How rare are 3.55 gears with a 5.0?

[1998rollover]

I'm thinking swapping 3.55 gears in place of 3.73's should up MPG a bit. But I've yet to find any Mountaineer or Explorer with a 5.0 that has anything other than 3.73. If 3.55 was a 2WD only option, that'll make the swap a bit difficult for AWD.

I have equipment and software to program tire revs per mile, so if the system can't be programmed for different gears, a different tire circumference can be calculated to fake it. It can change the axle type / tone ring teeth but I don't recall if it has anything for gear ratio.

 

[MAS Tequila]

My question is why?

At 65 mph you will be dropping a whopping 140 rpm.

How much fuel are you going to save?

You will gain the same drop in ratio by going from the stock 28" tire to a 30" tire.

If you EVER tow you will not be happy, trust me on this one. I have to re-gear soon, I'm running a 33" tire and I can no longer tow a simple motorcycle trailer on the interstate at speed and hold overdrive. My mileage at 65 with the trailer has dropped to around 11 mpg without the trailer I get around 14 mpg.

Ask yourself if it's worth the effort and expense.

You will gain more by doing a 4406 swap and running around in 2WD.

 

[CDW6212R]

I agree, skip the 3.55 idea. My first two Explorers were a 91 and 93 truck, both 4WD, the 91 had 3.27's, and the 93 had 3.73's. I got better mileage with the 3.73's, on a road trip 1100 miles we got just over 21mpg. The 91 truck never got close to 20mpg. It loses mileage getting up to speed, every slow period requires more gas to regain speed, more than people think.

The 4.10's hurt a noticeable amount on the highway, but the 3.73 is about the best gearing, for a 29-30" tire(which was stock).

My 99 has 4.10's, it works great for stop and go use. When I make it a V8, I'll keep the gearing, but use a close ratio gear set in the 4R trans. That's the AODE planetary and sun gear, shell etc. That brings the 1st and 2nd gears up closer to the 3rd gear, which is a big jump if you pay attention in your V8 truck, when it shifts from 2nd to 3rd. For me that will work, about like the 3.55 gears in 1st and 2nd of a stock V8 truck, and 3rd/4th like a 4.10 truck, with 29.5" tires.

Stock 4R70W 1st gear is 2.84:1, the AODE has a 2.40:1 1st gear, and the same difference in 2nd gears.

 

[juggar]

I'm thinking swapping 3.55 gears in place of 3.73's should up MPG a bit. But I've yet to find any Mountaineer or Explorer with a 5.0 that has anything other than 3.73. If 3.55 was a 2WD only option, that'll make the swap a bit difficult for AWD.

I have equipment and software to program tire revs per mile, so if the system can't be programmed for different gears, a different tire circumference can be calculated to fake it. It can change the axle type / tone ring teeth but I don't recall if it has anything for gear ratio.

Thats hardly worth the time and effort good lord. You probably won't see any difference in MPGs and will just make it even slower. Im not kidding when I say this is NOT worth the time and effort. Even if you wanted to gear swap a mustang from 3.55 to 3.73 it would be hard to justify the time and effort and thats a lot simpler.

 

[Mbrooks420]

There's no reason it has to be a 5.0. Gears are the same V6/V8. The only axle differences are the track bar mounts, which would be a trivial addition considering the other huge amount of work. 3.55s do exist in v8s but are very uncommon.

 

[Whisperingwayne]

Mine had a set of 3.55s in my 01 5.0. They were fine until I went up a tire size, then it was absolutely gutless. Save your effort for a manual transfer case. But if your set on 3.55s I've got a complete front diff with gears still installed. You pay shipping and it's yours. I threw the 8.8 gears in the trash. Figured no one would want them.

 

[CDW6212R]

LOL, no one would want them. I scrapped a 2.75:1 9" chunk like that too. I also have a 3.55 rear end from needing the axles. I should have pulled the brakes and saved the 3.73 rear from my old 93 truck instead. You can't save everything.

 

[SWIGIN]

I agree, skip the 3.55 idea. My first two Explorers were a 91 and 93 truck, both 4WD, the 91 had 3.27's, and the 93 had 3.73's. I got better mileage with the 3.73's, on a road trip 1100 miles we got just over 21mpg. The 91 truck never got close to 20mpg. It loses mileage getting up to speed, every slow period requires more gas to regain speed, more than people think.

The 4.10's hurt a noticeable amount on the highway, but the 3.73 is about the best gearing, for a 29-30" tire(which was stock).

My 99 has 4.10's, it works great for stop and go use. When I make it a V8, I'll keep the gearing, but use a close ratio gear set in the 4R trans. That's the AODE planetary and sun gear, shell etc. That brings the 1st and 2nd gears up closer to the 3rd gear, which is a big jump if you pay attention in your V8 truck, when it shifts from 2nd to 3rd. For me that will work, about like the 3.55 gears in 1st and 2nd of a stock V8 truck, and 3rd/4th like a 4.10 truck, with 29.5" tires.

Stock 4R70W 1st gear is 2.84:1, the AODE has a 2.40:1 1st gear, and the same difference in 2nd gears.

Unless you have seen this done and like it I would rethink the close ratio swap. My 94 GT (AODE) had the planetarys you are talking about And it was a TURD to drive around town. I went from 2.73 gears to 3.55 then to 3.90s and still was unhappy with it.

Then I did the wide ratio swap and all was right with the world.

All that being said, if you really want some I kept the close ratio parts if you need them.

 

[Rhett]

I'm thinking swapping 3.55 gears in place of 3.73's should up MPG a bit. But I've yet to find any Mountaineer or Explorer with a 5.0 that has anything other than 3.73. If 3.55 was a 2WD only option, that'll make the swap a bit difficult for AWD

My advice is do not do it. Your mileage may actually go DOWN if the 3.55's make your truck downshift on hills (and they might). You're in Idaho, and even if you're in the valley/flatter parts, I definitely wouldn't go down to 3.55.

In my opinion on a non-towing 5.0 powered Mounty on stock-size tires, 3.73 is pretty ideal. There's a sweet spot for MPG with all hp/TQ/tranny/tow/non-tow and tire size applications...too tall, it's gutless and has to downshift or wander all the time...too small, and you're revving out.

 

[SWIGIN]

I just went from stock tires to 31s and That did about the same thing as if I dropped my 3.73 for 3.55. My cruise RPM went from 2200 Down to about 2050.

Time to go tire shopping.

 

[Mbrooks420]

If you haven't done so I'd swap all the fluids for fresh synthetics. This might help with drag a minuscule amount. The only drawback to changing 'gear ratio' with tires, is that they weigh more which hurts efficiency.

 

[CDW6212R]

Unless you have seen this done and like it I would rethink the close ratio swap. My 94 GT (AODE) had the planetarys you are talking about And it was a TURD to drive around town. I went from 2.73 gears to 3.55 then to 3.90s and still was unhappy with it.

Then I did the wide ratio swap and all was right with the world.

All that being said, if you really want some I kept the close ratio parts if you need them.

Thanks for the offer, what mileage do those parts have you think? The math on the 2.84 versus 2.40 1st gear is about the same as two gear steps, so the 4.10 becomes about 3.55 with stock tires. My 98 302 is just like my 98 Mercury, it jumps from a start, tons better than my 91 Lincoln did with 3.27 gears(302 HO engine). I have 3.73's in that LSC now, and it's too easy to spin the tires, about 3.55 is good for the car(and 26.5" tires). That's my first project to put the AODE gears into, which matches the stock AOD gears, and go back to the 3.27's, with a 347 I have ready for it.

The 3.73:1 gears are very good for the 4500lbs Explorer, with stock engine/tires/trans etc. That's where Ford learned where the combination worked best. More gear(4.10) will help towing and low end acceleration, but they will begin to hurt highway mileage, more with more gear change. So judge your own usage, more in town slow speeds, or more high speeds on the highway.

 

[SWIGIN]

I took them out at 130,000 miles and my tranny guy said they looked like new. The math might look good on paper but in a much lighter Mustang with little tires they were awful.

IMO it would be like having a fully loaded trailer hooked to an EX all the time when pulling out.

 

[SWIGIN]

I took them out at 130,000 miles and my tranny guy said they looked like new. The math might look good on paper but in a much lighter Mustang with little tires they were awful.

IMO it would be like having a fully loaded trailer hooked to an EX all the time when pulling out.

You are correct, it always felt to me like my AODE was pulling out in second gear with a T-5.

 

[SWIGIN]

If you haven't done so I'd swap all the fluids for fresh synthetics. This might help with drag a minuscule amount. The only drawback to changing 'gear ratio' with tires, is that they weigh more which hurts efficiency.

You are right on with the hurting efficiency remark but what I was getting at was IF you went to 31s some 4.10 gears would bring your cruse RPM right back to stock.

I rarely seem to get my point across online...lol

Now is it worth the cost to re gear 2 rears for a 1/4 of a ratio....not to me with a V8 anyway.

 

[MAS Tequila]

Exactly, and he is only talking about 140 rpm at 65 mph.

My dilemma is that with 33’s and an original ratio of 3.73, I need something like 4.30 to get back to factory.

So do I go 4.10 or 4.56?

 

[SWIGIN]

The correct answer is 35s and 4.56....lol

 

[CDW6212R]

Exactly, and he is only talking about 140 rpm at 65 mph.

My dilemma is that with 33’s and an original ratio of 3.73, I need something like 4.30 to get back to factory.

So do I go 4.10 or 4.56?

33/30*3.73=4.103, so to get stock performance that calls for the 4.10 gears. If you want to go to bigger tires later, or tow some, maybe more is needed. But 4.10's restore the original ratios if you do 33" tires.

That is also assuming equal tire/wheel weight, which often goes up. I had 18's years ago that weighed 15+ pounds more than the stock 15's, that hurt performance a lot. Weigh your stock tires and see that they are only 55lbs or so. if you go much over 60lbs, it will be felt. I found some 17's recently to put 275/55 tires on, and together they will weigh 58lbs, which is very close to the stock weight, much better.

Watch the tire weights when you shop for tires. Often the multi-ply tires weigh a ton more than the optional few ply versions. It can change from say 35lbs to 45lnbs for the same size tire. Regards,

 

[CDW6212R]

The correct answer is 35s and 4.56....lol

35/30*3.73=4.35

That 4.56:1 is probably the right gear for 35's, if they aren't too heavy.