FYI -- I agree with TollKeeper, per his first post -- it's a question of being able to keep the rest of it on the road long enough to get the value out of however much money you'll spend on a new trans.
From a mileage standpoint, I'd figure anything under 100K miles after install on a new trans, if you weren't sure the truck would last that much longer, would be kind of a waste (unless you rip the trans back out before the truck goes to the recycler).
Since you answered that you're sure you will keep it on the road, even if you R&R the engine later on)... and the truck is where it (almost) never snows... and you seem to know what the 'good' parts are to upgrade... I'll give the project
my blessing (for whatever that's worth).
I see yours is an '06 -- make *sure* you salvage the TCM & wire harness off the old trans, as you'll need those for the new one. I'd also try and build it out to at least '03-up specs; most of the major updates had been done by that time.
You've covered the hardened sunshell; make sure to address the TCC / PWM issues (Sonnax, TransGo, whichever you prefer) in the valve body. Kits are available for that, too. Sonnax is supposed (?) to be the better fix, here, but it requires an expensive ($200 USD) reamer tool from them. (someone here bought the thing, about a year ago... search posts, as they may rent it out to you or be willing to do the valve body & ship it back (if you want the Sonnax mods). Most of us here have done the TransGo kits, and had good success with them, so it's your choice. But do address that (if your TCC bore shows signs of wear, you pretty much either have to go Sonnax, or get a replacement VB). Rebuilt VBs are available with the fixes already incorporated into them, as well.
If I do end up going rebuild does anyone supply a high quality "all-in-one kit" for these units? By that I mean the usual gaskets and o-rings, but also widened 2nd/OD band, Corvette servo, hardened shells, zpak clutches, dual cage sprags, etc.? Or do you just have to put it all together yourself?
Chasing down all the right parts and ensuring the builder gets it all done correctly seems way more hassle than just buying an aftermarket unit with a warranty, but I wanted to see you guy's opinions first.
They're out there -- and it sounds like you know what you want / what to get, parts-wise.
Questions:
- Is this your daily, or can it be in the garage for a bit (2 weeks to a month) ?
- How mechanically inclined are you? These are fairly simple to rebuild, and the manuals are readily available (I have some electronic ones, plus there's some on this site).
- If you think you'd like to go the DIY route, you'll need to rent / buy a transmission jack, and a (modified) engine stand can be nice to have, as you're feeding new parts into the case. Or a clean workspace (at least 3' x 4') is great. They weigh about 260lb or so, so you'll definitely need help getting it up on (and off) the workspace.
If you're going to put a 'hot' LS in it when the time comes, you may as well spend the $ now on the good parts. Built correctly, the 4L60 can handle about 700HP, so unless you're planning on more than about 500HP, you should be fine, if it's built right. And if you're going to (eventually) make it a race truck, then you already know all of this. New converter; if you want an increased stall, you can do your homework there. Check your flexplate once the trans is out; they've been known to crack (and a new one would be cheap insurance). Good opportunity to swap out the rear main seal, too, since you're there.
If you spring for the beefed up output shaft like the 4L65 / 4L70 has... remember that it's a few millimeters
longer, and I think it requires tailpiece / driveshaft work, as a result (you might be able to get a TBSS driveshaft, perhaps; otherwise, you'll need a shop). Unless you're going racing, I'd stick with the stocker, personally (although you might want to get a new one, given the mileage on the existing).
Oh... and on the big name rebuilders like Monster, et al... take a look around on the web (F-body forums are good for this)... you see a lot of complaints about Monster (or, at least, too many for my liking). Given their pricing, I'd pick someone else, myself. And you could probably rebuild it yourself (or get a core & build it) for about $800-900 in decent quality parts (a little more if you want the fancy 5-pinion planetaries).
The 'fairly simple' comes in handy for a local resource to do the work (unless you absolutely do not have anyone you trust, locally).