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Ford F-Series Axle and Ratio Questions

18 messages,  Last post on Apr 04, 2009 at 7:53 PM

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#1 of 18 3.55 vs. 3.73 by archer75 Apr 02, 2006 (9:58 pm)
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. Replies to this message: broncoman81 (Apr 04, 2006 3:20 pm)
#2 of 18 Re: 3.55 vs. 3.73 [archer75] by broncoman81 Apr 04, 2006 (3:20 pm)
Replying to: archer75 (Apr 02, 2006 9:58 pm) 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
#3 of 18 F150 2005 4x2 Limited Slip Problems by 7104 Jul 13, 2006 (3:17 pm)
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? Replies to this message: naybor (Jul 30, 2006 5:09 pm)
#4 of 18 questioning the stability of rear axle by tkrueger Jul 02, 2006 (12:22 pm)
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
#5 of 18 Re: F150 2005 4x2 Limited Slip Problems [7104] by naybor Jul 30, 2006 (5:09 pm)
Replying to: 7104 (Jul 13, 2006 3:17 pm) 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
#6 of 18 broncoman by draymond2 Jul 31, 2006 (6:13 am)
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. Replies to this message: wpalkowski (Aug 01, 2006 12:21 am)
#7 of 18 Re: broncoman [draymond2] by wpalkowski Aug 01, 2006 (12:21 am)
Replying to: draymond2 (Jul 31, 2006 6:13 am) 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.
#8 of 18 F-150 vs F250 axle and spring by 4belair Aug 16, 2006 (10:07 am)
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? Replies to this message: racemech (Aug 16, 2006 1:30 pm)
#9 of 18 Re: F-150 vs F250 axle and spring [4belair] by racemech Aug 16, 2006 (1:30 pm)
Replying to: 4belair (Aug 16, 2006 10:07 am) 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.
#10 of 18 1999 F150 AXLE RATIO by gasa765 Mar 15, 2007 (9:49 am)
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. Replies to this message: wpalkowski (Mar 16, 2007 3:18 am)

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