Rear end questions
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Joined: Feb 2004
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From: Texas
Rear end questions
I have a 2002 F-150 Supercrew with the 5.4L. I have been thinking about making some rearend modifcations for some time, and was wondering if anyone can help me translate the info on my differential's tag. The info is:
3 V 942 B
55 9 75 2F17
I guess that is 3.55 gears and i'm pretty sure its an open diff based on the one wheel burn out, but if anyone can correct me or translate the other #'s it would be very helpful, thanks.
3 V 942 B
55 9 75 2F17
I guess that is 3.55 gears and i'm pretty sure its an open diff based on the one wheel burn out, but if anyone can correct me or translate the other #'s it would be very helpful, thanks.
Postmaster
Joined: Dec 2002
Posts: 3,959
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From: USA
Yep, it's a 3.55 ratio open diff 9.75" Ford/Visteon axle, assuming only the '3' is being covered by the bolt holding the tag on. If there's an 'L' under there too, then it's a limited slip, but the one wheel burn out does indicate an open diff. Some of the other numbers are manufacture date and the others I don't know. Good luck with the 'modifications' 
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Joined: Feb 2004
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From: Texas
Thanks alot SoCalDesertRider. I plan on changing to a 3.73 limited slip set up (to pick up a little of the line), and just wanted to make sure i knew what i already have. Another quick question if you don't mind, right now the engine is running about an even 2000 rpm while cruising at 70 mph, after changing to 3.73 gears what will be the change. I don't figure it will be much higher since its only a 3.73 from a 3.55, but i would like to have some idea instead of just finding out after the swap. Thanks again.
Postmaster
Joined: Dec 2002
Posts: 3,959
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From: USA
Aggie, you're welcome, thanks. Engine rpm's will change by the same percentage as the percent difference in the gear ratio. 3.73 divided by 3.55 = 1.051... 2000 rpm multiplied by 1.051... = about 2100 rpm. You may consider going to 4.10's as well for a little more power. Engine speed with the 4.10's would be about another 200 rpms above the 3.73's (about 2300 rpm at 70 mph).
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mattthegreat
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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