You missed the question in post 119, I'm interested in the answer to that one, curiosity is killing the cat! 🤣I thought my original post covered this for every one... so here goes again.
Gen II engines have a bell-housing casting # 24206579 over the starter pocket and only have 6 bell-housing bolts & 3 more holes for the oil pan.
GM started the bolt on bell-housing in 1996 and up S/T trucks, they used the 1-piece case in full sized trucks through the 1997 model year. in 1998 they used the 2-peice case or bolt on bell-housing case. All 2-piece cases had 6 extension housing/4x4 adapter bolts. They started the 2-peice case for 2 reasons.
First and foremost, they could use the transmission in foreign markets by only casting a bell housing for the specific car/truck not a whole transmission case. That way any basic trans could be used in any market.
Second they were looking to be able to use the transmission/motor combo as a structural member, which reduced body damage in testing.
The 4L65E transmission came out in 2001 for the 1/2 ton 6.0L LS based trucks/yukons etc. It was given the RPO code M32. Through 2005 most were 4x4's only. They share the same bell-housing/converter as any other LS engine in 1999 and newer trucks and 1999 and newer F-body cars.
It will fit in any LS based engine in a truck. The bell-housing on LS based engines have a casting # 24206952 over the starter pocket. It is 5/8" deeper for the 300mm converter and has an added top center bolt, for a total of 7 bolts for the engine itself & 3 more for the oil pan for a total of 10 bolts.
THIS TOP CENTER BOLT DOES NOT DICTATE A 4L65E TRANSMISSION.
There is no external physical differences between a 4L65E and a 4L60E (LS based) transmission. you can only identify a 4L65E by the RPO code M32 and the specific transmission sticker code that has been shared on page 1 of this post.
Some one posted about the torque capabilities on a 4L75E being more than a stock 4L80E. The 4L75E is a GM Performance only unit. I'm not an engineer so I have to speculate. From the picture of the 4L75E transmission. I see a Sonnax 4th servo cover. So I believe they probably partnered with Sonnax and added a host of Sonnax parts. I speculate they used a Sonnax input drum w/ 9 frictions, Smart shell, wide band, 1-2 servo & 4th servo. Then some transmission engineer came up with the ft. lbs of torque based on the improvements.
I am confused as to why the 4L70E has a higher torque rating than the 4L80E... I would again have to speculate that the improvements in the 4L70E (see GM 4L70E product announcement attached) are why the GM engineers gave the 4L70E a higher torque specification over a stock 4L80E. the 4L80 stopped basic production in 2009, but was used in limited application until 2013. I have never heard of a factory hardened input or output shaft for a 4L80E The 4L70E however was given improvements in these area's. The 4L80E as stated in this article, The Legend of the 1999 Aston Martin DB7, came in the DB7 Aston Martin and in a few Jaguars and I've always heard they could handle closer to 600hp. Anyone here taken a stock 4L80 up to near that power before? Sloppy mechanics state that a stock 4L80E will handle 600HP and I have actually built a few for 800 plus... over 600 they need a few HP items.