What would happen if

[DonC]

My across the street neighbor has a 68 Mustang that he gave to his 18 year old son for graduation. They rebuilt the car together (mostly him but the youngster was right there with him with oil and grease up to his elbows).
Anyway, yesterday I noticed the son under the car and wandered over to see what he was doing. Changing transmission fluid (4 speed manual, case looks like it might be a TKO or similar but not sure of the parentage) also noticed that one of the bottles of fluid he had put in looked different than the others and took a closer look.
One of the three was a synthetic and the other two were non-synthetic. Anyone have any ideas as to whether mixed oils will cause a problem? The car is still up so he can drain and refill with all one type if he needs to.
Thanks,
DonC

[bobcowan]

Mixing them is not a problem. I wouldn't worry about it.

[DonC]

Thanks, just didn't want him to have to get it towed from somewhere. At 18 he isn't in the upper income bracket yet.
DonC

[joyridin']

I guess that would depend on whether the trans used synthetic from the factory or not. If it did (and requires it), he might be asking for problems. If not, then go for it.

[blykins]

Probably wouldn't hurt anything, but Toploaders really don't like the slick stuff. They shift a whole lot better with just plain gear oil.

If it's a TKO, those bottles should have had ATF in them, or something like GM Synchromesh.