300TE 4-3 downshift thump
 

Hi,
I have a 1989 300te that has a intermittent 4th gear downshift thump. If you are travelling at around 30km/h and accelerate normally, there will be a delay and a hard thump as it engages the lower gear.
The transmission has been rebuilt, one expert opinion is that there may be a crack in the transmission housing allowing the fluid to leak down in whatever mechanism is used to engage the lower gear.
If someone is an expert on these transimissons I would love to hear an explanation on how the transmission selects gears and what this thump could be.
If you drive in 3rd it won't thump into 2nd.
Thanks.
Grant.