Curent setup is in sig. My curent gear is 3.70. Im making about 480rwhp. I went to the track this past friday and made a motor pass this was the result.

60'....1.60
330....4.59
1/8....7.11
mph....97.38
1000....9.30
1/4....11.15
mph....121.89

If I change to the 4.11's how much would this help my 60' & 1/4 time and would my trap speed go up or down? I'm looking for possibly a 10 sec ET if I change to this gear?

 

Where does your motor makes its power and torque? I know with my set up I went from 3.73s to 4.10s and dropped .15ish and picked up 1.5 mph...I was coming thru the traps at 56-5700 and now I'm right around 6000-6100...My motor makes max power by 6300...I'm only making 375 rwhp on a Mustang dyno and my numbers are in my sig...You should be flying at 480 rwhp...

--Alan

 

It will probably lower your 60' and ET a bit, but I wouldn't expect much change in MPH. Your MPH does seem a tad low for your mods and power level. Any idea on the DA or elevation at the track?

 

My car was dynoed on a dyno jet. The motor makes max power at 6400rpm and max torque at 5400. The track altitude is 619'. I'm not exactly sure why mph is somewhat short of where it should be.

 

Find out what RPM your crossing the line at now, it'd be best if you had something more accurate than the stock tachometer.

Do the math to figure out what RPM you theoretically should be at @ 122. (assuming theres no slipping in the torque converter)

Take the difference of those two to find out how much your converter slips.

Use a gear/MPH calculator to find a gear that will give you 6400 RPM's total (RPM's on gear chart @ 122 MPH + converter slip = 6400 RPM) @ 122 MPH.

X + (converter slip) = 6400 , Solve for X, converter slip will be known.


If your goal is running best on motor this is the ticket. This might hurt you on spray. You might try running a 26" tire on motor, this will lower your gear ratio as well. If you have it crossing the traps on the shift point on motor your gonna end up in OD on the juice. I wouldnt want my tranny taking that kind of abuse.

 

Wow. After making this post I went and changed gears. Turns out I had 3.89's in my car instead of 3.70's. Which is what I thought I had. But my speedo tack was off by 10mph after I had my car tuned earlier which lead me to think I had something other than 3.89's. But I had 3.89's. Anyway after going from 3.89's to 4.11 gears not changing anything else I went out and made a couple passes. I droped .15 off my time and went 10.994 at get this 125.79mph. I picked up 3.9 almost a whole 4 mph just going from 3.89's to 4.11s. I was epecting maybe 1 mph difference.

 

At your racewight, I'm not surprised to see the mph gain. You've got alot of weight to get moving, and that gear change gives you alot better tq multiplication for sure.

Ditch the 4ljunkie and put a th400 in with a brake and ya probably could see 10.70, get the car to 3200 with you in it, and 10.30 is probably possible.

If you're spraying it... you'll need that 3.89 gear back in the car if you want to go much faster then 9.60 though, cause you'll probably be out of gear (spraying also is going to make getting that 4ljunkie out must)

 

I wasnt sure is a th400 a 3 speed. Do you think I could spray like a 150 or 200 shot as my max with a th400 and still have the 4.11's? I wasnt planing on going much fast than 9.80 to 10.0 at the track.

 

Yes th400 is a 3 speed. 4.10's and a 28 inch tire will work, depending on the converter effeciency you'll be close.

I went 9.6x @ 140 and was at about 7100 rpm thru the traps with a Th400 and 4.10 gears spraying a 150 hit, if you're planning on keeping at the et range you listed then you will be fine wth a 4.10 gear... if you decide to start trying to go faster, plan on changin to a 3.73ish, to get the room mph wise you will need.

 

Congrats, that's moving you must be like 3750 - 3850 raceweight right.

 

3795 with me in it.