Want deeper gear (higher numerically final drive ratio)

[ClutchFork]

My 2001 Ranger is pretty peppy, but does have a bit of a lag off the line unless I slip the clutch a lot. Also in overdrive on the freeway at 70 mph going up slight grade I have to put my foot into it a good bit. I was thinking it has a 3.73 rear end, so a 4.10 would be a 10 percent boost in power effectively. I could get a 4.10 rear axle from the junkyard, or I could slip smaller tires on it, which would be cheaper and more easily reversed if I end up not liking it. Now I turn about 2650 at 70 mph, with a 410 it would be turning over 2900 rpm at 70, maybe a bit high. But I could go 9 percent or 8 or less. So if I do it, most likely would be by tire size. But the big question is:

How, if I change my final drive ratio, do I get the speedometer re-calibrated to match?

[potownrob]

what about using your low range??

[ClutchFork]

what about using your low range??

Ah, a two speed transfer case would be helpful, but this truck is only a two wheel drive.

[potownrob]

what about using your low range??

Ah, a two speed transfer case would be helpful, but this truck is only a two wheel drive.

oh bloody bollocks

[theholycow]

Your 2001 model's speedometer/odometer will have to be reprogrammed via the OBDII port. Leaving it wrong and doing the math isn't so bad, though.

If you don't mind looking silly, smaller tires are the better way to do this, at least temporarily. You should be able to buy a set of wheels and tires for little investment and avoid having to pay to have tires mounted/balanced as well as being able to switch between them whenever you damn well please. Once you settle on a tire size you will have a second set of wheels on which you can put studded tires for those Michigan winters.

The axle is a lot more work than I thought. I know because I just finished mine last night. My truck's rear differential failed and I scored a whole axle for $80 at the junkyard, thinking it was going to be an hour of work. It's a simple job, but just so much time-consuming work. All those extra wheels from testing will come in handy as backup to your jack stands in case it falls off the stands. Break the biggest nuts loose with it still on the ground, BTW.

[ClutchFork]

Your 2001 model's speedometer/odometer will have to be reprogrammed via the OBDII port. Leaving it wrong and doing the math isn't so bad, though.

Hassle taking it in for the reprogramming. Too bad it's not an earlier vehicle with a mechanical cable where you can just change the gear. Some sites say that not reprogramming the computer will cause performance problems as the computer will not know you are going only 70 when the speedometer says 77 mph. Note advice from TheRangerStation website:

"The speed sensor sends its signal to the Engine Control Module (ECM), the Power train Control Module, transmission, and if applicable, the anti-lock system "brain." When tire height and/or axle gearing is altered, these control units receive erroneous information. In all but the most extreme cases (really huge tires), an incorrectly calibrated vehicle will operate, but not at its peak. For example: if a vehicle is factory equipped with 28" tall tires and they are changed to 35s, a 20% change has occurred. Unless remedied, the various control systems will "think" that the vehicle is traveling 20% slower than it actually is. To make matters worse, newer computer-controlled vehicles have become extremely sensitive to changes in tire diameter and axle gear ratio. The reduction in performance can be difficult to gauge, but it is real. Plus, the number and degree of malfunctions increase as speed signal inaccuracy increases."

If you don't mind looking silly, smaller tires are the better way to do this, at least temporarily. .

Well, I don't want to look silly, but it could take smaller tires easily. I have 225/70/15s. Have to stick with 15-inch rims to clear the front calipers. But simply going with a narrower tire 205/70/15 gives me a 4% deeper ratio and drops the truck half an inch, which would be fine as it sits rather high now. A 205/65/15 (this could be borderline silly looking at the lower profile) gives me a 7% deeper gear and drops the truck almost an inch. At 7% I would have to run an indicated 75 mph to be going 70 (this might just reduce my chances of a speeding ticket). Every 10,000 miles indicated would be only 9300 miles

You should be able to buy a set of wheels and tires for little investment and avoid having to pay to have tires mounted/balanced as well as being able to switch between them whenever you damn well please. Once you settle on a tire size you will have a second set of wheels on which you can put studded tires for those Michigan winters.

I actually am planning on buying a set of used wheels but to replace my rusty wheels, which I don't want to use any more as pieces keep flaking off of them. Poor design where the outer rim lip curves back to form the center part (cost savings over steel wheel with welded center?), which forms a water pocket that guarantees rust. Not sure we can run studded tires in My part of Michigan if anywhere in Michigan.

The axle is a lot more work than I thought.

I had a pinion go south on my F150 about 12 years ago and picked up a nice rear axle completer with brakes. Had it installed though. The axle was $350. For a deeper gear though it was more.

All those extra wheels from testing will come in handy as backup to your jack stands in case it falls off the stands. Break the biggest nuts loose with it still on the ground, BTW.

Not a bad idea even with my rusted wheels, but I plan to sell them with the tires if the new set works out okay.

It would be nice to have two sets of wheels so that I can have the tire shop mount and balance then take them hope and put the wheels on the truck myself so that I properly tighten the lug nuts. Last shop got them so tight it strained every muscle in my body to rotate my tires. I was sore for a week and my neck is still sore, four weeks later. They must have had 150++++ pound feet on those nuts!

[theholycow]

Hassle taking it in for the reprogramming.

Some handheld performance tune downloaders have the ability to adjust for gear/tire size, possibly without even having to download a whole tune. Probably way out of budget, though a friend on a Ranger forum might be able to help for a six pack of beer.

Too bad it's not an earlier vehicle with a mechanical cable where you can just change the gear.

Or even a pre-1996 elecronic unit. Don't know about Ford but with GM you could take a cover off an electronics box, make minor tweaks, and adjust your VSS.

Some sites say that not reprogramming the computer will cause performance problems as the computer will not know you are going only 70 when the speedometer says 77 mph. Note advice from TheRangerStation website:

It's overstated. In reality, especially with the minor changes you're considering, you will NEVER notice the difference.

Along similar lines, my dad drove his 2002 Toyota Tundra with 3 265/70-16's and one 245/70-16 and it didn't even cause any complaint from him about unwanted ABS activation, which I was sure would happen.

I have 225/70/15s. Have to stick with 15-inch rims to clear the front calipers. But simply going with a narrower tire 205/70/15 gives me a 4% deeper ratio

I see, I didn't realize you wanted such a minor change. The nice thing about 205/70-15 is they're in the same marget segment as 225/70-15 -- that is to say, the cheap and readily available market segment. You can find a set of almost-new ones for $100 on Craigslist without waiting too long, and if you keep searching you can then stock up on them for even cheaper.

Not a bad idea even with my rusted wheels, but I plan to sell them with the tires if the new set works out okay.

It would be nice to have two sets of wheels so that I can have the tire shop mount and balance then take them hope and put the wheels on the truck myself so that I properly tighten the lug nuts. Last shop got them so tight it strained every muscle in my body to rotate my tires. I was sore for a week and my neck is still sore, four weeks later. They must have had 150++++ pound feet on those nuts!

I can't rave enough about how great it is to have lots of extra wheels. They saved my car when I accidentally dragged it off the ramps and jack stands. They saved my truck last Saturday when my dad knocked it off the jack stands (and if I had been under it they would have saved me). I can have the tire shop mount my tires on them and I can swap them out per need and per mood on my own schedule and torque them properly.

Get a longer lever for loosening tough nuts. A breaker bar from Harbor Freight plus a pipe makes it easy, especially with wheels where you have plenty of room for a lever as long as you want. It's not expensive and it's more effective than even an impact wrench, though if they're within an electric (assuming you don't have a big compressor) impact wrench's abilities then it's certainly faster and more convenient.

[ClutchFork]

I didn't realize you wanted such a minor change. The nice thing about 205/70-15 is they're in the same marget segment as 225/70-15 -- that is to say, the cheap and readily available market segment. You can find a set of almost-new ones for $100 on Craigslist without waiting too long, and if you keep searching you can then stock up on them for even cheaper.

This would be a fairly safe option, but the 205/65/15s would give me 7%, which would guarentee a responsive feel. At4% it would be noticable but not necessarily give me quite the boost I am after. But as you note, tire size may be a limitation. Really it depends on whether I can live with a mis reading speedo and odo, as I don't know if or when I would get that adjustment made, certainly not until I decide to live with the change, which is more likely I will because I plan to buy new tires and just run with them for the long haul.

[theholycow]

Really the speedo isn't that hard to deal with, you get used to it quickly. At least I do. I switch between 205/75-15, 215/75-15, and 225/75-15. My car is most accurate with 215/75-15 and can be a little over 3% off. I do adjust my speed and use a multiplier in my fuel economy calculations/logs.

With the tires aesthetically too small there's nothing you can do about looking like some ghetto teenager and being treated like one. If that doesn't scare you off then it's a great solution.

You might even find some 205/60-15's, they're around. I scored a pair for free (not really enough tread that I'd want them on my wife's car but plenty legal and safe) that are going on a small lightweight boat trailer that currently floats on its 235/75-15's...lower clearance will help launching and landing the boat too. I'll still have to fix the other problems with the trailer and boat, but maybe they'll spur me to actually do that project.

195/65-15 is a common but in-demand size and should be a little smaller even, but may be too narrow to mount on your wheels.

If you don't have ABS or don't mind temporarily disabling it you could experiment with just two tires on the rear, then having decided on gearing, go with whatever more permanent setup you want.

Do you not do much high-speed highway driving?

[ClutchFork]

Really the speedo isn't that hard to deal with, you get used to it quickly. At least I do. I switch between 205/75-15, 215/75-15, and 225/75-15. My car is most accurate with 215/75-15 and can be a little over 3% off. I do adjust my speed and use a multiplier in my fuel economy calculations/logs.

A bit more work, but hey, Model T didn't have even a speedometer.

With the tires aesthetically too small there's nothing you can do about looking like some ghetto teenager and being treated like one. If that doesn't scare you off then it's a great solution.

Taller and narrower is better than low and wide, but in the end they will have the same lower profile regardless if I get it by a narrower tire or lower aspect ratio.

You might even find some 205/60-15's, they're around.

I think my rims are 7" wide and likely the used ones I buy would be 7". So that equates to 18 CM or about a 185 tire as likely the minimum to fit the rim, but I am not sure I want to go below 205s. Clutchdisc has the 2001 S10 and it specifies 205/78/15 which is only 1% off from my 235/70/15s. The trucks weigh about the same. Mine is a bit more powerful. So I feel quite comfortable with 205s. Perhaps 195s would work, those narrower tires really perform well in snow, and I'd rather the narrow look, not the low profile look.

195/65-15 is a common but in-demand size and should be a little smaller even, but may be too narrow to mount on your wheels.

I could stomach maybe 195/75/15 (3% lower) if they make them, possibly 195/70/15 (6% lower, about perfect).

If you don't have ABS or don't mind temporarily disabling it you could experiment with just two tires on the rear, then having decided on gearing, go with whatever more permanent setup you want.

I have broken ABS, the light is always on, covered by black contact paper. Maybe I can borrow some 195/60/15s on rims to go for a little joy ride!

Do you not do much high-speed highway driving?

Oh, I'd say close to 2/3 to 3/4 of my driving is freeway. But as I said, OD at 70 is a little weak.

[ClutchFork]

There's more than one way to skin a cat so they say (excuse me cat lovers, just a figure of speech).

Would a 10% down grade be roughly equal to a 10% reduction in tire circumference (gear ratio)? Probably not, but there must be a slope that is equal to a gear reduction that could be used to evaluate launches with deeper ratios. i tried it today on the down ramp at the parking structure, which is a 15%+ slope, if not 20%, and whoa yeah, she really launched nicely, just jumped out and went like all get out for about 20 feet and then of course I had to cool it because the ramp/flat/ramp.flat sequence is a bit rough at speed.

So the key then to using sloped pavement is to figure out the ratio or equation (hopefully linear) for equating a particular gear ratio change for testing purposes. (This could also work the other way for installing bigger tires). So, any physics majors out there want to figure out the equation? Meanwhile, when I get time, I'll have to Google for it.

Looks like what I need in order to figure this out may be contained in this page (particularly towards the end where the hill diagrams are):
http://www.thecartech.com/subjects/auto ... _Eng_1.htm
But for two problems: 1) lack of time, and 2) rusty math.

So now I get that a 1 percent slope (2 inch drop in 10 feet) would be equal to approximately 6% deeper gear. That is not much of a slope unless you are hand push starting a car, then you will appreciate it. My math and procedure (which is gleaned from several websites and likely is flawed):

Tractive Effort = torque * gear ratio * final drive ratio / tire radius

Torque estimated for 1400 rpm, first gear 3.72, final drive 3.73, tire diameter 27.3"

TE = 80 * 3.72 * 3.72 / 1.14' = 974 pounds on launch (never mind the vehicle weight as we only need to know the effort here presumably). Yes, that is right, only 80 pound feet around 1400 rpm, got it from a Ford brochure torque curve. This is where I sorely miss my 4.9L inline six F150. That engine had around 200 pound feet right off idle--like a tractor! Launch was so good in that truck that when I had to replace the rear end, I didn't go with a deeper gear, even though it only had a 3.30 gear in it.

Increase in TE due to slope = Weight of vehicle * sine of the angle.

Vehicle weight is 3300 pounds with me in it (estimated from dry weight listing).

For a 1 degree angle the increase in TE is 58 pounds. 58 / 974 gives about 6% increase which is what my tires would give me. The slope (rise/run) is the tangent of the angle or about 0.0175.

0.0175 * 10 foot run = 0.175 feet or a little over 2 inches.

But somehow I must be missing a piece of the puzzle. A 1 percent slope is very common on roads even in flat country like Detroit is in. You would think I'd notice these great power surges every time I take off on a slight down-slope, but I don't. There must be a missing factor in the above calculations.

[ClutchFork]

Well, after all this thread, I chickened out on the 6+ percent smaller tires and am I ever glad I did. The truck looks great now, but would have looked very Ghetto with the low profile tires.