Ok, I've got a 1989 F-150 with a 4.9l 300 six. It's 5speed and 4x4. I was just curious about how large of tires I could go with. I want to use it to go mudding from time to time, but it's primarily a work truck as of right now. A friend has a set of 38's on 15 inch wheels for sale, and I know I'd need a lift for sure. . . But my cousin told me that the 300 wouldn't be able to roll them that well. Thats understandable. But what if I changed out the rear end gear and match the front diff? Any ideas would be appreciated, I'm just getting into this stuff. - Nick

 

if it is still a work truck i would not go any bigger than 35 inch tires

 

Cool thanks for the help. Just wasn't sure if the old 300 could scoot the big tires or not

 

sure no trouble at all, but i don't know how well the 300 will handle 35's. a guy i know is running 33's with a 300

 

Well it also depends on your rear gears you have in the diff too but yeah the 300 will be working trying to roll big tires but rear gears will help

 

Cool... I figured as much.. I'll probably stick to 33's or a bit smaller.. Just something to crawl around in :P

 

Some 5-spd's have apretty low first gear ........all most like a T-18/19 granny.......this helps to get the truck moving along from a dry stop.......

 

yeah, mine is definatly geared low in first lol

 

Well I roll 35's with a 302 and a AOD Auto. I have very little probelms with the big rubber. I can bark them around a hard corner but not off the line. I did a gear change I am running 4.11's. I use the truck pretty hard at times. Just ran another load of scrap in yesterday. Single axel trailer with 1460 Lb of scrap iron. Truck had no problems pulling the load.

 

I currently have 37's on my '96 300. It really doesn't have trouble getting up and going, its the cruising speeds that is a killer. Keeping 70 mph up a hill is impossible without shifting into 4th.

I plan on switching to 35's, and then getting 4.10 gears to help out.

 

the 300 can handle the tires, it's the gears that will get you in trouble. as a rule of thumb, i believe every inch you go up in tire size your gear ratio goes down numerically .10 so if you have 31" stock with 3.55 ratio going to a 37" would be like having 2.95 gears in axle. my concern with that size tire other than the gears is the mazda 5sp and the 8.8 axle holding up to those tires for anything other that street and light offroad. the 300 has a low rpm range of power so you want to gear it to keep it in it's powerband.

 

Yeah I want to put in a new axle soon, just not sure what yet....I just read about a new 9.75 in a offraod magazine that looks real good, and $. Or dana 50 /60, just need to research more on what will bolt up nicely. I've got straight d44 in the front, which I'm happy with, but will need to change gears in also.

 

i had friends years ago that one had a toyota with the 22r 4cy and ran 44" boggers and his brother had an old cj with 44" boggers and the 258 straight six, once the gears were right they had no problems turning those tires going down the highway, it was scary being that high in such a small truck/jeep. but being light vehicles also made it hard to put any real stress on the drivetrain. it was great for them, they could float out in the mud and never get stuck. but if my brother or i got stuck in our fullsize trucks neither of them had enough a** to pull us out.

 

Where are you located. I'm looking for a set of 38's i just put a 6inch lift on my truck plus it had a three inch bodylift on it already so 38s would be right at home under it.

 

Your cousin is mistaken. A 300 will roll anything with the right gears. With 35's and 4.30 gears my old lifted 93 F-150 could spin them goooooood.