Re-Gearing 7.5 LSD from 3.73 to 3.08, manufacturer recommendations for Ring and Pinion Gear set.

[2011Supercab]

I had an 82 Ramcharger with 3.08 gears and 31"tires, it got 11 mpg at 60 mph

Switched to 4.10 gears and 31" tires, corrected the speedometer and went to 16 mpg at 60 mph

 

[19Walt93]

If you have 4.10's I definitely wouldn't switch to 3.08's, 3.73's maybe if the terrain you drive in is absolutely flat. 3.0's aren't known for having much low end torque and you'll lose mileage if the engine is running below it's torque range.
I never liked the overcomplicated 4.0 sohc so before I ordered my 04 Ranger I drove a regular cab short box 4x4 with a 3.0, 4.10's and a 5 speed. It wouldn't hold 5th gear at 60 mph on a slight grade. I ordered a 4.0 sohc in my 04 Supercab 4x4 and in the 2011 Supercab that replaced it.
My 93 Ranger has a 3.00 geared 8 inch and it works fine- but it also has a 351 and a C4 with no overdrive.

 

[sgtsandman]

Well folks,

It's for sure a 4.10 axle, I jacked up the rear, marked the tire and gave the driveshaft a couple of spins. Sure enough a little over 4 complete turns to spin the wheel.

What's most interesting to me is the fact that the door sticker lists it as being an F6 Axle, which according to the tech library at least, that's a 3.73 limited slip. It also says that the standard tire size is 225/70r15s.

Just about every VIN lookup I used however marked the vehicle down as having 4.10 Gears , and 235 tires.

I've actually called Mazda Canada to see if they could find any original documentation on the vehicle, specifically a build sheet or window sticker. The person on the phone was super helpful and genuinely sounded curious about the whole thing.

I even found a Mazda B-Series Brochure from 2003! (from the USA) To try and make sense of the what the hell this truck ACTUALLY is. From what I think the brochure is saying, the limited slip wasn't available on the B3000 dual sport models, only the B4000.

https://autocatalogarchive.com/wp-content/uploads/2019/01/Mazda-B-Series-2003-USA.pdf

My whole world is twist-turned upside down.

I wasn't planning on cracking the axle open anytime soon, but now I'm doubting my entire existence.

Once you confirm the gear ratio, if it is indeed a 4 10, you have a decision to make based on the expected terrain you will be driving in. 3.73 for hilly terrain or 3 55 for flat terrain.

The reason I separate it this way, is that hilly terrain may over work the engine and hurt fuel usage. The 3 73 would be a compromise but give you the best compromise of a highway gear vs a power gear like it appears you have now.

My 2011 came with 3.73 and even with the 4.0 SOHC, struggled a bit in the hilly terrain I live in with the factory 235/75R15 tires it came with. As I mentioned before, the 1998 with the 2.5 Lima engine had a 3.45 with 225/70R14 tires and it was constantly struggling in this terrain and fuel mileage didn't change when I switched to a 4.10 axle, illustrating that the engine was being over worked. If I had lived in flat terrain, like the midwest, I could have went to a 3.73 and probably realized an improvement in fuel uasage but here in PA, would have still struggled.

Only you can decide which gear is going to work best for where you are.

Of course, were going to have to help you determine if you still have a 7 5 or an 8.8 so you can order the right ring and pinion set

 

[bhgl]

Alrighty folks, here's the confirmation you've all been waiting for:

It's a 4.10, LSD, in a 7.5 axle.

As I mentioned in a previous post, I marked a tire and counted the rotations needed from the drive shaft, and at speed the RPMs line up with a 4.10 ratio. I confirmed it was an LSD by... laying down some 11s on dry bare pavement with my winter tires.

And here's visual confirmation that it is in fact a Ford 7.5 under there:

I did another long distance trip to pick up some tires today, this drive did involve quite a few hills. The truck really didn't seem to struggle with 30-40% grades. It rarely had to drop out of overdrive short of me actively trying to accelerate on the inclines. Aside from the return trip with just 4 tires in the back, I was driving with no payload.

My travels with this truck so far have included hours bombing across the Prairies, to climbing up and down the Canadian Shield. Short of some time in the Rockies coming later in the year, I don't have to deal with very long mountain inclines/declines.

I do typical efficient driving practices of neutral coasting on downhills, and gathering speed before an incline, dropping down to my target speed and holding at or just below.

From everyone's input and experience here, it seems that right now the ideal gear ratio is either a 3.73, or at a stretch 3.55. However, there are some things that may be better to do BEFORE swapping ratios that being some weight reduction (there's an easy 200lbs I can remove), aero, and some basic power adds for the engine (e-fan conversion, cleaning up the ignition system, power steering delete).

If I find a good deal on parts, or find an axle ready to go with 3.73/3.55 gears and an LSD then the ratio change will happen sooner, and I'll be sure to post an update on my fuel economy findings.

Thanks again to everyone for their input and experiences with their own trucks.

 

[scotts90ranger]

The plus about going with the axle swap method is once you're done you can likely sell your axle for what you bought the other for so all you're out is labor... money wise I did a disc brake swap on my '90 Ranger that I'd already swapped a drum brake Explorer 8.8 axle in and ended up $20 ahead (if you ignore labor) when I bought a disc brake axle for the parts and sold it as a drum axle...

Going for efficiency I would keep it with a 7.5" axle, don't need more rotating mass for your uses, 3.55 is a 8.8 ratio, 7.5's had 3.45... I don't remember what ratio is in my Ranger bed trailer but if you were closer I'd say just stop by and we'd swap things over... it's either 3.08 or 3.45 but '92 or older so a touch narrower...

 

[bhgl]

The plus about going with the axle swap method is once you're done you can likely sell your axle for what you bought the other for so all you're out is labor... money wise I did a disc brake swap on my '90 Ranger that I'd already swapped a drum brake Explorer 8.8 axle in and ended up $20 ahead (if you ignore labor) when I bought a disc brake axle for the parts and sold it as a drum axle...

Going for efficiency I would keep it with a 7.5" axle, don't need more rotating mass for your uses, 3.55 is a 8.8 ratio, 7.5's had 3.45... I don't remember what ratio is in my Ranger bed trailer but if you were closer I'd say just stop by and we'd swap things over... it's either 3.08 or 3.45 but '92 or older so a touch narrower...

You're definitely right about either breaking even, or making a small profit. Short of it being an 8.8, it's one of the more desirable stock axles out there.If I can confirm it was the original axle, it would only have 80 000kms on it, plenty of life for a solid axle. But I know that given where I live finding a buyer locally, or someone willing to drive up to where I live is gonna be a tall order.

I was looking at disk conversions on the 7.5 for a moment, but ultimately it's not necessary and may in small part reduce my efficiency goals, and it's unlikely I'll find a 7.5 with them on there thanks to someone else's handiwork.

I don't know if they ever came in anything with a 7.5 as standard, but they do make 3.55s for the 7.5 axle.

As for the axle in your ranger trailer, that's very generous of you! I'll be out West later in the year, and I'm never afraid of long drive/detour.

 

[19Walt93]

If you swap in a complete rear and decide you don't like it swapping back is easier than doing a gear change.

 

[gearfather]

What's interesting is that the air/fuel ratio really does lean out on the one test after 70 MpH, I've got no information as to what transmission is being used, but it ought to be running in it's final drive ratio for a dyno-test.

That could explain why I was able to achieve pretty good fuel economy despite the high RPM. I should definitely consider dropping down to a 3.45/3.55 instead after I do some more number crunching.

I have 3.08--3.31 and 3.45 gears if you need them.. 612-309-three999