I have a similar issue w/ steering on a Simplicity mower - I believe it's a manual mower - the steering is very loose & you have to oversteer to keep it going straight. I looked down below where the steering shaft connects to the gear - and it appears that it connects in a slot - and as you steer, that slot moves - so you have to steer alot to get a little movement - the nut is very tight, so it's not a "being loose" thing on the gears - but I don't understand why the huge slot is there - and why it is slipping.