3.55 or 3.73

StreetSnake · #1 (**permalink**) 01-11-2010, 12:07 PM

I have a 427 stroker with 550hp/550tq, 17" rims with 335/35s, TKO 600 w/ .82 5th. I currently have 3.55s in it but may be putting in a detroit locker truetrac (or something else if anyone has a recommendation). Just wondered if I should stick with the 3.55s or go to the 3.73s. I've used the calculator at secondstrike but wanted to see if anyone had some experience with the difference.

bobcowan · #2 (**permalink**) 01-11-2010, 01:04 PM

I prefer the 3.55 over the 3.73. You have enough to torque to m ake the 3.55 work well. And it gives you good highway legs. It's a nice comprimise. I consider changing my 3.55 to a 3.08 or a 3.25 for better track times. I certainly wouldn't go any lower than 3.55.

I had a stock LSD. Then I upgraded to a Detroit TruTrak. It performs better on the track than it did before. But street performance is the same. Since there's no clutches, it won't wear out under heavy use like the stock parts do.

RedBarchetta · #3 (**permalink**) 01-11-2010, 02:55 PM

I'd stay with the 3.55's. The car is too light for the 3.73's...traction out of 1st gear is always a challenge. I plan to step down a notch from my 3.73s whenever I get around to installing a TruTrak and 31 spline half-shafts.

-Dean

Ron61 · #4 (**permalink**) 01-11-2010, 03:10 PM

I ran 3:56s and 3:27s and really liked the 327s. Not good with my motor in 5th for cruising as I was just taching 1900 RPM, but great for track use.

Ron

Anthony · #5 (**permalink**) 01-11-2010, 03:27 PM

keep the 355's

392cobra · #6 (**permalink**) 01-11-2010, 04:17 PM

I'd keep what you have.

If you have to change I'd go to 3.25's.

Dwight · #7 (**permalink**) 01-11-2010, 04:34 PM

use the calulators to found out what rpms you will turn at 50, 60 70 mph. Compare the 3.27 and 3.55 gears. I think the 3.27 would be a better choice, you have the low end torque. I would think your motor needs to cruise at 2,000 to 2200 rpms without the trailer hitch jerk. You can use 4 th to cruise at 50 - 60, but I would think you would want to use 5 th for 70 and above.

Been there done that

Dwight

greg schroeder · #8 (**permalink**) 01-11-2010, 08:18 PM

For me the 3.73 gear is real nice for the 1/4 mile and finishing in 4th gear at a nice RPM. It works great on the street too. I ran a couple rear tire heights with my Roush 427R, TKO 600 .64 5th, Detroit Trutrac, 3.73 rear gear. The 15 inch wheels had 28 inch tall tires. It worked great. Initially I had 325 50 15 Mickey Thompson ET street drag radials. They're a bit wide in my opinion. I then went to 275/60 15s. They are also 28 inches tall and are awesome at 20 psi. The other set of wheels I used were not as tall on the rear with the 17s. Here's an image of them with measurement. They worked awesome with the 3.73 rear gear too. It makes for a fun snappy drive.

mdross1 · #9 (**permalink**) 01-12-2010, 07:44 AM

Let me say this about that! I for one while upgrading my drive train behind a 580hp 460,aluminum flywheel,(balanced everything including clutch) Tremec TKO,Strange aluminum center section in 9" 3:55 to 3:73.After one season,100% happy with the change.Also adjust diff angle down to 4 degrees, giving me an excellent launch.With the TKO's overdrive, turnpike cruising is an absloute joy.