How much of a difference - NJFBOA - Home of New Jersey's Camaros and Firebirds

jin1481 · 10-10-2007, 04:45 PM

How much of a difference am i going to notice with a Eaton Posi and 3.73 rears running in a stock 10 bolt with my current mods?

Its going to be going into the 94.

edpontiac91 · 10-10-2007, 05:09 PM

Quote:

Originally Posted by jin1481

How much of a difference am i going to notice with a Eaton Posi and 3.73 rears running in a stock 10 bolt with my current mods?

Its going to be going into the 94.

If you have the stock gears (2:73?) it will give you a nice boost of the line around town. If you have the 3:23 rear, then I would stick to that ratio. The problem with lower gears, is that if you increase the power to the rear tires, at some point you will lose traction if you don't have the proper(drag radials) tires or suspension parts.

WildBillyT · 10-10-2007, 05:15 PM

Quote:

Originally Posted by edpontiac91

If you have the stock gears (2:73?) it will give you a nice boost of the line around town. If you have the 3:23 rear, then I would stick to that ratio. The problem with lower gears, is that if you increase the power to the rear tires, at some point you will lose traction if you don't have the proper(drag radials) tires or suspension parts.

I agree.

Personally, I woudn't bother with an Eaton posi in a stock rear.

Tru2Chevy · 10-10-2007, 05:59 PM

What rear (gears and differential) are in the car now? Are you planning on building up the rear (cover w/brace, welded tubes, etc)?

- Justin

jin1481 · 10-10-2007, 05:59 PM

ok, i have the 2.73 rear

Tru2Chevy · 10-10-2007, 06:35 PM

Quote:

Originally Posted by jin1481

ok, i have the 2.73 rear

Does the stock posi work ok? If so, I would just swap the gears, unless you are planning on building up the rest of the rear.

Even if you do all that, the gears themselves are the weak point.

- Justin

JSPERFORMANCE · 10-10-2007, 09:03 PM

in short, since you have 2.73s you will notice a HUGE difference.

Mike · 10-10-2007, 10:36 PM

wouldnt he need a new posi with a 3 series carrier??????

Tru2Chevy · 10-10-2007, 11:34 PM

Quote:

Originally Posted by cbrrmike

wouldnt he need a new posi with a 3 series carrier??????

No, you can buy 3.73s for a 2 series carrier. Actually, they may even be thicker than "normal" 3.73s, which could add to the strength of the ring gear.

- Justin

Syzygy · 10-11-2007, 02:33 AM

huge difference

jin1481 · 10-12-2007, 10:01 AM

What a 2 series carrier or 3 series carrier?

so could i just get the gears now and then switch them into an eaton posi unit if i ever do get one?

I want to eventually build the car to the 400+ range, not planning on racing everyweekend but occasionaly, would i need to build up a rear and get an eaton then?

IROCdan330 · 10-13-2007, 08:23 PM

Quote:

Originally Posted by jin1481

What a 2 series carrier or 3 series carrier?

so could i just get the gears now and then switch them into an eaton posi unit if i ever do get one?

I want to eventually build the car to the 400+ range, not planning on racing everyweekend but occasionaly, would i need to build up a rear and get an eaton then?

if when you plan to race you plan to use a sticky tire with a setup suspension, you may want to look into beefing up the rear.

Blacdout96 · 12-08-2007, 09:22 PM

Quote:

Originally Posted by jin1481

What a 2 series carrier or 3 series carrier?

A 3 series is gears that are 3:23, 3:42, 3:73. 2 series are like 2:73 and 2:56, the only ratio that is not a 3 series but does start with a 3 is 3:08, they are 2 series, and 4 series is like 4:10, and 4:56. 2 series gears are thicker, and using 3 series gears on it would require a spacer since 3 series are thinner.

Tru2Chevy · 12-08-2007, 11:11 PM

Quote:

Originally Posted by Blacdout96

A 3 series is gears that are 3:23, 3:42, 3:73. 2 series are like 2:73 and 2:56, the only ratio that is not a 3 series but does start with a 3 is 3:08, they are 2 series, and 4 series is like 4:10, and 4:56. 2 series gears are thicker, and using 3 series gears on it would require a spacer since 3 series are thinner.

There are only 2 and 3 series carriers, no 4. 2 Series are 3.08 and below (numerically), 3 series are 3.23 and above (numerically).

You can (as I stated above) buy 3.73s (or most other gearsets that would normally be for a 3 series carrier) that are designed for a 2 series carrier. No spacer needed.

- Justin

maroman88 · 12-11-2007, 02:27 AM

my 88 has an eaton 373 posi rear and i had a 92 rs with the stock 273 non posi, same motors and exact setup and wat a huuuge differance

Fast92RS · 12-11-2007, 08:51 AM

I went from a 2:73 open rear to a 3:23 posi rear and it was a considerable difference.

NightRydaSS · 12-11-2007, 09:27 AM

How about 3.42 to 3.73; how much of a difference would that make??? I reallllly DON'T want 4.10's, i don't want to peg 3K RPM's @ 80mph. lol

btw, i have an M6

WildBillyT · 12-11-2007, 10:45 AM

Quote:

Originally Posted by NightRydaSS

How about 3.42 to 3.73; how much of a difference would that make??? I reallllly DON'T want 4.10's, i don't want to peg 3K RPM's @ 80mph. lol

btw, i have an M6

The rule of thumb (for better or for worse) is that 4.10s are no problem for a six speed transmission. You have a .5 to one top gear (if your car is a 94+). 3.42 to 3.73 would be a waste in my opinion.

NightRydaSS · 12-11-2007, 10:52 AM

well it's an '01 SS so it came w/ 3.42's. You're sayin that 3.73's would hardly make a noticible difference?

Pampered-Z · 12-11-2007, 11:05 AM

With my old heads/cam engine I went from 3:23 to 3:42 and picked up .3 then went 3:73 and didn't pick up any ET because I was spinning so badly but was then trapping in 4th gear and did pick up 2 MPH. The car certainly felt allot stronger on the 1-2 + 2-3 shifts.

If the car is a daily driver and you just want to pick up a bit then 3:42s are a night fit. We did a GM 847 cam, 3800 stall and 3:42s and the car cruises nicely and pulls REAL hard

3:73s do effect a DD, but again it is personal choice as to what you like in your car.

As far as the posi itself. Any one is fine up to a point of maybe 325-350 HP, after that you're gonna break it! When I put the blower motor in @ 480 RWHP I burned up a stock posi, then split a eaton on the 1-2 shift, I'm now trying an Auburn pro until I get my Dana 60. This was with Nitto DRs and soft launches, not slicks or 4K dumps! Point here, don't buy the Eaton if your long term plan is over 400HP, it's not going to last.

NightRydaSS · 12-11-2007, 11:35 AM

it is my weekend fun toy, no longer my DD. The thing is i just want a little more accel, but i don't want an all out drag car. I also don't want to be cruzin on 295 or the AC Expwy at 3K Rpm's or have lots of wear-n-tear on the motor.

my future plans for the car are either a ZL402 crate engine from SLP, or I'll rebuild my current motor and install a Procharger on it. That is down the line (way down) and I'm looking for somthing now.

Pampered-Z · 12-11-2007, 03:21 PM

Then I was say go with the 3:73s.

NightRydaSS · 12-11-2007, 03:43 PM

Quote:

Originally Posted by Pampered-Z

Then I was say go with the 3:73s.

W/ Eaton POSI?? I heard the Auburn ones aren't that good and they can't be rebuilt.

90FormulaWS6 · 12-11-2007, 05:28 PM

the choice is up to you, if you stick with your stock posi and burn it out then you are stuck having to purchase another 2 series posi, but if you upgrade your unit to a series 3 with series 3 gears, then you have more options if that unit were to go.

Tru2Chevy · 12-11-2007, 06:50 PM

Quote:

Originally Posted by 90FormulaWS6

the choice is up to you, if you stick with your stock posi and burn it out then you are stuck having to purchase another 2 series posi, but if you upgrade your unit to a series 3 with series 3 gears, then you have more options if that unit were to go.

No, the OP has a 2.73 posi rear (2 series), NightRyda has a stock 3.42 posi (3 series). There are two people asking for gear recomendations in this thread.

As for my recomendations it would be 3.73s for the OP, and 4.10s for NightRyda

NightRyda - with 4.10s and an M6 80 mph in 6th gear is only ~2150 RPM.

- Justin