Sorry if I sounded like a a$$ above. Yeah I've had 38's,40's and 42's...but all on gas powered trucks. I'm just familiar with with my X on 35's with 4:30 gears...which I love. Why didn't Tor like his 4:30 and 35" setup?

 

Tor have a 7.3. The power band is lower in the rpm

 

My point was, he had a bunch of guys tell him to go with the 4.30's, and it cost him twice as much when he had to redo the gears.

I already knew why I have the proper gear, so I'm not sure why you posted the mathematics on why it works other than to back-up my assertion, but thanks?

No such animal available that I know of, as you also noted below, so since that's not an option for him, I'm unclear on why you stated that.

I suck at math so I cheated and used a gear ratio calculator I found with Google.


Yeah, that's why I suggested he'd be happier with the 4.56 gears, since he has a diesel.

I disagree.

Since he has a diesel engine, they don't like to operate in the higher RPM's like gas engines do. Since the optimum ratio he wants is almost in the middle between the 4.56 gears and the 4.88 gears, it's better to be under with a diesel and still have usable RPM's, instead of going over and being at the top end of his RPM band while tooling down the highway.

If he had a gas engine I would agree with you, but the diesel engine power band is so much different than the gas engine.

When you're near the top of the usable RPM band, even a couple hundred RPM's too high makes a big difference in drivability and undue stress on an engine, especially when measured over time.

Stewart

 

Great info guys! Thx

I don't do any towing with the Ex...just a small dirtbike trailer. So I think 4.56's will do the trick.

 

Not at all!

Stewart

 

I did it to get on your nerve. It is off by 0.98mph not by 0.5mph like you said.

Work was slow and I was bored.

 

I'm going to just toss this out there. We have some F550s at work with 6.0Ls, they run 245/70R19.5s. I think that's close to a 33 inch tire. They came with 4.88 gear ratios. I run them down the hwy at 70-75 mph without a issue. The RPMs are up a bit, but they have plenty of power. Idk what kinda milage they make, but they are heavy as hell (16,000 lbs or so) and have been run hard there whole life, they all have over 200,000 miles on them.

 

ROTFLMAO!

I was basing my estimate off of the radar units that showed my speed as 71mph when the needle on the speedometer was a a hair over 70. If I drop the speed (as it shows on my dash) a bit more than a hair below 70 (69+), radar will show it as 70mph, so I was guestimating how far apart the actual difference was, versus what showed on my dash.

That's why I didn't use verbiage intimating a precise figure when I stated how much of a difference I thought there was.

Stewart