3.42 or 3.73?
Thread Starter
Drifting
Joined: Sep 2010
Posts: 1,311
Likes: 0
From: Chicago IL
3.42 or 3.73?
Would appreciate the pros/cons between these two gears. I have an 05 A4 that has the stock 2.73 in it now. CAI, headers, and CB are all thats done to it so far with a tune being done this Monday.
I went to the track for the 1st time in my life and ran a best 12.64 @ 111 and was wondering just how much improvement I can expect with the tune and the gear swap.
Would you guys go 3.42 or 3.73? How much fuel economy will I expect to lose on the highway? Is the 3.73 way too much for the stock runflats? Thanks guys!
I went to the track for the 1st time in my life and ran a best 12.64 @ 111 and was wondering just how much improvement I can expect with the tune and the gear swap.
Would you guys go 3.42 or 3.73? How much fuel economy will I expect to lose on the highway? Is the 3.73 way too much for the stock runflats? Thanks guys!
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
Would appreciate the pros/cons between these two gears. I have an 05 A4 that has the stock 2.73 in it now. CAI, headers, and CB are all thats done to it so far with a tune being done this Monday.
I went to the track for the 1st time in my life and ran a best 12.64 @ 111 and was wondering just how much improvement I can expect with the tune and the gear swap.
Would you guys go 3.42 or 3.73? How much fuel economy will I expect to lose on the highway? Is the 3.73 way too much for the stock runflats? Thanks guys!
I went to the track for the 1st time in my life and ran a best 12.64 @ 111 and was wondering just how much improvement I can expect with the tune and the gear swap.
Would you guys go 3.42 or 3.73? How much fuel economy will I expect to lose on the highway? Is the 3.73 way too much for the stock runflats? Thanks guys!
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
Would appreciate the pros/cons between these two gears. I have an 05 A4 that has the stock 2.73 in it now. CAI, headers, and CB are all thats done to it so far with a tune being done this Monday.
I went to the track for the 1st time in my life and ran a best 12.64 @ 111 and was wondering just how much improvement I can expect with the tune and the gear swap.
Would you guys go 3.42 or 3.73? How much fuel economy will I expect to lose on the highway? Is the 3.73 way too much for the stock runflats? Thanks guys!
I went to the track for the 1st time in my life and ran a best 12.64 @ 111 and was wondering just how much improvement I can expect with the tune and the gear swap.
Would you guys go 3.42 or 3.73? How much fuel economy will I expect to lose on the highway? Is the 3.73 way too much for the stock runflats? Thanks guys!
Thread Starter
Drifting
Joined: Sep 2010
Posts: 1,311
Likes: 0
From: Chicago IL
Ok, if I go with the 3.73 and use drag radials, should I be sure to get an updated differential housing? In my head, all I see is me at the starting block with drag radials and my 2005 A4....I brake torque to around 1,200, and mash the gas and then hear a pop. Scares the crap out of me!!!
Melting Slicks
Joined: Jul 2008
Posts: 2,014
Likes: 2
St. Jude Donor '09-'10
Would appreciate the pros/cons between these two gears. I have an 05 A4 that has the stock 2.73 in it now. CAI, headers, and CB are all thats done to it so far with a tune being done this Monday.
I went to the track for the 1st time in my life and ran a best 12.64 @ 111 and was wondering just how much improvement I can expect with the tune and the gear swap.
Would you guys go 3.42 or 3.73? How much fuel economy will I expect to lose on the highway? Is the 3.73 way too much for the stock runflats? Thanks guys!
I went to the track for the 1st time in my life and ran a best 12.64 @ 111 and was wondering just how much improvement I can expect with the tune and the gear swap.
Would you guys go 3.42 or 3.73? How much fuel economy will I expect to lose on the highway? Is the 3.73 way too much for the stock runflats? Thanks guys!
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
Ok, if I go with the 3.73 and use drag radials, should I be sure to get an updated differential housing? In my head, all I see is me at the starting block with drag radials and my 2005 A4....I brake torque to around 1,200, and mash the gas and then hear a pop. Scares the crap out of me!!!
i am doing the second generation rear now, i just did a 10.59 @ 130 mph right before it cracked with the original 05 housing
Melting Slicks
Joined: Oct 2009
Posts: 2,259
Likes: 1
From: Las Vegas NV
St. Jude Donor '10
This ought to be interesting, I've never seen anyone put larger than a 3.42 behind an automatic.
Also, the C6 diff is a sealed housing. So how are you upgrading it? A diff brace?
Also, the C6 diff is a sealed housing. So how are you upgrading it? A diff brace?
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Probably the 3.42 gears because the car has the stock cam & heads.
If you install higher flowing heads and a bigger cam, then 3.73 may be OK as your power band will be at a higher RPM so the shorter gears will get you into your power band there faster.
But with the A4 trans, the next mod would be a high stall converter after that.
If you install higher flowing heads and a bigger cam, then 3.73 may be OK as your power band will be at a higher RPM so the shorter gears will get you into your power band there faster.
But with the A4 trans, the next mod would be a high stall converter after that.
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Safety Car
Joined: Jan 2008
Posts: 4,711
Likes: 3
From: Middle of No where AK
Unless its a dedicated drag racer more than 3.42 will drive you nuts. I have the 3.42 and I run about 2400 rpm at 80mph and get about 21-23mpg with my new cam. Any more gearing and the highway driving would be ridiculous.
Thread Starter
Drifting
Joined: Sep 2010
Posts: 1,311
Likes: 0
From: Chicago IL
I thought the 2005 diff housing is different than later years....more prone to breaking. Maybe im wrong, im still learning. What I meant by "upgrade" is when I replace my diff, i'll go with a diff housing other than the '05.
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
you are right, there is a forum member jerry muniz has ran 410 gears in his a4, 373 is a perfect gear for the street and the interstate, i have also been 185 at 5000 rpm in 4th with no problem with lots to go, heres a run with just bolt/ons, i would guess over 400 passes rear held fine, avoid the wheel hophttp://www.youtube.com/watch?v=ZmisWFoprDk
Le Mans Master
Joined: Oct 2005
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From: Texas Where God intended me to be.
2023 Corvette of the Year Finalist - Unmodified
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St. Jude Donor '08 thru '11,'22 thru '26
I put the RPM stage 2 3:42 gear in my 2001 A4 and it work it up. It has ARH W/ cat back's & Vararam it will burn second gear all day if I get on her. Buy the new rearend
Le Mans Master
Joined: Aug 2009
Posts: 5,197
Likes: 190
From: ALL governments are legalized mobsters, so doesn't matter where I live :(
Unless you really want to dedicate your car to the track 342 is your best option...anything else and you might as well not ever leave city driving.
