I had a lower rear end gear.

Right now I have a best of 11.8 @114 w/1.7 60'. I BARELY got out of second gear on this run and I was still 500 RPM below redline in second gear when I shifted.

That was with et-streets, 26x11.5x15 and NO wheel spin.

With my regular tires (Kuhmo-Victoracer 245-45-16's) I was turning 1.8 60' times all day long with TONS of wheel spin.

It feels VERY slugish with the ET-Streets, I'm sure because my rear end gear is too high for that tall of a tire..

I have a Turbo 400 trans and Dana 44 with 3.31:1 gears and a 7000 RPM red line.

What might I run with a 3.73 or a 4.11?

 

Increasing your gear ratio will only decrease traction more. What RPM do you trap at? You don't want to run out of gear before you cross the finish.

 

As I said, I was BARELY out of second gear when I crossed the finish line. I still had close to 2000rpm to spare in third gear.

 

I understand that. What I should have asked was at what RPM does your motor make peak power? Even though you have 2k to spare you may be out of your powerband by then. If your motor makes peak power right below redline (which I would geuss that is does since you run 11's) a gear swap could make you faster.

 

I think the real question trying to be asked here is how much 3.73 or 4.11 rear gears will hurt his traction and help his first gear.

 

With the ET-Streets I don't THINK I'll have a problem. Right now, if they are hot, I can't spin them at all.

 

A 4.11 has roughly a 10% greater mechanical advantage over the 3.73's. Likewise, the 3.73's have a 12% advantage over his current 3.31's. That means that he is more likely to have traction problems. He will either have to live with what he has, change his launch techniques or improve the traction abilities of his car. A numerically higher gear "should" make his car faster. This will be evident in his end trap speed (since he has 2k to spare he is not at peak power, based on my afore metioned assumption) but not necessarily in his overall ET.

 

Using the ET-Streets I have traction to spare and @2000RPM to spare. I'm just wiondering what I might do with it.

 

Have you used the calculators found on the main page? With your ET streets is is clear that you would see improvement with a gear swap. However, a little math will help you choose which one best suites your motor. What are the gear ratios of the T400 you are running?

EDIT: Asumming a 1:1 gear (which I think it is, correct me though if not) for your T400 you should be at 4900 rpm at the traps with your 3.31's (at 114mph). 3.73's put you at 5500 rpm for the same trap speed. 4.11's put you at 6100 rpm for 114mph. That sounds like a pretty good gear to me.

 

Yes 3rd gear is 1:1.

My torque peak is at 5000RPM and my HP at 6500 with a 7000+ redline. If I shift at 7500 it will bring me back to 5000.

BTW, my rev limiter is set to 7800 and I've hit it several times with no ill effects.

So even the 4.11's would leave me 900+ RPM to spare.

Anyone have an estimate of the difference in ET I would get going from 3.31 to 4.11?

 

It would be tough to give an exact estimate but it should be recordable and evident on your next ET. You should see a gain (well... drop) in both your ET as well as your trap speed. For 114 mph you were running a good ET to begin with. If you can maintain the same traction and 60 times, as you did with your old combo, you could see a few tenths reduction and a few mph gain.

 

I'm thinkng that my BIGGEST gain would be in my 60' times.

I see a lot of people running similar ET's and MPH with 2 or 3 tenths faster 60' times.

The fact that I went from tons of wheel spin to no wheel spin and only picked up 1/10th with the (2") taller tires makes me think that me gear ratio is really hurting me.


With the shorter (~24") Kuhmo's I can do a big smokey burnout from a 35MPH roll in 1st gear. Once hot, I have yet to spin the ET-Streets.

For it to be worth while for me I would have to pick up at least 1/2 a second to consider a gear swap. I'm just wondering if that is a reasonable expectation.

 

I agree on the basis that you have traction to spare (as stared above).



A 2" taller tire reduces your gear ration even farther. The larger (in diameter) tire that you run, the numerically higher gear ratio you want.


I would do it. If you run 11.8's and trap short of your peak RPM there are serious improvements to be made.

 

24" tires? the stock size is 245/50/16 right. that is a 26" tire. i would imagine that a 24" tire would look terrible due to huge fender gap. Personally I am going with a 700r4 tranny with 3.73 gears in the rear and 28x11.5-15 ET streets.

 

I think 25.6 is typical, some are smaller.

My 245-45-16's are 24.3.

And BTW, what they look like is of no concern to me.

 

I have a friend that picked up 5 to 6 tenths when he went from 2.73 gears to 4.10.He picked up another 5 tenths when he switched from the stock converter to a 10".I will venture a guess that going from 3.31 gears to 4.10 with your combo will get you 3 tenths and 3 MPH.