The Truck is a 1995 f150 2wd with a 5.0 engine in it. The transmission is an automatic with a 4R70W. The current rear gear ratio is 3.08 open differential.

Sometime within the next month I am going to be scavenging the Junkyards around me for a rear end with a lower gear ratio in it. I know a 3.55 Limited Slip will be really easy to find but from what I have read a 4.10 limited slip is the way to go with my engine/trans/tire combination.

I am not sure how much or if any of the mods I have done will effect your guy's responses but i am going to list them anyway, better you guys have the information.

I put on a set of long tube headers and redid the rest of the exhaust. I have done the 6-litre tune up, my timing set at about 12.5 degrees. Drop in K&N air-filter, along with the air intake tubing from an i6 or 460 that mounts on the inside of the grille. Also have done an electric fan swap. 2-inch leveling kit in the front.

Right now I am running 31x10.5x15 inch tires, I do not plan on going any bigger for a while and if I did, it would be no more then 33s.

It is my daily driver, It does get some highway miles, but rarely any long trips(over a couple hours). I do not tow very often, maybe 4-5 times a year in the summer, nothing too heavy.

I am looking to just do a whole axle swap, from my understanding the truck needs to be a f150 from 92-96 so that it has the vss sensor correct?

I am looking to get more low end power but still be able to cruise going 70-75 on the highway.

Do you guys think the jump from 3.08 open differential to 3.55 limited slip will be enough?
I am leaning more towards the 4.10 limited slip, from what I have read on other posts everyone has been satisfied with 4.10's.

I know the 4.10's didn't come stock in many f150's but I think I could find
one if I decide to go that route.

Any advice or opinions about what ratio you guys think would be best, or any other relevant information would be appreciated.

Sorry for the long post but hopefully that is more then enough information about the truck if you need anything else let me know.

Thank you, Travis

 

4.10s would be the ideal ratio for 33" tires IMO, with 31's highway fuel milage won't be as good at speeds over 60mph but in both cases you should still see significant improvements in milage over 3.08 gears.

 

410 is gonna be night and day over 308's. 308's suck, even in fox bodies! I went from 355 to 373 in my 5.0 truck with 31's and it was nice but if I did again I'd go 4.10's even with 31's but I'm at 6000ft so the power isn't near as good.

 

I went from a 3.55 to 4.10 in my 5.0 with stock tires (29"). It made a big difference but felt I could have gone even lower, but being at high altitude (5,200') may have had something to do with it. Now that I have a 351w, I think 4.10 is perfect. Stock tires and 4.10's puts my RPM's at 2500 at 75mph in OD.

If I were you, I wouldn't go any higher than 4.10, especially if you do decide to do 33's.

 

My '71 Bronco has a 302, an over drive trans (NV3550 5 speed manual), 33" tires and 4.10 gears. I don't know how similar my rebuilt, carbed 302 is to your EFI 302. Certainly not identical power curves but probably close enough to be a useful point of reference.

I'm pretty happy with the 4.10 gears. I think I might prefer 3.55s, but that needs to be tempered with the understanding that I don't like having to listen to the engine spin and I don't mind downshifting when needed. Other people tend to like lower gears than me, so the fact that I'm OK with 4.10s means most other people will be too.

I typically start in 2nd gear, but on hills, or if towing even a pretty light trailer I'll use 1st. It might be a bit of a dog in those conditions with 3.55s. For easy cruising I'm into overdrive by about 40 mph so I certainly wouldn't mind another gear (or taller axes). It's turning about 2300 rpm at 70, so that's not too bad, I'd just rather it be a little lower, even though that would mean I'd need to hit 4th gear more often.

 

Conanski, you think the fuel mileage will increase with the 4.10's? Is this because the gears get the engine into a more efficient rpm range?

Ceetwarrior, I agree the 3.08's do seem like a rough gear for a full size truck, I also hate the open differential. I do not have to worry about elevation here in Michigan, just salt haha.

EllieMae94, Sounds like I would feel a pretty big difference from 3.08 to 4.10, exciting! I am keeping the 302 for as long as she will keep running strong. 2500 rpm's is not to bad at 75mph. Wish I had a tach in my truck so I could compare, that is also on the list of to do's haha

Nothing special, Great information, I am not sure how closely they relate either. I think I will love the 4.10 gears, I was just worried about going on the highway with them, but if its anywhere near 2300 rpm's at 70 I would have no worries at all. Great pictures in your gallery by the way! Looks like a great time.

Thanks for the responses everyone!

 

Yeah, that's a huge difference you will certainly feel. Like you, I don't do much highway driving but when I do I did not notice any difference in gas mileage.

Do you turn OD off when in town? Even that helps some with both performance and mileage.

As for tachs, they are a dime a dozen at the junkyards and well worth the little effort swapping out clusters.

 

Yes. Bogging an EFI motor does not help fuel milage it makes it worse because fueling is very much dependent on engine load. What kind of milage do you get now?

 

EllieMae94, Typically I leave OD on all the time, except when I am towing anything. Ill have to give turning it off around town a try. I think I am going to get a 3 pillar gauge for the tach, water temp, and maybe trans temp or oil pressure. With the Electric fan I installed id feel more comfortable with a better temp gauge then the one on the cluster, so might as well knock out a couple birds with one stone.

Conanski, that makes sense. I get around 10-12 on average on the highway and around town. If I drive very conservatively I can get it up to 13 haha.

 

10-12mpg!.. wow that is lousy. My 3.55 geared f150 did 14-15mpg and my 4.10 geared E250 does a pretty reliable 16mpg.

 

yeah it is pretty lousy, specially for a single cab. I was getting like 14mpg with stock tires. I do not think I could go back though, I love the 31's. It runs good, no CEL or codes. It would be pretty nice if 4.10's would give me a a little mpg boost.

 

Those gears will totally transform the truck, you will have to get used to it not downshifting out of OD when climbing grades on the highway.

 

Quick question, whats the axle code for the 4.10? Isnt the 3.08 H8 and the 3.55 H9? I'm talking about the 92-96.

 

H5 would be a 4.10 LS.

 

Looking forward to the transformation!

Does anyone have any tricks for inspecting junkyard rear axles? My thoughts were to spin it, listen for any abnormal noise or Resistance, then take the cover off drain the fluid and check the internals for any water, rust, or wear.