sharkthehunter77

Talked to some guys in the club last night at a classic/hot rod drive in aboutmods and things. Asked me to pay attention to the rpm's at around 60mpr to get an idea of my rearend gears. So i did and at sixty shes near 2700 rpm, at a hair under 3500 shes at 70+ and she wants to accelerate ( i guess typical V8 torque at work?). Anything over 3700rpm will get me arrested and the car impounded. I assume many of you know what i'm talking about, so what are my ratios, any guesses?

Chris69

Hmm, sounds like my numbers when I had the TH350 with 3.54 gears.

Bullyj

:iagree:

LiveandLetDrive

'77 TH350, stock rearend 3500 exactly has me a little over 80. 3000 is round about 70....

tippi58

Ive just done my strut rods and had the whole sheebang out on my 77. Its the same revs as yours at 60mph. I cleaned up the diff and checeked the numbers.:smash:

You (and I) have both got the 3.08 gears.:chevy:

If u want to be 100% sure the number is stamped on the bottom of the diff next to the strut rod bracket. OA is 3.08 and OD is 3.36

:cool: :cool: :cool:

sharkthehunter77

thanx for the verification, Now the question is...R these good gears for performance. I mean they sure seem good, i think she jumps off the line just fine and pushes very strong, but whats the consesus of the mighty forum?

Smokehouse69

3.54 is a good compromise rear end ratio, nice acceleration off the line and fairly low rpms cruising at 60. An overdrive tranny would make it perfect for high speed cruising, and even better pull of the line.

SCVetteGuy

My 1980 automatic has a 1980 camaro z-28 motor in it. Basically, just like the L-48 as far as i know. I did 65 mph the other day and was at about 4000 rpms. I'd really like to be able to drive my car down the interstate at 70 and not need to worry. Do you guys know what my rear would be, and what would be good to put it at?

I would also like to have good off the line acceleration.


[Modified by SCVetteGuy, 2:37 AM 12/16/2002]

Schmucker

I believe you have 3.55s. Sounds about right for me and I'm pretty confident I have 3.55s. Damn thing tops out at only 125mph, so it must be :D

gdh

With my 4 sp. 60 mph @ 2450 rpm with 3.55 rear end.


[Modified by gdh, 9:39 PM 12/15/2002]

SCVetteGuy

I'd be suprised if mine went that fast, I figure it might die before then. :sad:

redwingvette

I have the 3.55 gear and tubo400. 70mph at 3200rpm. 65mph at 2800

sharkthehunter77

So, 3.08 or 3.55? I should mention i have a three speed automatic. Does thast clear things up?

'79ProwlerOrange

i think you have 3.55s thats about how mine used to act. check the # on the rear diff, and post it. im sure there are some human catalogs that know exaclty what the ratio is based off that. :cheers:

Tomi72

I have exactly the same revs and speeds in my -72 and my rearend is 3.36:1. There's a code on the rearend that should tell you what's inside but I couldn't find it so I jacked up the rear, turned the tires one revolution and counted how meny revs the driveshaft made...

rgds Tomi

LABulldog

I have similar RPM's in my auto '80. My Haynes manual says that the 4 speed had 3.08 gears and 3.55 for the auto. Hope this helps some! :yesnod:

QuickVet

355s :yesnod:

GrandSportC3

:iagree:

bohaslup

try this to determine gear ratio- Ideal gear ration =(cruise rpm x tire diameter)/(336 x cruise speed)

LiveandLetDrive

Here's my calculations....

.............(RPM) * (2piR) * (60 min/hr)
Ratio = --------------------------------
................(Speed) * (63360 in/mi)

where R is tire radius and speed is mi/hr

setting RPM at 3500 and tire radius at 12 inches, you can just say

Ratio = 250/Speed

for my numbers (about 81mph at 3500) Ratio = 3.08

for your '70+' at 3500, you get 3.57 which is pretty darn close to 3.55.

This all assumes you're in top gear of course (1:1 at the trans)


[Modified by RUXperienced, 2:08 PM 12/16/2002]