jjcuff1

Hello just getting my next project car 88iroc 305TPI auto it is a G80 code posi with 2.77

Want to clean it up paint interior and have fun cruiser. Mod the engine as much as possible on the cheap and it goes or breaks do a swap so nothing crazy other then a tune headers exhaust maybe port polish heads and RR or cam

Hoping to have solid 225-270RWH if it runs good and storng maybe just have fun with nitrous.

All said and done I know the 2.77 suck. I had a 305TBI in past with 5 spd an the 3.73 which was a blast but also became too much gear once I heavily modded the car. always rev out of power band too quick.

So on a good running stock 305 or basic bolt ons. What gears give good red light performance and feel torqey and good for street stabs on a 700r?
and handle light mods

3.23, 3.42, 3.73? I am think 3.42?

big gear head

I'm assuming that because you have a 2.77 gear you have the 9 bolt rear end, which means that you have a 2 series differential. You can't go any farther with that 2 series. You will need a 3 series to use 3.27, 3.45 or 3.70 gears. Might be better to find a 7.5 10 bolt from a '90 to '92 and start with that.

The 10 bolt gear ratios are 2.73, 3.08 3.23, 3.42 and 3.73.

jjcuff1

Yes I think it is a 9bolt. I heard they are very strong, better then the 10 bolts? I went to 9bolt.comm and it look like I can buy a 3 series carrier to get the other ratios?

big gear head

Yes, you can get a 3 series so that you can use the other gear ratios. The 9 bolt is stronger than the 10 bolt. It cost more to build the 9 bolt. If you have the money to build the 9 bolt then it will be a better rear end. Just be ware that all of the 3.70 gears make noise. I think the 3.45 is all right.

Reid Fleming

iTrader: (2)

Not much point in switching to 3.23 or 3.27. If you do change though, go for the 3.42

I've driven 3rd and 4th gens with 2.73, 3.27, 3.42, and 3.73......I didn't like the 2.73 for anything other than 100 mph cruising. The 3.73 gets annoying on the highway (with loud exhaust)

3.42 gives just that little extra pep over the 3.27 without being too much gear.

jjcuff1

Thanks that was my thought as well. 3.42 for street cruising and weekend warrior. Not gas killer or sound but with auto and hi torque (compared to my LO3 days) the 3.42 should be good.

I had a 92 RS 305 TBI that I worked up in 94. Trick flow heads, edlebrock headers, zz4 cam, edelbrock intake manifold, custom prom, and worked TBI, catback and 3.73 with a t-5. Eventally I added a 75hp shot with fuel cuttoff and RPM limits tied to the distributor and WOT gas pedal switch with purge that came out the wiper ports

I was close to 300HP rwh NA and probably 350-360 with NOS. I remember though before cam/head mods the 3.73 was great with the t-5 but once I upped the power and for sure on NOS 1st gear even 2nd was useless especially on the track just redlined to 6000rpm so quick spinning I never got any good launches before I had to shift again.

I think with the TPI and more torque and the auto the 3.42 would be great for 0-60 street staying in the rpm band longer for better pulls. And with mild bolt ons (headers, gear, polish intake, up fuel, cam and tune I hope to have the same amount power as my old TBI setup.

Guest

NEVER GO ANY HIGHER THAN A 3:42 with -ANY- TPI motor.
<----has the setup...(L98)

I have a -non- 350 r-4 trans (my orginal 1 blew 3rd) that shifts at 4500rpm instead of a 350 -r4 that shifts at 5000rpm. I have to let the trans shift itself at 4500 instead of me holding it to 5000, because its dosent fall -all the way- back in to the trq range.

jjcuff1

Yes I understand 3.42 is best for auto thanks