he says that because you only have a 1500....the axles werent designed to handle that size tire....the lowest gears you can put in are 4.88 which might give drivable power but it will still drive like a slug and forget towing....not to mention you will go through wheel bearings like crazy....Our axles on 1500 dont like anything bigger than 35" tires....if you put those tires on with factory gears you willl burn up the tranny....shiftpoints will be all wrong and it will never even reach enough rpm's to ever shift into OD reliably.....
But you would already know all this is you did any homework before buying anything....this forum is loaded with info on this stuff....
I would look in the scrap yard for heavier avles and 1 ton steering setup...1500 can barely handle 35"s look at beefing up front end suspension components as well and adding dua stabilizers.... in short it going to be pricey.....
theres a guy selling one already lifted with 40"s here in buffalo. on craigslist (4grand)...He just changed the shot wheel bearings too as he couldntr sell it for the last 4 months with the bad ones... Bet he got sick of replacing them.

 

well i already said i was putting new axles and gears in before i put the tires on

 

wow totally missed that...sorry....didnt see anything in your sig about gears and just kinda assumed you were avoiding the upgrades...you do realize you would be way ahead of the game to just sell it and buy a 2500 or 3500 in the long run?
I was in this same boat when I lifted my jeep with a 4 banger....huge regret after dumping soo much time and money I was still limited.

 

What kind of axles are you gonna put in it?

You're gonna look like the TIV-2 with tandem Dana 60's that keep breaking with those 40'' tires on Dana 44s....

 

really hard...

 

hey the way i see it they both warned you.....lol

what about that drive shaft's? with the lift and then the diff axles

 

Start collecting spare parts, lots and lots of spare parts.

 

I dunno about about breaking the truck but I am positive it will break your bank. There's a lot of work to properly building anything to handle a 40 inch tire reliably. Even light vehicles, like a Jeep, require more than passing attention.

 

ladder bars

 

Upgrade your axle shafts, or save up for a tow truck