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Discussion Starter #1
A couple of days ago I was asking about gear identification and I got what I was looking for since I was looking at buying this diff I didn't know anything about so before I bought it I looked inside of it and com to find out it certainly wasn't posi turns out someone welded all the gears it had mounds on top of mounds of welding and looked like the shims on the sides were backing out and it was just a huge mess still bought it for about 120 than the original price since the case alone is probably worth it one positive thing I did find is the gear ratio has indeed been changed instead of I think 331 it came with it has a 4.10 is that a pretty good ratio? ill be doing a little highway driving with a th350 is there a huge difference between the 410 and 411 gas milage wise or would it be in my best interest to go down to the 373
 

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I'm going to chime in here with what little knowledge I have. You have to take a number of things into account here. The size of your rear tires, your transmission, I believe the Stall on your torque converter and your differential gear size. From experience I ran a TH350, 3000 stall, and 4:10's on my Z28 and on the highway was turning something crazy like 4000 RPM at 70 or 75. I hope JBimmolate (Miles) chimes in here as well cause he can school much better, but depending on your tire size, there's a ratio to determine the best size gears for your application. For example I'm running a 245/60/14, with a TH350, 2700 stall, and for my best of both world performance (street/highway) I would benefit from a 3.23 gear at 65/70. I would PM JBimmolate with your specs and I believe he'll get you straightened up. Good luck!!


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I'm going to chime in here with what little knowledge I have. You have to take a number of things into account here. The size of your rear tires, your transmission, I believe the Stall on your torque converter and your differential gear size. From experience I ran a TH350, 3000 stall, and 4:10's on my Z28 and on the highway was turning something crazy like 4000 RPM at 70 or 75. I hope JBimmolate (Miles) chimes in here as well cause he can school much better, but depending on your tire size, there's a ratio to determine the best size gears for your application. For example I'm running a 245/60/14, with a TH350, 2700 stall, and for my best of both world performance (street/highway) I would benefit from a 3.23 gear at 65/70. I would PM JBimmolate with your specs and I believe he'll get you straightened up. Good luck!!


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Thanks! About my wheel size I dont know yet what I'm going to be running I have a set of old mag wheels I think 14 in the front thinner wheels and about 15 maybe 16's in the back idk tires size though since I bout them tireless my mild 350 bored .40 has an edelbrock performer rpm cam its 1500 to 6500 range my trans is Going to be rebuilt dont know what stall size to use yet
 

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I take it you bought a 9" if I remember right. No difference between a 4.10 and 4.11 just different manufacturers numbers. I would stay with the 4.11. Reason being is the get up and go if you're going to be racing it. If not, and you're worried about gas mileage, go with a 3.08. For the kind of cars that we build, is fuel mileage really that much of an issue. My 65 has a 4.11, 30" tall tire with a powerglide. It runs around 27-2900 keeping up with traffic on the freeway. I don't have a speedo. My 57 I used to have had a 402BBC, t-400, and a 4.30 gear with a 28" tire and ran 3000rpm at 60mph. Drove it to Indy way back then. Had to figure out how far we went by the mile markers on the freeway so I didn't run out of gas. No speedo in that car either. Go figure. If you want the car to sound like a race car, but get mileage, go down on the gear and have fun. Dave
 

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A couple of days ago I was asking about gear identification and I got what I was looking for since I was looking at buying this diff I didn't know anything about so before I bought it I looked inside of it and com to find out it certainly wasn't posi turns out someone welded all the gears it had mounds on top of mounds of welding and looked like the shims on the sides were backing out and it was just a huge mess still bought it for about 120 than the original price since the case alone is probably worth it one positive thing I did find is the gear ratio has indeed been changed instead of I think 331 it came with it has a 4.10 is that a pretty good ratio? ill be doing a little highway driving with a th350 is there a huge difference between the 410 and 411 gas milage wise or would it be in my best interest to go down to the 373




Yes..
 

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Discussion Starter #8
I take it you bought a 9" if I remember right. No difference between a 4.10 and 4.11 just different manufacturers numbers. I would stay with the 4.11. Reason being is the get up and go if you're going to be racing it. If not, and you're worried about gas mileage, go with a 3.08. For the kind of cars that we build, is fuel mileage really that much of an issue. My 65 has a 4.11, 30" tall tire with a powerglide. It runs around 27-2900 keeping up with traffic on the freeway. I don't have a speedo. My 57 I used to have had a 402BBC, t-400, and a 4.30 gear with a 28" tire and ran 3000rpm at 60mph. Drove it to Indy way back then. Had to figure out how far we went by the mile markers on the freeway so I didn't run out of gas. No speedo in that car either. Go figure. If you want the car to sound like a race car, but get mileage, go down on the gear and have fun. Dave
No its a chevy 12 bolt out of an early 70's nova maybe 69 but I guess somewhere in its life some welded its gears and put bigger gears in from what was a 331 its going to be my weekend warrior with some highway driving I dont wanna leave any power on the table either so im thinking somewhere like a 373
 
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