I just spoke with Sid, a transmission builder retired from GM that holds the world record for fastest the automatic transmission. He is located in Snellville GA. I was recommended to him and called. I asked what kind of work would he recommend for my basically stock 05 4x4 truck with only some aggressive tuning.
The first thing he asked was what motor do I have. When I told him the L33 he said all the trucks equipped with the L33 had improved transmissions. If it is not broke don't fix it.
He was busy but did tell me some of, but not all the improvements.

1. The Sun Shell for one, got Torrington bearings vs. the thrust type. It is not as strong as the Monster brand but greatly improved over previous years.
2. They upgraded the clutches to better high energy clutches. He wanted to say more on them but we got interrupted.
3. They went from a four gear set planetary to a five gear set unit.

He said program it and have fun. It is much improved over the non-L33 units.
I went on to say that I had money burning a hole in my pocket for some sense of security and thought he would be willing to grab it. He said unless I make some major mods I would be ok. Removing the TM should not be an issue. He based all this from the improvements he knows of on the transmission and by how I told him I would be driving it.
The man races these things so I guess he should know.

We Will See

 

That sounds incouraging.

 

Look in your glovebox for the RPO code M32. If it's there then you have the 4L65E, the same tranny used in the SS & VHO trucks, Escalades, etc.

 

That was my thought as well....AFAIK 5-pinion planetaries = 4L65E.

 

Well, before I get too excited I will have to call Sid back to see if there is an external ID marking on the tranny housing, and if the M32 should be on my RPO list. I'll tell you this, from what I gather, he is MISTER GM TRANSMISSION around these parts. I'll try him tomorrow or Monday and repost.
He says he hunts these things down anywhere he can find them. I did not ask him if it was the 4L65E. I will be sure and do that.
According to him GM was putting these in F-Bodies and had a large over run and/or found it would be cost effective to just produce one model, and are now installing them in the CK15753's (ECSB) equipped with the L33 only.
My truck was US made so it may be a possibility that the US and CA units had some differences? Mine was also an early made unit.
While I am on the US and CA thing.
When I went to purchase my truck, there were 2 almost identical units side by side. The only difference is one (mine) has a locking spare tire access hole. Same colors and option's. One made in CA and the one I purchased in the US. Mine had been on the lot a month or so longer. It was $1050.00 less than the CA unit's MSRP sticker. The early bird may have the 4L60E.
This RPO thing has me on pins and needles now and until I get a positive ID on what I have.