35s&3.73s vs 33s&3.55s

[Strokin6.4]

Do these basically end up being the same ratio. Only reason I ask is when I had 305 55 20s on the truck I felt my 3.73s were hurting me. It wanted to shift out of the hole immediately. So everyone I talk to about it said I really should have 3.55s.... or 35s. Now theoretically it makes since they should be pretty close but its just hard for me to imagine launching on a 35 inch tire is healthy for my driveline parts. I've just been tossing around the idea of taking the 35s off and lowering it back down to stock when I add more fuel to it. Unless it comes out to being the same as a 3.55 with 33s. Input appreciated!

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[VanoFord]

theres an old formula for R&P sizing:

(New Tire Size DIVIDED BY Old Tire Size) TIMES Original R&P = New R&P

Example: 305/55/20 on 3.55

305/55/20= 33.2"

(35/33.2)= 1.05 * 3.55 = 3.73

35 would be best w/ the 3.73, 33 w/ the 3.55. This formula keeps your driveline in factory specs by only changing the R&P. hope this helps.

 

[Strokin6.4]

Wow crazy how EXACT that is lol. I've never seen that thanks a lot man. Hopefully some others can use it so this wasn't a wasted posted haha. At least now I can stick with my 35sssss!

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[VanoFord]

See, algebra just saved your LIFE!

 

[dommel01]

just lower it already travis! im runnin 3:73 an 33s

 

[Strokin6.4]

just lower it already travis! im runnin 3:73 an 33s

Lol and you've never had tranny troubles! I honestly think 3.73 with 33s is too low of gear man. That's why a lot of 3.55 trucks are always faster intake, tune, exhaust.

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[Cknox121]

How do I tell what gear ratio I have?




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[JDub]

Remember that overall ratio isn't everything...rotational mass and overall weight are going to affect things quite a bit as well.

 

[dommel01]

Lol and you've never had tranny troubles! I honestly think 3.73 with 33s is too low of gear man. That's why a lot of 3.55 trucks are always faster intake, tune, exhaust.

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well 3:73 an 33s would be easier on the driveline you would think, but I totally agree that I think 3:55 would work better, and I might get better than 12mpg then :doh: tranny troubles, what tranny troubles lol

 

[oneton]

How do I tell what gear ratio I have?




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look on drivers door or door jamb.there will be a axle code something like c9,f4,t24,etc(these are not the actual codes just for reference as what to look for) on the sticker

dont know if they still put tags on diff cover with ratio on sd.obs trucks had metal tag held on with diff cover bolt told ratio and if open or locker

 

[VanoFord]

look on drivers door or door jamb.there will be a axle code something like c9,f4,t24,etc(these are not the actual codes just for reference as what to look for) on the sticker

dont know if they still put tags on diff cover with ratio on sd.obs trucks had metal tag held on with diff cover bolt told ratio and if open or locker

my 06 Fiddy had one... havent checked this truck yet though.

 

[Jeff@Spartan]

I have 305/55/20's and 3.73 gears. I would like 3.55's but I don't see the need at 640 HP. The swap would be nice for fuel mileage, but I get decent fuel mileage with my current setup so no complaints here.

By the way, the stock tires that came on my truck were 33".