The lower dipstick is smaller diameter than the upper. My guess is someone before you did'nt have the lower tube, and broke off part of the upper tube; then you (or someone before you) drove the broken off upper tube in when the lower was installed. The lower tube will slip through the upper tube (at least the lowermost part of the upper tube) The hole in the block for the dipstick "tubes" is a stepped hole. That's why I said to pull eveything out and look; to see if there's about a 1/2" lenth of broken off upper tube in there. Make sense?