Same MPG after Regear?

[Peanut Butter]

I just regeared my truck and have almost the exact same MPG as before the regear. I couldn't do both the front and the rear at the same time, so I just did the rear for now. So, before the regear, I was running higher RPM's, with the speedo showing about 5 MPH slower than actual speed at 70 MPH. Now, it feels peppier, I am looking at lower RPM's, and about 75 on speedo when doing 70 MPH. Before rear regear I was getting about 14 MPG, and I'm still about the same. I regeared from 4.10's (yes, I checked the gear code on my door jam), to 4.56's. Anyone have any suggestions? I thought that a regear was supposed to help with the MPG. Shouldn't a v6, on 33's perform better with 4.56's than 4.10's? And shouldn't it make no difference what the front is at as the drive shaft drives the rear gears and rear wheels in 2wd? Thanks!

[Full_Tilt_Fud]

If the speedo is off then there is a chance that the odometer is off too and it could be misrepresenting how far you actually drove. Don't reall know just a thought

[01taco4x4]

Originally Posted by Full_Tilt_Fud

If the speedo is off then there is a chance that the odometer is off too and it could be misrepresenting how far you actually drove. Don't reall know just a thought

I second that!

[Miguel]

Originally Posted by Peanut Butter

I just regeared my truck and have almost the exact same MPG as before the regear. I couldn't do both the front and the rear at the same time, so I just did the rear for now. So, before the regear, I was running higher RPM's, with the speedo showing about 5 MPH slower than actual speed at 70 MPH. Now, it feels peppier, I am looking at lower RPM's, and about 75 on speedo when doing 70 MPH. Before rear regear I was getting about 14 MPG, and I'm still about the same. I regeared from 4.10's (yes, I checked the gear code on my door jam), to 4.56's. Anyone have any suggestions? I thought that a regear was supposed to help with the MPG. Shouldn't a v6, on 33's perform better with 4.56's than 4.10's? And shouldn't it make no difference what the front is at as the drive shaft drives the rear gears and rear wheels in 2wd? Thanks!

Try to get a hold on a GPS unit and find out your actual mileage for sure, I just borrowed one from a friend. But hey, if your mileage went up...congrats!

~Miguel

[mojavehanna]

Originally Posted by Peanut Butter

I just regeared my truck and have almost the exact same MPG as before the regear. I couldn't do both the front and the rear at the same time, so I just did the rear for now. So, before the regear, I was running higher RPM's, with the speedo showing about 5 MPH slower than actual speed at 70 MPH. Now, it feels peppier, I am looking at lower RPM's, and about 75 on speedo when doing 70 MPH. Before rear regear I was getting about 14 MPG, and I'm still about the same. I regeared from 4.10's (yes, I checked the gear code on my door jam), to 4.56's. Anyone have any suggestions? I thought that a regear was supposed to help with the MPG. Shouldn't a v6, on 33's perform better with 4.56's than 4.10's? And shouldn't it make no difference what the front is at as the drive shaft drives the rear gears and rear wheels in 2wd? Thanks!

Im confused here, lets start with a baseline speed of 70mph. With your 410's at 70 you should have been at around 2200 rpm with 33" tires. Now when you went to 456 gears at the same speed of 70 mph your rpm's should be higher, somewhere at about 2700 rpm. It is hard to say using your truck speedo because it changes when you change tires and or gears, you really need to use a GPS to calc your baseline speed.

This being said, if you adjust in the error factor for the amount your speedo is off then that should get you back close to your ACTUAL mpg, the figure you get when you divide the milage by gallons used is off because of this amount not being factored into the equation.

Unfortunatley, you will never get what you got stock due to the bigger tires with increased weight, rolling resistence and drag over the stock street type tires.

I get about 15 mpg around town with 410's, V6, auto, and 33x12.50 MT's which is close to what my truck was rated for (16 city, 19 hwy) I too am going to go with 456's mainly for increased pep and better drivability.

If all else fails inflate your tires to 36 psi and drive like a senior citizen.

[mojavehanna]

Also, DEFINATELY DO NOT shift into 4wd until you regear the front to match the rear.

[GOT COPE?]

Originally Posted by Peanut Butter

I just regeared my truck and have almost the exact same MPG as before the regear. I couldn't do both the front and the rear at the same time, so I just did the rear for now. So, before the regear, I was running higher RPM's, with the speedo showing about 5 MPH slower than actual speed at 70 MPH. Now, it feels peppier, I am looking at lower RPM's, and about 75 on speedo when doing 70 MPH. Before rear regear I was getting about 14 MPG, and I'm still about the same. I regeared from 4.10's (yes, I checked the gear code on my door jam), to 4.56's. Anyone have any suggestions? I thought that a regear was supposed to help with the MPG. Shouldn't a v6, on 33's perform better with 4.56's than 4.10's? And shouldn't it make no difference what the front is at as the drive shaft drives the rear gears and rear wheels in 2wd? Thanks!

You are lucky to get the mpg's you were getting before. THe new gears help get you engine back into the correct RPM range therefore optimizing your mpg's but you will never get what you got stock. You will always lose some mpg's because you are pushing bigger, heavier tires with the same engine.

[hytenor]

Originally Posted by Peanut Butter

I just regeared my truck and have almost the exact same MPG as before the regear. I couldn't do both the front and the rear at the same time, so I just did the rear for now. So, before the regear, I was running higher RPM's, with the speedo showing about 5 MPH slower than actual speed at 70 MPH. Now, it feels peppier, I am looking at lower RPM's, and about 75 on speedo when doing 70 MPH. Before rear regear I was getting about 14 MPG, and I'm still about the same. I regeared from 4.10's (yes, I checked the gear code on my door jam), to 4.56's. Anyone have any suggestions? I thought that a regear was supposed to help with the MPG. Shouldn't a v6, on 33's perform better with 4.56's than 4.10's? And shouldn't it make no difference what the front is at as the drive shaft drives the rear gears and rear wheels in 2wd? Thanks!

FYI: All TRD v6s (up to '04) have 4.10s. v6 ATs are all 4.10s and the 5-spds got 3.91s. 2.7s got any of 5 different ratios.


as suggested, get a gps unit and find out exactly what speed you are traveling vs what your speedo reads. this will be your error percentage.

stock readings should have been approximately 2180 rpms @70 figuring 31" tires and 4.10 gears.
with 33s and 4.56s the rpms should be around 2275 @70
this, of course, will varry depending on the actual tire diameter.
this is approximately a 4.2% difference and is about right since you have gone from a 4.10:1 ratio to an 'adjusted' ratio of 4.28:1. (31/4.10 to 33/4.56)

you can adjust your speedo/odo and get it pretty darn close by swapping out your speedo drive gear. you should have a 30tooth gear (you'll need to pull it and check) so going to a 31t gear will get you darn close to what your speedo read when stock.
http://www.norcalttora.com/~chris/mi...0drive%20gear/

but, you need to figure out your error % first.

Gas mileage:

this has so many varriables it isn't funny. Tire brand, size, air pressure, wheel width will all be contributing factors as will be your 5" of lift.
That much lift creates a lot of wind drag which will effect mileage greatly...part of the price we pay
Tire pressure will play a huge part. what are you running now, air pressure wise? 33x12.50s on 8" rims should be in the 35+ psi range but do a "chalk test" (search) to figure out the optimum pressure to run.

HOW you drive plays a huge part as well. Do you stomp on the gas right off the line all the time? What is your average hwy speed? etc, etc.
I know guys with lifted dcabs who get 20 or better with 33s and 4.88s but they drive on the conservative side

It will also take your ECU to get used to the different gearing and make adjustments.

[Peanut Butter]

I have the same MPG now as before the regear, but both are lower than pre-lift. If I had 4.10's before, and I now have 4.56's, I should be back around stock. Considering my lift, bigger tires, heavier wheels, sliders etc, I know I will have a drop from stock MPG no matter what, but shouldn't it improve after regearing?? I have my tires inflated to about 31, and don't drive too hard. 2/3 of my last tank was highway cruizing at 80 MPH, the rest in town. The main problem is still the MPG before regear and after. I looked at the mileage markers on the highway (no GPS available), and after 10 miles, my odo showed about 10.3. So the speedometer and odometer are still pretty close. Adjusting for that difference, I was expecting to be back between 16-18, not stuck at 14 like before the regear. So driving the same, same equipment, and new gears in the rear, no improvement in MPG, or total mileage.

[GOT COPE?]

Originally Posted by Peanut Butter

I know I will have a drop from stock MPG no matter what, but shouldn't it improve after regearing??

Correct, this time.

I got 19-21 stock with 30's and 31's with 3.91's.

I went to 33's for a couple months with the stock 3.91's and got 15 mpg or worse.

Once I put in the 4.56's I went back up to 19 mpg at best.

[hytenor]

Originally Posted by Peanut Butter

I have the same MPG now as before the regear, but both are lower than pre-lift. If I had 4.10's before, and I now have 4.56's, I should be back around stock. Considering my lift, bigger tires, heavier wheels, sliders etc, I know I will have a drop from stock MPG no matter what, but shouldn't it improve after regearing?? I have my tires inflated to about 31, and don't drive too hard. 2/3 of my last tank was highway cruizing at 80 MPH, the rest in town. The main problem is still the MPG before regear and after. I looked at the mileage markers on the highway (no GPS available), and after 10 miles, my odo showed about 10.3. So the speedometer and odometer are still pretty close. Adjusting for that difference, I was expecting to be back between 16-18, not stuck at 14 like before the regear. So driving the same, same equipment, and new gears in the rear, no improvement in MPG, or total mileage.

you are not back to "stock" as I explained, but rather you are running a slightly lower ratio now (4.28:1 vs your old 4.10:1) 4.30 gears would have gotten you close to stock to just under the old 4.10 ratio but those gears are not easy to find and are not available aftermarket.

IMO, your tire pressure is too low but do the "chalk test" anyway. 5psi can make a 3mpg difference or more.

driving at 80mph will suck gas, big time, especially now that your aerodynamics are probably 3x as bad as they were stock. Yes, a 5" lift and running that size tire makes that much difference.

your speedo/odo are about 4.2% off so your actual mileage should be about that much better than indicated, ie, 14.6 rather than 14.

Those of you with 33x12.50s on 8" rims...what are you running for tire pressure?

[mojavehanna]

Your never going to get better mileage driving 80mph in a lifted truck.

[jon_7248]

Not if you draft!! Muhahahahha


Lol

[AK95Taco]

Originally Posted by hytenor

Those of you with 33x12.50s on 8" rims...what are you running for tire pressure?

I am running 32 up front and 30 in the back with BFG AT's. Oh and I have custom front and rear bumpers as well as a topper (for weight considerations). Bone stock weight, I would probably drop a lb, depending on the chalk test of course.

Also to "Peanut Butter": You should seriously consider swapping out your front diff as soon as possible. Assuming you are an ADD setup, those spider gears are working extra hard right now and were not designed to have that kind of sustained high speed differentiation done to them.

Just my $.02

[hytenor]

Originally Posted by AK95Taco

I am running 32 up front and 30 in the back with BFG AT's. Oh and I have custom front and rear bumpers as well as a topper (for weight considerations). Bone stock weight, I would probably drop a lb, depending on the chalk test of course.

Also to "Peanut Butter": You should seriously consider swapping out your front diff as soon as possible. Assuming you are an ADD setup, those spider gears are working extra hard right now and were not designed to have that kind of sustained high speed differentiation done to them.

Just my $.02

interesting, even with 8" rims, that low a psi?
I run 30-32 front and 26 rear with 33x10.50s on 7s
I probably have 300# of extra weight on the nose.

[Peanut Butter]

I am swapping out the diff this weekend, and still getting crap for mileage. It just doesn't seem right!

[Toyota4ever]

Your in the ball park for mileage. Your V-6 is not going to get better mileage than stock, with a lift, and heavier (rolling mass) tires.

I get 16 mpg corrected, (thanks to Hytenor for the speedo help) combined driving, but mostly city. I run my tires at 40 psi.

I understand you can gain a 1 mpg increase, some people report 17 mpg with 4.88 gears under certain driving conditions. I didn't want to run my engine at that much above stock levels. The 4.56 with 33 tires best get you into the engine rpm designed for the truck, but with the rolling mass it robs a little power.

The 4x4 double gets 16/18 stock so if I wan't mileage I take the wifes Honda Civic.

Later