Rear Axle Ratio
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Elder User
Joined: Jul 2003
Posts: 895
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From: OK
Rear Axle Ratio
Hello, this is my first post in this forum. I have posted a few times in the 1948-1960 forum. I recently bought a 1981 F-100 Flareside. My problem is that speedometer is about ten m.p.h. slow. The previous owner swapped the front and rear suspension out from a 1980 F-150 and a C6 transmission. The new rear end has a different gear ratio. How do you read the i.d. tag on a 9 inch rear end? I need to know so I can get the speedometer fixed.
Thanks,
hotrod48
Thanks,
hotrod48
Elder User
Joined: May 2004
Posts: 506
Likes: 0
From: Edwards Air Force Base
Elder User
Joined: May 2004
Posts: 506
Likes: 0
From: Edwards Air Force Base
Usually it is in that format or else it will be a straight forward number like
XXXXX
4 10 88 xxxx
(X means it doesn't matter) In this example, it is a 4.10 ratio in a 8.8 rear end. If there is a "L" between the 4 and the 10 then that means limited slip.
XXXX ( usually Year code and other nonsense)
3L55 8.8 xxxxx
Would mean a limited slip 3.55 gear ratio in a 8.8 pumpkin.
Lee
XXXXX
4 10 88 xxxx
(X means it doesn't matter) In this example, it is a 4.10 ratio in a 8.8 rear end. If there is a "L" between the 4 and the 10 then that means limited slip.
XXXX ( usually Year code and other nonsense)
3L55 8.8 xxxxx
Would mean a limited slip 3.55 gear ratio in a 8.8 pumpkin.
Lee
More Turbo
Joined: Mar 2002
Posts: 508
Likes: 2
From: Easthampton, Ma.
Grab a 7/16 wrench and pull the speedometer cable out of the transmission.
Remove the clip holding the plastic gear, take the gear off, put cable and retaining bolt back in.
Take the gear to the ford dealer and obtain one with one tooth less and install.
Steve G.
Remove the clip holding the plastic gear, take the gear off, put cable and retaining bolt back in.
Take the gear to the ford dealer and obtain one with one tooth less and install.
Steve G.
