rear gear change
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Freshman User
Joined: Jan 2005
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rear gear change
I currently have a 3.00 rear gear in my F100, I have a 9'' 28 spline, I'm running a 390 3 speed, I was thinking of changing my rear center section to a "posi unit" I have a donor 9'' but I'm not sure if I can swap these out. the tag on the donor says the following. WFY-A5 6BC
2L75 9 480E
can someone let me know if this will work. also if its a 2.75 gear ratio I want to change to a 3.73 I did pull the axle and it does have 28 splines. thanks for any advise..
2L75 9 480E
can someone let me know if this will work. also if its a 2.75 gear ratio I want to change to a 3.73 I did pull the axle and it does have 28 splines. thanks for any advise..
Postmaster
Joined: Apr 2002
Posts: 3,613
Likes: 6
From: Coal country
As long as the punkin (3rd member, chunk, etc) has the same number of splines as your axles, you can interchange easily.
I know one fellow in California who uses a low geared (high ratio) rear end for stump pulling during the year, but when goes on a cross country vacation, he puts in a high geared (low ratio) rear end for better mileage on the freeway.
I know one fellow in California who uses a low geared (high ratio) rear end for stump pulling during the year, but when goes on a cross country vacation, he puts in a high geared (low ratio) rear end for better mileage on the freeway.
Laughing Gas
Joined: Jun 2003
Posts: 1,218
Likes: 2
From: Parkville, MO (KC)
That would be a decent "posi" or properly termed "limited slip" rear. But 2.75 behind a 390?
Rebuilding a 9" rear usually costs more than just finding the correct ratio to start with.
Your original post indicates you would rather have a 3.73 or so. You are better off with that ratio. If the chunk/pumpkin/3rd member you currently have is the wrong ratio, sell it and find one that is right.
Rebuilding a 9" rear usually costs more than just finding the correct ratio to start with.
Your original post indicates you would rather have a 3.73 or so. You are better off with that ratio. If the chunk/pumpkin/3rd member you currently have is the wrong ratio, sell it and find one that is right.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
jb, The 390 will pull the 2.75 gears, and as long as the truck is empty will do pretty good. The 3.50 or 3.75 ratio will give you more snap, make tire roasting a breeze, but you are gonna buy a lot more gas because the engine will be turning more rpms than it is now, and tire wear will likely fly out of the window too.
But it's only money, right??
John
But it's only money, right??
John
