Is anyone running the stock gears (3.55) with 285/75R16 tires and the 4.2L - Just wondering I want to go to this setup with the larger tires but do want to bog down too much.

 

I have that set-up. Not too bad. I can still bark the tires on command. If you add a chip I heard to is a lot better. Chip is my future when gass goes down...hopefully. When the A/C is on is when you can really feel it.

 

I moved up to 265/75R16 with mine and my mileage dropped considerably and power is noticably lacking. I want to go to 285's next, but only after I re-gear to 4.10s.

 

I put on 265/75/16 BFG's and could not feel a power loss at all. My city mileage dropped maybe 1 mpg if that, but my Highway mileage went up ( lower rpm's)...

 

Im running that set up with a 3.5 inch suspension lift with a superchip and its great. I love the look and I didn't notice much power loss.

 

I decided on getting the 285/75R16 in a Cooper Discoverer AT. I love the look - looks like a truck should. I didn't notice any power loss but I really haven't driven it a lot. Wouldn't get anything but the 285's now

SilverBullet

 

My 4.2L V6 recently just got lifted with a Fabtech 3.5" spindle suspension lift with 2" rear blocks to even out the rear.

I have 285/75-16 tires, and noticed a definite difference in acceleration; mind you I had the 3.55 and 5-speed manual.

This only lasted until I got to the off-road shop, where they added 4.10's!!! Much, much better!!!

I wouldn't personally add 33" tires unless you regear the rear end eventually, unless you get used to going so slow.

 

There is definately a power difference, but not so bad that it would deter me from jumping up. I have had them on for a month now and am very happy with them. I do plan to change gears over the next 6 months though.

My biggest problem is the speedo being off. Anyone know how to get new gears for the speedo? Mine is not a computer adjustment according to the dealership.

 

There are many threads through this board search on VSS (vehicle speed sensor) that should put you in the right direction. In order to make the speed right go to the ford dealer they should have the part or be able to get the correct VSS gear dfoir the different tire size - cost is about $10. Currently, I have a 20 tooth black vss gear - I am going to get probably the 18 tooth grey gear based on recommendations in previous threads - The Ford parts man said it's about a 4 mph difference at 65mph per tooth I'm off 10% so that should be about right maybe a little conservative (speedo running faster than actual). I see if I can get a part number when I order mine over the weekend.

SilverBullet

 

I'm running 265/70/17's which are about 1 1/2" taller than my stock 275/60/17. I lost some power out of the hole. No way can I bark the tires. I have 3.55's with an automatic trans.

 

I've been running 285/75/16's on my 4.2 with 3.08 gears for about 4 years and I love it. Performance dropped a good bit but I am used to it now. It still moves fast though and I don't have to push it hard. Just give the computer time to compensate for the differences. I got a new speedo gear and it is only off by 1 mph which is good. I say go for it.

 

how much should i expect to pay for some 265 or 275 AT's? prolly won't be able to do the 285's cause i'm not lifted yet and running a 2wd. thanks

 

Im running 315/75/16s on my 4x2 v-6 but have replaced my rears to 4.56's. You lose a ton of power, not to mention ruin your gas milage by not changing your gears if you go with bigger tires on your truck. On tip of that, it wears down your tranny and a bunch of other parts faster if you dont change your gears because your whole drivetrain is working a lot harder to turn your tires. If you are running 285's you should probably change your gears to 3.73's if not 4.10s. You will lose top end power but i can still hit the rev limiter with 4.56s in my truck so it cant make too big of a differnce. On top of changing your gears you should probably consider recalibrating your speedometer. It can be done at any local ford dealership. Gears can be anywhere from $450 to $2000 but personally i think its a necessary upgrade if you are running bigger tires on your truck. Hope i helped.
Courtney

 

I didn't notice any loss of power upon getting 285's - I changed the VSS gear to get my speedometer correct. I got my Cooper's for right around $600 installed including tax.

 

I recently put on 285's I still think they look too small but it's much better than before. I did notice a big difference in power too ( still running 3.55s). I was wondering who has switched to 3.73s and who has switched to 4.10s? Can you tell me which you think is best? for power and fuel economy? Also, has anyone out there put an overdrive box on a 120" wb 4x4 truck? any comments on that too would be apreciated.