Just got done rebuilding the 4l60e.....installed w/ new converter....went to test drive and everything worked....after 5 min of test drive 1-2 shift was great, 2-3 shift is great, felt t/c lock up at like 50 mph....so I accelerated and no 4th gear....just like running the truck in 3 instead of OD....what causes this problem...i pulled valve body back off ***** r all in right spots...could it be a electrical issue...i have never had no 4th shift actuation before with 1-2, 2-3, reverse, all working...any idea's?

 

if it was rebuilt right it has to be an electrical problem. cuz when that happin most of the time your tranny is done.... but if it was built RIGHT double check all connections

 

If the valves in the valve body have no issue, then look at the servo. Check seals to make sure none are missing or damaged.

 

Make sure you used the gold washer before installing the 4th gear outside servo. It happened to me the first time i did a set of the Superior billet servos .

 

I would agree on the servo , make sure you do not have excessive clearance, If the PCM is comanding 4th and there is no stuck valve then thats the place to look , on another note pull the servo washer or not, You may be able to see marks where the 4th servo has hit the separator good way to see if this is the case, Good luck

 

I dont think that could be a issue because i even shimed behind the servo's to try to make it work......

 

The shims in the transgo kit only affect 2nd not 4th ,