Transmission oil - changing from gear oil to ATF, is flush required?

[Click_It]

Hi guys

Have been running 80W gear oil for the last few thousand miles off the advice of a mechanic at the time, it's okay in winter but terrible in the hotter weather - 1st/2nd issues engaging, all started with the new oil so I'm 99% sure that's the problem.

So I bought some overkill (expensive) 100% Synthetic ATF today and I'm ready to go.

One question:
Is a flush required or recommended prior to the new stuff going in? Since its a big difference in consistency.
And if so, can I just use the ATF as I have way more than I need for the job.
Or no flush required, just fill and go?

Thanks in advance.

[Bert]

If it's a manual tranny you merely face the equivalent of an oil change, if it's an automatic then it's not so easy. The torque converter will not empty/replenish on it's own. You will not regret switching to synthetic; that material does not break down due to age or overheat and service intervals are considerably longer. And synthetic does not dry out seals and gaskets nor 'wick off' lubricated parts when not in use.
Hopefully the previous poor advice of running 80W (instead of ATF) does not come back to bite you through irreversible wear and tear.

[Click_It]

If it's a manual tranny you merely face the equivalent of an oil change, if it's an automatic then it's not so easy. The torque converter will not empty/replenish on it's own. You will not regret switching to synthetic; that material does not break down due to age or overheat and service intervals are considerably longer. And synthetic does not dry out seals and gaskets nor 'wick off' lubricated parts when not in use.
Hopefully the previous poor advice of running 80W (instead of ATF) does not come back to bite you through irreversible wear and tear.

Cheers, yes it is a 5sp manual, my bad I thought I mentioned that.

Yes the 80W is rediculously thick, his reasoning behind it was he thought the Australian climate would be more suited but with hindsite one of the worst things you could do to our gearboxes I think. I hope no serious damage has occurred like you say. I've probably only done 3000-4000 miles with the 80W so fingers crossed.