I have 96 4 wheel drive 4l60e and when its cold has all gears shifts fine but when it warms up loosed over drive and have to manual shift the previous owner changed the fluid and put dexron 3 think changing the filter and putting dexron 6 in it would fix it

 

Read this Best Fluid type on 4L60E - LS1TECH
I'm not sure it'll cure your issues though. To me it sounds like seals, But I may be basing that on mine running better warm rather than cold (before I got the trans rebuilt).
We'd all like the cheap & easy fix (Lucas for transmissions) - mine was $1800 & a STOUT transmission that's a brick chit house.

 

Which seals would it be I've only tore into one 4l60e and I had my instructor helping me the whole time

 

Ask your instructor, I mean if some have to be done then do the whole 9 yards & don't have to worry about it. Mr trans shift kits have been good to me.

 

I havnt been in school for 3 years

 

I dont know a heck of alot about the 460le I just had mine rebuilt but sounds like your shifting cylinoids are getting weak or your boost valave in the valve body.The recogmend changing them at 75k.That trans also is notorious for have problems the forward clutches.If you want a cheap fix drain all the fluid ,change the filter put in some fresh dextron and abottle of lucus.It worked on my truck.

 

I was gonna also throw some z max in it but I hate 4l60e there junk from the factory but once you rebuild them there good if you see what comes out of them compaired to the after market rebuild kit its amazing cause a lot of them the reverse sprag breaks the one in the kit it a whole lot stronger

 

Well after rebuilding my 400 turbo from my old truck I was pro at it after several times.Then I rebuilt a 350 turbo.Then the 700r4`s came out everyone said the same thing about them they are junk from the factory but the after market rebuild kits made them stronger.Since I had rebuilt a couple of GM trans`s before I thought I could do my 4l60e from my Jimmy.I actualy had it pretty close but time was an issue so I had one of buddies that knows what he is doing do it right for me.He also put a shift kit in it so it should be pretty strong.I have the same trans in my truck and it over heated a couple of times and started to shift weak.I dropped the pan and didnt find any burnt clutch material just black fluid.My trans man said i got lucky and recogamended that I change the cylinoids and the boost valve.Cash is tight since Im in the middle of my Jimmy project so I needed a quick cheap fix.New filter,fresh fluid and a bottle of lucus is working for now and buying me sometime for now.Yeah I had a heavy duty sprag put in mine when my buddy rebuilt it.