1998 gmc safari transmission has been fixed twice

I have taken the van in because it jerks very hard when it changes from 1st to 2nd ~ 10- 15 mph it is an auto tran. The mileage is 68000 It is under extended warenty and the dealer has rebuilt the gears and preformed a full tuneup. it started again about 2 weeks later I took the van in and they replaced the tork convrter and ajusted somthing and it started again only 3 days later and I droped it off again this morning letting them know that now when I come to a stop I noticed the oil pressure that normaly sits at 40 is at 20
Any info would be aprechiated
Dannon Have they looked at anything else, such as the electronics? How about the TPS (Throttle Position Sensor) or the VSS (Vehicle Speed Sensor)?? It sounds like your line pressure is too high during the 1-2 shift. Your transmission shifts electronically. In fact the line pressure and the shift points are electronically controlled. The computer gathers information from different engine and transmission sensors and with this information it can tell how fast the vehicle is going, how far you are pressing the accelerator, and how much load is on the engine. Using this information, the computer decides which gear the transmission should be in and how much line pressure it needs to apply to keep the clutches from slipping. If any one of these sensors is faulty and giving bad information to the computer, then your shift points and line pressure will not be right. For instance, line pressure increases as you press the accelerator farther. So, if the throttle position sensor is giving a full throttle reading when you are only barely pressing the accelerator down, the computer will command a higher line pressure giving you harsher shifts. If I were working on this vehicle I would put a scanner on it and a pressure gage on the line pressure tap on the side of the transmission and monitor first, the VSS readings, and the EPC duty cycle, along with the line pressure and line rise. We need to find out whether the computer is commanding higher line pressure and if it is, we need to find out why. If the electronics checked out, the only other thing is to go back into the unit. The accumulator pistons on these transmissions are prone to wear. It is possible that the accumulator piston pin which is steel has worn an egg shaped hole in the piston itself, which is aluminum. This would cause the accumulator piston to stick. This is a common problem in these transmissions. Another common problem is the separator plates which goes between the valve body and the transmission case is worn. What happens here is the check balls in the valve body wear completely through the separator plate which would cause some harsh shifting. I would hope that the transmission guy would have seen this during the rebuild and would have taken care of these problems. I had one of those transmissions come into my shop last week with a harsh 1-2 complaint and some other problems. I ended up rebuilding the unit but the 1-2 complaint was due to the 1-2 shift checkball had worn out the separator plate so bad that the checkball went through the plate and ended up in the worm tracks in the case. Well, I hope they can get your trans figured out this time. Post back and let us know what happens.


Good luck


transman