WhiteKnight '01

Right now my car has the 2.73's, I've been thinking that I may move up to 3.23's or 3.42's. I hear I will need the 2-bolt kind, I think, so I can't get regular OEM 3.23's or 3.42's.

My questions are, what are the gains on going from 2.73's and up to 3.23's or 3.42's? Is there better acceleration? More torque to the wheels? More power to the wheels? Will it be harder on my transmission?

Lastly, will I lose any fuel economy from going to different gears?

I assume that 3.42's are better than 3.23's?

Z28MJ

you would get better acceleration, you will lose some fuel economy

black_phoenix

iTrader: (27)

im in the process of upgrading my stock 2.73's to 3.73's and it will be a daily driver as well... Do your torque converter as well. Even though not installed yet, im already regretting with going 3400... I should have gone 4000+ lol

Oh and ive had a 99 trans am A4 with stock 3.23's before... Its tad a better gear over 2.73's but not worth the over the 2.73's imo... due to the labor and gear costs...

From what ive heard, for dd purposes 3.42-3.73 is the way to go for A4 ls1 car...

99Z28camaroman

iTrader: (10)

I had a 95 Z28 about five years ago I went from 2.73s to 3.42 what a diference it really woke the car up. It felt like a different car acceleration muuch bettr no flat spots I dropped .3 seconds in the 1/4 mile. I than swapped them for 3,73s you couldn't realy feel any difference between the 3.42s and 3.73s even at the track. Fuel economy you hardly notice the difference.

So 2.73s to 3.42 is a worth while swap you will need a thicker gear and longer bolts as 2.73 are 2 series carrier and 3.42 and 3.73 are 3 series carrier or you can use standerd gears with a spacer and longer bolts. They are both available. You will need your PCM tuned for the different gears either by a tuner or a HPP3 or Diablo hand held tuner.

It's a tricky job to do yourself as they are knight mere to get them shimmed right so there not noisey so professional install is best if your not experienced.

As has been said already you will see bigger gains if you put in a high stall TC at least 3000 to 3500 rpm.

I did the 3000 stall on my old 99 Z28 and it dropped 1/2 second at the track from 13.8 to 13.3.The car felt like an animal after the install and would light the tyres up from a dig at will.

BOBS99SS

iTrader: (2)

op i would at least go 3.73s or nothing, thats imho, for one gears are kinda pricey to do, if your not going to do them yourself.i would even say go 4.10s ,but thats just me,i will say if you plan on big mods ,plan on a new rear, i just sold all my 10 bolt stuff, had a set of 4.10s and a ta cover. i just thought it would be pretty dumb for me to put 500 into something that can blow at any time.i guess it really depends on the long term goal for your car,and what you are looking for.

RPM WS6

iTrader: (3)

The track gains will be almost nothing if you already have a 3500 or higher stall.

If you don't have a stall, I would recommend doing that first. The overall gains from a stall will be much higher without the loss of MPG from a gear swap on the highway. Only reason to do the gears is if you want to tighten up the feel of the stall around town....some people are bothered by this, others are not.

I wouldn't worry about replacing the 10-bolt in an A4 car unless the plan was for an extreme engine build in the future.

justin hover

I did my 2.73 to 3.73 swap this spring. I would've hated myself if I went with 3.42s like I was oringinally going to. For the money and the sotp feeling....get the 3.73s, their the right gear for an auto. Sotp went up alot, no more second gear lag, snappy off the line,"feels" like it pulls twice as hard throughout the whole rpm range, def. worth it..
Just take the right advice, get the 73s not the 42s, just like everyone who got a 3200 or 3400 stall and wished they'd gone bigger, if you get 42s you'll be wondering why you didn't do it right the first time..73s

Scott97LT1

I just put Richmond 3.73's in about a week ago from 3.42 that were installed prior to me buying it (had to take the diff apart anyways so why not upgrade). I noticed almost no change in my fuel economy but with my stall and it shifts through real nice. Id honestly say 3.73 is the way to go. even driving in FL in the heat, stop go traffic sometimes my gas doesnt seem to be that bad.

WhiteKnight '01

So going from 2.73's to 3.73's what's the expected fuel economy change?

The Camaro SS in stock form had 3.23's or 3.42's, not sure which, but people say it always posts better track times than an LS1 with 2.73's, so isn't that worth it?

I want to feel a difference without sacrificing too much fuel economy, this is still my DD, and as gas hovers around $4 a gallon and my commute to work may be tripling in the coming months, gas is very important to me, until I can buy a smaller better MPG's car.

99Z28camaroman

iTrader: (10)

The fuel economy change will be so small it is almost not worth mentioning when I did the swap on my 95 lt1 which gets almost as good mpg as the LS1 I didn't really notice a change. 4.10 are no good for a DD if you have a long commute

I will say that if you get yourself some 3.42 GM gears that have come from an M6 car as they have them as standard and change them there are a lot for sale on here. Then get them fitted you are more likely to get a them quite as some of the aftremarket gears are noisey. 3.73s will give the same sort of MPG as 3.42s you won't really notice much change from 2.73s and you can live with them as a DD.

RPM WS6

iTrader: (3)

All A4 SSs had 3.23s, and it should run slightly better times than a 2.73 car, but this is because they both came with ~1600rpm stall speeds.

Not when you consider the much greater gain of doing a 3500+ stall first. Once a stall speed of that size is done, any additional track gains from going to a 3.73 would be limited to about 1 tenth.

The stall is a better first mod, and MPG will be 100% the same at speeds where you're in lockup. City mileage might go down a bit because you'll be revving a little higher to get moving, but on the highway you will be at exactly the same rpms.

FirstYrLS1Z

iTrader: (4)

'Guesstimates' of real world mpg with a 98-02 A4,torque convertor locked,cruising in cruise control at freeway legal speeds.

2.73 - 25.9
3.08 - 24.7
3.23 - 24.5 *
3.42 - 24.0
3.73 - 23.0
4.10 - 22.2
4.56 - 21.5 *

* - what I got on many trips from Ohio to Florida

justin hover

I was going to do a stall first, but the 2.73s suck *** for city/dd driving... and if 2.73s get paired with a stall, the sluggish around town driving with a loose stall is no fun imao.
If 2.73s I'd gear first... stall later, cause your gonna get rid of them later anyway.If 3.23 or 42s I'd def stall first.
With 2.73s I was running 1900rpm at 70-72mph..with 3.73s I run 1900 rpm 55-57mph.
I didn't notice a difference with mpg...I'm sure I lost a couple but not enough to notice

RPM WS6

iTrader: (3)

Looseness of a ~3500 (even with 2.73s) has never bothered me nor felt sluggish, but that's a personal perception issue so opinons will vary. Quality of the converter will also effect this.

I wouldn't. For these cars/transmissions, stall should always be first, IMO.

I too would rather have the 3.23s, but I wouldn't spend the time or money to swap out the 2.73s unless I was building a max effort track car, or building an engine that needed a ~4500 stall (which would feel pretty loose with 2.73s, even for me).

ULTIMATEORANGESS

iTrader: (4)

me, id get rid of 2.73s but i agree on getting a stall first.

HumpDay

don't waste your time upgrading to factory gears. Get at least 373's and you will notice a big difference and lose maybe 1 mpg if any on the hwy.

99Z28camaroman

iTrader: (10)

I went to my American Car meet last night and one of my buddies has 99 Firehawk was there, Another buddy who no lomger attends has a 97 LT1 Trans Am. I did a deal with him on the pnone there to buy back a set of GM 3,42 gears that I sold him about 5 years ago. He never used them as they were for his wifes Firebird which they sold without using them. They came from a 98 TA M6 that I got from a want ad on CamaroZ28.com.

It may be a while until I can get them installed as I need a spacer and longer bolts before I fit them and some means of changing my PCM so I will be going 2.73s to 3.42s probably before I do the stall om my car.

It's kind of funny because these are the exact same 3.42 gears thet were in my 95 Z28 that I mentioned earlier in this thread!
I took thrm out and put 3.73s in and sold the 3.42s to Dave who still has them 5 years later now I'm buying them back!

99Z28camaroman

iTrader: (10)

Well I just got back from my buddies garage we spent all morning cleaning and buffing the Torque Thrust II wheels on my car as they are minging.

My other mate turned up owns owns the 97 TA with the 3.42 gears.
So I have the gears I now need to sort a spacer and a hand held tuner.

Cale234

very useful Thanks

ortiz11b

I just did a swap last weekend,,, went from 2.73 and steel driveshaft to 3.42 with aluminum 3" driveshaft. help tons... like a new car,,, I wanted to go with 3.73 but couldn't afford it rite now.. i got a used setup online from a 02 SS with low miles and in great shape,,, posi and gears for 140. driveshaft for 75.. fuel economy is about the same... but im sure putting more torque down.....