3:73 Gear for Blower Car?

[machz]

I have a 99 GT with a P1SC supercharger rated at 10 psi. The car has 3:73 gears in it now. My dilema is this: Although the power is cool, it really takes at least 4,000 rpm to feel any 'real' grunt. After that it gets interesting, but below that its a little soft. I know the 3:73 might be the best gear for drag racing ( 4th gear through the traps), but for the street I constantly find myself hauling tail just to hit the power of the blower. Would a 4:10 help it to stay closer to the power without hitting licensing losing velocities? As it is now, I can really only play around in 2nd gear, cause by the time the power ramps up in 3rd, its bye, bye license on these backroads, not to mention dangerous. What are you guys running with centrifugals for mostly street entertainment?

[austin5670]

I really think that having 4.10s and a centri will be a perfect combination
3.73 and 3.55 are, IMO, are for roots style or twin screw blowers.

Im going to set my car with with a novi kit set at 10 psi.
But after my tune I'll let ya know

[MGT2002]

get a 3.90

[MODMUSTANG]

Won't see much difference in only going to a 3.90. I would go 4.10's.

[TonyG]

I switched from 3.73's to 4.10's with a Vortech S-Trim (10-12psi). Truthfully, there wasn't a dramatic difference. After all, your rpms at any given speed will only increase by about 10% (4.10/3.73 =1.10). Don't get me wrong, I do like 4.10's better than the 3.73's, but sometimes I wish I went to 4.30's.

I have no problems on the dragstrip -I run 28" slicks, and I stay in 4th gear through the traps (MPH = 120+).

Short gears and a centri blower make a great combo -the gears pull hard down low, then the blower takes over at higher rpms and pull even harder to the redline. Here's a little video I made showing what 4.10's are like:

http://videos.streetfire.net/video/7...c5017b2503.htm

[machz]

TonyG-

I understand what you are saying about the 4.10's making up for the low end, then the blower taking over up top, that's what I'm looking for. I have stock cams, and at my current power level ( conservative tune at 381) I wouldn't reach much over 110-113 in the 1/4 I'm guessing anyway so maybe the 4.10's wouldn't require a shift to 5th? How about 4.30's? Will those take me through the traps in 4th at these theorotical speeds?

My guess is that 4.30's with cams would be much better for a fun street car with the centri blower than these 3.73's I got now.

Thanks guys for the help. I'm trying to consider my options wisely. By the way, I do like a big gear, just don't want to shift into 5th in the 1/4.

Not to hijack my own thread, but how high will the Anderson Ford blower cams rev out to?

[PC02GT]

3.73's + P1SC here also and completely agree it needs more gear for the street. 4.30's would be a wicked street gear.

TonyG, do you know what your RPM's are going through the traps? Could you go 4.30's and stay below redline in 4th with the 28" tires?

[TonyG]

This calculator is consistent with what I see on the track:
http://tchracing.com/tech/gearcalc.php?

With 4.10's and 28" slicks, I cross the traps at about 6000 rpms. If I had 4.30's, I would be crosing at 6300-6400 rpms. My rev limiter is set to 6400, so I would be able to make it through, but I don't like reving it that high.

I used to run 26" with the 4.10's and I would always hit my 6400 rpm limiter at the traps. For this reason, I switched to 28" slicks. Now I have plenty of rpms left, and the taller tire dropped my 60' time to boot.

[PC02GT]

thanks Tony that helps a lot

[hpbronco]

I was in the same boat, using my S-Trim with 3.73 and it just wasnt cutting it. Switched to a 4.10 and was a great improvment IMO. Almost wish I had gone 4.30.Like said above,a 4.10 i think is great for centrifigul and a 3.73 or 3.55 is much better suited for a roots style blower that makes more down low. Just my $.02 worht.

Scott

[machz]

TonyG

Thanks for posting that information, especially the calculator. This really helped me decide.

Based on what everyone has said, and the information obtained with the calculator, I feel the 4.10's would be the right choice. The only doubt that remains is those who say they kinda wish they went with 4.30's. Hmmmm

[Blown284]

I plan to stick with 3:73's and have considered going to 3.55 or even 3.27 gear

[machz]

Blown284,

Not sure if your serious. Why would you want to go back to 3.27s? I could see with a turbo, but a Novi 2000??

[Blown284]

Originally Posted by machz

Blown284,

Not sure if your serious. Why would you want to go back to 3.27s? I could see with a turbo, but a Novi 2000??

I'm joking. I'm sticking with 3:73's and actually have thought about moving to a 4.10's with a 28" tire.

[machz]

So, anyone got 4.30's ( with a 5 speed) in their centri cars?

[white99gt]

I have run stock gears,3.55's(with the kb) and 3:73's with my t trim combo.

It really depends on the final combo.Steap gears are nice on lower hp cars but as they make more power steaper gears make driving on the spirited driving harder.

So you should look at the final picture before changing gears.