It is Time...

[Clois Harlan]

Now that winter is here and I won't miss many good days of driving for a month or so I think I am going to change out my rear end from a 3:73 to 3:25 or so.

I am running a 428CJ and a Toploader Close Ratio. Last year at the Run and Gun and also at Mid-America near Omaha I found I was winding up to my peek RPM before I was ready to get off the gas. I want to know what the optimum rear end is for my set up. I like to road race and I also do a little drag racing too and with my current set up I have a lot of tire spin off the line even with slicks. I think I can improve my et by going to a higher gearing. I would like to have some suggestions, if anyone has an opinion.

Thanks in advance.


Clois Harlan

[blubyu2]

Im running 3.73s with my car and love them but in also running a tremec 5 speed and 289. Guess its cheaper to change the gears. my best guess would be 3.55s don't go too far you'll miss it..

July11/12/13th
Greg

[Excaliber]

With that much torque (428) you certainly could run the 3.25's and be OK. I suspect you will still have the burn out problem on launch, just be turning the tires faster is all. Hey, smok'em if you gott'em! 3.25's would bring your cruising rpm down to a decent level (considering your top gear is a one to one ratio on the 4 speed).

Me? I'd go with 3.55's for all around use. That be better on the road course for sure! Still to low for the 1/4? Lot's of guys just short shift into second. Hey, you can't have it all, choices have to be made!

Wide ratio 5 speeds are nice, by the way.

Ernie

[Jim Werth]

I have 3.27 in mine with a t-5. I've got a 351w and still have traction problems. I can get to about 70mph in 2nd gear. Higher gear for me would just be harder to control wheel spin. Jim

[hound dog]

Clois,
I'm running a 3.31 positraction in my Jag rear with a close ratio toploader. Taking off is not a problem and I really like the close ratio tranny on a crooked road. Downshifts don't kill the RPM like a wide ratio. I can light the tires on take off with no problem, but straight ahead traction and performance is still very good with the 275-60 BFGs on the back. I think if you switched to a rear gear with a ratio in this area you'd get better performance on the road course but slower ETs on the drag strip. Your top end speed on the strip should be a little higher but ET is what everyone is after. It's hard to have the best of both worlds. Actually I was kind of wishing I had opted for the 3.56 rear, but then I haven't tackled the back straight at VIR yet!
h dog

[Ron]

Clois, I also am running a 428 with a close ratio toploader. I started out with 3.25's and have since gone to 3.73's, only because I'm mostly town driving. However when I get out on the highway she's turning 3000rpm at 60-65 mph. Needless to say she likes fuel. I prefer the 3.73's and if your looking for 1/4 mile performance, I think you will too.
Good Luck.....Ron

[Ron61]

Clois,

I am running 3:27 gears in my car with the stroker and I like them. I don't drag race so a lower gear would probably work better for that but when cornering and starting to get on it coming out of the corners I still get wheel spin even with the Eaton posi unit that I just installed. I have the T-5 racing tranny and I did go to a .8 split for 5th gear which is a little to much. I can cruise on the freeway with this setup at 70 MPH tacing 1900 RPM. In 4th gear it is still plenty of gear for a light car unless you are really into serious speed. And your 428 has a lot more low end torque than my 351 stroker.

[SCOBRAC]

3.31 was a standard cobra ratio. With 305/50's should net you about the same as 3.27's

[KobraKarl]

what is the easiest way to determine r.e. ratio with out removing
the lid and counting teeth? ihave stamped into my housing +8123
and 67 (jag) mean anything?

[Captain Speed]

Jag rear ends usally have a tag on the back with the tooth count on them. Or jack up the rear, turn the wheels and count the turns on the driveshaft.
3.31 is the standard street cobra ratio, 3.54 was for the SC cars. I run 3.07 because of mostly highway driving, however, I have a wide ratio toploader to help out.

[rms427]

Street Cobra had a standard 3.54 rear. That's what my car came with. I also have an old sales spec sheets that says 3.54. The 427 SC I new of back in the early 70's had a 3.7 something rear.

Have fun, Ray

[decooney]

Clois,

IMHO - you are on the right track for your engine/trans setup.

both of my Cobras ran/run FE 428s, and the higher 3.31 or 3.08 ratios worked great - and especially with the torquey 428. I've ran both with close ratio and wide ratio Top Loaders, and either combination works well. From what I've been exposed to, the 3:31/Wide ratio trans setup tends to be the most popular combination with the FE guys. However, I sort of like the close ratio trans with the 3:31 setup too. Either way. I run the wide ratio trans, 3:31 rear now, with a 428CJ.

The car is so light, and with the 428 it seem to just pull its way right through the gears. Heck, I can still take off in 4th gear from a dead stop if needed... 3.27:1 would be a perfect rear ratio if that is what you are considering in a 428 combo. Good Luck.

[Cobrabill]

One thing the guys with the C/R toploaders and 3.31/3.27/3.25's aren't mentioning is wether they have an aluminum flywheel.This can change the manners of the car totally.

I originally had a 427/cr toploader/3.27's with a n aluminum flywheel.1st gear in a close ratio is 2.32.
I had David Kee change it to a wide ratio(2.78 1st).When you do the math,it works out real close to a cr&3.55's.But with a better final drive ratio.

The affore mentioned manners change completely.

3.31s & a wide ratio was an option on the originals.

[decooney]

Being conservative, I opted for the "middle" weight stainless flywheel from McCleod, and it works well. Its around 32lbs or so, lighter than stock, vs. the heavy 50lb (or whatever it was) stock/ford, but not as light as an aluminum... This works well so far with the W/R Toploader and 3:31 gears.

I'd be interested in hearing about how the aluminum flywheel works out with this same tranny/rear gear combo. I've heard pros/cons about using aluminum flywheels, but really don't have what i would consider to be valuable or specific information. i.e. does it wind up quicker, is it still durable, does the clutch act differently, does it feel as smooth during wind up, etc ??? What are the noticeable characteristics in going with aluminum flywheels on FEs?

Thanks.

[REAL 1]

I'm running 3:54. Seems just right to me.

My ERA was running 3:31 with a 428 and seemed fine.

[RACER X #99]

3.54 is the best all around gear for most street/race combos. Not the best drag gear and not the best road race gear but a good compromise.
Before I ever went road racing I asked an experienced pro road racer and 3.54 was his advise.
Of course you could always spring for a quick change rear and alway have the best setup.
Cranky