I am not familiar with upgrading the internal weak components of the 4l60e
Go back to 'Transmission Bench' vid '4L60e Common Problems' - he mentions them. At least one of them, he goes into in some detail on the later vids - the PWM / TCC valve, and the two solutions for it (he prefers the Sonnax 'reaming' method; most of us here have gone the TransGo route, with good long-term results.)
From my perspective, these are the things that
need attention in a full rebuild:
- PWM / TCC valve
- Sunshell
- 3rd / 4th clutch pack
- Plastic accumulators
- New / hardened separator plate (and / or Torlon check balls in the VB)
If you want to go 'bulletproof', you can look at a new fluid pump (10-vane is fine for most, although a 13-vane is available) and 5 pinion front / rear planetaries (vs. the std 4). After that, the output shaft. But unless you're racing with this trans (and many have), or perhaps towing on a full-time basis (I wouldn't), the first group of items s/b sufficient for most users.
GM added some of the second list to what became the 4L65 / 4L70 / 4L75 versions (and all of them are derived from the old Turbo 350, including the predecessor of the 4L60 - the 700R4, which I had in a '98 Grand Prix - which had to be the smoothest shifting A/T I've ever had in a passenger car).
I've said it before - GM made some pretty good slushboxes - especially compared to their other two domestic competitors. Some of our members don't like the 4L60 so much - but I think history has shown it to be a pretty good unit (at least until GM started doing things to reduce production cost at the expense of longevity - like those plastic accumulators, for example.) Or the TCC valve, which improved FE (marginally) and perhaps 'user experience / ergonomics', but again, sacrificed durability to obtain it.
Probably the 'best' mod you could make -- is an external cooler (separate from or plumbed in series with the stocker). Get something in the 20K BTU range, and you'll never have to worry about overheating, even towing up mountains in +90F temps. If you're not towing, a 10K would prolly be OK -- it's what I have in my Voy, but if I were going to keep towing with it, I'd swap it out for a bigger unit.
I'll second those Transmission Bench vids - in fact, I may pony up for the 4L80 series and build a 'stump puller' version for my Sierra this winter to swap in place of the stocker (which is already regarded as pretty strong, but parts do wear out...)
However, just looking at the tranny internals, there was a change in 2007 if you look at the shift kits available. Prior to that, 1996-2006 were the same kit. Looking up trannies on car-part.com, it lists only 2008 as a compatible year for the two versions it lists (TAD and TWD, whatever those are?). Listing for 2007 say 2006-2007 fit.
Ok -- I stand (partially) corrected...LOL. I know the separator plates changed additionally (2001-up comes to mind, along with 1997-2000).
TAD / TWD are internal (engine) codes (not RPOs) - it looks like the TWD were the beefier (?) versions, as they are listed in V8 applications, for the most part. TAD were mostly 6 cylinder).
(Don't feel bad - I had to look that up, myself)
No, I don't know HOW they differed... I think in terms of RPOs - M30, M32, etc.