can you run a single titan 12t on 3s

Probably, but not going to last very long depending on the discharge rating.

I don't have any experience with the 12t Titan but people complain of them not lasting on 2s lipo and 8.4v 7cell NiMh. I doubt 3s is going to help motor longevity.

Sure you can run them on 11.1V........ Just understand that they are not quality motors and you shouldn't expect the Titan to last long even at 7.4V.

I've learned that if you break a brushed motor right they'll last a loong time...I've got one thats been running for more than a year now...i only run it on 2s...i just figured that the titan would be a good one to through in my parts bin slash monster bc they can handle the weight of a maxx..

That statement makes me wonder if you know there are two different 550 size Titans, the 12T (what you mentioned in your 1st post) comes in the XL5 vehicles, Slash, Rusty, etc. The 21T Titan comes in the brushed EMaxx and Erevo.

The 12T Titan definitely can't handle the weight of a Maxx and you need two of the 21t motors on an EMaxx. If you think you can gear it properly I think the 21t Titan on 3s would be the better of the two Titans to use for an overweight slash.

Thanks for the clarification....its not gonna be geared all crazy and stuff..but i want the punch of a 3s...I'll probably be running 90/21 gearing

Actually I think I should clarify my post. I didn't mean you'd gear it crazy, I meant if you think the available gearing of the trans would work with the 21t on 3s. The 21t on 4s is probably roughly equal to the rpm of the 12t on 2s, so on 3s the 21t is going to be spinning a bit slower. But it should have more power to pull the higher gearing and increased weight of your Slash better than the 12t. There's also no reason you can't run the 21t on 4s depending on what you have on hand and/or are willing to buy for the project.

I'm not going for higher speeds...the stock slash was plenty fast for me..i had the vxl already cuz i was running it in a touring car..i just ran it stock to get a feel for the stock characteristics...when i entered the rc scene "for sure" there was the great debates on lithiums and brushless....i feel that we dont have to stray away from brushed...they are cheap and fun

Wheelies everywhere...