PROs and CONs of changing to a 3.42 diff? PICS of new diff
10-27-2010, 01:54 PM
#1
Melting Slicks
Thread Starter
PROs and CONs of changing to a 3.42 diff? PICS of new diff
Hey guys i have a 1998 A4 Coupe. I was wondering what are all of the pros and cons are of changing the stock 1 rib 2.73 diff to a 3 rib 3.42 diff. I already bought the diff but i want to know what to expect. The new diff is a 3 rib 3.42 with 34k miles. i am sending my PCM to ECS for a retune of the new gearing.
here are pics of the new diff. it will be here tuesday
here are pics of the new diff. it will be here tuesday
10-27-2010, 02:17 PM
#2
Le Mans Master
Member Since: Aug 2005
Location: CA.
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St. Jude Donor '13-'14-'15
You''ll have to re-use the front plate form your A$ diif as most likely the 3.42 was in a manual trans and dosen't have one---- I did the same mod---I replaced the half shaft seals just as a safety--
In hind site----I went from a 3.15 to a 3.42 and really didn't get the results i was looking for--If i were to do it again i would have just gone with a bigger stall converter than my 2600--maybe a 3000---A stall converter is a much better mod and you'll get way better results with that mod---3-4 tenths in the 1/4
PS On a C5 there is NO need to make a speedo correction in the ECM--only on an F bodyy beacuse the speedo pickp is on the output side of the diff and not on the input side of the trans like on a camaro----You will howver need to make a "shift point" correction especially on the TCC----While having the diff out GET a stall converter--!!!!!! my mileage didn't suffer much at all--still get 26-27 on the frwy !!
In hind site----I went from a 3.15 to a 3.42 and really didn't get the results i was looking for--If i were to do it again i would have just gone with a bigger stall converter than my 2600--maybe a 3000---A stall converter is a much better mod and you'll get way better results with that mod---3-4 tenths in the 1/4
PS On a C5 there is NO need to make a speedo correction in the ECM--only on an F bodyy beacuse the speedo pickp is on the output side of the diff and not on the input side of the trans like on a camaro----You will howver need to make a "shift point" correction especially on the TCC----While having the diff out GET a stall converter--!!!!!! my mileage didn't suffer much at all--still get 26-27 on the frwy !!
10-27-2010, 02:32 PM
#3
Team Owner
Prios:
That is a great upgrade, especially going from 2.73's. IIRC, the 3 rib case is stronger and if it came from a Z06 the gears are stronger. The car will pull a lot harder off of the line. I test drove a 2.73 car before I bought mine and the acceleration was underwhelming.
Cons: You lose some MPG
That is a great upgrade, especially going from 2.73's. IIRC, the 3 rib case is stronger and if it came from a Z06 the gears are stronger. The car will pull a lot harder off of the line. I test drove a 2.73 car before I bought mine and the acceleration was underwhelming.
Cons: You lose some MPG
10-27-2010, 02:47 PM
#4
Resident moron
Going from 2.73 to 3.42 in an A4 car is pretty much a no-brainer. I agree that a stall converter (at least 3000rpm) is another no-brainer. You might save some labor swapping that out at the same time, since all of the same stuff has to be removed (and more - the torque tube and the tranny), so you'd avoid a lot of hours of labor....
Just a thought.
Dope
Just a thought.
Dope
10-27-2010, 03:31 PM
#5
Drifting
One of the best mods you can do. Yes you will lose some MPG but the grin on your face as you mash the go pedel is well worth it. I didn't even change the converter. If I do I will use the one from the ASTRO Van as in the write-up by Mike Mercury. I have put about 50K on this combo without any problems so far. Except your tires wear out sooner.
10-27-2010, 05:47 PM
#8
Melting Slicks
Thread Starter
You''ll have to re-use the front plate form your A$ diif as most likely the 3.42 was in a manual trans and dosen't have one---- I did the same mod---I replaced the half shaft seals just as a safety--
In hind site----I went from a 3.15 to a 3.42 and really didn't get the results i was looking for--If i were to do it again i would have just gone with a bigger stall converter than my 2600--maybe a 3000---A stall converter is a much better mod and you'll get way better results with that mod---3-4 tenths in the 1/4
PS On a C5 there is NO need to make a speedo correction in the ECM--only on an F bodyy beacuse the speedo pickp is on the output side of the diff and not on the input side of the trans like on a camaro----You will howver need to make a "shift point" correction especially on the TCC----While having the diff out GET a stall converter--!!!!!! my mileage didn't suffer much at all--still get 26-27 on the frwy !!
In hind site----I went from a 3.15 to a 3.42 and really didn't get the results i was looking for--If i were to do it again i would have just gone with a bigger stall converter than my 2600--maybe a 3000---A stall converter is a much better mod and you'll get way better results with that mod---3-4 tenths in the 1/4
PS On a C5 there is NO need to make a speedo correction in the ECM--only on an F bodyy beacuse the speedo pickp is on the output side of the diff and not on the input side of the trans like on a camaro----You will howver need to make a "shift point" correction especially on the TCC----While having the diff out GET a stall converter--!!!!!! my mileage didn't suffer much at all--still get 26-27 on the frwy !!
Prios:
That is a great upgrade, especially going from 2.73's. IIRC, the 3 rib case is stronger and if it came from a Z06 the gears are stronger. The car will pull a lot harder off of the line. I test drove a 2.73 car before I bought mine and the acceleration was underwhelming.
Cons: You lose some MPG
That is a great upgrade, especially going from 2.73's. IIRC, the 3 rib case is stronger and if it came from a Z06 the gears are stronger. The car will pull a lot harder off of the line. I test drove a 2.73 car before I bought mine and the acceleration was underwhelming.
Cons: You lose some MPG
Going from 2.73 to 3.42 in an A4 car is pretty much a no-brainer. I agree that a stall converter (at least 3000rpm) is another no-brainer. You might save some labor swapping that out at the same time, since all of the same stuff has to be removed (and more - the torque tube and the tranny), so you'd avoid a lot of hours of labor....
Just a thought.
Dope
Just a thought.
Dope
One of the best mods you can do. Yes you will lose some MPG but the grin on your face as you mash the go pedel is well worth it. I didn't even change the converter. If I do I will use the one from the ASTRO Van as in the write-up by Mike Mercury. I have put about 50K on this combo without any problems so far. Except your tires wear out sooner.
10-28-2010, 11:13 AM
#10
Team Owner
10-28-2010, 01:13 PM
#11
Melting Slicks
Thread Starter
ok thx. it was just a curious thought for later...car will stay how it is after it gets the new diff in.
10-28-2010, 04:35 PM
#14
Safety Car
S/A mine, about 420, but I have up-graded clutches as well as the hardened output shaft, about 100 passes at the drags later, no issues.......(yet)...
