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tire sizes to gear ratio
- Thread starter DEEPWOODS
- Start date
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- Aug 23, 2007
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At 70 mph you will be around 2021 rpm with 3.50 gears in overdrive. 4.11's would put you at about 2321 rpm. I think 2000 rpm would be too low for a 302.
Broncobowsher
Total hack
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Gear ratio = [(engine RPM) x (tire diameter)] / [(MPH) x (336)]
2000 RPM at 60 with 32" tire needs a 2.72 final drive. Divide by the .70 overdrive of the 4R70W and you get a theroetical 3.88:1 final drive ratio. 2000 RPM is a little low to be pushing a barn door at 70. I would try for a 4:10 gear. With clean aerodynamics (mainly no lift and no big things hanging out in the breeze) and a good engine that is not hotrodded (may I recomend a bone stock 351) it should work well. Any upset (lift, performance cam, etc.) and it will be a dog. This will also limit you from ever going bigger in the tire department as well as you will already be at your ceiling. But get it right and it could be real sweet.
If you are not sure if a ratio will work right. Put it just in the rear and take it for a drive. Do not use 4WD while doing this, but in 2WD you can get a feel for it. Changine the gears in a 9" is about as easy as it gets. You could go through a couple of sets for fairly cheap before dropping the big bucks and setting the front up to match what you finally pick for the rear.
2000 RPM at 60 with 32" tire needs a 2.72 final drive. Divide by the .70 overdrive of the 4R70W and you get a theroetical 3.88:1 final drive ratio. 2000 RPM is a little low to be pushing a barn door at 70. I would try for a 4:10 gear. With clean aerodynamics (mainly no lift and no big things hanging out in the breeze) and a good engine that is not hotrodded (may I recomend a bone stock 351) it should work well. Any upset (lift, performance cam, etc.) and it will be a dog. This will also limit you from ever going bigger in the tire department as well as you will already be at your ceiling. But get it right and it could be real sweet.
If you are not sure if a ratio will work right. Put it just in the rear and take it for a drive. Do not use 4WD while doing this, but in 2WD you can get a feel for it. Changine the gears in a 9" is about as easy as it gets. You could go through a couple of sets for fairly cheap before dropping the big bucks and setting the front up to match what you finally pick for the rear.
Here play around with this. http://www.ringpinion.com/Calc_RPM.aspx
As was posted you may want t go with 4.10's and build your engine for low rpm there are a few RV cams that will make power in the lower RPM's but 302's are no torque monsters they need to rev a little to be happy. I agree a 351W would be a better choice.
As was posted you may want t go with 4.10's and build your engine for low rpm there are a few RV cams that will make power in the lower RPM's but 302's are no torque monsters they need to rev a little to be happy. I agree a 351W would be a better choice.
oleguy74
Bronco Guru
with 4.11 2150@70 mph with 32" tires.
22213evl
Bronco Guru
broncnaz Here play around with this. http://www.ringpinion.com/Calc_RPM.aspx
As was posted you may want t go with 4.10's and build your engine for low rpm there are a few RV cams that will make power in the lower RPM's but 302's are no torque monsters they need to rev a little to be happy. I agree a 351W would be a better choice.
Viperwolf1 At 70 mph you will be around 2021 rpm with 3.50 gears in overdrive. 4.11's would put you at about 2321 rpm. I think 2000 rpm would be too low for a 302.
theese three guys are awesome;D
oleguy74
Bronco Guru
4r70w .7 in od = 2.87 gear ratio with 4.11 gears.or 4.11 x .7
Broncobowsher
Total hack
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V6 Explorer do not have the 4R70W. 4R70W is a V8 transmission except for 2 engines. the 3.8 V6 mustang after '94 and the 4.2 V6 truck after '97.
Socal Tom
Bronco Guru
Keep in mind the exploder weighs less and had better aerodynamics than the EB. The V8 EB engine was rated for about 135HP, the later model V6s are rated around 160 HP.
Tom
Tom
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- Aug 25, 2006
- Messages
- 2,190
My 98 5.0 Exploder has 3.73 gears and 31 inch tires stock. 3.92 would be close to that final ratio with 32s. Seems to be a pretty good ratio on the road but probably optimized for a few MPH faster than you will probably drive the Bronco. That's with the Explorer 5.0 anyway. 4.11s would probably work well.
spatacuulous
Full Member
This thread is interesting. I'm lugging in OD at 70mph. 5.0-4R70W-NP205-31's setup with the stock 9" rear. I could change the rear gears and it would do better? Do I just buy the gears and swap em out? Donor?
Broncobowsher
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I will counter that with my realtors Explorer. He went as far as a 4.30 gear and stock tire (he was still using it to take clients out) and the extra gear help it a lot and didn't really touch the gas mileage. It was down into the 15's on the track by the time he was done, full second faster then stock. The rear end finally ate a bearing and a stock geared Explorer rear end went back into it. I should have bought that truck...
Yes stepping up to 3.90's or 4.11's will help. You can get a spare pumpkin and try different ratios out you can usually find them pretty cheap might be able to pick up a 4.11 pumpkin for cheap. Donors other broncos can net you 4.11's or 4.56's you might be able to find some from the early mustang crowd but you have to make sure it has the correct spline count as some mustangs with 3.93 gearing got 31 spline axles.
- Joined
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That's the problem with the perfect gear ratio. It depends so much on intended use, personal preferences, and driving habbits. My initial setup with the Explorer engine and 4R70W will be with 3.73s and 31 inch tires because I have a set of stock axles with posi. Ultimately I'm planning on 4.11s with 31 inch tires. We do a lot of interstate driving with the Explorer and cruise 70-80 quite a bit and get 20 to 23 MPG on long trips with the 3.73 and 31 inch tires. It is a 2WD so its pushing about 500 less pounds than the 4X4 version and not turning a front drivetrain.
I can also say that 3.55 with 31" tires and a ZF OD transmission is too low with a good 5.0L. It hits the sweet spot at about 80. 3.73 would be a lot better maybe even 4.11s.
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