that is true

if the 60 was such a weak trans then why was it used behind the Series 2 */C in 96 and there have been more problems with the 65 behind the SC than the 60 and yes in 97 the cars got the 65. But the fact that the 60 is weaker than the 65 is not believable

mkaake is a GM 4L60 guy we need him in here for Official info

Common sense would tell you that the higher the number, the stronger the tranny. And in this case, common sense is right. The 4T60 is stronger than the 4T45, the 4T60-HD is stronger than the 4T60, the 4T65 is stronger than the 4T60HD, and the 4T65-hd is stronger yet, the 4T80 is stronger than the 4t65hd. Look up the torque ratings. The torque rating for the 4T60 isn't anywhere near 280ft.lbs, I don't know what it is off the top of my head, but I know its not that high, yet it is for the 4T65.

What says the reliability is better? It doesn't seem like they fail as much...thats a bunch of crap. Maybe they don't fail as much because they are put behind engines with less power (for the most part). When my 4T60 was subjected to 320+ft.lbs. it definately did not last very long. (and might I add my 4T60 is not your typical 4T60 because GM built it up for the turbo cars to handle the extra power and they still had to program turbo lag into the computer to help save the tranny) Yet my dads 4T65e-hd on his GTP never even seemed like it was going to quit with over 20k miles of pure abuse with 400+ft.lbs for most of that time. We beat the crap out of the SSEi, yet wtih 130k on it, the 4T65e-hd is doing just fine and its never been touched, and this is on a car making over 350ft.lbs, probably actually around 400ft.lbs. Don't get me wrong, the 4T60 is a good tranny, but what makes it more reliable than the 4T65...just because its on cars making less power???

Shawn

I think that you may be right. the 60 dont handle all the abuse that the 65 do because the 60 had the S1 and the S2 for a short time. yes the S2 makes more power and more important torque that kills the 65'* quicker relative to the 60

I will agree that the 60 last longer because the S1 is setup beside it, that wont thrash the trans like the S2

you guys are pretty much spot-on with your thinking there. in gm, nomenclature looks like this:

_ _ __
4 t 65

1. number of speeds.
2. transversal or logitudinal mount
3. relative torque rating.

in the real world, the relative torque rating doesn't actually correspond to any number, it'* just ranking the trannies against each other. and they don't cross reference between the T'* and L'*. a 4t65 handles much less torque than a 4l65.

Of course, within the product line, there are variants (that'* why your trans has a 3 digit model number) that produce trannies that can take far more, or far less torque than other models. It makes for a pretty wide range.

and you're also prolly spot on with why the 60'* had less failures than the 65'*. from a post i was reading at clubgp (referenced in a question i had asked in performance), the STOCK L67 SII is putting out over 300 ft-lb of torque for many people. That'* a LOT of torque for a FWD tranny, and would likely be better off mating that to the 4t80. of course, they're going to mate the LS4 (290/325) to the 65 for the upcoming GP GXP and Monte, so maybe it'* not as bad as what we all think it is

Kind of funny to think that in stock form, there are (not all of them, mind you) L67'* running around with nearly as much (or more) torque than the LS4 will provide...

4T60

The 4T60 was the transitional model from the old Hydramatic (formerly called the 440-T4 aka 4T60) to the new electronically controlled transverse family. Introduced in 1984 on the 1985 C-bodies, it was enhanced with electronic controls to become the 4T60-E in 1991. By the mid-1990s, the 4T60-E was the transmission of choice in nearly every front-wheel drive GM vehicle with the exception of compacts. A heavy-duty 4T60-E HD was produced only in 1996 for the supercharged GM 3800 engine. The 4T60-E was phased out in favor of the 4T65 beginning in 1997.

4T65

The 4T65-E was introduced to replace the 4T60-E in 1997. The 4T65-E included a larger 258 mm torque converter for some models and many other changes to improve reliability. It is able to handle vehicles up to 6500 lb (2948 kg) GVWR with up to 280 ft·lbf (380 N·m) of torque. A number of final drive ratios are available, with many distinct models. Starting in mid year 2000 models, all 4T65-E models received an upgraded valve body. Starting in 2003 the internal electronics were changed, hardened 4th gear shaft, ratcheting sprags for input and 3rd gear were added.

4T65E-HD

The 4T65E-HD (code MN7) is a heavy duty version of the 4T65-E used with more powerful engines such as the LS4 V8 and L67/L32 supercharged V6.

The only difference I see in GM tech book on HD is the lockup differential to make it posi trac.