I just bought a 96 blazer and the trans is giving my some trouble. I believe it is a 4l60e. Sometimes it does not shift into overdrive. It does not slip, in fact it does noot even try to shift. If you slow down or come to a stop then it will work fine. Does anyone have any ideas?

 

The 3-4 shifter Solinoid B may be hanging open which is causing it not to shift. Could also be low line pressure which could be causing it not to shift. How do the other shifts feel?

 

The other shifts feel fine. It is just the 3-4 shift. It just does not shift.

Thanks

 

How do I go about checking the solenoid? Any other ideas?
Thanks

 

If the 1-2 and the 2-3 shifts are fine, I would be inclined to think the shift solenoids are OK.
If only 4th gear is effected, then you will want to:

A) have it scanned for codes, some codes will prevent 4th gear, and also while the scanner is hooked up, make sure that its even commanding 4th gear

B) take a look at the servo assembly (specifically the 4th piston which is right behind the cover on the side) making sure all of the seals are OK. Also measure how far the servo cover can be pressed in. .165" is about the max it should travel. Any further movement might indicate a broken band (and yes, I have seen broken bands that cause no 4th and 2nd to be OK and vice versa).

C) If all else fails, pull down the valvebody and make sure the 3-4 shift valves are not hung up. Its not uncommon for a piece of casting flash or other debris to fall down and cause a valve to hang up.