Need help with choosing a good rear axle ratio

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LILCBRA

I wish I didn't have all of these balls in the air
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Dec 6, 2005
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Thanks for the input, guys! I used a couple different gear ratio calculators and knew what cruising RPMs I'd see with each ratio, bur really wanted some feedback with real world experience. I think I'm going with the 3.55.

I think you'll be happy with them!
 

General karthief

wonder how much it would cost to ship you a pair
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355 ftw, that is what I have and I have made a lot of bonsai runs up the interstate all over central FL. I used the black gear in the trans for the speedometer and it is accurate. Can't remember how tall my tires are, maybe 26" or 28" , I can measure when I go out there.
25" rear tire.
 
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DudeStang

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When I was looking for a Fox, I drove two with 3.73s (one was bolt ons + cam, the other was just bolt ons) and I can say that both were a blast to drive. This isn't as relevant because of the different drivetrain but I had 3.73s in my LS1 fbody years ago and loved them too.

My fox has the stock 2.73s and I spend way too much time thinking of getting 3.73s.....eventually. :)
 

Willybill32

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Jul 16, 2019
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When I was looking for a Fox, I drove two with 3.73s (one was bolt ons + cam, the other was just bolt ons) and I can say that both were a blast to drive. This isn't as relevant because of the different drivetrain but I had 3.73s in my LS1 fbody years ago and loved them too.

My fox has the stock 2.73s and I spend way too much time thinking of getting 3.73s.....eventually. :)

I've done 98,000 miles on mine with the 2.73, and it's served well. I had a tune done on it Monday, and the last pull went to 5,000 RPM in 5th, and the dyno showed 149 MPH! But I want to make the change to improve drivability.
 

90sickfox

Wasn't a pretty sight...and I've got big hands
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3.73:1 is my favorite gear ratio. Cruising at 72mph in my 89 I got 26mpg. It was a blast to drive with z spec transmission and 26 inch tires. 3.55:1 are decent and will help with that 5th gear reach for another gear....that doesn't exist.
 

revhead347

Apparently my ex-husband made that mistake.
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3.73:1 is my favorite gear ratio. Cruising at 72mph in my 89 I got 26mpg. It was a blast to drive with z spec transmission and 26 inch tires. 3.55:1 are decent and will help with that 5th gear reach for another gear....that doesn't exist.

Most 6 speeds are on the market are BS. It's actually 5 speeds with a spare 5th gear. The change in ratio between 5th and 6th is barely noticeable.

Kurt
 
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90sickfox

Wasn't a pretty sight...and I've got big hands
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Most 6 speeds are on the market are BS. It's actually 5 speeds with a spare 5th gear. The change in ratio between 5th and 6th is barely noticeable.

Kurt

True...very true. I was talking about when you have 3.73:1 gears and trying to cruise. The rpms are so high that it makes you want another gear to bring the rpms down. Most configurations of 6 speeds are just BS. The magnum t56 6th gear is .50...the cobra z spec is .62. I'd say that's an improvement....small but improved. That's almost the difference between the 3.55 and a 3.73.
 

revhead347

Apparently my ex-husband made that mistake.
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True...very true. I was talking about when you have 3.73:1 gears and trying to cruise. The rpms are so high that it makes you want another gear to bring the rpms down. Most configurations of 6 speeds are just BS. The magnum t56 6th gear is .50...the cobra z spec is .62. I'd say that's an improvement....small but improved. That's almost the difference between the 3.55 and a 3.73.

It's more about the exhaust and the tune than the actual drive ratio. My Focus has a 4.08 FDR I believe, but it's not bothersome at all to cruise at 80mph.

Kurt
 

DSB88GT

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Mine has 3.90's and it seems to be a nice compromise between acceleration / highway revs. A bit high, but tolerable.

Just curious why this isn't a popular choice??
 

revhead347

Apparently my ex-husband made that mistake.
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Mine has 3.90's and it seems to be a nice compromise between acceleration / highway revs. A bit high, but tolerable.

Just curious why this isn't a popular choice??

Not sure. I haven't even heard of a 3.90 gear in at least a decade. Seems everyone goes straight from 3.73s straight to 4.10s. It might have to do with the availability of speedometer driven gears.

Kurt
 

DSB88GT

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Good point. Yeah, I did change the gear, but they don't make one for the 3.90's. Got it close, but it's still off a bit.