Which ratio rear end?

[Cannoball888]

I just recently bought a 1965 Fastback restored with a Borg-Warner T5 5-speed and a high performance 302. It dynos at 400HP. The car is a daily driver, but I want to make it competative in the 1/4 mile. What rear end ratio would be best but without taching too high at highway speeds?

Also, is a Detroit Locker the best choice for a limited-slip differential?

 

[66moneypit]

This database of gears/rpms might help a little bit.

http://www.stanginfo.com/Gears/GearOptions_view.php

You can at least see what setup are being used.

 

[57fairlane]

What rear end is in the car? What height tires will you be doing your highway driving on?

More then likely you probably want something in the 3.70-3.80 range.

Also, with a t-5 and 400 fwhp you are getting close to the limits of the transmission. I would suggest staying away from powershifting it at all. Oh, and if it doesn't go into third beating on it, let off of it and ride it out. Forcing it into third = pretty loud boom.

 

[steel1212]

Yeah, third is the one that always goes first. IF that thing dynoed at 400 to the wheels thats impressive and I hope its a T-5z. I run 4.11s and cruize at around 2400-2500 rpms at 70 with a 0.63 overdrive. Try this website http://www.randysringandpinion.com/content/calculators/RPM.asp

 

[grego37]

Many factors:
tire height, final gear ratio (tranny), and desired fwy. rpm.

Use the following to help you decide:

http://www.richmondgear.com/01calculators.html

 

[65 fastback]

What is the ratio of your overdrive gear? T-5's came with 0.80, 0.68 or 0.63 overdrive ratios, that with tire diameter and rear gears will determine your final drive ratio.

Tim

 

[HistoricMustang]

Too keep it simple, go with a 3.53 (or there abouts) gear for street use.

HistoricMustang
www.historicmustang.com

 

[cagedhatch]

i liked the 3:91 i had in mine

 

[MustangMatt1966]

I run a t-5 with around 325 hp and have a 8 inch rear with 3.80 gears...great on the street, great on the strip...good all around gear choice

 

[YellowMach69]

I have a 351w with a automatic with 3:91 and they are great for street and strip,But terrible for thruway or far cruise night locations Im running like 3100 rpm at 55-60 with 15 inch wheels

 

[iskwezm]

dont mean to question your purchase, but do you have the build sheet on that engine or the dyno sheet???I see very few strokers that dyno that high,most are 350-375.

 

[Cannoball888]

dont mean to question your purchase, but do you have the build sheet on that engine or the dyno sheet???I see very few strokers that dyno that high,most are 350-375.

Unfortunately I don't have documents. But contrary to popular belief, you can build a naturally aspirated 400HP 302 WITHOUT stroking it.
http://www.fordmuscle.com/archives/1999/10/400horse/index.php

 

[12sec67]

we know its possible but its hard to believe it since everyone says they has one these days and don't have the dyno sheet to show for it.

my 306 did 312rwhp/331rwtq thru an AOD which is pretty close to 400 FLYWHEEL horsepower.

 

[iskwezm]

Unfortunately I don't have documents. But contrary to popular belief, you can build a naturally aspirated 400HP 302 WITHOUT stroking it.
http://www.fordmuscle.com/archives/1999/10/400horse/index.php

oh i understand that,i was just unsure of the numbers wwere at the wheels or flywheel.

Oh,i suggest 3.55 gear for cruising

 

[69Rcode_Mach1]

Bah with a T5 don't need to fear the gear, plus if you are making that power with a 302 I assume that you are spinning it up there a bit. If you want a good medium go with 3.89's if not go with 4.11's. That is what I will be using. And Detroit Locker all the way Limited Slip sucks.

 

[Cannoball888]

I've heard Detroit Lockers are too noisy for a street car. Anyone know if the Detroit SoftLocker is quieter but just as good? And what exactly is a Detroit EZ Locker?

 

[iskwezm]

I've heard Detroit Lockers are too noisy for a street car. Anyone know if the Detroit SoftLocker is quieter but just as good? And what exactly is a Detroit EZ Locker?

Everybody told me the same thing and talked me out out of one,so my buddy put one in his 65 coupe,i cant even hear it,now i have this TSD from Currie which i think is crap

 

[vodoo103]

Tech calculators

This might help you out... Check out the cruise RPM fomula
http://www.mopacautosupply.com/techchart.htm