UIPanGestureRecognizer Not Panning In One Direction - iphone

Question

I've been battling with this for about an hour. I am trying to have my UIView to pans the same way the iOS Facebook app pans the main UIView and shows a navigation table at the left. So when you swipe to the right, it will pan all the way to the right and show you the navigation table. You can slide it back to the left. So it's basically like a slider.
I have a UIPanGestureRecognizer assigned to the UIView. And here is my selector for the gesture:
- (void)swipeDetected:(UIPanGestureRecognizer *)recognizer
{
CGPoint newTranslation = [recognizer translationInView:self.view];
NSLog(#"%f", newTranslation.x + lastTranslation.x);
// only pan appropriately when view is within correct bounds
if (lastTranslation.x + newTranslation.x >= 0 && lastTranslation.x + newTranslation.x <= 255)
{
self.navController.view.transform = CGAffineTransformMakeTranslation(newTranslation.x, 0);
if (recognizer.state == UIGestureRecognizerStateEnded) {
// if navcontroller is at less than 145px, snap back to 0
if (newTranslation.x + lastTranslation.x <= 145)
self.navController.view.transform = CGAffineTransformMakeTranslation(0, 0);
// else if its at more than 145px, snap to 255
else if (newTranslation.x + lastTranslation.x >= 145)
self.navController.view.transform = CGAffineTransformMakeTranslation(255, 0);
lastTranslation.x += newTranslation.x;
}
}
}
This works perfectly when sliding the UIView to the right. It will then stick at 255px so a part of it is shown on the screen, and so it does not disappear. However, when it's at the position, when I slide it back to the left, it jumps all the way to the origin instead of following the pan gesture.
Why is that? How can I fix it?
Thanks