How To Flush A 91 Ls400 Tranny

[jqzhang]

I flushed my tranny of 1991 LS400 last week, using about 13 quarts. I don't think the way I did was right, or it won't cost that many quarts. Here is what I did.

1) release all the fluid in the old pan (about 2.5 quarts);

2) fill the pan with fresh fluid;

3) disengage the radiator inlet line from the tranny and asked my help to start the engine, important is to put the gear in N.

4) the fluid rushed out from the disconnected line and poured into a container;

5) waited until about 2 quarts of the oil out, stop the engine and pour about the same amount into the tranny;

6) repeat 5) until the old coming out of the tranny looks fresh and cherry.

Can I just first vacant the tranny completely and then fill in the fresh oil? If it works (I was told it might hurt the converter), there won't be any mix-up among the old and fresh oil. That way I wouldn't nee 13 quarts of oil and 8 to 9 might be enough.

Thanks in advance!

jqzhang

[monarch]

Toyota & Lexus factory repair manuals recommend just draining and refilling the tranny oil pan which is a risk free way of maintaining the transmission.

[jqzhang]

You're right about it but we cannot ignore the fact that about 2.5 quarts of fresh oil will be mixed with the rest of the capacity which is about 6 quarts of old oil. It's not efficient, is it?

Thanks for the quick return!

[99lsguy]

jg,

you've got the right operation going there........its a pain but a good way to go.

After that flush, just do a pan drain every 10k and your fluid should stay clean for a long time...