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2.73 to 3.42

This is a discussion on 2.73 to 3.42 within the Automatic Transmission forums, part of the Drivetrain category; is this swap worth it in the stock 10 bolt? I was gonna buy and have the rebuild kit put ...

  1. #1
    Member pewterz55's Avatar
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    light pewter metallic
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    2.73 to 3.42

    is this swap worth it in the stock 10 bolt? I was gonna buy and have the rebuild kit put in anyway so i was thinking about gettin some used 3.42 for cheap. any ideas? just go new/used 3.73s? what you guys think?

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    3.42 in an a4 car is nice upgrade from 2.73. i am not sure but i think 3.42 will get you though the 1/4 in 3rd and 3.73 put in you in overdrive.

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    Exalted Cyclops 67CamaroRSSS's Avatar
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    2002 Z28 A4 NBM
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    IIRC, if you have 2.73's you can't use stock 3.42's as you have a 2 series carrier while the 3.42's need a 3 series carrier.

    OTOH, aftermarket makes gears that are thicker and will work with a 2 series carrier.
    67 Camaro: K-K + 797-z (look it up), 454/Th400/4.10 12-bolt = 6mpg, PS/PDB/PW tilt, tach, gauges...

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    Just doing gears I'd go new 3.73. 2.73's have a 2 series carrier, used 3.42's will probably be from a 3 series carrier and not fit. New 3.73 gears for a 2 series carrier are available. Proper set up is essential, even with new gears.

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    Moderator Firebirdjones's Avatar
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    If it were me, I wouldn't bother with spending money on gear swaps in the 10 bolts. To do it right you'll spend more money on the gear swap than you would just finding a 6 speed rear that already has 3.42's in it.

    If you are starting with a 2.73 car, that's the route I would take. Simply find a 6 speed rear and swap the whole thing out. You won't really find any performance difference to matter between a 3.42 and 3.73.

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    Member pewterz55's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    If it were me, I wouldn't bother with spending money on gear swaps in the 10 bolts. To do it right you'll spend more money on the gear swap than you would just finding a 6 speed rear that already has 3.42's in it.

    If you are starting with a 2.73 car, that's the route I would take. Simply find a 6 speed rear and swap the whole thing out. You won't really find any performance difference to matter between a 3.42 and 3.73.
    yea i would definitely like to just sack up and buy a 12 bolt but funds are holding me back on that. in a perfect world i would just put in a 12 bolt with 3.73. but i figured for now just swap gears maybe for a year or 2 year before i can afford the 12 bolt. and i thought if i could get 3.42s instead of 3.73 it would help save the stock rear while still giving me some more go.
    my only plans before the 12 bolt are exhaust, maybe a stall(but thats not helping the rear end situation either), maybe a small cam, and ls6 intake.
    also the car hasnt seen the track yet. and future plans are maybe once or twice a year to see what times it can get.

  7. #7
    Member pewterz55's Avatar
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    light pewter metallic
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    and i didnt even think about the 3.42s coming for a different carrier, damnit!

  8. #8
    Moderator Firebirdjones's Avatar
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    In that case, since it's something you aren't going to keep, all the more reason I wouldn't invest the money in a gear swap,,,and just stick a 6 speed rear in the car that already has 3.42's.

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    Member pewterz55's Avatar
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    never really even considered that. i figured the swap would cost a ton.

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    Quote Originally Posted by Firebirdjones View Post
    If it were me, I wouldn't bother with spending money on gear swaps in the 10 bolts. To do it right you'll spend more money on the gear swap than you would just finding a 6 speed rear that already has 3.42's in it.

    If you are starting with a 2.73 car, that's the route I would take. Simply find a 6 speed rear and swap the whole thing out. You won't really find any performance difference to matter between a 3.42 and 3.73.
    That's what I did years ago, but low mileage and knew the person buying it from - he decided to put a 12 bolt in his M6 car. Neither car had ASR/TCS and it was a direct swap.

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    Senior Member redbird555's Avatar
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    2002 Camaro Z/28 Pewter

    I just completed the gear swap and its def worth it. It really brings the car to life I cant catch traction anywhere if 1st gear its a problem but a good problem lol. I got mine with the carrier used from a salvage yard for 50 bucks. You can do that usually a carrier used is 125ish along with another 50 for gears or you can buy 2 series gears, or do the 6 speed swap, whichever you choose its a difference you can feel everywhere, my mpgg even increased in the city. Even though you spin a bit more rpms the motor isnt working as hard to rev there.

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by pewterz55 View Post
    never really even considered that. i figured the swap would cost a ton.
    Well not really as far as I'm concerned. I've heard some say they get $400 for a complete 7.5 rearend, but that sounds high to me.You'll spend close to $400 on a gear swap anyway, maybe more if you are paying labor.
    In my opinion a complete 7.5 isn't worth more than a couple hundred bucks, if that. Hell I threw 3 of them in the dumpster when I moved out here, I couldn't give the damn things away.

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    Member JRENIGAR's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    If it were me, I wouldn't bother with spending money on gear swaps in the 10 bolts. To do it right you'll spend more money on the gear swap than you would just finding a 6 speed rear that already has 3.42's in it.

    If you are starting with a 2.73 car, that's the route I would take. Simply find a 6 speed rear and swap the whole thing out. You won't really find any performance difference to matter between a 3.42 and 3.73.
    ^^^ Best advice Ive heard all damn day!!! I tried the 373 for a 2 series carrier with proper set up and it made a howling noise. I got a diff 3 series carrier and some NEW!!! 342 gears and it seemed like it pulled a lil better through the gears. Get a whole rear out of a 6 speed car and call it a day...

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    Member pewterz55's Avatar
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    All right. The search begins haha. If anyone knows of one for a decent price I'm willing to drive and pickup

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    Member AKA Speedy's Avatar
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    Quote Originally Posted by JRENIGAR View Post
    ^^^ Best advice Ive heard all damn day!!! I tried the 373 for a 2 series carrier with proper set up and it made a howling noise. I got a diff 3 series carrier and some NEW!!! 342 gears and it seemed like it pulled a lil better through the gears. Get a whole rear out of a 6 speed car and call it a day...
    I agree... The only other route is motive sells a series 2 set : part #G875342X
    for about $200

    the X means it fit a numerically 3.08 or lower case. Don't get a set without the X on the end of the part number. Install kits go for anywhere between $50-100. From there its just getting a tune to recalibrate you speedo. Motives are good gears if you are going to buy a set. They seem to break in easier and be quieter from personal experience.

    Bottom line 3.42's are the way to go. Like someone said earlier any higher and you start getting out of your power band at the end of the 1/4 in an Auto. you'll notice a huge diff going from a 2.73 to 3.42

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    Senior Member TLS_Addict's Avatar
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    I am in the same boat. Not sure if I want to put in 3.73 gears or if i want 3.42s instead of my 2.73 set.

    I looked at getting a complete rear from a wrecked 6-speed car but was told the brake line set up is different. Something about aa two input vs a 1? I had no clue what the guy was saying really beacuse I cant imagine they would be set up different but perhaps they are. Also, I was told that 3.42 rears have a 3-wire plug in where my rear has a 4-wire. Is this true and what do you to to fix that?

    I am in the same boat as the OP. The car gets good mileage but doesnt have enough pick up for me.

  17. #17
    Veteran Blackbird WS6's Avatar
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    if you have an A4 and are going to waste the money on the 10bolt then i would get 3.73 just my .02

  18. #18
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    different setup-3 wire and 4 wire-true but wrong terminology.
    3 channel is ABS
    4 channel is ABS and Traction Control
    If you want to retain/maintain your system,you have to use a rearend assy that is the same as yours.
    as far as swapping in a complete rearend(applies only to Z28,SS,TA,V6s are mostly 3.08 non-posi),
    98-02 ABS only 2.73,3.23,3.42 fully interchangeable
    98-02 ABS & TC(ASR) 2.73,3.23,3.42 fully interchangeable

    depending upon the urgency of your need,watch the for sale threads of the various car forums. You should be able to find one local to you with a price range of 100-200. over the past couple months I sold 3 4 channel 3.42 rearends for 100 each. I was accumulating too many takeouts.
    Last edited by oldmanZ28; 08-06-2010 at 06:22 PM.

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    Quote Originally Posted by Firebirdjones View Post
    If it were me, I wouldn't bother with spending money on gear swaps in the 10 bolts. To do it right you'll spend more money on the gear swap than you would just finding a 6 speed rear that already has 3.42's in it.

    If you are starting with a 2.73 car, that's the route I would take. Simply find a 6 speed rear and swap the whole thing out. You won't really find any performance difference to matter between a 3.42 and 3.73.
    This is exactly what I want to do, I don't want to mess with gear and carrier swaps.

    Only problem is I've been looking for one for over a year and still haven't managed to snag one yet. I just can't seem to find one locally.

  20. #20
    Moderator Cutlass's Avatar
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    Quote Originally Posted by StuntmanMike View Post
    This is exactly what I want to do, I don't want to mess with gear and carrier swaps.

    Only problem is I've been looking for one for over a year and still haven't managed to snag one yet. I just can't seem to find one locally.
    There is one at North Smithfield Auto Recycling in North Smithfield, RI. Its listed as GU6 (3.42) non traction control for $150. Question to ask them though is if its a V6 rear w/out G80 (posi traction) or if its a V8 posi rear.

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