whippled 383...lol

Are you 411 swapped? Just curious...

If I'm not mistaken, I think you can use one of the digital input wires and turn it into whatever you need it to be utilizing the software the TCM2650 comes with and believe there was options for PPM. I used a couple of those digital inputs to make up for the NSS delete. I'll double-check the software to see if this is plausible, so I owe you an answer.

I am humbled to know you are tackling this as well. If I could be of help, let me know!

 

[Old 96]

Niiiice!!! That 383 is gonna tear up the road! I'd definitely be stoked to follow your progress! With that 4:1 first, you'd be a rocket from a stop...besides having a whippled 383...lol

Are you 411 swapped? Just curious...

If I'm not mistaken, I think you can use one of the digital input wires and turn it into whatever you need it to be utilizing the software the TCM2650 comes with and believe there was options for PPM. I used a couple of those digital inputs to make up for the NSS delete. I'll double-check the software to see if this is plausible, so I owe you an answer.

I am humbled to know you are tackling this as well. If I could be of help, let me know!

Thanks for replying. Yes I am 411 swapped. Eventually looking to go p59 with the Mexican tune so I can run e85. Actually going to regear the rear end to 3.23 from 3.73. The CTSV is geared with 3.23s and the 6l90e which has the same trans ratios as the 6l80e. Trying to make 1st gear somewhat usable instead of a throwaway (compound low) type gear. I will keep updating as I progress. Somewhere back I posted my solution to the neutral start switch problem. There is also a thread on Performance Trucks related to 6l80e swaps into the gmt800 platform which has a lot of good information

 

[Supercharged111]

Thanks for replying. Yes I am 411 swapped. Eventually looking to go p59 with the Mexican tune so I can run e85. Actually going to regear the rear end to 3.23 from 3.73. The CTSV is geared with 3.23s and the 6l90e which has the same trans ratios as the 6l80e. Trying to make 1st gear somewhat usable instead of a throwaway (compound low) type gear. I will keep updating as I progress. Somewhere back I posted my solution to the neutral start switch problem. There is also a thread on Performance Trucks related to 6l80e swaps into the gmt800 platform which has a lot of good information

You don't need a Mexican tune for flex fuel, that's all unlocked for the stateside tunes now.

 

[Old 96]

You don't need a Mexican tune for flex fuel, that's all unlocked for the stateside tunes now.

Good to know! One project at a time. After the trans I'm looking to do the F.I. interchiller. Then e85

 

[Supercharged111]

You don't need a Mexican tune for flex fuel, that's all unlocked for the stateside tunes now.

Good to know! One project at a time. After the trans I'm looking to do the F.I. interchiller. Then e85

I need to clarify here that I was speaking in P59. P01 can have flex fuel too, but no custom OSs. You're stuck with the one off Suburban OS. No segment swaps either I don't think. With the P59 though, the SUV and Corvette, while different numbered OSs, can be segment swapped between themselves from what I understand. And you can do a custom OS for boost with the P59.