tripingeorge3

i believe i have one in my iroc. i did the whole counting of driveshaft turns to wheels ratio and came out at about 2:73. is there anybody dominating with this rear. i like the idea of fast off the line ,but i'd rather have a higher top speed. on the freeway wouldn't it be better downshifting and flooring it and gaining more ground faster. i'm now installing a t5 with stock motor til i deside what power i'm going to build later

Stevo

iTrader: (45)

Thats the thing, 2.73 is only a highway gear. Good for highway mpg and ya you'll have more top end pull.

I actually enjoy the 2.73 rear in my gf's 2000 T/A that thing pulls like a bat outta hell on the highway. Before you even look down its just sailing past 100...her car still runs a 13.5 on the 1/4 with 2.73s. Just really takes awhile to get that thing moving.

But the downside is her car even still has a hard time just chirping the tires from a stop lol. 3.23 is a lot better gear for mix city/highway.

If your swapping a 5 spd your going to at least want 3.23 in my opinion it'll make the car a lot more enjoyable. 3.23s will still give you great highway mpg too.

tripingeorge3

my automatic had a shift kit. every once in awhile i could spin the tires but the kicker was 1st to 2nd. it would chirp and spin the wheels and u had to let off to gain traction front end would stay lifted. thats y i'm wondering.

sofakingdom

iTrader: (1)

Nothing much...

Just one thing really.

It SUCKS.

Other than that, it's fine.

That gear isn't doing you any favors in that department, no matter what kind of "calculations" you've done.

JamesC

iTrader: (5)

JamesC

Reid Fleming

iTrader: (2)

Should give you a bit better top speed in 3rd gear since most of us can't get the cars to shift into 4th at WOT.

Nice for long drives on the highway.

Changing from auto to manual with 2.73's? You'll miss the 700R4's 3.06 first gear.

BigBadJohn

iTrader: (4)

Im thinking of going with a carbureted 350 in my car and want my car for mainly weekend driving and maybe dragging for fun. Should I be looking at a 3.73 or what? Im not concerned about gas mileage

alpine247

i have 2.77 and i love it

still can break traction at 25mphbone stock

vasquezmrysvll

iTrader: (5)

2.77 or 2.73?

alpine247

2.77 but isnt the 2.73 basically same thing or its more then i think

naf

iTrader: (7)

2.77 is a nine-bolt ratio, 2.73 for ten-bolt. Only thing I lost swapping from 2.73 to 3.27 was the downshift to second at highway speeds, which was kinda fun now and again.

JamesC

iTrader: (5)

Basically the same.

JamesC

alpine247

but wouldn't a lower gear like 2.77 be best for a tpi since it losses the top end.so why install 3.27 or higher if u have a tpi u take off like m-fer but after that u out of the power band right?

Air_Adam

The problem with a really tall (low numerically) gear is that at low vehicle speeds, the engine has to work much harder to accelerate. On the highway its not really a problem, but around town it can be.

Think about it like this... get on your pedal bike and start moving from a stop in top gear - its pretty hard isn't it? Now start from a stop in 1st gear - cake. Once you are moving, you won't notice it as much, especially if you are already up to speed. The same thing applies with your car.

allgood

i have a 92 ta vert stock 305 with 2.73 gears, i plan on adding so hp power just wondering should i change my gears, if so to what
i want my car to have little more power but it want see the track, just 4 cruising and a little rubber burning not much.

Air_Adam

If you want to upgrade the gear just to make for some entertainment on the street, a 3.42 or 3.73 gear would be a good way to go. Should give a pretty noticeable performance boost without killing your mileage around town or on the highway.

allgood

[quote=Air_Adam;3656068]If you want to upgrade the gear just to make for some entertainment on the street, a 3.42 or 3.73 gear would be a good way to go. Should give a pretty noticeable performance boost without killing your mileage around town or on the highway.[/quo

i am new to this so what would be the best way to go. i want disc brakes too, i have rear drums now.
also what the diff. between 3.42 and 3.73
also my car is an auto if that makes a diff.

1montess

Different car, but my 85 ss monte carlo has a 3.73. It'll SMOKE the tires 50-60 feet just stomping the accelerator from a standstill, but it's wound out at 85mph..That's it...it's done...numerically higher gears are great for tire smoke, but don't expect to fly down the highway!

allgood

what would be good for the highway and street

vipershark11

iTrader: (6)

3.23's or 3.42's are mid gears which are a little bit of both worlds.

2fast4u92z

Sounds like you need a T56 with 3.32! 70mph 1800rpm.<---funny cuz my car runs at 1500rpm(due to the injectors and line press.)

Uglybronco

iTrader: (2)

Wow, you must have a 3500RPM rev limit or something. Time for some upgrades.

allgood

ok i have 2:73 with rear drums limit slip (so are all 2.73'S 10 bolt)

so i want to change to disc and may be 3.23's or 3.42's

and what are the 3.23's and 3.42's (9 bolt,10 bolt)

whats the diff from 9 or 10 bolt

Pat Hall

iTrader: (31)

Just wanted to add something else to Reid's statement since nobody's bothered to point it out yet. Your clutch will have an extremely short life if you keep 2.73's in there with a manual trans. 3.08's should be the starting point with a manual trans, and even those are marginal. I ran a 2.56 geared 10 bolt in my 69 Camaro with a 4 speed manual for about a month while I was getting 3.73's installed in a 12 bolt rear. I smoked the clutch disc in that short period of time and had to replace the clutch when I put the 3.73 rear in. Man, looks like Allgood majorly highjacked your thread.

JamesC

iTrader: (5)

Those ratios are 10-bolt. The 9-bolt is a bit stronger.

JamesC

jean

2.73 is the best ONLY if you have a big block with big power , I knew a 67 camaro with a mighty 573ci ,650hp , running low 10 with a 2.73... .

allgood

so if i have a stock rear with 2.73 gears would that be a 10 bolt and if so does it make a diff if i have a 10 bolt and change to a 9 bolt

Air_Adam

The difference between 3.42 and 3.73 is ONE tooth on the pinion gear... both have 41 teeth on the ring gear, the 3.42 has 12 teeth on the pinion, the 3.73 has 11. Its roughly a 10% difference in gear ratio, which is basically nothing. Its really up to you which one you go with - there probably won't be any significant difference between the two. The 3.73 will give you SLIGHTLY better performance than the 3.42, and the 3.42 SLIGHTLY better economy than the 3.73 - more than likely so slight you wouldn't really even notice the difference.

allgood

thanks so 3.42 and 3.73 10 or 9 bolt

Air_Adam

If you have a 10-bolt axle, the ratios are 3.42 and 3.73

If you have a 9-bolt axle, the ratios are 3.45 and 3.70

Which one do you have? If you don't know for sure, take a picture and post it, we'll tell you.

JamesC

iTrader: (5)

Or simply scoot your hindquarters under the car and count the diff cover bolts.

JamesC

allgood

i have a stock 92 ta vert 2.73's gears

VenomX-87

I have 3.73's, stock 305, stage 2 shift kited 700R4 trans and stock 215/65R15 tyres and it is anoying at times because anything over 1/4 throttle off the lights and I smoke the tyres and turning a corner with it changing from 1st to 2nd is impossible in wet weather without losing traction no matter how slow you are going.

89irocTPI

iTrader: (1)

if it hasnt been replaced you have a 10 bolt keep it 9 bolts suck for aftermarket parts.
----------
i have the same exact problem except 3.27 gears and a 350

VenomX-87

yeah 70/80% of the time its good (and FUN!) but that 30/20% where you are trying to drive carefully like if you have someone in the car or you have a cop up youre a$$ the 3.73 rear+shiftkit is very anoying. When i get my ZZ383 im getting a TH400 and ford 9" with 3.25's, I'd like to keep the 700R4's 4th gear but i don't think it would take the ZZ383's 449 lb.-ft. of torque.

allgood

May be i need to just keep what i got, so if i add some power would it be cool with i have now, i also want to upgrade to rear disc

Pat Hall

iTrader: (31)

Trust me dude, you should at least go with 3.23's. Like the one guy said, 2.73's worked great in a big block car with gobs of torque and probably close to 500 HP. With the power levels most of our 3rd gens are at, 2.73's just don't cut it for any kind of "performance" application. 2.73's would also be great for a Bonneville Salt Flats car pushing over 1000 HP, and they're trying to set a land speed record, but here in the real world of street perfomance type cars, forget it. My car breaks traction in the wet weather with 3.23's occasionally, but you couldn't pay me to put 2.73's back under it! Most street races are over by the time you reach 90-100 mph, and you'll get to those speeds a lot quicker with 3 series gears.

allgood

so 3.23's are what 9, 10 12 bolt ? aslo what did you do for your swap

naf

iTrader: (7)

IMO, with a 700R4 I wouldn't go above 3.42 and 3.23 would be ideal.

Before buying a new ring/pinion set up to change gears, I'd check the local JY's for a rear end that already has the ratio you want. You'll find that a lot of the six cylinder cars have the better ratios, and they haven't been beat on as much. Limited slip is pretty much irrelevant in a 20+ year old rear end anyway. The LSD will be worn out and parts aren't available to rebuild them. Round here a plain jane rear can be had for less than $200. Look for a later one with 28 spline axles, weld the tubes and add an aftermarket posi carrier when you get the $.

allgood

so how wil i know what to look for, what years aslo i want rear disc too

naf

iTrader: (7)

You can use the tech data on this site to narrow your search, but I would NEVER buy a used rear end without opening the cover and checking. Ring count is stamped on the ring gear in teeth ratio. 41:15 = 41/15 = 2.7333333, etc.

Rear discs may be a tougher find, especially in the later, PBR years which roughly coincide with the later 28 spline axles. A fourth gen rear from a 95/95 up(?) V6 will normally have the good ratio with rear discs but it will be slightly wider than a third gen rear.

mcgarnicle

iTrader: (14)

The best rear for the dollar is a 98-02 LS1 rear end 12 inch rotors, huge single piston caliper, and out of a M6 car you'll find 3.42's with a torsen diff.
As long as you're not putting huge power on the ground and running slicks it is fine.

Lucid

iTrader: (4)

I have 2.73 gears in my 86 and 3.23 gears in my 87 (both tpi & both autos)

The 2.73 gears really dont get going in my car until i hit about 80mph and then the car really takes off. They are good for off the line grunt and torque but you really have to be on the highway to enjoy them. They are good for fuel economy and high speeds and are plenty strong. Cruising at 70mph is right at 2000 RPM.

The 3.23 gears are better for acceleration, they have a noticeable difference in just the seat of your pants performance. IMO, they are the best for all around performance, they will accelerate pretty good and you can still cruise in overdrive at 70mph around about 2250-2500 RPM.

If you are going with a stockish engine with the 5 speed you might want to consider going to a numerically higher gear ratio, like 3.23. You are missing the torque converter and the torque multiplication that it provides and you can try to make up for it by spinning faster.

IROCmonkey

Not to highjack the thread even further but get more tire: more tire=better traction. Also, beef up your rear suspension.

When I got my IROC the tires on it were slap wore out (gee I wonder why?) so I took the brand new set of tires (stock Z28 15x7, w/stock size rubber) off my wrecked SC and threw em on the car...cooked em in less than 5k miles. After that I put the 16x8 IROC rims back on with the right tire... and tweaked the rear suspension. Now it only breaks loose when I want it too

Back on topic.....what is wrong with 2.73's? Nothing if you are lookin for a DD. If you want to get out of the hole and launch, get a better gear.

If you are done at 85mph with a 3.73, you got problems beyond your rear gear. I have 3.42 in the IROC and it squats and launches when rolling at 85...say hello to triple digits

allgood

4th gen rear so that means i couldn't put stock wheels back on it right.
irocmonkey what is DD?

avro206

I doubt that...5 speeds are 2.95

In any case...2.73s are not THAT bad. That number by itself means nothing...you have to take in account the transmissions gear ratios. You don't have some TH-350 (2.52 1st)---then 2.73s would REALLY suck!

Great thing about the 700R4--you can throw some steep gears in the rear but that o/d will help keep the revs low when on the highway.

allgood

I like the way my car pulls on the highway so should i keep the 2.73s or what could be a good step up but do not have much change on the highway

Air_Adam

I've seen worse... I know of a '74 Camaro with a close ratio Muncie (2.20 first gear) and 2.56 geared 8.5"

Never driven it, but the poor basterd must have to slip the clutch untill he hits 40!

IROCmonkey

Right you would need spacers for the wheels.

DD=Daily Driver.

If you go to a 3.23 or 3.42 gear you will see better use of torque, i.e. harder acceleration. you'll also reach the end of your power band a little quicker, slightly higher RPM's at any given speed and see a slight drop in mileage.

If you are happy with the way your car currently accelerates and drives around, and its comfortable, keep the 2.73. Your rear with the 2.73 is no more or less durable than any other stock 10 bolt.

Also, keep in mind that swapping a ring and pinion or differential carrier into an existing rear is not a beginners job, expert help is a good idea, otherwise errors made will cause component failure rather quickly.

black89ws6

700R4/2.73's in an LG4 or an L03, really sucks. These engines are to lacking in torque, and lower (higher #) gears help to make up for that.

700R4/2.73's in a TPI suck less, but still kinda suck. The extra torque of the TPI motor doesn't need a lower gear as much as the other motors.

700R4/3.23's with a TPI are much more fun to drive, will get a little hard on tires if you are not careful. When I swapped mine, I quite enjoyed it. My city mileage actually improved, maybe .5 or so, but highway mileage dropped about 2 mpg.

Yes, I know it was an old post... I just felt like adding to it anyway.