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What gears are in my 8.75 rear end???

Mr. Belvedere II

Mr. Belvedere II

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Even though I'm a bona fide, certified *** man, I have paid little attention to what is going on in my girls 8.75 rear end. I'm running the edelbrock rpm top end with the heads and cam and a 750cfm perched atop an air gap intake. All good yeah? But I just read that the cam likes a 3000 stall converter. Meh! I got myself a 2500. :( and I have no clue what gears are spinning in that rear end. Car is peppy and pulls all the way up to around 5000 per, but am I missing out on something with a 2500 stall? Low end torque maybe? A tire squeeling line launch perhaps? And what of my gears? Could they be making for a slushy launch? Little Help here? and another thing!! Pretty sure only my passenger side rear wheel is powered. I do mean one legged burnouts and my passenger side rear tire wears way more than that of the driver side. What's that all about!?
 
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Besides marking the driveshaft and rotating the wheels with the car in the air and counting the revolutions of the wheel to driveshaft....

Remove the center section and change out the old oil with some new Mobil 1
Or Royal Purple or...

While the center section is out, look on the side of the ring gear and pay attention to the numbers stamped on it. The gear ratio will be there.
 
rumblefish360 said:
Besides marking the driveshaft and rotating the wheels with the car in the air and counting the revolutions of the wheel to driveshaft....

Remove the center section and change out the old oil with some new Mobil 1
Or Royal Purple or...

While the center section is out, look on the side of the ring gear and pay attention to the numbers stamped on it. The gear ratio will be there.
Click to expand...
I assume the driveshaft is the higher number and the wheel is the "?:1" yes?
 
Mr. Belvedere II said:
I assume the driveshaft is the higher number and the wheel is the "?:1" yes?
Click to expand...
This method only works IF you have sure grip. Otherwise, You can figger the rear end ratio if you have both tires on the ground, roll it in a straight line one revolution of the tire. count the number of driveshaft turns down to 1/10. Three full turns and just a touch over 2/10 would be 3.23 ratio. three full turns and a touch over 5/10 would be 3.55 ratio..etc............MO
BTW , with both tires off the ground, rotate a tire and if the other tire turns the same direction, it is sure grip. If the other tire turns the opposite direction , it is a conventional ( open ) differential. There are exceptions if your diff has problems.........
 
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If I had to take a wild guess I'd say maybe 2.94 gears in the rear currently.

As far as determining the gear ratio on an open diff. (and I could be wrong on this, please correct me if I am) I think if you chocked one front tire so the car can't move forward of backward, trans. in neutral, then jack up just ONE rear wheel (keep the other on the ground so it can't rotate) then rotate the free wheel exactly one revolution and while doing so count how many times the driveline rotates. This should give you your ratio.
 
I'm running 3000 RPM at 80 miles per hour and I have 3:23 rear. And that's right in The Sweet Spot! By the way I have Sure Grip so it lays down a good amount of rubber on both tires, I'm talking a hundred feet but I have a 4-speed.
 
69roadr said:
I'm running 3000 RPM at 80 miles per hour and I have 3:23 rear. And that's right in The Sweet Spot! By the way I have Sure Grip so it lays down a good amount of rubber on both tires, I'm talking a hundred feet but I have a 4-speed.
Click to expand...
Yeah I figured 3:23 as well, I'm right in the same place and like I said 65 on the nose at exactly 2500
 
SublimeSixpack said:
If I had to take a wild guess I'd say maybe 2.94 gears in the rear currently.

As far as determining the gear ratio on an open diff. (and I could be wrong on this, please correct me if I am) I think if you chocked one front tire so the car can't move forward of backward, trans. in neutral, then jack up just ONE rear wheel (keep the other on the ground so it can't rotate) then rotate the free wheel exactly one revolution and while doing so count how many times the driveline rotates. This should give you your ratio.
Click to expand...
69roadr said:
And that's with a GPS can't rely on the old Mopar speedometer
Click to expand...
lol me too!
 
Not sure about your gearset but every big block Mopar I have messed with that has Edelbrock heads from 383-493 inches just hazes the street tires no matter what stall and gear
 
dieseldazzle said:
Not sure about your gearset but every big block Mopar I have messed with that has Edelbrock heads from 383-493 inches just hazes the street tires no matter what stall and gear
Click to expand...
dieseldazzle said:
Not sure about your gearset but every big block Mopar I have messed with that has Edelbrock heads from 383-493 inches just hazes the street tires no matter what stall and gear
Click to expand...
I can do nice burnouts for sure I guess I just wondered if anything about my setup would create a dog or if I was missing out on some more zip
 
Well there's ALWAYS more zip somewhere! Thinking $$$$
 
SublimeSixpack said:
If I had to take a wild guess I'd say maybe 2.94 gears in the rear currently.

As far as determining the gear ratio on an open diff. (and I could be wrong on this, please correct me if I am) I think if you chocked one front tire so the car can't move forward of backward, trans. in neutral, then jack up just ONE rear wheel (keep the other on the ground so it can't rotate) then rotate the free wheel exactly one revolution and while doing so count how many times the driveline rotates. This should give you your ratio.
Click to expand...
You might think that would work, but it doesn't. The spider gears still come into play.........................MO
 
Mr. Belvedere II said:
I can do nice burnouts for sure I guess I just wondered if anything about my setup would create a dog or if I was missing out on some more zip
Click to expand...

Well if you have a purpose built car like a drag car or something then sure you can set it up to optimize it etc etc

But a street car sure you are missing out on the perfect setup, hell its a steer car and well one day the optimum performance you need is 40-80mph roll trying to out accelerate an s500 Mercedes getting on the freeway... then the next day it's 0-60 trying to get in front of a line of cars cuz you missed your turn into sonic for a hot dog and the next turns are no u turn intersections. Then the next day your optimum performance you needed is stopping 60-0 in less than 100 feet cuz the guy 4 cars up was texting lol... well you get the idea.

I say keep your cam, gear, converter etc etc in the rpm range a street car is in most of the time and call it good.

There is a reason these companies are starting to sell generic packages like "top end kits"
 
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