94 4.0 possible re gear for mileage.

offduty · Dec 9, 2011

I know when this truck was built they built it for a speed limit of 55 mph, thats why the speedo is marked with red @ 55. So since I drive closer to 70 - 75 mph should I re gear the rear end? When I am doing 55 my tach is at 2000 rpm's and I would like it to be at 2000 rpm's doing 70.

My question is has anyone ever re geared a stock 4.0 OHV that was built about the same time as mine and designed primarily for 55 mph on the highway? Meaning you have a red mark at the 55 on your speedo and are turning about 2000 rpm's @ 55 mph. If so how did it go and what were your mileage improvements. I am debating re gearing but want to make sure it is worth it. My truck is a 94 extra cab with a 4.0 OHV and I am currently getting about 14.5 mpg. Motor and trans have been replaced and truck is stock except for the Delta cams rods and rocker arm assembly. newer 4 hole injectors and a cold air intake.

I also have no idea what transmission I have I know it has an overdrive but would like to know what it came with. I also dont know what rear end it came with either or the gearing but if anyone has the answers I would appreciate it? I am currently stuck at work and had time for a quick post so I thought I would ask. Once I get some time to get with the truck or use the search function I will figure the rear and trans out.

Thanks

Rose2300 · Dec 9, 2011

what gears does it currently have

martin · Dec 9, 2011

Your truck has the aerodynamics of a brick, it sounds like it's in the optimum range right now. just my opinion.

Gotta_gofast · Dec 9, 2011

Slow down? As stated the truck does not cut through the wind as easy as a car. You can regear to something along the lines of 3.08:1 or 3.27:1 but you may find that your engine stuggles to maintain overdrive if you want to do 70mph at 2000rpm.

Try a good tune up of the entire drivetrain including synthetic fluids in the trans and rear axle (front axle and transfer case if its 4x4). Then invest in some low resistance highway tires.

straycat · Dec 9, 2011

You don't have an specs on your truck in your Avatar. Is it 2wd or 4wd? Your rear axle should have a plate on it that says what size rear end and what gear is in it. Your 4.0L should have the 8.8 rear end unless somebody before you had issues and put in a 7.5 rear end. Every Ranger or BII I have owned had or has that plate on it. It is a small plate that is attached to the rear end inspection cover. What size tires are on it now? The original size or are they smaller or larger than the stock size? I have a 99 Ranger 2wd 4.0 L motor with 33x12.5x15 BFG KO tires and a 4:10 setup. I get 24 mpg on the highway and I run at 70 mph. Not as much around town with bumper to bumper traffic. I get right at 18 mpg in town. You might need to take that Ranger in for a checkup if you don't know how to do a tuneup or check your sensors or plug wires and ignition system. Any codes come up since you had it? Maybe it is worth the $35-50 to have somebody run a diagnostic o it for you.

Remember that swapping a gear is not a cheap thing to do. Unless you can do it yourself you are looking at around and average price of $400-500 for parts and labor.

offduty · Dec 9, 2011

All great info guys, I am aware of all that stuff and yes I can do a tune up and have. I guess the real question was has anyone done this and what were the results? As far as 24 mpg that is an SOHC not OHV engine aint it. Seems that if it will stay in overdrive at 2000 and 55 it might at 2000 and 70. If I am not understanding this please feel free to offer up an explanation. When I have time to crawl under the truck I will, but I dont have that luxury while on duty.

Thanks

jcd302 · Dec 9, 2011

I had a 1994 2wd 4.0L and with the 3.08 gears I was running about 2000 -2200 on the hwy. I got 20mpg on average.

offduty · Dec 9, 2011

jcd302 said:
I had a 1994 2wd 4.0L and with the 3.08 gears I was running about 2000 -2200 on the hwy. I got 20mpg on average.

jcd302

Thank you that is exactly the info I was looking for. What speed were you getting at those rpm's? I drive from Ventura Co, Ca to Riverside Co, Ca once a week for a 3 day shift and its 160 miles each way. I dont feel safe not flowing with traffic and 70 to 75 is how they roll trying to get to work in So Cal. Our highways are a BIOTCH and although I have seen some heinous stuff the traffic coming and going is the most stressful part of my job.

I did forget to mention that I have the JBA headers and y pipe and just went to the Screamin Demon coil and some high dollar wires that would take the extra heat of the headers. I was getting code 214 for a while but it went away after replacing a crankshaft sensor. I also just replaced the cat and have a magnaflow muffler. Tires are about an inch taller than stock, but doing 2700 to 3000 rpm for 3 hrs dont seem right. I believe they would have designed this thing to do 65 @ 2000 if the speed was 65 when it was built, so why shouldnt I try to fix that?

Truck was running real sluggish due to wear from the push rod tips into the rockers. Once I replaced with the Delta Cam kit I had 15% to 20% more power and it ran a lot cooler, the wear was strangling the motor. The truck is a extracab 2 wheel drive with a vision shell that is about a 45 deg angle in front over the cab, it is about a foot taller than the cab.

I will have to climb under the truck and figure out the gears in the rear but that aint gonna happen while I am in uniform at work. I also have a 88 full size Bronco that I pulled 3:55's out of and had 4:56's installed in. Kinda wondering if I should put the 3:55's from the Bronco in the Ranger as it appears they both have the 8.8 rear.

Hahnsb2 · Dec 9, 2011

My explorer had 3.27s, I got better mileage by not using 5th gear, an average of 1.7MPG better...

Gotta_gofast · Dec 9, 2011

The engine is capable at operating over 2000rpm for extended periods of time. However, there is a lot more resistance at 70mph and the numerically lower gears require the engine to produce more torque than it would if it sat at said rpm at 55mph.

Chances are with an aftermarket camshaft you have essentially shifted your torque curve farther up the rpm range. This might be hurting your fuel mileage and swapping to a lower gear might make it worse (and feel slower). The extra wind resistance from the shell plays a huge roll at 75mph, too.

Oh, and 99 rangers were OHV, 2001 is the first model year of the SOHC.

If you drive this far and need better fuel economy look for a small car.

LameDuck · Dec 9, 2011

The red mark has nothing to do with what speed the truck was built for. It's the average speed that most of the US roadways use. Your 94 extra cab likely has 3.09 or 3.27 gears. You don't want to go lower. Lugging the engine down will not get you better milage. You want to keep the load down and higher gearing is where you need to be. There is an axle code on the drivers door sticker so you don't have to crawl under the truck. Still don't know if you have an auto or manual.

Sent from Satan, using Tapatalk

offduty · Dec 9, 2011

LameDuck said:
The red mark has nothing to do with what speed the truck was built for. It's the average speed that most of the US roadways use. Your 94 extra cab likely has 3.09 or 3.27 gears. You don't want to go lower. Lugging the engine down will not get you better milage. You want to keep the load down and higher gearing is where you need to be. There is an axle code on the drivers door sticker so you don't have to crawl under the truck. Still don't know if you have an auto or manual.

Sent from Satan, using Tapatalk[/QUOTE

Auto trans

ronclark · Dec 9, 2011

My 87 4x4 4.0L 5 speed with 4.10 and 30's at 75 i average about 16mpg i get my best mpg around 55 to 65 i average about 20.
Town driving kills me, i average about 14 mpg.

How many miles on the truck?
5 Speed or Auto?

From what i see on a 4.0L a cold air intake hurts more than it helps.
Make sure you have good wires, motorcraft sparkplugs. check for codes.
You might want to look into replacing the O2's, thy seem to get laze when thy get high mileage on them.

offduty · Dec 9, 2011

ronclark said:
My 87 4x4 4.0L 5 speed with 4.10 and 30's at 75 i average about 16mpg i get my best mpg around 55 to 65 i average about 20.
Town driving kills me, i average about 14 mpg.

How many miles on the truck?
5 Speed or Auto?

From what i see on a 4.0L a cold air intake hurts more than it helps.
Make sure you have good wires, motorcraft sparkplugs. check for codes.
You might want to look into replacing the O2's, thy seem to get laze when thy get high mileage on them.

Truck has about 500000 but the new motor and trans have about 100000 on them. Oxygen sensors are new, wires are new, New Motorcraft plugs installed about a month ago and it is an auto with no lift. I do my own mechanical work when possible and there is nothing wrong with the motor. Appreciate the help guys this is really a thread where I am looking for someone who has done this in a similar truck and they will post results. I certainly appreciate help but I was not triyng to start a let us trouble shoot your truck cause it aint running right thread.

offduty · Dec 9, 2011

offduty said:
LameDuck said:

The red mark has nothing to do with what speed the truck was built for. It's the average speed that most of the US roadways use. Your 94 extra cab likely has 3.09 or 3.27 gears. You don't want to go lower. Lugging the engine down will not get you better milage. You want to keep the load down and higher gearing is where you need to be. There is an axle code on the drivers door sticker so you don't have to crawl under the truck. Still don't know if you have an auto or manual.

Sent from Satan, using Tapatalk[/QUOTE

Auto trans

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I understand what you are saying but I do not consider the engine lugging at 2000 rpm as this is where it runs at 55. According to my mechanic and my drive line and rear end guy a gas motor should be around 2000 rpm at freeway cruising speed. I have to assume at the time it was built they tried to make it efficient at 55. I understand the red mark is only the red mark but to me it is a reminder of what the speed limit was when the truck was built. I think the Ford engineers probably chose those gears in the rear end and transmission because they were efficient for the times. Times have changed and the speed limit is 65 and where I am at the folks drive 70 to 75 quite a bit and I want to flow with this nasty So Cal traffic, it is just unsafe not to do so even though it is illegal. So if the truck was designed to do 55 at 2000 rpm well and I am doin 70 to 75 at 2700 to 3000 I dont think I am using my power as effectively as it was originally intended.

94 4.0 possible re gear for mileage.

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