4L60e swap causing shift problems?
 

This is a 2 part question. I have tried searching and maybe I'm not doing so.ething right but I'm not finding a answer that suites the situation.

Here we go.
Can a 99-03 (early epc solenoid) 4x4 4l60e be used in a 04-05 (late stlye epc solenoid) 4x4 vehicle with no problems? Or vice versa late trans in early vehicle back to 99.

I thought the answer was yes. If not what kind issues would arise. Here is the reason for the question. I recently built a my00 trans to swap onto a 04 s10. After the swap we had P,R,N,1,2. Wouldn't freewheel when trying to go to 3 or 4, I fact it wouldn't try to go at all. I didnt have tools to see if the 3 shift was commanded or not but it wouldn't shift. Was there an issue with the model year interchange or with the trans.

Bonus question: I think I know the answer but input drums with ISS on shaft with matching pump can't be swapped into a early style case can it?.

Any help is appreciated

Sorry for the slow reply; I've been on the road for several weeks without much time to keep up on this forum.

The answer to your first question is Yes. Again, all LS-style 4L60E from '98 to '05 are mechanically and electrically interchangeable (swappable) as long as they are 2WD or 4WD as needed. And for LS1 PCMs, you can also use '06 and '07 units which have ISS.
(Not sure about '08). '09 and later are electrically incompatible.

Bonus question -- Your are correct. The ISS pump uses a seal built into the case, while earlier pumps have an o-ring seal. IIRC, the '05 non-ISS pump also has the seal built into case. (A pro builder might confirm/correct me because I am going from memory.)