The transmission (TH400) in my 69 Firebird has been restored before I bought the car. The transmission is not original to the car, it decodes to originate from a 67 GTO, but that would be similar to a 69 Firebird 400, in my opinion. It works like a charm, but the shifts are harsher than I'm used to from automatic transmissions (I have only owned low performance cars before). The car is an A/C car, so it has 2.78 gears in the axle.
The first to second shift always bark the tires, when I accelerate fully (it shifts at around 5000 rpm). When it shifts to third gear (still wide open throttle acceleration) the speed is so high (around 80 mph), so the tires don't lose their grip. Instead, there is a VERY hard "thump" that shakes the whole car, it almost feels like something is about to break. Of course, in normal driving it shifts much smoother, but you still feel the shifts. It is not as smooth as the average automatic trans.
Does this sound normal for a standard TH400 trans (together with a standard 400 engine), or could a shift kit have been installed when they restored the trans?
