Different Gear?

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Taking the Mrs out tonight. I’ll take the cover off in the morning and solve the gear mystery!
 
Jesus, everyone is whining about that stock converter!!
And how am I drive the car 165 miles to Carlisle with 391s? She’ll be screamin’
 
Jesus, everyone is whining about that stock converter!!
And how am I drive the car 165 miles to Carlisle with 391s? She’ll be screamin’
Well, the higher the gear ratio the more you can get away with the stock converter.
With 3.55’s you will want more stall.
 
Yea D/D 3.55's - You say it goes like hell, so I bet it's not a 2.45. If your going to cruise long distances, consider a 3.21-3.23
 
Yeah. I’ve avoided opening it long enough. I’ll report tomorrow
 
You don't have to look inside.
You can just jack up one wheel, index both the Driveshaft and the tire, then rotate the tire one time and count the driveshaft revolutions. On an open diff, divide the driveshaft turns by two.
Oh yeah, lol, the trans has to be in neutral.
 
You don't have to look inside.
You can just jack up one wheel, index both the Driveshaft and the tire, then rotate the tire one time and count the driveshaft revolutions. On an open diff, divide the driveshaft turns by two.
Oh yeah, lol, the trans has to be in neutral.
I didn’t think you could do that with an open diff...
 
If you say it runs strong, you probably have 2.94:1, but it depends on "how strong". 3.21 or similar with a good converter is probably the most you'll be able to stand on a long trip. I'm an around town kind of guy with short highway blasts kind of guy, I love me some 3.90-4.56 gears...
 
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I swapped to a 8 3/4 from a 67 gtx, i was trying to find a jeep with a 3.55 but no luck.
You can swap out the carrier to the better one.
 
Ok
With 1 rotation of the tire, the driveshaft rotates 1-3/8 times.
 
Jesus, everyone is whining about that stock converter!!

And so will you if you don't change it, lol.

The gear change will for sure make a big difference, a proper converter will put it over the top. Do the gear change and drive it, you'll see for yourself. It will still lack a lot from a standstill. Once you get up into the powerband it will come alive. A converter swap will make it come alive from a standstill.

I swapped from 2:76's to 3:55's and it did indeed make a huge difference, I have yet to replace the converter, but I'm wanting to.
 
I’m going to the paint store before they close then I’m going to read the whole 8-1/4 thread.
 
I'm going out to see what my 2.76 set does here, I will get right back to you.
My results came with one wheel off the floor and of course trans in neutral.
So I’m thinking you multiply the drive shaft revolutions not divide with open diff.
The car goes about 65 at 2100 rpm with a 245/60/15 tire
 
Sounds like 2.76 gear ratio?
You would think. Looking to gather parts for suregrip and better gears. Never have had cover off and the car tucked in until the glass guy shows up to replace the front glass. I know it’s not a big deal to open it and drain it, but I’m getting pulled in 5 different directions today.
 
Yep! Correct you are on your formulation, my 2.76 in the 7-1/4 goes just a little past 1-1/4 turns. I think 8-1/4s were 2.71 or 2.73 ratio, so you should have the carrier type and pinion location that allows you to go up to the 3.21 gear set, or deeper gears, if you like. I put one of those out 8-1/4s with 3.21 gears out of a 73 340 duster into my first /6 duster and made a set of superstock springs by the specs in mopar chassis book out of the two sets of springs, it was night and day between the 2.76 gears. I recommend the 3.21 and converter if you are going to put A/C back in it.
 
If you say it runs strong, you probably have 2.94:1, but it depends on "how strong". 3.21 or similar with a good converter is probably the most you'll be able to stand on a long trip. I'm an around town kind of guy with short highway blasts kind of guy, I love me some 3.90-4.56 gears...
I thought it was divide by two as well as AJ stated, but it is multiply by two, I realized this after checking and then remembered how fast a tire in the slick gets going in the "one wheel peel", drive ratio drops in half. My bad!
 
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