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Discussion Starter #1
I've done the searchs but so many different opinions to make a sound choice. So I'm hoping this is the ultimate end to it all...

Thanks
 

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What will you be using the car for? Daily driving, dragstrip, roadracing.......

I have 4.10s in my 15psi Cobra and I like them a lot. Would have gone 4.30s if I stayed around 8psi and 400+ rwhp but pushing close to 600rwhp they would have been just a bit too much so I'm sticking with the 4.10s (this is a daily driver, everyday get me to work car).

Tom Crews
 

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Discussion Starter #5
Well.....I'm in the market for a beater car and....well.....lets just say I've put maybe 25 miles on the thing since November. So I'm hoping to keep it a nice days in the summer/Drag car.

My only reservation is at the track......don't I want to be able to keep it in 3rd????=higher RPM range=in boost?????


Keep'm coming guys. I know I can't be the only one out there with this issue
 

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Like Tom said above...What's the use? I have 4.10's and at the strip crossing the line a little over 120 I think I see 6500-6800 (not really looking at tach then) on 275X50X15 26" tall tires, so if you don't mind turning it into the 7000 range, and with traction, for drag racing, you could (and maybe should if you are real serious) run 4.30's.

However, I sold my race wheels, and am now more interested in more relaxed cruising in the 70-75 MPH range. With 4.10's and 285X35X18 tires (about 26" diameter) I see about 2600 @ 70 on SpeedCal corrected speedometer. I'm waiting to see the diameters of the 18" DR's coming this spring, to see if I can take a few RPM out at cruising that way (like a rumored Nitto DR 305X35X18 would take out about 50 RPM @ 70...not much but a little help), otherwise I'm gong back to 3.73's for my more casual use. With over 500 RW you can light up any street tire with about any rear gear.

BTW there is a guy with a blown 97 Cobra who posts on here running low 11's with 3.27's and TKO. I believe he crosses the line in 3rd. He has less of a traction problem.
 

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Discussion Starter #7
Ralph Greene said:
BTW there is a guy with a blown 97 Cobra who posts on here running low 11's with 3.27's and TKO. I believe he crosses the line in 3rd. He has less of a traction problem.
This last part is what is of interest to me and also whats holding me back from the 4.10s or 4.30s. Low 11s with a 3.27:eek: So its possible but would 4.10s be better.

And I think the car will end up seeing the street more than the track.
 

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I think 4.10's are best all around gear. I was just pointing out that you can run quick with other gears also. For some guys who OT and Auto X some, 3.27's, 3.55's, and 3.73 seem better for them, and still can allow decent 1/4 times. If I were building an all out 600 RWHP race car, and still be streetable, I would run 4.56's, get some 28" tall slicks, and use T 56 with tall 6th gear for cruising with street tires.

You just have to decide the use and where you are going with car. One thing I have learned with my car is, when in doubt to do nothing for a while, and save myself some money.
 

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One thing you can do (and it's free), is go to the strip with your 3.27's, and see how you run. If you run low 12's, or close to high 11's, and don't want to put in cage, then I guess your rear gears don't matter much (for drag racing at the strip). That will give you a good idea of your traction situation, your skill level, and then go from there. You can change the rear gears anytime you wish, after you get accustomed to driving a blown car, get your driving technique down pat, figure out what tires to run, and after you figure out how serious you are about drag racing. MHO
 

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Discussion Starter #10
Well......I'm still deciding, although now I'm ready financially to get this done. I've narrowed it down to 3.73's and 4.10's. I guess the only things keeping me from the 4.10's is traction and the damn speedo compensator that'll run me another $100. The car is just for weekends and the track and I will have DR's on it as well (I have a beater now). So does that help in the decision?...what are your thoughts now?

Thanks
 

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It's been a while since I expressed my views above, and I have only this to add.

If you have a hi HP centrifugal blower car, that hits the tires hard as the boost spools up at higher RPM, for maximum acceleration on the street with street tires, you can't run too much gear, or every Honda around will beat you for a while. On street tires, I think 3.73's are just as fast (or faster) as 4.10's for street use for centrifugal blower cars. Jimmy V says he thinks so too. He and I have talked about that very subject.

On the other hand, if you are a serious drag racer, and are gearing it for drag racing with very sticky tires, then I would gear the hell out of it. I would race with 4.30's and 26" tall tires, or 4.56's and 28" tall tires.

I just think it all comes down to what you're doing with the car, and tires, tires, and tires for hi HP applications. .

MHO
 

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I have 4:10s, I may be switching to a 3:55 because I drive allot of miles. The 1st gear and 4:10s + boost+TQ= traction issues.
I put lower control arms on and still have a heck of a time planting Dr's.
If you are torn between 3:73 and 4:10- you may as well go with the 4's, not a ton of difference but if you have traction you will see better times IMHO.
All my power is down low in the rpm range hence the switch to 3:55.
 

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RioRed1997GT said:
I've done the searchs but so many different opinions to make a sound choice. So I'm hoping this is the ultimate end to it all...
Thanks
As a general rule, the better your P/W ratio is, the less you need big gear ratios. That's because traction rather than power is going to be your limiting factor.

Most of the drag racers go for 4.1 and bigger ratios, something like 4.56 for N/A cars and 4.1 for blown cars. The autoxers and trackers tend to go for 3.73s because 4.1s will slow you down on an autox course (because you'll bump the limiter in 2nd).

The only way you're going to do a 1/4 mile in 3rd gear without hitting the limiter is with a 3.27 ratio, and you definitely don't want that ratio unless you've got well over 500 RWHP. So you're going to be in 4th as you cross the line pretty much no matter which ratio you choose.

I'm N/A and use 3.73s but my car weighs less than 2500 lbs. Just an example of why it's not raw HP but rather P/W ratio :D
 

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See Sig.:D
 

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The way I see it is you want to be going through the traps at the end of the quarter at the top of 4th gear as this means that you have had the highest average hp throught the run. This is especially important when you have a centrifugal supercharger as the hp increases continuously with rpm, therefore, more rpm= more power. Estimate your mph at the end of the quarter, fill out the other info and pick gears using the rpm estimate in the tech section of this site.

Going up in gear ratios only hurts your 60' times if you can't control your right foot (and clutch foot for that matter). Unless you do a lot of highway driving, I wouldn't worry about going too high.

As far as the speedo compensator, just get a new speedo gear for about 15 bucks. I have never had a problem doing that.
 

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Discussion Starter #16
Thanks guys....I think I'll go 4.10's after everyones imput. My only question is.....is the speedo compensator really only $15??

Thanks
 

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RioRed1997GT said:
Thanks guys....I think I'll go 4.10's after everyones imput. My only question is.....is the speedo compensator really only $15??

Thanks
For '96-'98 cars 3.73 is the biggest diff ratio for which there is an official Ford part # for the speedo gear. For 4.1 gears I've heard there's an "unofficial" part # that works but was made for a different car, and I've also heard it lasts a while then self-destructs into a mess of plastic. From what I've heard your best option may be an Abbot compensator.
 
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