Should I get my transmission serviced after 300k km

[Bae]

Hi there,

So recently I swapped my cracked radiator with a new one and noticed a tiny leak coming from the lower transmission cooling line. I tightened the line and kept my eye on it for approx 2000km. Everything was fine until my check engine light came on and I started to hear some squeaking noises.

I wrapped the threads of my transmission cooling lines with Teflon tape and put them back and added about 3 quarts of ATF. Now everything is running again. No check engine light, no funny noises.

I might have overfilled my transmission but I can't seem to get a clear reading. I wanted to bring it in to get the transmission serviced and change the filter because I don't know when the last time this truck has had it done.

My friend mentioned that because it's an older truck, the metal grit in the transmission might actually be helping it to not slip, and he recommended that I shouldn't get it serviced.

 

[Bae]

I know the old saying "if it ain't broke don't fix it" but I'm just wondering if the benefits changing the filter and adding new fluid outweigh the risk of potentially needing a whole new transmission

 

[alwaysFlOoReD]

Any damage is already done. IMO putting in new fluid and filter won't harm anything.