Join Date: Jan 2008
Location: SE Wisconsin
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Your 1996 has a 47RE transmission.
For a 47RE transmission (that has a functioning 1st gear) to make a 1-2 shift, it needs the following things:
a.) The trans needs to have its front band as well as the front band actuating mechanism intact. This mechanism includes the servo, apply lever, band anchor, strut, adjuster. You can check the front band adjustment from outside the transmission. If you loosen the locknut and can turn in the adjusting screw more than two revolutions, it is loose. If it turns way in, there is trouble inside the trans.
b.) The trans needs governor pressure. Governor pressure is the hydraulic pressure equivalent of a speedometer. More speed = more governor pressure. A 47RE has its governor pressure created by the PCM via the governor solenoid. Electrical sensors and wiring could be a source of trouble as well as the solenoid itself. I suggest you put a 0-100 psi gauge on the governor pressure test port and take the truck for a test drive. If you have about 1.0 to 1.5 psi governor pressure per mph of truck speed, you are OK.
c.) The valvebody needs to have its spool valves able to move freely. As the governor pressure increases, it puts more force on the governor plugs. Once the force is high enough to overcome the TV pressure and spring that are pushing in the opposite direction, the 1-2 shift spool slides in its bore and makes the 1-2 shift. If the trans had dirty oil, the 1-2 spool valve may have gotten stuck. Additionally, IF the TV pressure was excessive, the 1-2 shift may not take place until very very late.
Hydraulic pressure tests will almost always help you pinpoint exactly where the trouble is. Is the governor pressure OK? Is the line pressure correct? Do you ever get hydraulic pressure at the front servo pressure test port?
Last edited by Art; 02-16-2011 at 10:03 PM.