I bet you'll never look at the metal scatter shield on the side of the fuel tank the same way again!
Since you're going with a 4L80-E you have the option of using a fixed yoke and a splined steel driveshaft. I'm not sure what length becomes the cut-off point for most shops to get it as a one-piece. A splined shaft moves easier under torque and a slip yoke and relieves the transmission output shaft of thrust loads from the slipyoke binding under torque.
I am running a 3.5" splined steel shaft with foxed yokes on mine. It's heavy but it's so solid I have confidence enough to go 130mph - that's almost 6900 RPM with my tires and I've done it a few times.

 

James,

Do you have a picture of your driveshaft prior to install? I'd like to see what style yokes you are talking about.

The scatter shield took minor scrapes but the tunnel above it got some good chunks shaved out of it.



Update:

Pulled the trans today. Found some interesting things.

TQ converter bolts:



Of the three only one was more than finger tight



The rear seems fine. When I pushed the Hoe onto lift etc there was no noise and when it was in the air I gave it a few turns and everything seems ok.



I went to turn the motor over after I pulled the trans and it just clicked. My heart dropped. I heard a metal on metal clank. After some searching I was pretty sure it was just the starter. To be sure I grab a 24mm socket and turn the crank bolt to see if I get any binding. The F'in crank bolt broke loose! WTF! Tightened that back down as much as I could but it will need some attention before I get on the road again. Nothing binding that I could feel.

So I tried to start her up again and the battery would not turn the engine over So I put a jump box on it and clank again. The mechanic in the shop I was working in came over and I hit the key again. Clank. He said to do it a few times in quick succession so he could see if the alt pulley was moving. On the 3rd or so key turn it fired up. (Keep in mind the driver side exhaust is removed from the tranny pull, open header) Scared the crap of the guy who just happened to be looking under the hood. Sounded mean as **** too.
Maybe it was slightly hydro locked? Not sure why it didn't want to fire off. Rev'd it up to 2K or so and it felt fine.


Also found out that something that broke loose on the dyno cracked my inline fuel pump and its pissing fuel everywhere. Got to order one of those tomorrow.

Also, while I was replacing the charcoal filter canister I noticed that the bracket on top was bent pretty badly. I couldn't get the new canister to line up on the 2nd bolt hole so it received some white zip ties.

The 80E comes in Tuesday. Should get to work on it Thursday. Then measure for the driveshaft and start making some calls. Too bad as of know I have no tune to run on. I think that’s all.

I didn't get anymore pics. I forgot my camera and used my cell phone for the tq converter bolts. I spent 6 hours tinkering with that truck today. Its beer thirty

 

Damn, what a hand full.

I've been working on my L76 intake install and after 2 days straight to find that there was a glitch in one of my file flashes that caused all kinds of **** to mess up.

 

These driveshafts are both the same dimensions. The Aluminum has a slipyoke and the steel one uses a fixed yoke bolted into the tailshaft. The steel shaft is splined for linear movement.


The output shaft on 4L80-E's is hollow and threaded for a fixed yoke, unlike a 60-E, unless the 80 has an aftermarket output shaft in it that's solid.

 

I understand the aluminum one but dont understand the steel one.




The steel one, the splines look to go inside the shaft, do they? And the shaft slides in and out at that point to flex for supension travel? The yoke in the bottom of the pic bolts to the steel shaft and then threads onto the transmission output shaft?
What is the advantage of this? Seems like extra parts that could cause issues.

 

Putting the slip section in the driveshaft makes movement easier when the assembly is under torque loads. That reduces thrust load on the tailshaft from resistance to movement. Also, remember all the problems people had with their slipyokes binding up and "clunking"? This setup prevents that.
Look under a semi truck next time you have a chance - same setup.

 

I got my 3 1/2" shaft from Denny's Driveshaft in New York. 1350 U joints, billet steel yokes on the trans end, and the rear end.

 

I wish my autotrac was threaded so I could put a fixed yolk in it

That sucks man but atleast the 80e will hold up better.

 

Getting the sucker in there is the first step.

Then a tune to run it. (Not as easy as it sounds.)

Then I need to find out how to check my pinion angle.

Then a few days of driving to work out any kinks.

Than a smokeshow for my troubles.

 

the slip yoke in the drive shaft is better than the slip yoke in the transmission. The splines are bigger, and they usually have tephlon coatings in the inside. It makes for a better contact area, and less friction surface area for free movement.

Bottom line, it's a beafier, it's an upgrade, and it works. There's all kinds of kits that are out for Jeeps, that do the same mod. Their drive shafts are much more shorter, and they need less binding in the drive line.