I have a 99 F150 XLT, ext short, 5.4, 4x4. I installed flowmaster catback, K&N intake, Hypertech power programmer and I didn't feel the power difference. I am now ordering new wheels/tires, 18x9 with probably 33" Nitto terra grapplers. This is a daily driver, only about 2K annually and off roaded a couple of times a year.
I used to race mustangs (mainly an 89 12sec) and if I had a 5.0, my next upgrade would be to change the gears. I am not too familiar how 4x4 gearing works. I am guessing if I change the gearing in the rear diff I also have to change it in the front diff if I want to use the 4x4. Is this correct? In Philly we do get snow a few times a winter so the 4x4 does get use. I just submitted another thread about adding HP that is noticable. I would like to install a SC in the future, but don't see that happening soon. MONEY!!!!
What is the factory gearing in my truck? What gearing is recommended in basically an all purpose truck? I hope I don't ever need to do any severe tranmission work and I plan I keeping the truck for several years, it only has 68K on it. With the recommended gearing, will I feel the speed difference?

 

Gearing makes a huge difference no matter what you are driving. Just factor in the change in overall ratio when you put larger diameter tires on. You probably have 3.55 gears now, possibly 3.73. Check the axle code on the door and it can be looked up. Also, there is a tag on the rear diff with the ratio and whether it is a traction lok.
And yes of course you have to change both front and rear diffs gearing.
I have a 2002 and I felt a big difference when I installed just the Superchips program. Sometimes opening up the exhaust causes a loss of low end torque.

 

I think I have stock 3.55. I do realize that with large tires I will lose a little performance until I gear it properly. If I increase my tire size, which I probably will, the increase is on about 1.25" in diameter. It is lees than a 4% increase in diameter. Do you think I will feel the performance difference? In the past I had a couple of 5.0's and I either installed 3:73 or 4:10 as my third upgrade. They were both 5sp and I saw a big differerence. What should I install for performance on this F150? 4:10 or bigger? Don't forget it is a daily driver, but only 2K annually.

 

What is the axle code on the door jamb sticker?

 

It does not say on the tag on the drivers door jam. It doesn't have any numbers that could be a gear ratio. It did have the wheel size, tire size, GAWR, even said 26 spline axle, but no gear ratio. I also looked on the rear diff. There are two metal tags. Both have numbers on them but none of them could be gear ratios either. Is there any other way of finding out?

When I do replace them, since I am installing 33" tires, what ratio do you recommend for a 4x4. I am guessing 4:10, I don't want to go super aggressive, but I want to really feel the power gain and I drive it under 3K annually.

I am familiar with the older mustangs, so let me compare the gearing to if it was a mustang. If it was my 91 5.0, I would install 3:73 since that was a daily driver. I also had a 89 5.0 and it had 4:10, but it was rarely driven, mainly drag raced. So how can you translate that to my F-150? 4:10?????

 

Underneath where it says "axle", there's 2 characters - either a letter and number, or 2 numbers. Mine says "H9". What does yours say?

 

In the door jam, where it says axle, under it says 26. Above it says RC16.
I thought the 26 meant 26 spline axle.

 

No, that's a 3.73 non limited slip. Is yours the 7700 model? "26" is actually a F-250 code. Going to 4.10's is not worth the expense and 4.56's may be too much for a daily driver. 4.30's would be the best, but you can't get those for the front axle.

Post the numbers you do see on the actual rear axle tag, please.

 

Can I take a picture of it and email it to you? Please email me and I will reply with the pictures since there is 2 tags on the rear diff.

SORRY WRONG EMAIL ADDRESS!!!!!!!!!!!!!!!!!

 

What rpm do you want your truck to turn at say 70mph? Check what it turns like it is and just multiply that by the ratio of proposed gears versus the current ones. Same goes for tires.

For example, if you change from .373's to 4.56's multiply your current rpm by 4.56/3.73 and you will know what rpm the engine will turn after the change.

For tires, say you go for 33" diameter tires and you current tires are 30" in diameter, multiply your current rpm at 70 by 30/33 and you will know what rpm your truck will turn after wards. It's really simple.

 

Upload the pics to Photobucket or somewhere and post links to them here.

You may want to edit your email address out or the spambots will have a lot of fun at your expense.