3:54 in Gen IV?

[Paul Hawker]

Anybody put a 3:54 in a Gen IV?

Thinking about going to a bigger gear in my 09.

Have 20" rims with Pilot Super Sports and they seem to stick good enough to hold the extra torque.

Did this on my 96 and 03 with good results, but wondering if the tires can hold the 600 horsepower.

 

[Hamrhead]

Yep - I have 3.55's in my '08.

On the street, in the summer heat w/ PS2's, first gear holds for the most part. Spring, Fall, Winter temps - don't plan on it.

I only made it to the strip one time in October 2010. Got two runs in and never even squeaked a tire off the line or through 1st gear. I admit I did not launch very hard at all as I didn't know if it would hook or not?

First run I completely tanked trying to feel out the car - 11.88 @ 125
Second run I left the line a bit stronger, but still bogged - 11.44 @ 128. Think I pulled a 1.9 60 on this run, but still a lot of room for improvement.

Maybe someday I can find the time to go again...


I'd love to try a set of Super Sports, but it'll take me forever to wear out the stock PS2's.

 

[JonB]

PAUL......I have always considered gears as the BEST bang-4-buck, as YOU know firsthand.

But don't do a 3:54 (GM ratio) ........while it fits, and is cheaper, the metallurgy will NOT handle the torque of a Gen 4. Go with a shot-peen-hardened-USA-made Spicer-Dana 3:55. If you are worried about the 15.6% extra wheelspin/rotation consider a 3:33 with a 9% faster spinup.....

And installing in a USED Gen 4 diff can be tricky biz.....luckily you are a short hop to the BEST...

JonB ~~~~~:<~

 

[Paul Hawker]

Thanks, Jon.

Did not know about the two different manufacturers.

Good tip on the Dana gear sets, and replacing most of the bearings when I do the install.

3:55 it is.

Only plan to put the good stuff in a Viper : >)

This will be mostly for street use, but SoCal ViperClub is setting up a bunch of local drag strip events, and will really be giving them a workout then. Don't want to be sliding all over the place.

 

[Viper X]

I know that the 3.55's would cause a bunch of unwanted wheel spin in my 09 ACR on the street and would screw up the car on the track. Heck, I can spin them pretty easily now with the 3.07s and PS2s.

Wouldn't do the gear swap in a Gen IV but if I were doing it, I'd go 3.33s.

Dan

 

[BAD BOYZZ GARAGE]

Good question Paul on gear ratio change.. With the 20" rim the Dana 3.54666 gear (better know as the 3.55) will give you a much more responsive driving machine and help cut down on the DBW and VVT lag that Gen IV owners complain about. If your all about the track, (which it sounds like your not hence 20" wheel set-up) then the 3.33 or 3.07 are best depending on which track your at.. Also Paul one needs to ask themselves are you really going to be running 185 mph all the time? With the 3.55 installed your definelty gonna wake up those massive 20"x13" 345PSS's..

Here's the scoop on the Ring / Pinion gear sets:
3.07 Dana
3.33 Italian
3.5466 (3.55) Dana
3.73 Dana
4.10 Dana

At BBG we mandate that the 3.33 Italian gear set be race prepped (cryogenically frozen and polished) to meet our installation standards. This will bring the Italian gear set up to a stock Dana gear set quality that has not been race prepped. A race prepped Dana gear set will be superior!

Hope this info helps..


BAD BOYZZ GARAGE, INC.
Toddy

=DISTRIBUTORS OF POWER=

 

[redtanrt10]

Hey Paul, I always liked my 3:55's in my gen II and III. But I found that at the road tracks running 3:55's and 18's in the rear on my III I now had about a 3:70 plus and too much shifting.

With the rear 20's you now have, you effectively reduced the 3:07 to a 2:92.

If you get a 3:55, with 20's you'll have a 3:43.

If you get a 3:33, with the 20's that will be a 3:22

good luck, hope to see you at the track or a club event. Mike

 

[TrackAire]

Paul,

I had BBG build me an over the top 3.55 with an OS Giken. I have their full race clutch and the 3.55 makes stop and go city driving a breeze. Love the fact that I can use 6th gear on the freeway and not feel like I have to be going 85 mph to keep the car from that lugging feel. Car feels much more European in the fact that I have compression braking coming into corners when in 2nd gear....car just feel more lively.

As others have said, it depends what you want to use the car for. In a perfect world, I think having two or three rear ends set up with 3.07, 3.33 and a 3.55 would be ideal since it is fairly easy to swap rears ends out....only downfall would be cost.

Even though I'll be slower on certain tracks and I have to shift more, the 3.55's have been the best modification I've done to my car.

Cheers,
George

 

[Longdaddy]

what happens to the redline speed in 4th when moving from stock ratio to 3.55 (assuming stock tire diameter)?

 

[redtanrt10]

what happens to the redline speed in 4th when moving from stock ratio to 3.55 (assuming stock tire diameter)?

At 6K rpm you'll be at 158 mph on stock 19" tires. With a 3:55's you'll be at 137 mph.

 

[Nader]

Curious where did you get the outside diameters of the 20 inch setup? My 20 setup (HREs and Pirelli's) in the rear are actually shorter than the stock 19 inch setup due to the 25 profile.

 

[redtanrt10]

Tom, Tire Rack, OP's on the new 20" Pilot super Sports (345 30 20) , Longdaddy asked on the OE 19" Michelin PS2's (345 30 19)

 

[ViperGeorge]

Curious where did you get the outside diameters of the 20 inch setup? My 20 setup (HREs and Pirelli's) in the rear are actually shorter than the stock 19 inch setup due to the 25 profile.

Look up the tire on TireRack they have the specs including the diameter of the tire. Or you could just do the math. The first number is tire tread width in mm. The second number is the profile (the height of the tire from the ground to the rim) represented as a percent of width. Last number is the diameter of the wheel in inches. Take the first number divide by 25.4 mm/inch (for a 345 this results in a tire 13.58 inches wide). Multiply this number by the profile. For a 25 profile tire multiply the width of the tire in inches by 0.25. Multiple this number by 2 since you have two sidewalls - one on either side of the wheel. Then add the dimension of the wheel. For a 20 inch wheel add 20.

To recap, for a 345 30 19. the height (or diameter of the tire) would be (((345/25.4)x0.30)x2)+19=27.15 inches in diameter. That's the height. You can compare tire height but just doing this for any size tire.

 

[ViperGeorge]

One more thing you can compare circumferences of the tires by multiplying the diameter by pie (3.14159). For a 345 30 19 the circumference is 27.15*3.14159=85.29 inches. This is the distance the tire will travel for one revolution. Different diameter tires travel a different distance for one revolution. You can then compare distance traveled for one revolution and calculate effective rear end ratios. If you go to a smaller diameter tire it will travel less distance per revolution. A taller tire will travel further. The smaller tire effectively changes the rear end ratio.