Which Gear?

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321Scamp

321Scamp

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I am getting ready to get my Mopar Sure Grip and new ring and pinion set. I have a 2.45 gear now, but I have been looking at 3.55's, I also have looked at 3.91's. I want to be able to run it on the interstate w/o screaming at 70+ MPH but also have great take off pull. I thought that the 3.73's would be a good in between gear.
What do you all think? :dontknow:

Thanks
 
I'm running 60 mph at 3000 rpm with 3.91 gears and 27"dia x 15" tires. You don't want these gears if you're doing a lot of highway driving, I'd recommend the 3.55's for that.

Terry
 
i like 3.73's.
with a little stall, say around 2400 for a street car.
great for tearassin around town and still will cruise decent.
if your going to run 70mph for long distances 3.55's.
 
321Scamp said:
I am getting ready to get my Mopar Sure Grip and new ring and pinion set. I have a 2.45 gear now, but I have been looking at 3.55's, I also have looked at 3.91's. I want to be able to run it on the interstate w/o screaming at 70+ MPH but also have great take off pull. I thought that the 3.73's would be a good in between gear.
What do you all think? :dontknow:

Thanks
Click to expand...

What case do you have? I might be interested in your 2.45s.
 
It is a 8 1/4 rear. My tire size is a 245/60 14 so roughly 25.5''.
 
Anywhere form 3.55s to 3.91s Should work. Just remember the
higher the gear. The more rpms on the highway.
I got 3.23s for the street and 4.30s for the strip.
But I have a 8 3/4 rear, so it's easy to exchange them.
With your rear you should find something in the middle.
Good luck. Green Duster.
 
I've got 3.91's in my duster and they scream on the highway,fortunately it very rarely see the highway,but they're and excellent street/strip gear..i'd go with the 3.55's if i were you and your planning on a lot of highway driving,my buddy has a set in his '68 dart with a crate 360 that has run a best of 12.60 and a consistent 13.0 car with lots of highway driving... :thumbup:
 
With that short tire if you want to do much hwy drivin you better go with the 3.55's or taller. According to my calculations with 3.55's at 70 mph you'll be turning about 3200 rpm which is pretty much screamin so you don't want to go lower than that. I personally would go with 3.23's if hwy rpm is a concern. 3.23 gears will still put you at 3,000 rpm at 70 mph.

If you want a close simulation of what 3.91 gears will be like go run your car at 70 mph in 2nd gear.
 
you do not want a 3:91 gear i can tell you that much... i would say a 3:23 or a 3:55 depending how much hiway driving you want to do..
 
Agree, if it is one the highway more than 30% stay with 3.55 max. Maybe a 3.73 with a taller tire. My truck for example has 4.11 but the tires are over 32" So the correct thing is calc the tires & gears to get the real RPMS at 60-70 mph. I would say try to stay under 3k at freeway speeds if it is a highway car.

I used to run 4.10s on a 24" tire in my Dart for a time. it was in no way a highway car. I recall 4k at 60, car overheated etc. on a long trip. So 3.91 would be iffy even with a 16" tire.

Cant have it all without an overdrive..
 
Put 3.21's in it, your motor will last much longer and the car won't even be noticably slower. I had 3.91's in my Valiant and ran 11.38 best, I put 4.30's in it and have a best of 11.32 at the same track. So going for 3.55 to 3.21 would not be much of a lose in performance but going from 2.45's to 3.21's will be huge in performance. I just did the same swap from 2.45 to 3.21 in my '77 Cordoba w/400 and it is much better and I can still cruise on the freeway.


Chuck
 
I have 4:10's now- Can I go to 3:55's in that case??

Motor is a 440 525 hp 625 torques

I am running 245/60/14's on rear and 205/70/14's on front
 
chasb said:
I have 4:10's now- Can I go to 3:55's in that case??

Motor is a 440 525 hp 625 torques

I am running 245/60/14's on rear and 205/70/14's on front
Click to expand...


Actually the ratio in a Dana 60 is 3.54 and yes you can put those in with your 4.10 carrier and case.



Chuck
 
340mopar said:
Actually the ratio in a Dana 60 is 3.54 and yes you can put those in with your 4.10 carrier and case.



Chuck
Click to expand...

Thanks CHuck. I have 4:10's in the Dana now and was thinking of either a 3:55 or 3:73.

Any good vendors for the gears that you can recommend?
 
Really the only time it will see the highway is the 15 min drive to work or the trip to the Mopars, which is about 200 miles from my house. But I do think that 3.21 will be a great performance boost from the stock 2.45's.
 
I was back-and-forth between 3.55s and 3.21s. I'll eventually be running 27 or 28" tall rear tires, so a 3.55 would be roughly the same as a 26" tire with 3.21s.

Then it all got decided for me when I got a set of very low mileage 3.55s for next to nothing. Why buy a new set of 3.21s for an 8.25 rear axle when I could get 3.55s for $30?:thumbup:

I wanted as much gear as possible while keeping it "reasonable" for 60-65mph highway driving. Some day I will go to a AOD with 4.10s..when I have the extra cash burning a whole in my pocket.
 
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