Gearing
Logistics Pro
Joined: May 2017
Posts: 3,523
Likes: 483
From: Southern OH
I had a f350 fx4 and there is an auto locker in the rear. I find them on craigslist and other sites for 300 and up. The average price is 800. I did find one that was 400 with 4:30's but I didn't have the cash at the time. If I buy the ring and pinion the locker and the master rebuild kit then have it installed it's over 1000. Buying a rear would be cheaper then I sell mine and save even more $.
Mountain Pass
Joined: May 2011
Posts: 222
Likes: 11
From: Strasburg,CO
I believe the factory locker on the 2011+ only came with 3.31, 3.55 or 3.73 gears so you would still have to regear it, also the 05+ axles are about 4" wider than the Excursion or 04 and down Superduty axles so you would need wheel spacers in the front to make it even with the rear.
I had a 03 f350 with the 6.0l and it had a locker in it. The only rears I have found with 4:30 is 02 to 04. I wasn't planning on getting anything newer than my year EX cause of the small changes ford always does and I know the models after 04 were all 373.
Logistics Pro
Joined: May 2017
Posts: 3,523
Likes: 483
From: Southern OH
Ford never offered a factory locker until 2011. Your 03 either had the factory limited slip which isn't very good or someone put a locker in before you got it.
Moderator
Joined: Jul 2010
Posts: 12,064
Likes: 1,573
From: Media PA
Are you still stuck on the idea of only upgrading to the 4.30 ratio? I really think that you should consider going deeper (like 4.88s) given your elevation and offroading usage with the 35"s and possible future 37"s, but hey, it's your money, just hate to see folks have to spend it twice.
Mountain Pass
Joined: May 2011
Posts: 222
Likes: 11
From: Strasburg,CO
it may have been installed before I got it. The truck had a little work done to it when I got it then I did more. I got 800hp & 1000ftp of tourq @ the wheels in New Jersey. The dyno guy was really surprised when we dyno'ed it. Of I had it now I wouldn't be worried about gears. But it was stolen and now I have the X with the V10
Mountain Pass
Joined: May 2011
Posts: 222
Likes: 11
From: Strasburg,CO
What 444 said and you are mistaken on the availability of 4.30 gears from the factory, you can still get a 4.30 today from Ford on 250/350 6.2 gas trucks, it has been an available optional gear ratio all along in a Super Duty. And there are a few more different ratios besides the 3.73 and 4.30 that have been and are currently available.
Are you still stuck on the idea of only upgrading to the 4.30 ratio? I really think that you should consider going deeper (like 4.88s) given your elevation and offroading usage with the 35"s and possible future 37"s, but hey, it's your money, just hate to see folks have to spend it twice.
Are you still stuck on the idea of only upgrading to the 4.30 ratio? I really think that you should consider going deeper (like 4.88s) given your elevation and offroading usage with the 35"s and possible future 37"s, but hey, it's your money, just hate to see folks have to spend it twice.
Fleet Mechanic
Joined: Jul 2010
Posts: 1,753
Likes: 34
From: Los Angeles, Ca.
The power capability of the engine isn't changed, but the power required to move the vehicle is. The engine will be forced to work harder to propel the vehicle, similar to adding a trailer or cargo to the truck, and that extra power has to go through the transmission. The transmission will have to deal with the extra heat generated by the torque converter while accelerating for a longer time under a higher load, down shifting more often, etc.
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Fleet Mechanic
Joined: Jul 2010
Posts: 1,753
Likes: 34
From: Los Angeles, Ca.
Super Moderator
Joined: May 2004
Posts: 29,380
Likes: 118
From: Central Coast of CA
No, it's not the same. Completely different dynamics.
There is no "extra power" being produced by the engine. The engine produces whatever power it produces at whatever RPM's it's at on the scale, and it's the same power going through the transmission, period. The engine doesn't magically produce MORE power because the gear ratio is changed. It produces the same power.
Now upgrade the engine and make it produce more HP and torque and yeah, you're putting more power through the trans, and making it work out of OEM spec.
Stewart
and that extra power has to go through the transmission..
Now upgrade the engine and make it produce more HP and torque and yeah, you're putting more power through the trans, and making it work out of OEM spec.
Stewart
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,739
Likes: 2,669
From: SE Florida
You're all correct to some degree.
At a given road load (the amount of power required to maintain X road speed) the torque going through the transmission is higher with lower numerical gears. But it's still within the limits of the torque that the engine can produce. The transmission was designed and tested to last through the design life with the engine that it is mated to. Changing the gears does NOT change the maximum load that the transmission sees. If the gears are lower numerically the trans sees more torque at a given speed, but as Stewart said it can't exceed the torque that the engine produces. If the engine is stock the trans isn't going to be helped or hurt regardless of the gears chosen.
At a given road load (the amount of power required to maintain X road speed) the torque going through the transmission is higher with lower numerical gears. But it's still within the limits of the torque that the engine can produce. The transmission was designed and tested to last through the design life with the engine that it is mated to. Changing the gears does NOT change the maximum load that the transmission sees. If the gears are lower numerically the trans sees more torque at a given speed, but as Stewart said it can't exceed the torque that the engine produces. If the engine is stock the trans isn't going to be helped or hurt regardless of the gears chosen.
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Trailering
Joined: Aug 2008
Posts: 17
Likes: 0
From: Orlando
You're all correct to some degree.
If the gears are lower numerically the trans sees more torque at a given speed, but as Stewart said it can't exceed the torque that the engine produces. If the engine is stock the trans isn't going to be helped or hurt regardless of the gears chosen.
If the gears are lower numerically the trans sees more torque at a given speed, but as Stewart said it can't exceed the torque that the engine produces. If the engine is stock the trans isn't going to be helped or hurt regardless of the gears chosen.
Cargo Master
Joined: Oct 2006
Posts: 2,097
Likes: 5
From: chicago northwest suburbs
Yes it is the same. If atruck has 3.73’s and you go from a 31” tire to a 35” tire you have placed all that added stress (load) on the engine and trans. It is just like adding a load or trailer to the same 3.73’s with stock tires. That is why the truck is slower to accelerate and won’t hold O/D (or hunts) when empty going up a grade.
Fleet Mechanic
Joined: Jul 2010
Posts: 1,753
Likes: 34
From: Los Angeles, Ca.
It seems so simple and logical, I can't believe this it being argued. Put on bigger tires and it takes more engine torque to get up to speed and to maintain that speed. That torque goes through the transmission. The transmission will spend more time with the TC unlocked and it'll be downshifting more often. Bigger tires will have essentially the same effect as adding cargo or a trailer, it'll take more torque to get up to speed and maintain that speed. Change the gear ratio to compensate for those bigger tires and you minimize the load put on the engine and trans.
Big tires and stock gears killed my friend's transmission very quickly, twice. The added torque required overheated it, just like a heavy load can do. The trans. temp in my F-350 dropped when the gears were changed, it also stopped unlocking the torque converter and downshifting for every little hill on the highway. Many times it would drop to 2nd, after the re-gear the most it did was drop to 3rd.
Big tires and stock gears killed my friend's transmission very quickly, twice. The added torque required overheated it, just like a heavy load can do. The trans. temp in my F-350 dropped when the gears were changed, it also stopped unlocking the torque converter and downshifting for every little hill on the highway. Many times it would drop to 2nd, after the re-gear the most it did was drop to 3rd.
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