I'm getting ready to LS swap my 99 2 door 2 wheel drive Tahoe with a unhappy 5.7l/4l60e, and I'm currently debating on which trans to go with. I'm swapping in an LQ9 with 799 heads, tbss intake, 1 3/4" long tube headers, and a mildish cam, so basically an iron block TBSS LS2 engine, and plan on running 3.73 gears with a 29.5" tall tire. I know if you read in the swap groups they all say a 4.8l needs a 4l80e to keep from getting 7 neutrals but I try to be a bit more realistic.

I know a 4l60e is going to take some building to hold up for any length of time, but is the 3.06 1st gear really that much more beneficial? Can the 4l60e be RELIABLE in a 5500 pound rig that will see spirited driving AND some towing with around 475 fwhp? Or should I go with a 4l80e that all it will really need is a converter, & hd2 shift kit?

Now, with all this being said, I already have a 2000 4l80e that needs rebuilt, but I have found a couple of 4l65e's for decent money, or some cheap 300mm tcc 4l60e's. I just don't want to get this Tahoe together and have it be a dog on take off, or need a 3400 stall converter(I prefer to run as low a stall as possible, personal preference).

 

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

 

If you like the gearing and highway cruise RPM as it is now then I’d go with the 4l60e unless you’re going to beat the dog sht out of it on a constant basis.

 

I would go 4l60e myself