3rd Gen Mpg's with 4.88's & 33's vs 35's

[xcmountain80]

Good afternoon all. I may be going crazy but hear me out. I have been running a form of 33's (295,285,etc) and 4.88's as long as I can remember. It will be time for tires soon and for the life of me cannot fathom how 35's could be better with my gear setup. I average 14/16 with a 2002 Auto & 4.88's running a 285/70/17 MT.


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[SpidermanGeek]

Is there supposed to be a question in there somewhere?

 

[kolelt]

Is there supposed to be a question in there somewhere?

Lmfao. Love this forum. Anyway, I average same mpg with 285/75/16 with stock gearing. So..... Unmmmm idk

 

[Clayton74]

Good afternoon all. I may be going crazy but hear me out. I have been running a form of 33's (295,285,etc) and 4.88's as long as I can remember. It will be time for tires soon and for the life of me cannot fathom how 35's could be better with my gear setup. I average 14/16 with a 2002 Auto & 4.88's running a 285/70/17 MT.


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It would seem to me that you are running higher RPMs than stock with 4.88 gears and only 33" tires. 35" would bring your RPMs back down increasing fuel economy. The $1M question is would the reduction in RPMs be enough to overcome the added weight of the tires when affecting fuel economy.

 

[xcmountain80]

That would have been a more appropriate title. Around town, I cannot see how the added weight could be offset, on the interstate once the rolling mass was rolling, sure. I'll post some "correct" rpm/speed numbers today and see what the 35's crowd has to compare.


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[xcmountain80]

45 mph @ 1700 rpm
55 mph @ 2000 rpm
65 mph @ 2400 rpm
75 mph @ 2750/2800 rpm


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[kolelt]

45 mph @ 1700 rpm
55 mph @ 2000 rpm
65 mph @ 2400 rpm
75 mph @ 2750/2800 rpm


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My rpms are like in the 3000-3500 @ 70-80+ mph. But I have a swapped 5 speed and that changes a little from auto.

 

[Bandit Runner]

FWIW, 14-16 MPG is about what I get with my 2002 auto. Running 35's and 5.29 gears.

 

[Scramble]

Lmfao. Love this forum. Anyway, I average same mpg with 285/75/16 with stock gearing. So..... Unmmmm idk

Ummmm, these trucks came with 4 different sets of STOCK gears...
Not knowing what you have doesn't help!
I love this forum too! :bigok:

 

[kolelt]

Ummmm, these trucks came with 4 different sets of STOCK gears...
Not knowing what you have doesn't help!
I love this forum too! :bigok:

Oh I didn't know. Sorry. Well mine was auto with no locker. Assuming it came with 4.10?

 

[gamefreakgc]

This is true for most vehicles (there ARE exceptions):

4x4 autos have 4.10
2x4 autos have 3.90
4x4 autos with locker have 4.30

Manuals have a 5 speed, so totally different setup.

 

[SupaSupra]

FWIW, 14-16 MPG is about what I get with my 2002 auto. Running 35's and 5.29 gears.

For comparison, with the stock 235/75/15 tires my truck had I was getting 16-18 city. 2 MPG loss with 35"s and a regear isn't bad at all.

 

[kolelt]

This is true for most vehicles (there ARE exceptions):

4x4 autos have 4.10
2x4 autos have 3.90
4x4 autos with locker have 4.30

Manuals have a 5 speed, so totally different setup.

So the 5 speed wouldn't come in 4.10 or 4.30 ? Or they would ?

 

[Toy2play]

So the 5 speed wouldn't come in 4.10 or 4.30 ? Or they would ?

IIRC, e-locker 5 speed came in 4.10.

 

[kolelt]

IIRC, e-locker 5 speed came in 4.10.

Assuming mine are 4.10 because of auto. I swapped in a manual tranny. Now I'm getting front diff and rear axle out of a 98 auto elocker. Assuming it will be 4.30. Will the manual tranny still make it feel different then auto.

 

[Toy2play]

Assuming mine are 4.10 because of auto. I swapped in a manual tranny. Now I'm getting front diff and rear axle out of a 98 auto elocker. Assuming it will be 4.30. Will the manual tranny still make it feel different then auto.

Yes I would assume you would would be different and match up similar to a 4.56 auto if you have 4.30 gears with your 5 speed. By all means I'm not an expert, but read about every gear thread on these forums because I couldn't decide which to choose 4.88 vs 4.56. It's important to note if you have an Auto or 5 speed because the output ratios are different. This is why the 5 speed is a little more peppy. 4.30 Auto and 5S will act differently. Perhaps someone else would like to chime in and give a more educated answer.

 

[Scramble]

Assuming mine are 4.10 because of auto. I swapped in a manual tranny. Now I'm getting front diff and rear axle out of a 98 auto elocker. Assuming it will be 4.30. Will the manual tranny still make it feel different then auto.

If its a Limited most likely 4:30. If it a SR5 - 4:10. But there are no guarantees. Check the code on the door & compare it with the list on Sonoran Steel's website or do the spin test. Yes the manuals ratio is far more peppy than the auto & you pick the rpm's that you want to switch gears at.

 

[gamefreakgc]

So the 5 speed wouldn't come in 4.10 or 4.30 ? Or they would ?

I don't know enough about them to say. Plus you have 5 gears instead of 4, so they are different, smaller ratios and such. Someone with a 5 speed will need to reply.

 

[Roc Doc]

It would seem to me that you are running higher RPMs than stock with 4.88 gears and only 33" tires. 35" would bring your RPMs back down increasing fuel economy. The $1M question is would the reduction in RPMs be enough to overcome the added weight of the tires when affecting fuel economy.

No gets my vote considering the increased aero drag as well.

 

[T4R2014]

This is true for most vehicles (there ARE exceptions):

4x4 autos have 4.10
2x4 autos have 3.90
4x4 autos with locker have 4.30

Manuals have a 5 speed, so totally different setup.

V6 4x2 autos with 15 inch wheels have a 3.73 gear ratio. I think the 4x4 autos without the 16 inch wheel option have 3.90 gears.