opinions on rear-gear ratio for LS swapped 72' Cutlass
03-03-2015, 03:29 PM
#1
Teching In
Thread Starter
Join Date: Feb 2015
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
opinions on rear-gear ratio for LS swapped 72' Cutlass ok guys, working on the motor and about to tear into the 4l60e for my 1972 Cutlass, and am currently deciding on rear gear ratio, so i can tell my guy that is making my harness and flashing my ECU. the car currently has a 10 bolt with 2.73's. the car will end up with 275/60R15's on the rear, a 28" tire. the car will be a daily-driver, and i would like to keep the highway RPM's decently low, while not being a slug around town. im considering 3.08's, 3.23's or 3.42's
what do yall think?
what do yall think?
03-03-2015, 04:54 PM
#3
Teching In
Thread Starter
Join Date: Feb 2015
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
03-03-2015, 05:30 PM
#4
what's the weight of a 72 cutlass ? I'm guessing it would be less than a 4th gen F-bod.
4L60E has a .7 overdrive 4th gear and you haven't mentioned anything about the torque convertor. I assume it'll be an aftermarket with 'lock-up'.
sounds like you gonna be a computer controlled LS motor. 28" tire has a larger rolling diameter than the typical F-bod tire(26"). I think it'll surprise you how good your mpg is gonna be.
Some typical mpgs' with A4 I've gathered from posts.
2.73-26.9
3.08-24.7
3.23-24.5 1800rpm @ 60mph 2200rpm @ 72mph
3.42-24.0
3.73-23.0
4.10-22.2
4.56-21.5 2500rpm @ 60mph 3000rpm @ 72mph
4L60E has a .7 overdrive 4th gear and you haven't mentioned anything about the torque convertor. I assume it'll be an aftermarket with 'lock-up'.
sounds like you gonna be a computer controlled LS motor. 28" tire has a larger rolling diameter than the typical F-bod tire(26"). I think it'll surprise you how good your mpg is gonna be.
Some typical mpgs' with A4 I've gathered from posts.
2.73-26.9
3.08-24.7
3.23-24.5 1800rpm @ 60mph 2200rpm @ 72mph
3.42-24.0
3.73-23.0
4.10-22.2
4.56-21.5 2500rpm @ 60mph 3000rpm @ 72mph
03-03-2015, 08:17 PM
#5
Teching In
Thread Starter
Join Date: Feb 2015
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
Yes, computer controlled, I'm having my ecu flashed and having a custom harness made now. I'm planning on using the stock converter from my 2002 Tahoe donor vehicle, along with the shaved truck intake and throttle body. I'm refreshing the motor, but not doing anything crazy for now. Hoping to find a deal on a LS6 cam, or another decent budget cam. Also refreshing the trans and installing the HD2 shift kit
03-04-2015, 10:28 AM
#6
Teching In
Thread Starter
Join Date: Feb 2015
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
well, ended up ordering a set of 225/70R14 Cobra's and am going to use my original SSII wheels for now, so that is a 26.8" tire. using this calculator, i think i am going to go with a 3.42
http://www.coastdriveline.com/htmlfo...lculator2.html
http://www.coastdriveline.com/htmlfo...lculator2.html
Trending Topics
03-05-2015, 07:59 AM
#9
^^^ 3.73s' would be ideal.
IF I were building that car,
-since it's a framed vehicle and not a unibody type,the basic platform will be adequately rigid.
-the 8.5" GM 10 bolt should be able to handle anything you throw at it. I'd do 4.10s' to make it a 'shocker' on the street.
-a torque convertor of Yank SS3600(or CircleD equivalent) to give 'lock-up' for the freeway to get decent mpg and spin around 2250rpm at 60mph. LS engines like rpm. I ran 4.56s' with A4 for 4 years. That put me at 3000rpm @ 72mph. Even took 4 trips to Florida from Ohio with 4.56s'.
-I think the 72 cutlass had upper and lower control arms for the rearend,change the factory OEM rubber bushings for the new stuff and a set of adjustable rear shocks to be able to change the ride characteristics from comfortable to 'fun' for traction.
IF I were building that car,
-since it's a framed vehicle and not a unibody type,the basic platform will be adequately rigid.
-the 8.5" GM 10 bolt should be able to handle anything you throw at it. I'd do 4.10s' to make it a 'shocker' on the street.
-a torque convertor of Yank SS3600(or CircleD equivalent) to give 'lock-up' for the freeway to get decent mpg and spin around 2250rpm at 60mph. LS engines like rpm. I ran 4.56s' with A4 for 4 years. That put me at 3000rpm @ 72mph. Even took 4 trips to Florida from Ohio with 4.56s'.
-I think the 72 cutlass had upper and lower control arms for the rearend,change the factory OEM rubber bushings for the new stuff and a set of adjustable rear shocks to be able to change the ride characteristics from comfortable to 'fun' for traction.
03-05-2015, 07:15 PM
#10
as for gears the 4l60 has a very low 1st gear like the 700r4 did so you have a wide range of gears that can work - a highway gear will still pull well in 1st and as mentioned if you go with a more aggressive gear the od will keep the rpm's in check at highway speeds.
