I have a 1978 CJ7 Jeep we have done a 1999 5.3 4L60 , 36 " Tires , 4.10 Gears. Swap in with Shifting Problems ....Trans would not Shift out unless you Lifted off Throttle & eased Back in to it....would not Stay in 4th & shifts would Vary from Hard to somewhat Smooth. After A lot of Trial & Testing the Trans Finally went out & has now been Rebuilt By a Professional Shop & only needed Clutches .
After Rebuild my Trans Guy says it is Still not Shifting out ....it will shift Fine under control of his Trans Scanner but as Soon as he Releases it Back to the Ecm it will not Shift out .....again.
I have modified Throttle Position Values Resulting a nice Smooth 1-2 Shift BUT still Requires you to Lift a LIL for 2-3 ....3-4 Shift .....it now Stays in All Gears & Seems to Downshift Good . ANY & ALL Help is Greatly Appreciated !