Alright im going to be upgrading my rearend to 3.45s as the topic says. I dont have any baseline testing done on my car in the 1/4 mile, lets assume it runs the 15½ or whatever it was rated at when the car magazines tested it in 1989.

What kind of increase in 1/4 mile times can I expect from this gear change??? Providing of course that I can still hook up alright...

Thanks...

 

I say somewhere between 2 or 3 tenths

 

Wow thats all its good for?? Oh well I guess I cant expect too much from my old powertrain anyways.

Thanks for the answer

 

I have heard of a few people gaining as much as 6 tenths in the quarter, i just got my swapped for a 3.42 and it made a world of difference.

 

around town you will definitly tell the difference. at the track, expect maybe 4 tenths about. Good swap and definitly worth the money.

 

Well on a basically stock car you wont see to much especially since its tuned port and you already have alot of power down low. I would say youll knock down like 3 or 4 tenths.

 

you think four tenths is not that much you must be crazy

 

4 tenths is almost 5 cars!

 

what about 3.42 to 4.10? i wouldnt expect much cause i dont have any traction!

 

4.10's are good to go to but expect to be topped out at around 85 to 90 mph, good for the 1/4, but definitely not the street.

 

You don't want 4.10's on a street car. Gearing is just part of the puzzle if you are stock look to improve times in alot of other areas. Intake, exhaust, suspension for starters. If you get 4 tenths as someone said thats a great improvement for one mod. don't go crazy looking to gain more than that just from rear end gearing.

 

My predictions:
- You won't see an increase in 1/4 mile times.
- You won't be any faster, but you may be quicker...

Okay, semantics. Your MPH will probably stay about the same, the ET reduction will depend upon traction more than anything else.

When I went from 3.08 to 3.73 in the '57, it dropped a good 1/2 second off 1/4 mile ET.

Other changes that produced significant ET reductions (all after the gear change):
Radial TA's to ET Drags (later Quicktime Pro DOT) - 1 tenth
Self-ported heads & new valve springs - 1-2 tenths
VS to DP carb - 2 tenths
2200 to 3500 stall - 3 tenths
Open element to cool air intake - 1 tenth

MPH stayed ~96-97 throughout all this.

My average late-2003 run was 1.5 sec quicker than my best early 2002 run. No significant engine changes (other than the porting - and you can see how much difference that made).

 

whoah 15.5 on an l98 with a full exhaust no i think you will be in the 14's at least with those gears too.

 

I was refering to the 4.10s in my street car that i drive daily. I love them and woudnt want any less. I topped my car out at 127 after i corrected the speedo. they are awsome!

 

i have run 3.73's and 4.10's on a 700r4..
they are both streetable gears in OD. My et's dropped .5 seconds going from 3.42 cogs to 4.10..
the 3.73's were about 2 tenths slower than the 4.10's at the same mph thru the traps. My car tops out around 125 or so. and is at 3000 rpm at 70mph....

I run consistant 2.0 60' times on street tires too.

 

Street car and 4.11's OK if: 1. You've got an overdrive tranny 2. You're running Tall tires in the rear , like 28" compared to the 26-26.5" OEM tires

 

I picked up between 0.2 and 0.3 going 2.73 to 3.42's.


Those are track proven times, not estimates.