3:55 to 3:73 gears

[Roscoe]

3.55 to 3.73 gears

Have any of you guys ever looked into changing gear ratios.

I will be installing 285/75R16 BFGs next spring and the stock size for my 2000 XLT 5.4 4x4 is 255/70R16 or 30". Based on my calculations, I will lose a considerable amount or power due to the larger tires. I was thinking of lowering the ratio to 3.73 from 3.55.

Any ideas?

Roscoe

 

[JUST4FUN]

the only thing your really changing is how wide yor tires are,your going from a 255 to a 285 thats 30 milemeters wider on the tread pattern. no gear change is nessary

 

[ELVATO]

You mean going from 3.55 to 3.73, right?

If you want to lower the ratio, if you're at 3.73, go to 4.10, and if you're at 3.55, go to 3.73.

Then again, it's said the difference between 3.55 and 3.73 is not worth the cost of a gear change.

 

[Roscoe]

Thanks for the help guys.

I was under the impression that the number 255/70R16 means that the side wall profile is 70% of the tire width, which is 255mm. 30" give or take.

On a 285/75R16, the sidewall measurement is 75% of 285mm. Which means that it will be a larger diameter tire. 33" give or take. That is an increase of 3". How much rolling resistance would those extra 3" make?

As for the 3.73 being almost not noticeable in difference compared to the 3.55, I can't say for sure.

I am trying to get the best of both worlds. I need a lower ratio to keep my towing capacity in the 6-7k lbs. rating, but I also want the larger tires to help keep the RPMs under 2000 at 60mph.

I would definitely entertain the idea of going to a 4.10.

Also do any of you have any links to websites to assist me in my endeavours?

Thank you all

R

 

[AvroAero]

I don't think 3 inches is enough to justify new gears. 4.10s would hurt your milage. I'd try the stock 3.73s and see how you like em. Ussually people don't change their gearset until they've put a lift and 36's or more on. Even then I've seen me stick with stockers.

 

[ELVATO]

This site might help?

http://www.allfordmustangs.com/Detailed/608.shtml

 

[Roscoe]

Thanks for the tips. I will install the 33"s and keep the stock 3.55 gears. I'll see how the truck handles.

Maybe I will just look into changing to 3.73's just to get some of the torque reduction back so that I can tow a heavier trailler.

Thank you.

Roscoe.



Avro,

I see that you had installed Gibson Headers and a Super Chips on your '99 Expy. Did you notice any difference? Positive or negative. Thinking about doing the same.

Cheers.

R

 

[AvroAero]

The headers gave it the most power of any addition I had. The superchips I ran at stock shiftpoints and shiftpressure. But I did notice an increase in low end torque. You could tell changing lanes on the highway in stop and go traffic.

I had the headers done at a place in etobicoke, Hot Rod Scott. Don't know whereabouts you are.