88 irocz 350 5-spd

what is the difference between a 2-series carrier & 3-series carrier in a 9 bolt rear end?
&
if i have a 2.77 ratio in my 9 bolt right now (stock) could i fit a 3.70 ratio in it or not?

89Vert

I don't think they make a 3.70 replacement for a 2.77
you need a 3.27 and up carrier I belive

3.70 is a bad gear for stock TPI

88 irocz 350 5-spd

but what is the difference between the 2?
and why would 3.70 be a bad gear

89Vert

motor is not capable of high enough rpm,

steep gears need a high reving motor, be better off with a 3.27 or 3.45,
to take advantage of the TPI power band

sparafucile17

By high reving, do you mean that it must run at higher RPM's to be useful? Or are you saying that the power band of the motor must be located at higher RPMs? (Say 3000+ )

I was thinking of doing the same 3.73 ratio with the stock 7.5" 10-bolt, so I'm also curious about gear selections.

Jeff

elementaltoad

well im not sure 3.73 gears would be bad in a TPI...it would kill your top speed and gas mileage but if you want absolute neck breaking aceleration i guess thats your best bet... Im not sure what my 1989 formula has but it will spin the tires off at about 20-30mph and out accelerate a 2002 z28 - stock, but my top speed may be like 130mph.

87DJP2001

9-bolt gears available:

2 series carrier- 3:08 & 2:77 Ratios
3 series carrier-3:27,3:45 & 3:70 ***3:73 avaible
With your present rear you are SOL and your only recourse is to find a 9-bolt 3-series carrier if you want to change gear ratios.
My opinion: unless you have a highly moded car forget about changing the gears. My opinion is it a fad now and the expense for parts, labor and failed setups is not worth it.

88 irocz 350 5-spd

if i do find another 9-bolt somewhere, how would i be able to tell the difference between a 2 and 3 carrier?

RussStang

If you can outaccelerate an 02 z28, your car has a lot more done to it than a gear swap.

89Vert

you aren't using your power band,
for a gear like that you should have a high reving motor,
I'm sure it would feel fast,
but get it in the 1/4 mile, and it might even make your car slower,
I run better with 3.08s then I do with 3.45's cause 3rd is such a good gear in my car with 3.08's, 3rd is to short with 3.45's and 4th is a big jump even with 3.45,

witha 700r4 your first and second are already so low a 3.73 makes the gears too low and basicly makes first useless

RussStang

89Vert is right. That could very well be too much gear for a stock TPI motor.

88 irocz 350 5-spd

then what would be the best gear i could get if i were to get my hands of a 3 series carrier, i just have a stock for now l98 with a 5 spd. also what would be the best gear for now but also maybe in the future if i decide to go with a 383 stroker?

Zepher

not really. I can out accelerate most LS1's out of the hole, but they catch up and pass me very quickly.

RussStang

Then they aren't very good at racing, or they are launching off of idle.

89Vert

my bro's vert has a 350 5 speed, it was running a low 14 at 105mph bone stock with a 3.27 rear before we yanked the motor