I'm trying to gather info on the differences between these final drives to find out their compatibility. More sepcifically going from the 3.06 to either of the other two.
The 3.33 differential and assembly will give me a 3.33 final drive ratio. This has been done in the past and seems like the easier of the two. The 2.9something differential will give me a 3.29 final drive ratio since the 4t65-hd comes with an underdrive chain and gears. The feasibility of the 4t65 diff is still up in the air though.
If your curious, like me, here is what I have so far:
Diagrams of my current transmission:


Of a 4T60-E w/ 3.33 FDR:


Of a 4T60-HD w/ 2.9x (3.29) FDR:



Not so sure on the last diagram for the 4t65 though...
I know that I'll need a differential extension and 4t65-hd p/* axle if it will work.
There are subtle differences but no too much difference with the final drives.
If there are any tranny gurus out there please speak up.

I've also been intrested in doing this. . . .I've found a place that sells hardend 3.33 final drive sun gears just not sure how much is involved. . . .

Only final drive I can find is the 3.33 sun gear. . . . .Only $17 I just wonder how hard it would be to change?

Really are they on-line or anything?

http://www.transmissioncenter.net/alto_2.htm bottom of the page. . . ...

ahhh i've been to that page before. I must have missed that. Thanks.

No problem . . . .keep me updated if you find anything more on this as I'd like to do this in the near future.

I found some visual info today:
http://www.l67swap.com/forum/viewtop...88ea5796f31583
it shows the differences between the 4t65 and 4t60.
And ebay has final drive assemblies fro the 4t60e for 49.99.