Made a trip down to the parts counter to see if there is an actual difference between F250 and F350 rear axles.Well, it depends!!!! Ford uses two different diffs. Sterling 10.5 and Sterling 11.5. My first assumption was the 250 gets the smaller diff. Not so. It depends on the engine!! F250 and F350 both get the 10.5 if equipped with gas engines. F250 and F350 both get the 11.5 with diesel power.Interesting is that they both have the same GAWR. So why have an 11.5 which weighs 100 lbs more than the 10.5? Higher tow rating which the diesel is capable of. So it really doesn't matter which one if you are just hauling a TC.BUT.....he said that is not cast in granite!! He has seen gassers come through with 11.5 and diesels with 10.5. The only way to check your specific truck is a build sheet or axle tag. So I guess I'm just as confused as when I started out!!! Seems they would save money to just build one diff for 250/350 like they used to!! :@

It depends on the engine!! F250 and F350 both get the 10.5 if equipped with gas engines. F250 and F350 both get the 11.5 with diesel power.Similar with GM trucks. Duramax (and the 8.1(?)L gas) get an AAM 11.5 axle, while other gas SRW vehicles don't - at least from ~2000 to ~2011.Maybe the bigger axles are enough more expensive, or enough heavier as you mentioned, that it make sense to use different ones -- otherwise, no clue why they have two.

It would seem to have more to do with engine torque than GAWR .

Hmm Ive never heard of an 11.5 Sterling? Sterling 10.25 pre '99 (though still made), '99 up Sterling 10.5.Ive seen some referance in differnt spline count on the 10.5.Dana 80 is 11.25the aam is 11.5 ?comparing ford & gm

cewillis wrote:It depends on the engine!! F250 and F350 both get the 10.5 if equipped with gas engines. F250 and F350 both get the 11.5 with diesel power.Similar with GM trucks. Duramax (and the 8.1(?)L gas) get an AAM 11.5 axle, while other gas SRW vehicles don't - at least from ~2000 to ~2011.Maybe the bigger axles are enough more expensive, or enough heavier as you mentioned, that it make sense to use different ones -- otherwise, no clue why they have two.Not quite. ALL 3500 trucks got the 11.5 regardless of engine. The 2500 6.0 got the 10.5, the 2500 8.1 and diesel got the 11.5

I believe Ford lists the 250 as a 250/350 when it's a single rear wheel model and it's a 350 when it's a dually.

Interesting info on F250/F350 rear axles. UPDATE 01 24 14

18 Replies

_DJ_1
Explorer II
Jan 20, 2014
AnEv942 wrote:
Hmm Ive never heard of an 11.5 Sterling?
Sterling 10.25 pre '99 (though still made), '99 up Sterling 10.5.
Ive seen some referance in differnt spline count on the 10.5.
Dana 80 is 11.25
the aam is 11.5
?comparing ford & gm

I searched and searched but could not find a Sterling 11.5 either. I wanted to compare the weight capacity specs against the 10.5 for myself.

The only mention of it was on The Diesel Stop where one guy mentioned "the new Sterling 11.5".

I'm going to keep digging. Maybe this parts guy was all wet. I need to run down one of the truck mechanics at Ford!!!
Bedlam
Moderator
Jan 20, 2014
The SRW Ford diesels and larger gasoline engines use the larger Sterling axle. The smaller gasoline engine uses the smaller axle. The specification page muddles this fact which leads to the confusion. It is done strictly for cost saving when you buy the base engine.

DRW uses a different axle if you have a Ford - Dana 80, if my memory is correct.
AKSuperDually
Explorer
Jan 19, 2014
I believe all DRW Fords are F350 or larger, and feature the Dana 80 in the rear and the Dana 60 in the front.
skipnchar
Explorer
Jan 19, 2014
I believe Ford lists the 250 as a 250/350 when it's a single rear wheel model and it's a 350 when it's a dually.
KD4UPL
Explorer II
Jan 19, 2014
cewillis wrote:
It depends on the engine!! F250 and F350 both get the 10.5 if equipped with gas engines. F250 and F350 both get the 11.5 with diesel power.

Similar with GM trucks. Duramax (and the 8.1(?)L gas) get an AAM 11.5 axle, while other gas SRW vehicles don't - at least from ~2000 to ~2011.
Maybe the bigger axles are enough more expensive, or enough heavier as you mentioned, that it make sense to use different ones -- otherwise, no clue why they have two.

Not quite. ALL 3500 trucks got the 11.5 regardless of engine. The 2500 6.0 got the 10.5, the 2500 8.1 and diesel got the 11.5
AnEv942
Nomad
Jan 19, 2014
Hmm Ive never heard of an 11.5 Sterling?
Sterling 10.25 pre '99 (though still made), '99 up Sterling 10.5.
Ive seen some referance in differnt spline count on the 10.5.
Dana 80 is 11.25
the aam is 11.5
?comparing ford & gm
ticki2
Explorer
Jan 19, 2014
It would seem to have more to do with engine torque than GAWR .
cewillis
Explorer
Jan 19, 2014
It depends on the engine!! F250 and F350 both get the 10.5 if equipped with gas engines. F250 and F350 both get the 11.5 with diesel power.

Similar with GM trucks. Duramax (and the 8.1(?)L gas) get an AAM 11.5 axle, while other gas SRW vehicles don't - at least from ~2000 to ~2011.
Maybe the bigger axles are enough more expensive, or enough heavier as you mentioned, that it make sense to use different ones -- otherwise, no clue why they have two.

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Interesting info on F250/F350 rear axles. UPDATE 01 24 14

18 Replies

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