can i put 38s on my 1998 f150 without gitting an after market axle or messing with my transmission?  

ya wont have to mess with the tranny, you'll need some 5.38 gears for the 38's and heftier axles if your gonna do anything other than pound pavement.  

mudb8-.:
ya wont have to mess with the tranny, you'll need some 5.38 gears for the 38's and heftier axles if your gonna do anything other than pound pavement.

Even if you just pound pavement you are going to need more than stock gears with 38's and brakes are going to suffer too. The rear axle should be a 8.8 which should live fore a while if you do not lock it but the front drive axle will be on borrowed time. I would suggest limiting it to 35's with stock drive axles. (I would still regear it though with say 4.88's)  

ok thanks!  

yep, 35's max and 4.88's would definately be a good idea!  

u wont need any tranny upgrades i have 38.5 baja claws on my 99 150 with 4,88 in front and rear axles and have no problems