One good gear is more than enough. I own an atomic warhead with damaged 1st gear. I loosened 2nd gear lock and car goeas on 2nd gear all the time, see how it goes...

http://mieszkancy.ds.pg.gda.pl/~jimi...ead_jazda4.avi
http://mieszkancy.ds.pg.gda.pl/~jimi...ead_jazda5.avi