G3 rpm/gear ratio

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1973Barracuda

1973Barracuda

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those that have done the swap, what ratio are you running? I have read different things as far as the rpm the g3 will be happy cruising at.

I am ready to pull the trigger on a rear end, but want to buy once(hopefully).

I thought I wanted a 3.55 or 3.23 to keep highway rpms down, but read it may be unhappy there.

Thoughts?

6.1
46rh
27 inch tire
 
1973Barracuda said:
those that have done the swap, what ratio are you running? I have read different things as far as the rpm the g3 will be happy cruising at.

I am ready to pull the trigger on a rear end, but want to buy once(hopefully).

I thought I wanted a 3.55 or 3.23 to keep highway rpms down, but read it may be unhappy there.

Thoughts?

6.1
46rh
27 inch tire
Click to expand...

What tranny OD ratio are you running?

My 6.1 SRT8HEMI manual tranny has a 0.70 OD with 3.91 gears. In hindsight, a 3.55 gear would have been better for me - but depends on what you want to use the car for. You can calculate RPM with different setups using this: HyperMart

Jim
 
.69 overdrive.

I have figured the rpm thing, what I don’t know is where the engine is happiest.

1800 at cruise on the highway sounds great until you find out it is a dog there.
 
1973Barracuda said:
.69 overdrive.

I have figured the rpm thing, what I don’t know is where the engine is happiest.

1800 at cruise on the highway sounds great until you find out it is a dog there.
Click to expand...

The 6.1 is no dead dog!!!! The torque curve is very flat - especially at lower rpm.. eg
300 ft-lbs @1200 rpm
325 ft-lbs @1600 rpm
340 ft-lbs @2000 rpm
350 ft-lbs @2400 rpm
 
1973Barracuda said:
those that have done the swap, what ratio are you running? I have read different things as far as the rpm the g3 will be happy cruising at.

I am ready to pull the trigger on a rear end, but want to buy once(hopefully).

I thought I wanted a 3.55 or 3.23 to keep highway rpms down, but read it may be unhappy there.

Thoughts?

6.1
46rh
27 inch tire
Click to expand...
I'm running 3.89 with NAG1.
 
I have a 0.63 6th, 3.91 and 28.4” rear tires. I have no problems with highway crusing torque. If I started from scratch, 3.7x in the axle would be a hair better for me.
 
Goody, you must cruise at really low rpms.

With 3.55 I think I was looking at 1800 at 80mph I think.
 
1973Barracuda said:
Goody, you must cruise at really low rpms.

With 3.55 I think I was looking at 1800 at 80mph I think.
Click to expand...

at 65mph I am about at 1,900rpm, 2,300rpm at 80...

If you had 3.55s, 0.69 OD and turned 1,800rpm at 80mph, you would have to have a 36" tall tire...the correct calculation is 2,368rpm using the 27" tall tire you reference earlier.
 
Last edited:
GoodysGotaCuda said:
at 65mph I am about at 1,900rpm, 2,300rpm at 80...

If you had 3.55s, 0.69 OD and turned 1,800rpm at 80mph, you would have to have a 36" tall tire...the correct calculation is 2,368rpm using the 27" tall tire you reference earlier.
Click to expand...

Ran the numbers again. You are correct.
 
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