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Ford F-Series Axle and Ratio Questions

archer75archer75 Member Posts: 1
What difference would one experience with a 3.55 rear end as opposed to a 3.73?

I'm looking at a XLT with the 5.4L. I'm not doing any towing. Mainly just alot of camping gear in the bed and driving over mountain passes to our favorite camping spots.


  • broncoman81broncoman81 Member Posts: 2
    3.73 will have a better off the line start and a 3.55 will have a better freeway speed might make a world of difference might not notice but a 3.73 can run a little larger then stock size tire and get better gas milage then a 3.55 would
  • tkruegertkrueger Member Posts: 2
    We have a 2005 F-150, driving at about 40-45 mph there was a 4x4 (piece of wood) in the lane, now swirving to miss it the driver side rear tire caught the median wall and totally snapped the entire tire , hub from the axle. So, the bolt just underneath the rear shock was what we were driving on! We didn't hit the median hard enough to snap the axle the axle (my opinion). Just last night someone with a Ford F-150 2005 came around the corner at about 20 mph just barely hitting a small car and his front drivers side tire and hub completley snapped off from the front end. It just seems to me this right. If anyone has this problem can you get back to me. thank you
    T. Krueger
  • 71047104 Member Posts: 1
    I own a 2005 F150 4x2 King Ranch with 5.4L engine and 3.55 limited slip rear end. At about 18,000 miles the truck developed a habit of producing a "chunk" when pulling away from a full stop. The sound and feeling are as if one of the rear wheels fell into a deep chuck-hole in the street. The problem was intermittent, but when I took the truck into the dealership the diagnosed the problem as a problem with the limited slip clutch in the rear end. The replaced various parts and declared the problem fixed. However after the repair the problem returned. The "chunk" occurs less frequently now, but it still occurs 3-5 times a week. Also, a new problem developed after the shop visit. Now I feel a slight buzz in the steering wheel between 36 and 42 MPH. Again, the problem is intermittent, but it is rather annoying. We took the truck back to the dealer, but the dealer reported that he could not detect any problem. I now have 20,000 miles, approaching the end of my warranty. Any ideas on the causes? Any suggestions?
  • naybornaybor Member Posts: 1
    I had the same problem with my 2004 F150. 5.4L auto with a 3.55 rear axle. Dealer replaced the driveshaft, said that the plating on the splines had flaked off and it was causing the slip. Hope this helps
  • draymond2draymond2 Member Posts: 134
    What do you mean by better hwy speed with the 3.55? I'm in the process of purchasing a 2002 4x2 6cy with the 3.55 axle unsure what the pros and cons are vs the 3.73. :confuse:
  • wpalkowskiwpalkowski Member Posts: 493
    Engine will turn a little slower at 60 mph hour with the 3.55 vs. the 3.73. So you'll get somewhat better gas mileage. Conversely, the 3.73 is a lower ratio (engine spins 3.73 times for each revolution of the rear wheels), so it gives you more torque. You can tow a trailer with a little more power, or the truck will accelerate better onto the highway than the higher gear ratio. As far as better highway speed goes, in theory the 3.55 will allow the truck to travel a few mph faster than the 3.73s will before you hit the rev limit of the engine. (Engine only turns 3.55 times for each revolution of the rear wheels.) Whether the 6 cylinder actually makes enough power to overcome wind drag to go faster is up to debate. :confuse: ;)
  • 4belair4belair Member Posts: 1
    I'm needing to change or rebuild the rear axle on my 84 F-150. Since sometimes I carry a 1500 lb slide in camper, I would like to upgrade to a F-250 rear axle and suspension. Does anyone know if this will fit right up to my F-150 frame?
  • racemechracemech Member Posts: 3
    You should be able to. The one difference will be if you use a heavy duty rear or not. The heavy duty rear may be a floating rear. And 8 lugs vs 5 lug.
  • gasa765gasa765 Member Posts: 6
    I have a 1999 F150, with 4.6L V8, supercab, auto transmission. The code for the axle ratio is H9.
    When I called a Ford service dept, they told me they could only check back to 2000, but the H9 indicated a 3.55 axle ratio. I checked the owners manual and couldn't find anything. Can anyone verify the H9 is a 3.55 for a 1999?
    The reason I'm asking is depending on what the axle ratio is help determine how big of a travel trailer we can buy.
  • wpalkowskiwpalkowski Member Posts: 493
    Get your VIN # and enter it into this Web site.

    Should break it down to tell you what all the numbers mean along with the axle ratio:

    Ford VIN Decoder
  • gregkaygregkay Member Posts: 1
    I have a ford 2006 reg cab stx package with a 4.6v8 and 3.55 axle. They are now offering a 5.4v8 with a 3.31 axle. Obviously more horsepower, but better fuel economy? how about towing comparisons? engine life, etc? Comments would be welcome.
  • mschmalmschmal Member Posts: 1,757
    It has vari-valve timeing, electronic throttle. this gives comparable gas milage.

  • lphilipslphilips Member Posts: 1
    I've got a 92 F350 that needs a new rear end. The axle has the following markings:

    B124 D
    3.55 10 2 2C02

    I've found a junk F250 with the floating rear end (8 lugs) same as my current rear end but markings on the end of the hub are different. The axle markings are:

    S125 P
    3.55 10 2 7F23

    Hub markings for old and new axle are:

    old: 5T8 CA / A55 MW
    new: 5T8 CA / DO DF

    Measurements from backing plate to backing plate and leaf spring center to leaf spring center are the same.

    It appears the gear ratios are the same. Does anyone know if this axle will work?
  • cayoteruncayoterun Member Posts: 1
    Hi, new here and first post:

    I'm needing to put the highest differential gear ratio in this truck.
    Does anyone know the highest ratio available for them. I'd like as close to 3. as I can. Putting a low max rpm, high torque motor in front of it. No heavy use on it tho, just hiway use, with light loads.
  • want2go2want2go2 Member Posts: 1
    Have you received any reply's on your post. I just took delivery of a 5.4 V8 F-150 and found out it has a 3.31 axle ratio. I don't know if thats good for towing about 4400 lbs Do you know if a 3.55 would be better for all around towing and regular driving. Thanks.
  • campman1campman1 Member Posts: 1
    Have 2003 F150, 4.6L, rear axle ratio of 3.08...How much can I tow, e.g. a small camping trailer....what about tongue weight? Should I consider changing the axle ratio? Thanks
  • snowbrdjnkysnowbrdjnky Member Posts: 6
    Im not sure if this is the correct spot to put my question, but i will try it and hope for the best. I am trying and learning to rebuild my rear axil. This is the first place i thought of for help. Its off of a 1978 F 150. It has a 3rd member. I am having trouble removing the bearing on both (FORGIVE MY TERMINOLOGY) shafts going to each rear tire. there is a press on stop of some sort that i can not remove. Any any information would be greatly appriciated. On any aspect of the rebuild.
  • spartan74spartan74 Member Posts: 1
    I've got a older Ford axle with 9" third member in my project car. The current gears are 4:56's and I'm wanting to switch to a 3:50. My axles are the 28 spline style and I'm searching for a salvage yard third member with those gears. My salvage yard sells complete assembled rear end and doesn't break them down just to look at spline count because at that point they can't sell as a complete assembled axle.. They've got several Ford pickups with these older 9" rear ends but don't know which ones have the 28 or 31 splines. Is there anyway to tell, without dissasembly, which axles are in each P U ?
    Because of different axle widths and bearing diameters I'm not sure if any would be interchangable with my axle tube..
  • higinbothamhiginbotham Member Posts: 1
    my rear end locked up on my 02 f150 and it has the 3.08 non-LS gears in it and i was wondering if the rearend would work off of a 2000 f-150 with 3.55 gears in it and would everything bolt up the same
  • hackattack5hackattack5 Member Posts: 315
    I noticed that in the Ford forum some guys are reporting 27 to 28 MPG on the highway with super crew F150s with the ecoboost and the 3.15 gears. I am interested in this set up because I plan to tow nothing and would love the MPG from such a nice ride. Does anyone here at Edmunds have that set up? what is your real fuel mileage?
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