3 mpg better!

[murf]

I put 33's on my LC as soon as I got it. This goes for both my first 91 and my current 96. Both would give me 11.5 mpg. Even after the supercharger, 11.5 mpg. Premium, light foot, heavy foot, city, highway, whatever. It would never change. And I still got 11.5 with the new 35's. Nothing mattered it seemed.

To my suprise, (I had to run through 2 tanks to verify I wasnt seeing things) the 4.88 gear swap has made my engine more efficent to the point that I am now getting 14.5 mpg! I knew the engine wasnt working as hard anymore and was happy driving in the power band but what a nice result. Saves me about $450 in annual gas costs.

Went to go tell the how it was money well spent and will pay us back....now if I can only use that logic with a rear bumper/tire carrier...

**EDIT** GO TO MY NEXT POST. FALSE ALARM - I NEED TO GO BACK TO SCHOOL....

 

[jvazquez53]

I have a set of 33's sitting around, I'll try it.

 

[retrofive]

To clarify if I read that correct. It was the 4.88 gears.... correct

 

[Fiveo]

3 mpg increase with 35" and 4.88? I wonder if I will increase my mpg by going to 4.56 with 33"

 

[Eicca]

Forgive me for being a rookie, but are you replacing the whole gear box, or just one or two specific gears?

Was this process very expensive/difficult?

 

[bull]

How did you measure your mileage? Speedo? GPS?

 

[Eicca]

How did you measure your mileage? Speedo? GPS?

There's a number of ways to do that. You can get a device that measures fuel intake, but I imaging that's pretty expensive. I found a measurement trick on google earlier today... I can't remember where it was, but it involved resetting your trip mile counter thing and driving until the gas light comes on then doing a little math.

 

[jeepocabra]

Forgive me for being a rookie, but are you replacing the whole gear box, or just one or two specific gears?

Was this process very expensive/difficult?

They are talking about replacing the ring an pinion gears (2 individual gears times 2 axels= 4 gears total for a 4 wheel drive) in their axel differentials (where the rotational power of the motor path takes a 90* turn to power the wheels)

It is not the most difficult job to do, however you need special tools to do it, as well as time.

Expense for the gears can range from about $200 to $400 for each gear set. (for a 4 wheel drive you need 2 sets) plus install kits about $120 total. Thats just parts. Install, can range from $300-$600 depending the shop and how much of the work you do yourself.

Re gearing, in my opinion, is the best modification that can be done and is tied with getting a lift and larger tires.

 

[murf]

How did you measure your mileage? Speedo? GPS?

Bit me in the butt.....of course I should of done the readings before and after with a gps unit. After reading your post I realize that I rushed to judgement. As the stock ring and pinion set up with the 33's gave me lower speedometer (therefore also odometer) readings, I was actually registering less odo miles than actual which in turn gave me lower miles per gallon used. Now with the 4.88's I am reading the opposite of approx 8-9% OVER actual so I am getting fat odometer reading over actual and perception that I am traveling farther per gallon used. Between the two dispcrepancies is where I am sure the difference lies. Sorry folks. I didnt look before I leaped on this one. :whoops:

It still feels good to fool myself.....Ill have to get the gps unit to see what the real mpg is. I figure it must be at least a tiny bit better due to driving more in the powerband than before.

 

[ralphy1997]

You didn't tell your wife did you? Does she still think your "investment" is paying back?

 

[bull]

There's a number of ways to do that. You can get a device that measures fuel intake, but I imaging that's pretty expensive. I found a measurement trick on google earlier today... I can't remember where it was, but it involved resetting your trip mile counter thing and driving until the gas light comes on then doing a little math.

Eicca == Fail.


I was asking the question hoping he would figure out the discrepancy in his numbers without making him feel bad or putting him down.

Yet here you are failing at being funny and bringing nothing to the table.

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Use the GPS next trip. It won't be dead on, but it should be close enough. You can also just do the math for the new gearing and tires.

http://4lo.com has calculators you can use. Enjoy.

 

[-Spike-]

it involved resetting your trip mile counter thing and driving until the gas light comes on then doing a little math.

Way to come off like a complete dickhead. Your previous question about the gears proves you're new to the 4x4 scene. Why don't you sit back and spend some time learning why the 'trip mile counter thing' might not be reliable before you make any more wisecracks.

-Spike

 

[Eicca]

No seriously, the name of the dang thing escapes me at the moment. Stop flaming me, I found it on like 6 different pages from google. I don't see how you think it's wisecracking. Do it over time. Sheesh.

Odometer... I think that's what it's called.

And yes I am a little new, but I'm not stupid.

 

[CJF]

Ok, so how exactly did google say to calculate your mileage?

 

[Eicca]

Something along these lines:

Fill your tank(s)

Reset your trip counter (odometer?)

Drive as normal until your gas light comes on

Read the trip mile counter thingy (I know! Someone tell me what it's called!)

Divide the number on the counter by the total number of gallons your tank(s) can hold

Tada, you should have a close approximation of your mpg.

I hope I remembered correctly, I'm not on my computer at the moment so I can't look it up at the moment.

 

[e rock]

Something along these lines:

Fill your tank(s)

Reset your trip counter (odometer?)

Drive as normal until your gas light comes on

Read the trip mile counter thingy (I know! Someone tell me what it's called!)

Divide the number on the counter by the total number of gallons your tank(s) can hold

Tada, you should have a close approximation of your mpg.

I hope I remembered correctly, I'm not on my computer at the moment so I can't look it up at the moment.

Holy cow you were serious.



The point being made is that if your odometer is reading incorrectly (either due to a change in tire size or a change in final drive gearing), then any calculation method using said odometer's reading will also be incorrect.

FWIW, the tank holds about 25 gallons. When the light comes on, there are still about 5 gallons left in the tank. In order to quantify the amount of fuel used, you should not rely on the light as an indicator. You should refill the tank, keeping track of how many gallons it takes to fill it up.

 

[edgextreme]

Holy cow you were serious.



The point being made is that if your odometer is reading incorrectly (either due to a change in tire size or a change in final drive gearing), then any calculation method using said odometer's reading will also be incorrect.

FWIW, the tank holds about 25 gallons. When the light comes on, there are still about 5 gallons left in the tank. In order to quantify the amount of fuel used, you should not rely on the light as an indicator. You should refill the tank, keeping track of how many gallons it takes to fill it up.

I agree, your odometer and you TRIP odometer will both be off when any changes are made to the drivetrain that affect a vehicles drive ratios. To calculate your distance your best bet would be to use a GPS and don't rely on the fuel light to calculate fuel used. Simply start with a full tank, log your miles on the gps, and when you go to top off the tank again it's as easy as looking at the gas pump to see how many gallons you've used. mi/gallons and there ya go..... To bad you can't go back and do this with the previous setup.

 

[hzavarce]

So everybody went off track about calculating the MPG….

I am actually curios to hear what people have to say about the MPG improvements when re-gearing to 4.88 and having 35s.

Murf started a good thread, but too bad the numbers are not good.

 

[murf]

Since I dont have a baseline measurement from the previous set up I wont know what, if any, gains were made mpg wise. If I do the math using the calculators on tire size and axle ratio before and after. I come up with subtracting 8.5% from current miles logged and add approx 4.5% (approx)from the old set up and the bottom result is both come in around 12 mpg. So it appears that no difference in mpg. BUT - Im now pushing a very recently added heavy and un aerodynamic Arb front bumper and the truck has a higher profile (from the 35's) to push through the wind. If Im almost the same as before, I will count that as an improvement.

 

[Eicca]

that's why I said approximate. It works well enough if you don't want to pay money to have your consumption tested which is bound to be not cheap. Stuff like that never is.