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Different front and back axle ratios?

  
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Different front and back axle ratios?

 
backwoodsboy916 backwoodsboy916
Enthusiast | Posts: 260 | Joined: 10/06
Posted: 10/13/08
09:49 PM

I thought the front and rear axle ratios had to be the same, or so close it didnt matter. I have a buddy with a 00 F-350 flatbed and he said it has a 3.73 front and 4.10 rear axle ratio, which sound dumb as hell to me. If that was true when he put it in four wheel drive the front would spin faster and the back would spin slower but with more torque, right. I havent seen it but another friend claims he showed him the owners manual and it says it in there too. I just dont see how that would make any sense. My old dodge had 3.73s front and back, so why would it be different in a ford. The only thing i could think is fords have a wierd transfer case that doesnt just reduce the gears and split the power front to back, but it also some how makes the staggered gears work, but i dont know. Just to clarify, the tires are stock size, and they are the same size, and the gears are stock. Who is right, me or him?  
2005 Dodge Ram 3500 4 Door 4Wd Longbed 6SPD manual, Silverline 4 inch exhaust,ATS Performance Exhaust Manifold, K&N Intake,CFM Intake Manifold, Edge Juice w/Attitude, Recon Smoked Roof and Fender Lights, 285/70/17 Firestone M/Ts,  MUCH MUCH MORE to come, one day...when im not so BROKE.....


Member: Blowin Smoke Gang

ksd5 ksd5
User | Posts: 80 | Joined: 11/07
Posted: 10/13/08
10:37 PM

no way it came stock from ford with 3:73 and 4:10s!! and if that really is the combo then he would plenty of binding problems in t case when in 4x4 i really doubt those are the true ratios he just might not know any better Cool  
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backwoodsboy916 backwoodsboy916
Enthusiast | Posts: 260 | Joined: 10/06
Posted: 10/14/08
05:16 AM

Thank you! I thought so. Anybody else agree, i need good ammo to prove im right.  
2005 Dodge Ram 3500 4 Door 4Wd Longbed 6SPD manual, Silverline 4 inch exhaust,ATS Performance Exhaust Manifold, K&N Intake,CFM Intake Manifold, Edge Juice w/Attitude, Recon Smoked Roof and Fender Lights, 285/70/17 Firestone M/Ts,  MUCH MUCH MORE to come, one day...when im not so BROKE.....


Member: Blowin Smoke Gang

MarineOne MarineOne
Addict | Posts: 2009 | Joined: 10/08
Posted: 10/14/08
08:14 AM

When one talks of gear ratios, it's generally that of the rear end.  Normally we shorten it up (3.73's or 4.10's) however it's really 3.73:1 (3.73 to 1) or 4.10:1.

What this means is for every 3.73 turns of the transmission shaft, the rear tires make one turn.  The same is true for 4.10's.

IIRC, the front box will be 0.01 off from the rears due to the transfer case turning the front shaft.  So 3.73 rears should have 3.72 in the front.  Keep in mind I haven't had to do the math on this in a while and it might be slightly off.

The only way you could get away with 3.73's and 4.10's would be different size tires, with the 3.73 driven tires being larger in diameter than the tires driven by the 4.10's so that you won't have traction binding (one set of tires turning more than the other).



Kris  
_____________________________________________________________
2006 Dodge Ram 2500 QC 5.9L - Smarty CR S-06 on SW #4
2008 Dodge Ram 3500 QC 6.7L - H&S MiniMaxx on DPF tune for towing, Titan Fuel Tank, Aero Muffler 4040XL, Nathan AirChime K3LA

maddmechanic maddmechanic
New User | Posts: 5 | Joined: 08/08
Posted: 10/14/08
09:54 AM

Not exactly MarineOne.

The rear drive shaft is driven by the transfer case too.  Engine bolted to transmission, bolted to transfer case, both shafts bolted to transfer case.

All 4x4 light trucks (1 ton and under) have the 'same' ratio in the front and back from the factory.  The reason for different ratios, like 4.09 and 4.10 is the difference in axles and tooth combinations for those axles.  Every GM that has a Dana 44 front axle and GM rear axle has different ratios due only to design differences in the differentials (factory differentials that is).

Example:  Typical 1/2 ton GM, 10 bolt, 8.5" rear axle and Dana 44 front axle.  The 8.5" 10 bolt (used in cars and trucks from since 1970 or so) has a 41 tooth ring gear and a 10 tooth pinion to make a 4.10 ratio (41/10).  The Dana 44 front axle could have had a 45 tooth ring and an 11 tooth pinion, giving a 4.090909 ratio (4.09).

The Ford trucks with the 9" rear and Dana 44 front would have 37 tooth ring and 9 tooth pinion in the 9" rear, giving a 4.1111 (4.11) ratio, while having the same 4.09 Dana 44 in the front.

The difference in ratio in factory trucks has nothing to do with the transfer case, it's only the manufacturer and design of the axle.

If a 4x4 truck has a different ratio in the front and rear (3.73 and 4.10), it would buck and bounce like mad when driven in 4 wheel drive, and if on dry pavement, could break something.

Unless that truck is some strange setup with larger diameter rear tires from the factory, it does not have different ratios from the factory.

And yes, the higher the number (4.10 vs. 3.73)  the lower the ratio, the slower the differential turns (given constant rpm), and the higher the torque output.  
2006 KJ, 2.8 CRD
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1984 K5 Blazer, 6.2 Detroit Diesel
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2007 WK, 3.0 CRD (bought back by Chrysler)

Edward A. Sanchez Edward A. Sanchez
Administrator | Posts: 2112 | Joined: 07/06
Posted: 10/14/08
09:55 AM

In theory, if you had different-sized front & rear tires, MAYBE you could run different axle ratios, but I've always been told they need to be the same.  

gunman41mag gunman41mag
Guru | Posts: 1175 | Joined: 01/08
Posted: 10/14/08
12:20 PM

BOTH DIFF HAVE TO BE THE SAME !!! I once had a flat and put on a smaller tire just to make it to the gas station to fix the flat, and my truck had the wheels grinding, I could not drive it. Tell your buddy, not to B U L L-S H I T you.  
2008 F250 SUPER-CAB 6.4 PSD 2WD 1999 F250 super-cab 7.3 PSD 2WD(sold)
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backwoodsboy916 backwoodsboy916
Enthusiast | Posts: 260 | Joined: 10/06
Posted: 10/14/08
01:54 PM

Thats what i thought. Hes one of those "buddies" that no matter what you're talking about his uncle has 10 of them in a chicken house, and i mean EVERYTHING! That chicken house sure is getting big. Im going to get him to show me where he claims his owners manual says that. Hes probably lookin at the options it could have had. Thanks yall, im gonna print this out and go HAH!  
2005 Dodge Ram 3500 4 Door 4Wd Longbed 6SPD manual, Silverline 4 inch exhaust,ATS Performance Exhaust Manifold, K&N Intake,CFM Intake Manifold, Edge Juice w/Attitude, Recon Smoked Roof and Fender Lights, 285/70/17 Firestone M/Ts,  MUCH MUCH MORE to come, one day...when im not so BROKE.....


Member: Blowin Smoke Gang

MarineOne MarineOne
Addict | Posts: 2009 | Joined: 10/08
Posted: 10/14/08
02:17 PM

LOL .... See, I told you guys my math was gonna be off.  It's been quite a few years since I've had to do that.

And your "friend" needs his urine tested, because he's smoking some good stuff or really high off diesel fumes.

Do you realize what kind of freak of nature this thing would look like going down the road with a set of big tires on one end and stock tires on the other?

The next question I'd be asking is, "Is the circus in town?".


Kris  
_____________________________________________________________
2006 Dodge Ram 2500 QC 5.9L - Smarty CR S-06 on SW #4
2008 Dodge Ram 3500 QC 6.7L - H&S MiniMaxx on DPF tune for towing, Titan Fuel Tank, Aero Muffler 4040XL, Nathan AirChime K3LA

backwoodsboy916 backwoodsboy916
Enthusiast | Posts: 260 | Joined: 10/06
Posted: 10/14/08
06:43 PM

Well the tires are all the same, its bone stock as far as tire size goes, i know that, ive spent alot of time in that truck, hes just think hes smarter than he is, and hes wrong, and i knew that but he wouldnt listen so i needed some other opinions to prove him wrong.  
2005 Dodge Ram 3500 4 Door 4Wd Longbed 6SPD manual, Silverline 4 inch exhaust,ATS Performance Exhaust Manifold, K&N Intake,CFM Intake Manifold, Edge Juice w/Attitude, Recon Smoked Roof and Fender Lights, 285/70/17 Firestone M/Ts,  MUCH MUCH MORE to come, one day...when im not so BROKE.....


Member: Blowin Smoke Gang