L31/6L80e

[97Centurion]

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

Not at all. There is still space, but it's smaller. You just got to look out for crushing any loose hanging plugs/wires. I did have to waller out the transmission crossmember bushing mount holes just shy of 1/2". Forgive me of the dirt....lol

 

[Erik the Awful]

I didn't get a chance to ask you today, but why a 6L80? Are you wanting two more gears, or just wanting something that a 350 can't break? I do think a 4L60 isn't enough transmission for a Centurian.

In that last pic it looks like the nuts are crushing the washers into the holes. Have you considered drilling two holes in some flat stock and welding it to the bottom of the crossmember? Or at least using 3/16" thick washers? If you don't have a welder, say the word and I'll drag mine over.

I wish I could help you on the technical side, but I know nothing about 6L80s.

 

[Supercharged111]

I didn't get a chance to ask you today, but why a 6L80? Are you wanting two more gears, or just wanting something that a 350 can't break? I do think a 4L60 isn't enough transmission for a Centurian.

In that last pic it looks like the nuts are crushing the washers into the holes. Have you considered drilling two holes in some flat stock and welding it to the bottom of the crossmember? Or at least using 3/16" thick washers? If you don't have a welder, say the word and I'll drag mine over.

I wish I could help you on the technical side, but I know nothing about 6L80s.

If I had to guess, I'd say that 4:1 first gear and short spread between gears must have something to do with it. 5th would make a sweet towing gear too. 6L80 is easier than 6L90 because it has the same output shaft as a 4L80.

 

[SS Performance]

I'm glad you are doing this post. I was thinking about doing this swap in my 96 3500 2WD. Partially for the towing but it helps that I have a 6L80 sitting on the floor of my shop.

Thanks
Craig

 

[Vikingdude]

Very cool project! I eagerly await your results

 

[97Centurion]

If I had to guess, I'd say that 4:1 first gear and short spread between gears must have something to do with it. 5th would make a sweet towing gear too. 6L80 is easier than 6L90 because it has the same output shaft as a 4L80.

Every bit of what you said hit the nail on the head!

 

[97Centurion]

I've got a couple things accomplished these past several days. Got the transfer case in, rear driveshaft(s), and started to clean up the wiring. As suspected, everything bolted in place like it did before, with the exception of the transmission crossmember bushing (see previous post). I am quite surprised about how easy this is!

The 6L didn't come with the shifter linkage bracket or the miscellaneous ones to dress up your wire bundles, so I ended up buying 2' of 1/8" angle iron and made my own shifter bracket. I cut the 4L's and welded the piece onto the newly created bracket. I also wired in the TCM-2600 loosely to see what programming would be needed. As the website says, TPS signal, tach signal, 12v constant, 12v switched, and ground! Pics to follow!

 

[Supercharged111]

I'm waited with baited breath. Chop chop!

 

[97Centurion]

Mounted the TCM next to the wiper motor as that was fitting per wire bundle routing. Probably not the best spot as we all know water drippage is horrible there, but for now it will suffice....plus Oklahoma hardly gets any rain these days. Still need to clean it up some though. As far as the shifter bracket, I should have angled the 4L piece down some for a better angle of attack, but the goal is to get it driving on the road and working right before my OCD kicks in. Since I removed the neutral safety switch, I had to splice some wires together to get the truck to start (see plug pic, in red). Now I've got to figure out how to send the signal to the reverse lights while in reverse from the TCM as it was previously signaled by the neutral safety switch.
Regardless, the maiden voyage is set for tomorrow, so we shall see how she does. I'll put up pics of the TCM programming next.

 

[CrustyJunker]

Both cool and informative, I'm just gonna have a seat right here!