Let me start off by saying this message board is a wealth of
information. I think that Ford should consult this forum before
building new trucks. In any case, yesterday I was reading some
threads regarding wheels and gears. I checked the sticker on the inside of the left door and it said that the axle was H9 which I believe equates to a 3.55 limited slip according to one thread I read. Now the big question - what does this mean? Is this good, bad, or indifferent, can it be easily changed. or should I not concern myself with it.

 

You have a 3.55:1 ratio with a clutch style Limited Slip Differential. You can't easily (or cheaply) change the gears. You're looking at about $500-600 in gears alone, then about that much again for the labor to install them. This isn't a project that the average shadetree mechanic can do in the driveway. For the most part don't concern yourself with it, or at least until you put bigger tires on.

 

Powerstroke, funny you should mention larger tires because I'm looking at a set of 265/70-16, what's on it now are 235/70-16.
will this make a difference?. The reason for the tire change is the truck looks goofy with smaller tires on it, lots of open space in the wheel wells.

 

I think the Limited Slip is good.
(It costs more to get it than not get it, if that helps)

The gears available I believe were:
3:08
3:55
3:73

These numbers mean how many times the driveshaft rotates for every single rotation of the axle. (Big whoop de do)

If you crawled up under your truck and marked that steel or aluminum, one-piece or two-piece object otherwise known as the driveshaft, and then rotated that 'driveshaft' 3 and 55/100 times (about 3 and a half) then the axle would have made one rotation.

The 3.08 usually came on the V6. Sure, it's gonna be slower to get going but it has the least horsepower and needs the lower ratio at highway speeds to keep the tach down somewhat.

The 3.73 usually came on the 4x4. The 4x4 usually has larger tires and this higher ratio helps offset that fact.

That leaves the 3.55 (you). It's in the middle, splits the difference.

Changing gears is expensive.
You can 'simulate' changing gears by changing the diameter of your tires.

A larger diameter tire will simulate moving you closer to the 3.08.
A smaller diameter tire will simulate moving you closer to 3.73.

Do you have some particular reason to be concerned about this?

 

Well you're close raoul. The majority of the 4x4s had 3.55 gears least from what I've seen. But the 4x4s did even get the 3.08 even in a V8. I've heard of a very few that did get them. Waldo who used to go to FTW has a 99 4x4 with a 5.4L and had 3.08 gears stock.

Anyhow going to 265/75/16s like you want won't need anything done to the suspension or axles. Heck I'm running 35s and 3.55 gears. Yeah it sucks big time. I used to run 265s on my truck with 3.55 gears quite a while back and it does fine. Just might shift out of OD a little sooner on hills is all.

 

I am running the current tire you want to go to and have no problems and powerstorke was right. No gear change is needed. You could go to a lower gear ratio and put in 3.73 but it would not be worth the $$. I don't know where powerstorke gets his gears done but you could probably get gears installed for you truck for about $800. You may even be able to ask a mechanic at a local shop if he will do this job off the clock for cash and save $$. Oh Raoul-a 3.08 is a higher ratio then a 3.55, where a 3.73 is a lower ration than a 3.55!

 

Yes, I should have known that from my bicycle riding.
3.08 rotations of the pedal crank = 1 rear tire rotation = higher gear

3.73 rotations of the pedal crank = 1 rear tire rotation = lower gear.

Which brings up a point on gear swap.
Unlike a bicycle, you can't gear swap a car on the fly.
Whatever you choose is what you have to live with.
If you choose a higher gear, you will be a dog out of the hole but will cruise easily.

If you choose a lower gear, you will have a quick takeoff but will eventually run out of motor.

 

Gears are expensive. You're looking at between $800-1000 or higher depending on the shop that you have install them. I can't remember off the top of my head what reverse cut 8.8 IFS and either 8.8 or 9.75 gears run as far as price. I was looking at having them installed in my F150 and it was going to be between $600-700 and thats having someone I know do the install for $200. So most likely a gear install will be AT LEAST $800, but probably more up towards the $1000.


And yes low gears will give you lots of low end power but you'll run out of top end and will not be able to go as fast. But why do you even need to go that fast when most speed limits are only up to 75mph. Seems to me that going fast enough to be limited by gears is going too fast for everyones safety. Unless that is, you're doing that kind of thing at a 1/4 mile track or something.

 

Yep, I'm looking at some 21:36 gears for my truck.
I don't plan on leaving the neighborhood.
As a matter of fact, I just need them to get to the mailbox at the end of the drive,
but I want the mail like, right now.

 

"Yep, I'm looking at some 21:36 gears for my truck.
I don't plan on leaving the neighborhood.
As a matter of fact, I just need them to get to the mailbox at the end of the drive,
but I want the mail like, right now."



Now that was funny.

I have the 3.55 non LS. What i want to do if find a 3.75 LS from a 97/98 F150 that has been wreaked and just switch the whole rear end out.

 

I forgot that we are talking about a 4X4. That doubles the cost, so yeah you are probably looking at 1500 for new gears. Like I said though, go to a local service store and ask one of the mechanics if they would instll the gears for cash, they will usually do it for cheaper.