I am going to be getting a Rancho 4" lift kit for my truck. I am going to be putting 325/65/18 BFG AT tires on it as well. I dont tow that much and if i do the trailer is not that heavy. Would i need to get new gears for my truck or would stock gears be ok? I dont know a whole lot about gears so any information would be greatful.

 

What gears do you currently have? What engine?

 

I am deployed right now to Afghanistan, so i dont know off hand what gears i have. I do have the 5.4L though.

 

Its not neccesary, but it will prolong the life of your transmission and bring back some of you power loss from the larger tires. If you have stock 3.55s, then you are probably going to want to upgrade. If you have 3.73s, then you will be ok, and it will be more of a personal choice if you want to get more power.

 

Generally speaking, for a tire of that diameter (about 34.6"), a 4.10 gear would be ideal. It will give you more leverage for slinging those heavy tires around, but not destroy your milage any more than necessary.

If you have a 3.73 gear already, you'll be ok. Either way, don't forget to buy a tuner so you can correct your speedometer for the new tires and/or gears.

 

I am going to have the wheels and tires installed the same time i have the lift kit put on (otherwise i would do it myself) by a shop. They should have a tuner there correct?

 

Probably not

 

They likely won't. A shop just wants to throw parts at a truck. A tuner is a simple thing that you can do yourself. But it adds a few hundred to the cost of your project. It's a necessity though. Your milage calculator, and transmission programming is dependent on an accurate speedometer reading.

There's lots of options out there. I'm using a Hypertech Max Energy programmer. The only thing I changed in my computer was the speedometer and transmission shift firmness.

 

If your truck is an fx4 the 3.73 gears are what you have thats the standard on fx4 trucks.....if its not 3.55 is the normal, but there are just as many xlt and lariats that had 3.73 gears put on also, you will have to figure that one out.
if you have the money to gear, do it....I gotta wait.

 

Yeah I have an XLT. I am probably going to get the new gears, I was just curious if I needed them. Now the only thing is waiting til March when i get back, so I can get all of this done. EsJayEs thank you for the info on the tuner. I will most likely be purchasing one of those as well.

 

Anytime.

And thank you for your service. Cheers mate

 

I got them when I got the same lift as you...I highly suggest getting them! I went through one trans at 60k probably due to the 33s I had with the stock gears on my truck. Also, 4.56s on your truck make it accelerate like a lowered F150 with a 5.4. It's a whole different animal to learn to drive.

 

i doubt stock gears and 33's caused your transmission to go out. it is more likely use and abuse... spinning a 33' is a very small change compared to the 30's and 31's they put on these trucks stock. going from stock to a 35 is what will put alot of stress on your truck. i've been running 32s on my stock 3.55 gears for years, and have had absolutely no issue.