Gear ratio advice

Posted By: galen

Gear ratio advice - 03/11/11 07:27 PM

In the belvedere. 500" 4L80 with 0.75 overdrive. 3800stall. I currently am runnong a 9" ford, 4.30 gears and a spool. I am going to build another third member with a posi unit for cruise night stuff. The spool eats up tires. Do not want to sacrifice all of my accelleration but with the torque it blows the tires off anyway. Tires are MT drag radials on 12" rims. 325/50/15s. 28" tall. I am thinking a 3.91, What would you guys suggest?

Posted By: crlush

Re: Gear ratio advice - 03/11/11 07:50 PM

My valiant cruises pretty good down the highway with no overdrive,391 and 28 inch tires.

Posted By: Pacnorthcuda

Re: Gear ratio advice - 03/11/11 07:54 PM

.87 x 3.91 = 3.40..... 3.40 seems like a REALLY nice cruising gear ratio to me (I have 3.55 w/28" tires)

Posted By: DaytonaTurbo

Re: Gear ratio advice - 03/11/11 08:34 PM

.87? I thought 4th in that trans was more like .75?

Posted By: 446acuda

Re: Gear ratio advice - 03/11/11 10:37 PM

Quote:

In the belvedere. 500" 4L80 with .087 overdrive. 3800stall. I currently am runnong a 9" ford, 4.30 gears and a spool. I am going to build another third member with a posi unit for cruise night stuff. The spool eats up tires. Do not want to sacrifice all of my accelleration but with the torque it blows the tires off anyway. Tires are MT drag radials on 12" rims. 325/50/15s. 28" tall. I am thinking a 3.91, What would you guys suggest?

I saw in the spool post that you have 40 spline axles. I don't think there is any posi or locker for 40 spline axle so you are stuck with a spool unless you drop down to 35 spline axle to use a detroit locker.

Posted By: StealthWedge67

Re: Gear ratio advice - 03/11/11 10:44 PM

I run 3.91's with a 27" tire. Its great around town, but not so much on the highway. Even though you're running 28" tall rubber, If I were going to set one up for JUST street action, I'd go to 3.73's, maybe even 3.55's.

Posted By: Pacnorthcuda

Re: Gear ratio advice - 03/11/11 10:45 PM

Quote:

I run 3.91's with a 27" tire. Its great around town, but not so much on the highway. Even though you're running 28" tall rubber, If I were going to set one up for JUST street action, I'd go to 3.73's, maybe even 3.55's.

He has an overdrive.

Posted By: 68GTS383

Re: Gear ratio advice - 03/11/11 10:50 PM

You may have a problem with that 3800 stall with a 355 or 373 and overdrive.

Posted By: Pacnorthcuda

Re: Gear ratio advice - 03/11/11 10:54 PM

Quote:

You may have a problem with that 3800 stall with a 355 or 373 and overdrive.

VERY good point! Gonna be pretty loose during steady cruise!

Posted By: StealthWedge67

Re: Gear ratio advice - 03/11/11 11:04 PM

Quote:

Quote:

I run 3.91's with a 27" tire. Its great around town, but not so much on the highway. Even though you're running 28" tall rubber, If I were going to set one up for JUST street action, I'd go to 3.73's, maybe even 3.55's.

He has an overdrive.

Oh, I see..... Never Mind!

Posted By: galen

Re: Gear ratio advice - 03/12/11 12:37 AM

Quote:

.87? I thought 4th in that trans was more like .75?

Daytona you are right, I changed my post. I had it wrote down wrong. Gear ratio is 2.48, 1.48, 1.00, 0.75. Not sure why I was thinking .87, brain malfunction I guess. I use Compushift and I can program the shift speed and when I bring in the overdrive. I also have a set of 35 spline axles as well as the 40s. Going to keep the 40s and pro gears and spool as a unit in case I want to put it back in. Most of my driving is in town and the overdrive is only used when I hit the highway. Thanks for your input guys.

Posted By: ProStDodge

Re: Gear ratio advice - 03/12/11 03:03 AM

Galen,

I have a set of 3.55's with a 35-spline detroit locker you could try for awhile to see if that would be a good set for your usage before you spend money on something you don't need.

My car is far from completion at this point, so I could be without then for a time.

Scott

Posted By: galen

Re: Gear ratio advice - 03/12/11 04:27 AM

Quote:

Galen,

I have a set of 3.55's with a 35-spline detroit locker you could try for awhile to see if that would be a good set for your usage before you spend money on something you don't need.

My car is far from completion at this point, so I could be without then for a time.

Scott

Thanks for the offer Scott, it will be a little while before I am ready. The engine is still in pieces since fall. On a good note my wife is going away for the weekend. I picked up my heads last week and started filing rings tonight. I get to spend the whole weekend in the shop. Galen

Posted By: 383man

Re: Gear ratio advice - 03/12/11 02:36 PM

I run 4.30's but with a 30" tall tire. I drive it everywhere like this. At 60 mph on the highway I cruise about 3200 rpm and I drive it all the time on the highway. Ron

Posted By: DaytonaTurbo

Re: Gear ratio advice - 03/12/11 10:04 PM

Quote:

Quote:

.87? I thought 4th in that trans was more like .75?

Daytona you are right, I changed my post. I had it wrote down wrong. Gear ratio is 2.48, 1.48, 1.00, 0.75. Not sure why I was thinking .87, brain malfunction I guess. I use Compushift and I can program the shift speed and when I bring in the overdrive. I also have a set of 35 spline axles as well as the 40s. Going to keep the 40s and pro gears and spool as a unit in case I want to put it back in. Most of my driving is in town and the overdrive is only used when I hit the highway. Thanks for your input guys.

Well then a 3.91 would give you a nice highway rpm with that overdrive.

http://vexer.com/automotive-tools/speed-rpm-calculator