Gear ratio limits
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4wd High
Joined: Dec 2021
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Gear ratio limits
Can anyone with any amount of knowledge tell me why gears are only made to 4.88 on the 2017+ super dutys instead of going to 5.38? I dont really wanna go back to 4.88 being on 40" tires id prefer 5.13 or 5.38. If anyone has any info that would be great. Thanks in advance
Last edited by jeepontons; Aug 11, 2023 at 04:11 PM.
Laughing Gas
Joined: Jul 2011
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Don’t know what axle you’re asking about, but at some point you run into the ring gear & pinion get too large for the carrier (housing, pumpkin).
Also, demand would be a factor I’d think. Why would Spicer build and sell a 6:88 gear set that will only sell a handful a year.
Also, demand would be a factor I’d think. Why would Spicer build and sell a 6:88 gear set that will only sell a handful a year.
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4wd High
Joined: Dec 2021
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Yes I’ll agree from 2016 down , 2017 and up everything changed so only the 10.5 allows lower gears but the new 2017 front is a “super” 60 not the 10 lug but what ford is calling it now. It’s been 5 years idk why they’re not going past 4.88
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More Turbo
Joined: Dec 2003
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From: Park County, CO
It's a torque vs pinion size thing. Let's say to carry the torque you need, it takes a 2" pinion to hold the tooth profile. Now for a 6:1 axle, that forces the ring gear to be 12 inches. There is a reason you see monster sized differentials in big trucks.
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4wd High
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so what makes these axles any different? They’re actually beefier than prior years, I don’t see what they’re doing
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More Turbo
Joined: Dec 2003
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From: Park County, CO
I thought your question was more generic in nature and not specific to a change in Ford with model year.
More Turbo
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You can get up to 5.38 ratio in a Dana 44 jeep axle... and thats an 8.5" ring gear...
I wont argue that as you go to a lower ratio(like a 5.38 for example) the pinion to ring engagement surface is quite a bit less and strength suffers... thats spot on.
But to say they dont make them for that reason, its just not true...
Im sure I can find other "small" ring gear setups that have much deeper gears than 4.88...
More Turbo
Joined: Dec 2003
Posts: 534
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From: Park County, CO
That dont hold water...
You can get up to 5.38 ratio in a Dana 44 jeep axle... and thats an 8.5" ring gear...
I wont argue that as you go to a lower ratio(like a 5.38 for example) the pinion to ring engagement surface is quite a bit less and strength suffers... thats spot on.
But to say they dont make them for that reason, its just not true...
Im sure I can find other "small" ring gear setups that have much deeper gears than 4.88...
You can get up to 5.38 ratio in a Dana 44 jeep axle... and thats an 8.5" ring gear...
I wont argue that as you go to a lower ratio(like a 5.38 for example) the pinion to ring engagement surface is quite a bit less and strength suffers... thats spot on.
But to say they dont make them for that reason, its just not true...
Im sure I can find other "small" ring gear setups that have much deeper gears than 4.88...
More Turbo
Joined: Nov 2021
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@jeepontons
Dont know if this thread from pirate has any insight. They are mostly talking 10.5" rear and the changes and what you need to do in order to run the older gear sets. Looks like in 2011+ they changed to a 37 spline pinion, but sounds like you can swap back to the older 35 spline pinion, bearings, etc... and run the older gears, which are available in deeper ratio's... I didnt read every post in there so may not be applicable to 2017+ stuff. And I dont know that I saw anything on the D60 front end, but the "super 60" has been around since 2005, so again, dont know what changed in 2017+ to cause them to not be compatible with the older gear sets... Researching on a forum like pirate with all the offroad guys might be a better avenue as they are more likely to know the in's and outs.
https://irate4x4.com/threads/5-13-ge...ng-10-5.95028/
Dont know if this thread from pirate has any insight. They are mostly talking 10.5" rear and the changes and what you need to do in order to run the older gear sets. Looks like in 2011+ they changed to a 37 spline pinion, but sounds like you can swap back to the older 35 spline pinion, bearings, etc... and run the older gears, which are available in deeper ratio's... I didnt read every post in there so may not be applicable to 2017+ stuff. And I dont know that I saw anything on the D60 front end, but the "super 60" has been around since 2005, so again, dont know what changed in 2017+ to cause them to not be compatible with the older gear sets... Researching on a forum like pirate with all the offroad guys might be a better avenue as they are more likely to know the in's and outs.
https://irate4x4.com/threads/5-13-ge...ng-10-5.95028/
More Turbo
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Again, is it a good idea strength wise, I would argue no. Lots of guys in the Jeep community recommend stopping at 4.88 in the D44 housings due to pinion/ring gear strength.
But the OP isnt asking if Sterling or Dana are making these gears, just wants to know if they are available at all...
But your explanation of why manufacturers arent making them doesnt hold water. Aftermarket manufacturers dont give a **** about the same things OEM's do, they only care about a market. If there is a market for these things they will make them. It sounds like there is no market(or at least not a big enough one) for what the OP is looking for, hence nobody makes them...
BUT as I linked to the thread from pirate4x4 he might be able to get a set of older gears to work with some parts swapping.
