THEFERMANATOR

I'm getting ready to 6.0l swap my 99 2 door 2 wheel drive Tahoe. I'm building an LQ9 with 799 heads, tbss intake, 1 3/4" long tube headers, and I'm leaning towards a cam like the TSP stage 3 high lift truck cam, 3.73 gears, and a 29" tall tire. I already have a 00 4l80e, but now that I'm getting ready to build my trans, I'm questioning wether I should go to the 4l80e, or if I should pick up a 4l60e to build? I know the 4l60e will probably cost me more to build than the 4l80e since the 4l80e would only need a stock rebuild, shift kit and converter where the 4l60e will need a full build to last. My concern though is I don't want it to be a dog taking off because of the 80's 2.48 1st gear vs the 60's 3.06
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strutaeng

That's going to depend who you ask:

1. Guys that have swapped to 4L80e would say that's obviously the only option.
2. Guys that have a built 4L60e will tell you they can handle some abuse.

Probably comes down to choice. I think with an aftermarket stall converter matched to you overall components, the gearing is not an issue.

shakenfake

I have been running a stock 4L60 in my 6.0 with cam, 862 heads, FBO, 3.73 gears and 29" tires for 15k or 20 miles and 4 years. No issues here.

MaroonMonsterLS1

Either will work fine
A decent 4l60e will have no issue with your power
in a 2wd tahoe, an 80e swap is easy enough as well
I wouldn't discourage you from either option
If you're worried about gearing from a start...just put a proper rear gear in the truck

IIGW

you have an 80 but you dont have a 60.
that seems to be the route you choose.

strutaeng

Yeah, I was a little confused:

1.) Do you already have the 80e swapped and running? If so, just stick with that.

2.) Or do you "have" as in, I got a 4L80e in my garage floor thinking of swapping it in place of my current 4L60e my truck has?

Also, who's doing the rebuilds? A shop or DIY? And what kind of budget do you have in mind for it?

THEFERMANATOR

My Tahoe currently has an unhappy 5.7l vortec and tired 4l60e. I'm building the LQ9 to be basically an iron block TBSS LS2 engine with a mildish cam(hoping for around 450 flywheel HP), the weight & size of my Tahoe is pretty close to a TBSS, so I was using the TBSS as a sort of guide. I wanted to go with a 4l60e to start with for the gearing, but everything I read on the TBSS boards says it's not if, but when will the 4l70e quit with some saying that even built units don't last, so that is why I picked up the 4l80e core to build. I've had some more time to read and think about it(I know, 2nd guessing is a killer), and I'm worried the 80's 1st gear is going to make this thing a dog on take off with the 3.73's and 29" tire. I don't want to get this thing together and have it be a pooch out the hole, but I also don't want to have trans problems or have to baby it.

I was hoping to hear from others who have actually done similar swaps and what worked for them and not just internet hear say. I'll be building the trans myself for either unit. I'm not a pro, but I've built a few trans in my day. As for budget, I don't want to spend a fortune building it, but I REALLY don't want to have to dump money in it continually to keep it going.

strutaeng

Ah, okay. Thanks for the background story. I'm telling you from my experience going swapping a 4L80e into my 99 Silverado ECSB 2wd. The gearing is not as bad as you'd think. I personally like how the gear difference are closer on the 80e; the RPM drop is more consistent when the transmission is shifting and the slightly numerically higher OD of 0.75 cruises a bit higher on the freeway. Which means the transmission can hold out 4th better without downshift. Good for towing. And my favorite part is how smooth shifts are (stock form, of course.)

I've rebuilt a few 4L80e units and they are pretty simple, but that's the only transmission I've messed with so IDK really. Rebuild kits are pretty economical. Only a few valves really need to be addressed and probably the input shaft rubbing on the forward drum is what most common wear you'll see. And bushing wear. You don't really have to spend big money on aftermarket upgrades unless you are like 600-800HP+. There's some common upgrades you can do that don't even need a "shift kit", like the dual feed the direct. You can do that with like $5 in some plugs. Set your clearances on clutchpacks and front/rear endplay and you are good to go.

With a LQ9 and a cam, I'd personally be more worried about traction in a 2wd lightweight truck. Vehicle curb weight plays a big role on transmission life. I still will say either work in a 1500 chassis. If you stay with the 4L60e, go over to the LS1TECH forum, they got some excellent writeups, and tip-and-tricks, and get your hydraulics correct. Maybe invest in a vacuum pump setup?

I hope this helps and good luck 👍.

Fullpower

LQ9, 3.73 gears will shred 29" tires with either transmission- Definitely go with the 4L80.