I want to get a set of BFG mud terrains in a 33 X 12.5, i was wondering if this is hard on my tansmission and if i should get gears to help it out, i am doing mostly city driving, very rarely am i offroad, its a 4x4 with the 4.6, any imput would be great, thanks

 

It depends what gears you have now if you need to regear.

 

Like powerstroke73 says, it will depend on what gears you have now. For mine with 265/75s and 3.55 the only time I notice any problem is when going uphill at highway speeds (50-60mph type of speeds). My preference would be to have lower gears (3.73 or 4.10) but I don't feel the cost is justified in my case. The 3.55 seems to be a pretty common ratio among these trucks even with differing tire sizes. I don't know what type of power drop you would feel with 33's though. As far as being hard on your transmission, it might depend on how hard/easy you drive the truck....how often it has to change gears, how much of a load is in the truck, whether or not you might tow a trailer, etc.

 

how do i tell what gears my truck has

 

Different axles have different codes. There is a manufacturer's lable of codes for specs on your truck along the door jamb on the driver's side. I don't know all the codes but hopefully someone else can help you. Mine is a "19" and I have 3.55 gears with an open differential. You might try doing a search. Another option is to stop by the local Ford dealer and just ask.

 

Get the door jamb code and search it here. The codes have been posted a zillion times. You can also get the actual ratio off a tag under one of your differential cover bolts on the lower of the 2 lines of information. As to your original question; if you increase tire size dramatically, your transmission is strained.