What size gears should I get?

[prayers1 153]

I need to pull the rear to fix a concern and I'm thinking of changing gears. Right now I have 3:55's, my off line starts are struggling with the 351 Cleveland.  I need higher rpms for it to wake up.  I'm also concerned for driving any distance which is why I switched from a Top Loader to an AOD.  Right now I'm at 1850 rpms @ 60 mph.  I have the 9" 28 spline Trac Lok rear.

 

I use 2 different sets of tire on Magnum 500 steel wheels, 275's 28" dia and 295's 26.6 dia.

 

The AOD ratio is this- First: 2.400:1, Second: 1.467:1, Third: 1.00:1, Overdrive: 0.667:1

 

In have a 2600 rpm stall, my cam profile is 541/559, 270/283, 50@ 220/231, lsa 110

 

I'd like to go either 3:89 or 4:11.

 

With a 26" dia tire, I've been told that I'd get 2240 rpm's @ 60 mph with 4:11's. Do you think that's manageable for long distance. I'd like to go to a Good Guys show that's 6 1/2 hours away.

 

What do you all think?

[BuckeyeDemon 211]

I have a tire that's ~26.5" tall, 0.64 overdrive with 4.11's.  on the highway at 65-80 it's really nice.  doing 45-55 it wants to lug a bit in OD.  I wouldn't want any less but would even consider something like a 4.30.

[prayers1 153]

Buckeye what is your rpm's at that speed.

[BuckeyeDemon 211]

low to mid 2's

[prayers1 153]

What are your thoughts about long trips. I know your motor has a lot more in it than mine and I'm also concerned about the motor revving around 2300 for extended times, such as a 6 hour ride.  My build is somewhat middle of the road, not racing, not economical.

 

I have a hydraulic Cam 541/559, 270/283, 50 @ 220/231, lsa 110 that was nitrated, a Mallory Unilte dist w/ the optic module and  a high volume oil pump around 45-60 psi's.  I was concerned about all 3 on a long trip, if it could handle it.

 

How do you feel driving your car that long, of course there would be rest stops.

[BuckeyeDemon 211]

I generally trailer if it's around 1.5 hours or longer, so i'm not the one to get any real advice about long trips in a car like this.   I would have zero issue with a v8 revving 2300 rpm for extended periods. 

 

4.11's with a .65 overdrive would be the same as a car without overdrive that had a 2.67 rear gear. 

 

if someone were to go on a forum and talk about their 2.67 rear end gear and if it was too high on the highway they would probably be laughed at.

[RPM 1,190]

Are you concerned 2300rpm is too low or high? It sure seems like great cruising revs to me.

[barnett468 418]

.

it would help if you clarify what you mainly want it to do . . if you want to drag race but take long trips at 65 mph then i would at least go to 3.89 and possibly 4.11, but it you just want a little better acceleration and want to go 70 mph on trips, i would only go to 3.73.

 

also, if you have not set your timing curve to your engine or have less than 9.0 static compression, you could get a little more power by fixing those things.

 

also, if you have a vacuum secondary carb with the stock secondary spring, you will get more power if you use a lighter spring.

 

http://www.wallaceracing.com/gear-speed.php

 

Using Transmission Gear Ratio: .667 gives these RPM data:

 

..............................3.73 Gear            3.89 Gear           4.11 Gear  

8000 RPM            254.46 MPH        244.00 MPH        230.94 MPH

7500 RPM            238.56 MPH        228.75 MPH        216.50 MPH

7000 RPM            222.65 MPH        213.50 MPH        202.07 MPH

6500 RPM            206.75 MPH        198.25 MPH        187.64 MPH

6000 RPM            190.85 MPH        183.00 MPH        173.20 MPH

5500 RPM            174.94 MPH        167.75 MPH        158.77 MPH

5000 RPM            159.04 MPH        152.50 MPH        144.33 MPH

4500 RPM            143.14 MPH        137.25 MPH        129.90 MPH

4000 RPM            127.23 MPH        122.00 MPH        115.47 MPH

3500 RPM            111.33 MPH        106.75 MPH        101.03 MPH

3000 RPM            95.42 MPH          91.50 MPH          86.60 MPH

2500 RPM            79.52 MPH          76.25 MPH          72.17 MPH

2000 RPM            63.62 MPH          61.00 MPH          57.73 MPH

1500 RPM            47.71 MPH          45.75 MPH          43.30 MPH

1000 RPM            31.81 MPH          30.50 MPH          28.87 MPH

.

[shaun071 62]

If it's any help, in a previous car with 351c, c4 and 3.25 rear, I would do a 600 mile trip at 60-70 mph average speeds at 2800-3000 rpm for 8-10 hours with 2 half hour fuel stops. No ill effects for the car at all.

[prayers1 153]

What I want? I guess the both of 2 worlds a street car and a cruiser. I've never taken a "Muscle Car" out of town for long extended drives, not until last Summer, so this is new to me. Anytime I would go more than an hour, I would take something that I didn't build. So, I always have that doubt that something will break.

 

I have settled on the 4:11's

 

I appreciate everyone's thoughts, thank you.

[RogerC 136]

351C engines are endurance engines by design and are fully capable of running up to 7000 rpm all day long. I'd have no problem cruising 2500-3000 rpm on a long trip. 

[barnett468 418]

 

I have settled on the 4:11's

 

 

buy some spare tires, lol

[1969_Mach1 333]

I don't know, 6 hour drive in a classic Mustang.  I'm more in line with barnett468 and 3.73 or 3.89 ratio at most for extended highway driving.  Maybe after a few hours on the freeway you'll wish the motor was running at a lower RPM as you envision the ring and bearing wear.  Nothing wrong with a trailer like BuckeyeDemon does.

[MOCK 302 10]

I have an AOD and run 4:08  gear and it is great on the hi-way , 1900 rpm at 65 mph on a 245/55 18 tire .

 

Where did that pic of the motor come from ??? It is not mine !!!!

[MikeStang 247]

I clock along at 70 MPH at 2100 RPM's with a 4R70W and a 275/40/18.

I need to buy an aftermarket converter before this stock unit bites the bullet LOL.

[1969vert 55]

if you have the right converter almost any gear will work on take off...I have 3.5 gears in mine with a 4500 stall...works great for my combo..you can have drivability with  highway gears as long as the converter matches..

[Rsmach1 71]

if you have the right converter almost any gear will work on take off...I have 3.5 gears in mine with a 4500 stall...works great for my combo..you can have drivability with highway gears as long as the converter matches..

4500 stall?