L31/6L80e

[97Centurion]

Well, my first official post here. As the title states, I am in the middle of swapping my 4L60e to a 6L80e, yes, behind the L31. I've done countless hours of research and contacting companies on how and what the swap would entail. Some of this swap is trial-by-error. I haven't really seen any forums/posts of folks swapping over to a modern transmission behind an older engine, but in fact, the reverse. I see threads on this site talking about a 6L80e swap, but with gen 3 and up engines. So...I figured I'd take you folks along my journey if you're interested. And yes, I do have the means of swapping an LS, and yes, I have argued with myself about how much of a waste of time this could be, etc... I don't need power as I have a Whipple'd 2014 Silverado, and a built 2010 Camaro SS. But I do like different. The goal is to keep it as simple and cheap as possible going this route.

Without boring you with my life story on where I started with this... I've got the 6L80e, modified the L31 torque converter (168 tooth), and just purchased the TCM-2650 from zerogravityperformance to talk to the TEHCM. One problem that I am very unsure of is the 6L80e torque converter's snout is too long, and thus I pose my question for help to you folks: The bolt pads are about an inch away from the flexplate. Keeping in mind I need at least 1/8" of play, would torque converter bolt spacers of that length mess with anything?

 

[94K3500PROJECT]

Prett sure you would space the entire flexplate back with a spacer on the crank

 

[97Centurion]

Prett sure you would space the entire flexplate back with a spacer on the crank

So I tried that, but then the starter teeth won't reach the flexplate. Even have a dished LM7 flexplate that would line up nicely and solve the snout issue but ran into the same problem with the starter (trying to stay as cheap as I can).

 

[Supercharged111]

Sub'd. I'd like to see how this turns out for you. I sniffed out the 2650 some time ago but haven't gone for it as my 4L80s are pretty stout. I'd love be to swap my wife's Envoy, but that one's easy as it's already a GenIV 5.3.

 

[97Centurion]

I forgot to mention, my 97 is 4wd with the NP243. The transfer case does indeed bolt right to the back of the 6L80e (also came out of a Z71) perfectly, but you have to change the input shaft to a 32 spline. Easy peasy! The dimensions of the front of the bellhousing to the end of the output shaft of the 4L60e (4wd ; 26.941") and 6L80e (26.968") are almost perfect. So far, front and rear driveshaft(s) do not need modification!

 

[Supercharged111]

The 6L90 uses the bigger 29 spline like the Dmaxxes. I did the 32 spline on my NP243 as well. In addition, I installed a circlip eliminator and new shift fork pads.

 

[97Centurion]

I'm supposed to receive the 2650 sometime today. In the meantime, I am changing my oil pan gasket, oil filter adapter gaskets, and building the transmission lines to include the cooler lines from steel braided ptfe-AN fittings. To mention, I have these lines going into the ICT Billet 551121-6AN adapter onto the transmission. The other ends are 6AN - 5/8-18 inverted flare, to include the stock transmission cooler. TCM-2650 update to follow!

Also, as far as the torque converter to flexplate issue, I ended up going with spacers between the bolt pads and flexplate. I'll mock it all up and snap a few pics soon.

 

[97Centurion]

Made little progress on the truck since my last post. Work got really busy. I've got the 6L80 bolted to the engine, and to my surprise, the torque converter snout isn't an issue at all. In fact, it leaves just enough play to have 1/8"! Obviously, the 6L is slightly bigger bellhousing-wise, so the transmission tunnel got a little smaller, so where my hands and arms used to fit don't fit no more... Transmission lines are built and awaiting install. Also received the TCM-2650, or more appropriately, 2600. Says 2650 on the website, but this 2600 says it controls the 6L and 8L. Unfortunately, I have to work this weekend, so I won't get to mess with the truck too much, but here are a few pics I snapped!

 

[SS Performance]

Did you have to modify the tunnel at all for it to fit?

 

[Supercharged111]

Made little progress on the truck since my last post. Work got really busy. I've got the 6L80 bolted to the engine, and to my surprise, the torque converter snout isn't an issue at all. In fact, it leaves just enough play to have 1/8"! Obviously, the 6L is slightly bigger bellhousing-wise, so the transmission tunnel got a little smaller, so where my hands and arms used to fit don't fit no more... Transmission lines are built and awaiting install. Also received the TCM-2650, or more appropriately, 2600. Says 2650 on the website, but this 2600 says it controls the 6L and 8L. Unfortunately, I have to work this weekend, so I won't get to mess with the truck too much, but here are a few pics I snapped!

The 50 part is added Zero Gravity as a regular 2600 doesn't get it done off the shelf. IIRC.