I know this is probably a frequently asked question, but im new to this website. I have 3.55 gears in my 05 1500, and i have 35" tires. I did all the math and it brought me to about 4:10's to get me back to roughly where i should be. But my question is has anyone done this to theirs with that tire size? Or what do you recomend. Thanks for your time.

 

3:55's with 35's? Ouch! I bet your truck feels like a snail. I would not go any less than 4:56's but with 35's I would actually do 5:13's. I'm assuming you have the 5.7 in your truck which is probably compensating for the small gears and big tires but in turn putting huge stress on your drive train. If you have the 4.7, I will truley be amazed. Please don't ask about fuel mileage as that question is old and busted in a full size truck forum. With 35's I assume fuel mileage is not an issue anyway......
If/when I go 35's on my Jeep, it will be 5:13's all the way so I'm practicing what I preach. The billfold, warranty and misses say different right now or it would already be done. I currently have the 4:56's in my truck with the stock 17" 245's and IMO it's a perfect combo that's why I say go to 5:13's. I know there is a R&P for the rear but I do not know about the front - assuming it's 4WD that is.
www.ringpinion.biz

 

How do you like those little 245's and your 4:56 gears?

 

How did you math bring you to 4.10's?

You have a .67 overdrive. Did you use that in your math??

Instead of useing 3.55 or 4.10s as your gear ratio You need to figure out your OVERALL gear ratio.

OVERDRIVE x REAR GEAR = OVERALL GEAR RATIO just to give you an idea... 4.56 x .67 = 3.05 <--- that is your overall gear ratio!

Then you take that OVERALL GEAR RATIO and use that ANYWHERE that requiors you to input your gear ratio..

So to figure out your RPMS at speed:

SPEED x OVERALL GEAR RATIO x 336 / TIRE HIGHT = RPMS


Let us know what the numbers look like after you the correct math formula mentioned above...
I will bet it will have you going to a 4.88 rear gear! At least thats what I recomend... And YES the 4.88 gears will improve your fuel economey over the 3.55's by a whole lot!

SPEED SAFE, AIR RAM

 

I am going to 35" tires on my 4.7, what would be better? 4.56's or 4.88's... I usually travel about 70mph on the freeway.

 

Use the math formula I posted to get an idea what your RPMs would be... its simple math and will suprise the heck out of you. In my opinion 4.88's would be best with the 35" tall tires... but again dont take my word for it... do the math so you can make an informed decission.

SPEED SAFE, AIR RAM

 

I would start by figuring out what RPM you are willing to run at highway speeds. Then back calculate gear ratios based on tire size.

 

with the 5th gear OD, it's a mighty fine set-up. If it was a 4 speed, not so much but the .67 OD gear lets you get decent mileage with the 4:56's.
I know driving in reverse feels like a tractor....well a cheap tractor but you get the point.

 

I have a 93 Ramcharger with a 5.2mpi that had 3.55's. I put 35"s on it and I could never use overdrive. I switched out to 4.56's and it's just right. I was supposed to go 4.30 to be equvilent to stock but I want the extra gear for the little engine. I run the highway at 80 mpg and the engine RPM is good. I'm still getting 15 mpg.

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