The old motor shaft is smooth at the tip for like 1/4 inch down then few threads then smooth again. The OS is threaded all the way so how is this going to work casue the old bell was held on by a c clip on the end? And to me looks like the shaft on the old motor is a hair longer than the 18. I was actually thinking of takeing the crank out of the 15 and putting it over in the 18 will this work?

You did the same thing that I did, you purchased the wrong engine. No worries though. They make a crank just for this conversion. [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&W=000590686&I=LXGMM8&P=K]Here it is.[/link]

I installed this crank and haven't had any more issues so far, and the engine is installed.

Hope this helps.

that is still a threaded tip where the stock motor has the c clip to hold it together. This is what i have look at the tips http://www2.towerhobbies.com/cgi-bin...?&I=LXHTN0&P=0 this is what i bought http://www2.towerhobbies.com/cgi-bin...?&I=LXGGP7&P=0 and like i said the new motor has a shorter crank than the 15 which everyone says you have to cut it well there is nothing to cut. And that part is like 40 bucks il just return the motor and get the right one cause there the same price.

My appologies, I forgot to add the clutch nut that goes on the end of the crank that adds the place for the e-clip. [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&W=000590686&I=LX3371&P=K]Here it is.[/link]

so that shaft is longer than the one you took out of the 18?

It's actually shorter, but the clutch nut puts the clutch bell right where it needs to be. If you were to add the clutch nut on to the shaft that came with the motor, it would be to long to line up w/ the spur gear. The crankshaft actually needs to be shorter, so that the clutch nut will line up the clutch bell properly w/ the spur gear.

wouldnt just putting a clutch nut on the end work?

If the version you linked to is the version that you purchased(there are 2 versions of the same engine, one for the RC10GT and one for other trucks. The one you linked to is the one for other trucks.) that would put the flywheel side of the clutch bell right on the spur gear. Like you said before, your best bet is to probably return the engine and exchange it for the short crank version and buy the clutch nut, it would be cheaper that way. If your LHS doesn't have the short crank version, then just get the short crank and the clutch nut. Either way it'll work out for ya. [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGGP8&P=0]This[/link] is the engine for the GT.

ok thanks for your patience and help il return it tomorrow hope they have the other.

No problem. I went through the same problems when I did mine. I just went through a several month long ordeal trying to do mine. As a matter of fact, it was so long that I've lost some screws, so I'm going to have to order more to get her going again. So I understand what you're going through. I'm just glad I could help.