Car goes into reverce but does not engage completely works fine in forward, when in reverce it seems lik it wants to ingage but does not. it makes a chattering sound and feeling. what electric part puts...
Hello. As you know, the transmission is one of the more sophisticated components in any auto. It takes the most transmission pressure to engage reverse, third, and fourth gear in an auto tranny. In an auto tranny, the shifter is connected to a linkage that manually shifts between the different gears in the transmission. When you shift into reverse, all transmission pressure is concentrated to engage reverse. When you shift to drive the transmission will operate normally, building pressure until it can shift into the next gear. With third, second, or first gear selected it will lock out all higher gears (Unless the TCU detects overrevving of the engine, in which case it will override gear selection and upshift to avoid engine damage). All the TCU does in a modern auto tranny is control shift points. Years and years ago, shifting was controlled by a spring attached to the gas pedal. When the gas pedal was depressed, the spring would expand. As tranny pressure grew, the spring would become compressed until it was fully compressed, engaging the next gear. The harder you stepped on the gas, the longer you went until the tranny shifted. In modern transmissions the TCU dictates shift points, and not much else. The TCU will also control when the torque converter will lock, but that's where it's duties end. The problem with engaging reverse is either a linkage issue, or a problem with the pump not building enough pressure to fully engage reverse.
Try putting the shifter in reverse, holding the brakes firmly, and giving the car gas. If the car reaches a higher RPM and suddenly slams into reverse it is the pump. The pump will only build enough pressure to engage reverse with higher RPM's. If the pump is severly damaged it won't engage at all, but if this is the case it probably won't engage third or fourth gear either at that point. If the problem is with the linkage, reverse just won't engage whatsoever, despite RPM's. I'd say start with the shift linkage. If it's bent or misadjusted it could cause reverse to not be fully engaged. The TCU doesn't control reverse at all, since there are no shift points and no need for the torque converter to lock.
Nov 20, 2009 |
2007 Saturn Aura XR Sedan