Went by the local dealer to have the oil changed...ended up doing ther rear brakes as well of course...
Noticed they were selling new F-150's with bigger tires and lift kits.
Spoke w the aftermarket guy who does the conversions.
The F-150 SCREW I saw had 305 Pro-Comps w a 3'' lift. The aftermarket dude told me he would would install 315's with a 4'' inch lift or higher.
What I found interesting is that he does not install any gears or chips to compensate for any power loss etc. because he feels there is no need to.
I left wondering if this guy was right or wrong.

Back to my racing days w the 5.0 Mustang

On the 16'' Pony rims I used to run 255's w the 2.73's in the rear because I liked to run on the highway and the 2.73 gave me top end speed.
I would run my Buddy's stang w 4.11's at the track...of course I know these gears help out with the slicks and reaching better results in the quarter mile and from time to time I would also run my car at the track and light to light races on the street.

My point is that both my buddy and I both had the same stock Borg-Warner tranny and it never crapped out on us w either gear in the rear.

I would think that the tranny in my truck is way more heavy duty than any mustang.

How many of you guys have had tranny problems going w the 315's and how many feel that you should absolutely change gears w the 315's?

I feel the only performance impact/probem will be offline performance and I am not planning on doing any dragging w my truck.

Sorry for the long post...

 

I recently bought some BFG 315/70/17s that I'll put on the truck after I lift it, and I had no intentions of changing the gears. I will buy a Microtuner beforehand though, so I can correct the tranny shift points, speedometer, etc... I think our trucks should be able to turn 35s without a problem.

One of my old high school friends had an '85 4Runner with the stock drivetrain and the 22R 4-banger. He ran 35s and never had a problem, so I'd think we've got to be able to!

Mike

 

I'm gonna be in the shoulda category here. I've had 35s on my truck for a little over a year (since last May). Short of the story tranny #2 is developing issues and my steering is all but completely shot. If I get crosswind or going down a bumpy road you get a nice adrenaline rush trying to keep it between the lines. And as far as power wise (4.6L with 3.55) its about as nutless as you can get. If I had to do it over again, no way in hell would I ever do it like this again. A chip will help a little with the power loss, but you'll still be taxing your tranny and the rest of your drivetrain. The best way to fix this problem is regearing. If you want 35s wait and save your money for a set of 4.56 gears. This will put you to just a hair deeper than stock gears and you'll save your drivetrain. Only thing it won't help is the steering issues but there really is no fix for that. Thats what happens when you run larger tires. To be honest this swap has created so many extra repairs that I hate driving my truck now since I don't know whats going to break next and its a challenge to keep speed and keep it on the road. I'm looking around to trade trucks because of it, and I hate to get rid of the truck but I can't afford another $1500 tranny.

 

I drove my truck with 315's, a 4.6, and 3.55s for a year and a half. I've had 4.56s for a year and a half.
Me and powerstroke agree most of the time, but I'll have to disagree on one issue here. 4.56s don't mean you wont have problems. My steering is also going bad and i'm on my 2nd tranny also (and it's having problems)...luckily I have a 3 yr warranty on it, and as soon as it breaks...it's ford's problem. Here's my take on it though. Truck stuff wears out. We've had Fords, Chevys, Dodge's all in the family and they've all had problems, stock or not. My truck had problems before I ever lifted it and it's had problems after. I think bigger tires accentuate problems that already exist. I think the same about 4.56s. I had tranny problems before and I've had them after. I've had tons of people tell me that the lift and tires caused my problems. I say thats bull. If you can afford the gears, do it. Just do it. It'll make your truck more pleasurable to drive, and you wont regret it. I don't. In my opinion, which may mean nothing to you, installing the gears is worth it, but not installing them does not mean you are doomed to breakage. Good luck. Let us know what you decide.

 

I am currently running a 4.6L with 3.55 i the rear and 35's(315/75R16) and am not really liking the power loss. I had the front seal replaced on my new tranny about 3 months after the new tires were put on and I asked the ford guy if the seals just go bad and he said not really. I think that is had something to do with the tires but I may be full of it. The bigger tires add extra weight and the increased circuference(sp) that taxes the entire engine and drivetrain. I am going to be going to 4.30's for the rear. It put my truck a little lower(higher numerically) than stock but it will be like having 3.73 stock I think. I think that 4.56 are a little low unless you really need the extra power, that is like 2 gear sets above stock. I also hate the fact that I now rub on the frame a full turn but i pretty much nkew that that was going to happen given the fact that I am only running a 3" spindle lift on a 4X2. I have not had steering issues yet as I have only had the tires on my truck for about 3 months now, but they will come I know, but not really worried I have a warrantee for another 25K.
I would do the gear change if I were you if you get 35's. It will be better for your power and you drivetrain.

 

Thanks for all the helpful info guys. After much debate I decided to stick w the stock tire size and slapped some Dueler A/T's (non-revo) on my truck for only $433 at Costco...a hard price to pass up for a very good tire.

I have to say that loss of power was a big concern of mine...like I said my drag racing days are past me but I do sometimes miss the 1995 BMW M3 (hence the name converted) that I traded in for this truck. I am very impressed w the acceleration power that a truck like mine has and I did not want to do anything to cut into that power.

I can't really afford to replace a tranny if it craps out because the money I have saved up is suppossed to go towards a house. The 5.4 has a lot of torque so I can see the greater stress the 35's would create on the tranny even w the 3.73's

I guess I'll have to make 35's and gears a combo project for the future.

 

I have 35s on the stock rims with original 3.73:1 gear ratio. I had them on for over 30,000 miles now with no steering issues, tranny issues, etc.

I can't speak for the guys with the 3.55:1 GR but I have to say that the 3.73 gears work very well with the 35s. I think 4.10s would be perfect though.