The torque convertor CAN be worn where the seal lips ride --- not very likely - so there may be no good reason to replace the torque convertor.
BUT --- when the front seal leaks from the pump housing --- it MIGHT be from lack of a seal retainer (sometimes the factory doesn't use it and other times cheap-assed bench builders won't bother with it either) ... it's super easy to install and is super cheap and sometimes the new seal comes with the new retainer.
HOWEVER -- there's usually a reason why the seal starts leaking and it has to do with the pump housing or convertor nosecone bushing that has "walked" out of the housing and that's time for a new or reman'd pump and bushing assy.
The convertor nose in this situation is usualy damaged - scored and has grooves in it --- all bad.
When a seal walks out of the pump housing, it damages the machined pump boss into which it is pressed and the neophyte won't ususally recognize the damage unless the damage is huge and obvious. Don't count on noticing it.
At this point, the pump is junk.
There are other mitigating reasons why the front seal starts to leak --- pressure losses from a bad bushing inside the pump can allow a lot more fluid than is normal - to blow past the bushing and this fills the small cavity behind the seal because the drainback passageway is small (by rebuilder's standards) --- we always bore that passageway out at least a few drill sizes to help allow the excess fluid to run back into the pan, less restricted.
The seal can usually handle this excess flow - it's not much pressure after all.
It WILL shorten the life of the seal by inverting the lips or pushing it out of the pump housing however.
Understand that?
There are symptoms of losing the front bushing, 'way before it walks out and tries to go through the seal and you develop a leak ... you will likely experience soft shifts - drawn out or long shifts and/or no "countable " shifts at all.
Wow! This transmission is shifting so smoo-oo-thly! (NOT!).
This is where the transmission is really shifting, but the pressure loss inside the pump doesn't help insure a smart-bright-tight hookup of the friction material and it just slides into the next gear - all the while the previous gear has long ago (in shift-time) let go of the previous friction material.
Once this happens, the fluid goes dark rapidly and can be burnt to the taste (Yes --- I said; "Taste").
FTR -- there is NO SLIP-N-SLIDE in the clutches or bands.
NONE!
The hook-up is so violent and abrupt, you'd chirp the tores every shift.
If there wasan't a torque convertor between the engine and the transmission, you'd lose all your teeth every time it shifted.
That takes pressure and if it's not there things burn.
