4x4 Gear swap -> 2.73 Rear

[Stic-o]

Probally the lowest you will find are 3.45's That is what Came in some of the B2's

 

[rudypoochris]

I just found 2.73, 3.07, and 3.31 for the D35... now I need to find them in reverse rotation. Correct?

It looks like it would be much easier to fit a T5 in there than to regear the whole thing. Unfortunately I don't see any kits available for adapting a T-5 to our borg warner cases. Advanced adapters only has a half kit and the output shaft is now NLA unfortunately.

I think only option is to set it up in a 2WD configuration which is less than ideal.

 

[askingxforxit]

Aldive, who get's 30+ mpg in his explorer, runs 3.73 gears, and has done extensive research to prove they are the best gears for gas mileage in our trucks.

It's not going to be cheap to regear both axles, and you will regret it.

here is the link.
http://www.explorerforum.com/forums/showthread.php?t=137531&highlight=mileage+monster

 

[carlover]

I had 3.27's with stock tires. Hell i ran 32's with the 3.27's. Freeway mileage was ok, but even the smallest incline and the engine was struggling alot. I actually get better freeway mileage with my 4.10's and 33's then i ever did with the 3.27's and any tire combo.

 

[rudypoochris]

Ahhh. Darn, I didn't want to run hydrogen though. Unfortunate. In the future I do want to run some boost through it, maybe I will switch to 2.73's then as I will have extra power. I guess I will just have to try it.

 

[4x4junkie]

Yes, this IS out of the power band... for a reason, power costs fuel simply put.

You're missing the point.

Being out of the powerband means the engine struggles to work harder (you're lugging it). Working harder = more heat produced (both engine & trans) = more fuel guzzled.
Also one can only guess at how much you'll be shortening the life of the engine's bottom end with all that lugging, too :roll:

 

[rudypoochris]

The engine is working harder, this results in more throttle opening and thus less pumping loss. At 50% load the ECU aims for ~14.6:1 AFR. At 20% load it aims for ~13.9:1 AFR. Lowering the RPM and increasing the load requires less fuel, to a point of course, which is why stock cars typically run long gears. I doubt 1630rpm is that point seeing as that is almost exactly what the car turns at 55mph... which is undoubtedly the speed the car was designed for. Remember the red block on the "55" mark. Additionally there are MANY cars out there with similarly shaped torque curves as the 4.0L running 1600~ rpm at freeway speed. I will be cruising closer to 72mph+ anyway which should push me around 1800 turns. The gears though are set for ideal economy at ~55mph, I am just trying to extend that.

I doubt the bottom end will break at 1600rpm and 180ftlbs any easier than it would at 2000rpm and 210ftlbs. We all have theories, this entire project for me is a THEORY. If it works awesome, if not, I will just swap back and try to figure out why it did not work. I just really want help with the actual, which would be where to source 2.73 gears for the D35 or any other ideas out of the box for keeping 4x4 and achieving the RPMs I want to achieve. For instance if there is a supplier of .68:1 OD's for the M5OD, that would be very useful information! Thanks.

 

[carlover]

have you ever done re gearing?????? its not an easy task. and will run you about 600$ an axle to have a shop do do. There is a reason why everyone is telling you its not a good idea. Alot of us have been there with the gears, and have the experience. The explorer v6 trans is probably one of the worst out there. Very weak and VERY sensative to heat and picky about loads. If you want better gas mileage (which we all do) i would abandon your gear ratios change idea and look to make your engine more effecient. Intake, exhaust, under drive pulley, E-fan, all of these things will help out with mileage alot...

If your dead set on gears though check Randy's ring&pinion. If they dont have it then it doesnt exist.

 

[rudypoochris]

have you ever done re gearing?????? its not an easy task. and will run you about 600$ an axle to have a shop do do. There is a reason why everyone is telling you its not a good idea. Alot of us have been there with the gears, and have the experience. The explorer v6 trans is probably one of the worst out there. Very weak and VERY sensative to heat and picky about loads. If you want better gas mileage (which we all do) i would abandon your gear ratios change idea and look to make your engine more effecient. Intake, exhaust, under drive pulley, E-fan, all of these things will help out with mileage alot...

If your dead set on gears though check Randy's ring&pinion. If they dont have it then it doesnt exist.

Thanks for the tips on the fan, pulleys, intake, exhaust, etc. I will put some thoughts into those. I think a Taurus 2-speed fan would be awesome considering they pull more CFM's than any aftermarket fan I know of costing less than $200 or so. I do eventually plan on turbo charging it to suit the 2.73's as they should help build boost and keep economy out of boost.

I have never re geared a Ford 8.8. The only issue I could think is if it has a 600ftlb torque requirement somewhere, I would have to see what kind of tools I need to make. I have re-geared many Nissan R200 differentials though so I wouldn't imagine it being an issue. A complete regear, carrier swap, and bearing replacement was $200 in labor at my local shop last time I took one in.

I do appreciate your opinions and suggestions about pinion and such suppliers. I have a feeling though the gears for the D35 do exist, I just am not finding the right supplier or maybe they are in OEM front diff's somewhere. I found a supplier of 2.73's for the D35... but thats for the rear. Lowest I found for front was 3.07 which would correspond to a 3.08 in 8.8" sizing, but I don't think that is low enough.

My cruise speed typically is 72-75mph which will put me right over 1800rpm, which should be very nice in my opinion. Worse comes to worse, I will be down shifting more often... this modification basically just turns 4th into what used to be 5th gear. I don't think anything will be exploding despite the typically weaker construction of OD's. I really wish a T-5 would just fit in, or even better, the availability of a steeper ratio OD. There is a gear supplier near me though that could probably cut one.

Also, I know the M5OD is pretty weak. I am at 197,000 miles and the second transmission. It is holding up well. I do typically shift below 1,000rpm around town with fairly high loads and it seems to do fine. I don't burn the synchros or grind it up which is nice. We shall see!

 

[Spdrcer34]

Rudypoochris:

THERE IS NO WAY IN HELL YOU SHIFT @ 1,000 RPMs with 3.27 gears. I have 3.73's now, and a custom made intake spacer, lowering my torque curve a few RPMS..and I KNOW you don't have this done to your motor. I have to shift @ 1800-2100 rpm to prevent lugging. Before the spacer install, I had to shift @ 2400-2500 depeding on grade to prevent lugging.

Here's a CHEAP way for you to test your theory on gears...

Get some wheels/tires from craiglist from a 5-lug Mustang.....they are about 26" tall. Roughly 10% smaller than the stock tires on your X....check your mileage...did it go up or down?



Dear members of the Explorer Forum,

This member 'rudypoochris' is not listening to any of us. General Motors, Chrysler Corporation and yes, even the Ford Motor Company have figured this out. The members here on Explorer Forum ALSO know what is going to happen, but this member refuses to listen to logic, and reasoning.

I know he will lose mileage. He thinks he'll gain mileage. Only 1 of us is wrong.

But since he's not listening to any of you, I'll just add my ACTUAL EXPERIENCE

From the factory my `92 X had 3.27 gears in the rear. I swapped in an entire rear-end assembly out of a `94 with 3.73 gears.

3.27 = 17.8 mpg averaged over 6 months
3.73 = 20.9 mpg averaged over 6 months

That is a 3.1 mpg increase....for going to a lower (numerically higher) gear! My commute is almost exactly 50/50 highway (55+) and city (stop/go, 30-35 mph max.)

This was done with a 5 speed manual transmission.

The idea is to get to speed as soon as possible, without going into a 'closed loop' (i.e. full throttle) cycle. Higher gears (numerically lower) make you have to accelerate longer, and use more gas......contradicting what you are trying to accomplish.

Once you are at speed, the motor needs to be in it's powerband. If you are traveling at a speed lower than it's powerband, you will experience 'lugging'. Lugging is wasted energy, and again you will experience lower mileage.

We know we don't know as much as the engineers that designed these vehicles, but we know more than 'rudypoochris' on this subject....


Ryan

 

[rudypoochris]

Well, I can't say I appreciate your input in regards to my knowledge, but I actually think I have done a pretty good job of listening to you all.

On the other hand, my question was simple. I wanted to know if there are D35 front gears near 2.73, what an acceptable discrepancy between front and rear gears is, and lastly if there is anything higher than a 2.73 for the Ford 8.8. I additionally asked at a late time whether or not a T-5 could be swapped easily or if there were other available after market OD's for the M5OD.

Out of about 30 posts I can honestly say only 2-3 actually answered any of the questions I asked, and I am greatful for those few. The rest are just basically various opinions about my idea, comments implying I am an idiot, don't know what I am doing, etc. etc. I asked for help with something simple, I didn't ask for everyone to let me know what they THINK will happen. So thank you all who actually helped me out. To the rest who basically only had negative things to say about me and my ideas, well... thats just too bad.

 

[Spdrcer34]

Well, I can't say I appreciate your input in regards to my knowledge, but I actually think I have done a pretty good job of listening to you all.

That's just it....YOU ARE NOT LISTENING.

You haven't listened to a single word we have said.

GM put 2.73 gears in the A-body (78-81) Cutlass equipped with a 260 V8. When upgrading that rear-end to 3.42 gear, and NOTHING ELSE it took the 12mpg Cutlass up to 16 mpg.

So GM even tried to get better mileage by installing taller gears....and it didn't work. So why should it work now, almost 30 years later? IT WON'T.

We're all for getting better mileage. But like they say: A fool and his money will soon part ways

Ryan

 

[rudypoochris]

I didn't ask you for your opinion about whether or not what I am doing will work. Although I STILL appreciate it until you start insulting my intelligence. I know you are so much smarter than me and got it all figured out, now let me go figure it out.I merely asked you for help in sourcing some gears. I am listening to your thoughts, noting them, and then deciding that I want to do it anyway. That is not 'not listening'. That is me trying to do what I want to do regardless of whether or not it works. May be foolish to you, but it isn't your car. Yes, I may burn up $400 of my own money, but either way I am going to learn something. I don't even know why I am explaining this as I only wanted to know where I could find some darn gears. I didn't ask you what you want me to do. I am asking you for some help finding a source of gears. It really isn't that hard, or maybe it is?

Thanks again for all of you who kindly provided insight on the project and answered my actual questions. It was much appreciated.

 

[LBarr2002]

This is the site I've been looking at for 4.56's and spools, http://www.accuautoparts.com/. They seem to have a lot of stuff and good prices, but the lowest gear they have for the front is 3.27 and rear is 3.08. The ratios you found for the D35 rear (Jeep) mean nothing, because there's not many options out there for our reverse cut front.

As far as different ratios front and rear, I don't know how much of a difference you could get away with, but I wouldn't have a different ratio at all. I value my transfer case and u-joints.

 

[carlover]

Just talked to a buddy who has been doing gears in offroad race trucks, and road cars and everything else you can think of for the past 10 years. Unfortunatly no one makes anything higher than a 3.08 for the reverse cut d35's. He checked all the major gear companies, and found nothing. Sorry man, those gears just dont exist. if you wanna try the 3.08's they are out there. you could always ditch the front diff and do a 2wd swap and run whatever gears you want...

 

[rudypoochris]

Just talked to a buddy who has been doing gears in offroad race trucks, and road cars and everything else you can think of for the past 10 years. Unfortunatly no one makes anything higher than a 3.08 for the reverse cut d35's. He checked all the major gear companies, and found nothing. Sorry man, those gears just dont exist. if you wanna try the 3.08's they are out there. you could always ditch the front diff and do a 2wd swap and run whatever gears you want...

Thanks! I appreciate the help immensely.

Apparently advanced adapters has a T-5 to BW 1354 kit, but the special main shaft is NLA or something. They referred me to another guy who might have one left. He says he thinks it is the right one, but he only has one. I think I am going to have much more luck taking it to the gear cutters local to me. I have to see what they can do though. They aren't able to do rear gears at all since the helical cut is very complex on them. I bet they could do a simple helical cut OD though which is really the only gear I need. A .68:1 or so OD would really be heaven sent in my opinion.

If it makes anyone feel any better I will drive highway in 4th for a week to see if I get any better or worse fuel economy. That is essentially what switching from a 3.27 to a 4.11 would do. I think it would be an interesting test. There is such a thing as too high and too low of a gear, I guess this is a good way to find out.

 

[Four0Sport]

not to put down anyones opinion, bc what everyone does with their truck is their choice. but from my experience, the more money you put into your truck negates any money your truck will save you. re-gearing is expensive, like 10 tanks of gas expensive. just my opinion though.

 

[rudypoochris]

not to put down anyones opinion, bc what everyone does with their truck is their choice. but from my experience, the more money you put into your truck negates any money your truck will save you. re-gearing is expensive, like 10 tanks of gas expensive. just my opinion though.

I agree. I am now looking much heavier into the possibility of getting a new OD cut. Something around .68:1. That is something that could be economical and even marketable, provided it doesn't blow my engine up and kill my economy.

 

[Four0Sport]

im not trying to agree with everyone or dissprove anyone but out of my 2 vehicles, i get better gas mileage with an awd v8 with 3.73 gears than i do with a v6 part time 4wd with 3.27s.

 

[rudypoochris]

im not trying to agree with everyone or dissprove anyone but out of my 2 vehicles, i get better gas mileage with an awd v8 with 3.73 gears than i do with a v6 part time 4wd with 3.27s.

I believe you. I just want to see what can be done. If I am wrong then I am wrong, but I suspect that fuel economy can be picked up by getting a steeper OD in there. I know for sure driving around in 4th gear (equivalent of switching to 4.11's in 5th) would kill my economy and eventually my engine. Would you drive your Explorer around at 65-70mph in 4th all the time? Then again there is such thing as too low or too high.