Rear Axle Code
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Joined: Dec 2004
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From: Hope Mills, NC
Rear Axle Code
I was going through this forum last night and found a post listing the rear axle codes found on the drivers door post. I just recently bought a 2003 F150 4x4 that was built in Canada and has a rear axle code of 27. What is the gear ratio for this axle? I also noticed that one rear tire will spin when on loose or slick surface, so it's not a limited slip; however, when I lock it in 4 wheel drive and take a sharp low speed turn, it seems that the axles are locked, because the truck wants to "skip" indicating that both wheels are turning at the same speed. Is this normal for this truck? I also own a '94 Mitsubishi Montero, so I'm familiar with how 4 wheel drive operates with that vehicle, which does not have limited slip on either axle. ANy information would be greatly appreciated.
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Joined: Dec 2001
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From: Louisville,Ky.
It doesn't have limited slip, if so it would have a letter/number code like L9 which is 3.55LS.
You can also look at the rearend tag under one of the cover bolts. The 1st 3 digits on the bottom line will tell you the axle ratio.
You can also look at the rearend tag under one of the cover bolts. The 1st 3 digits on the bottom line will tell you the axle ratio.
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Joined: Jul 2001
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From: South Kitsap County, WA
The 27 axle code is the 3.31 open rear. Your rear axle tag should indicate 3 31 8 8 xxxx on the second line or may even say 3 31 9 75 xxxx. The "xxxx" is merely a placeholder for build data. The first 3 may be under the bolt head and hard to read. The next set of digits is the the ring gear size in inches. 8 8 is the 8.8" and, of course, the 9 75 is the 9.75" rear.
I've experienced a truck "skipping" in 4 wheel. In my case it's because the power train was binding on a surface that doesn't allow for the slippage necessary when cornering. If this is your case then may I remind you to use the 4wd when on slippery or forgiving surfaces (mud, ice, snow, slush and sand) only.
-Kerry
I've experienced a truck "skipping" in 4 wheel. In my case it's because the power train was binding on a surface that doesn't allow for the slippage necessary when cornering. If this is your case then may I remind you to use the 4wd when on slippery or forgiving surfaces (mud, ice, snow, slush and sand) only.
-Kerry
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Joined: Dec 2004
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From: Hope Mills, NC
I crawled under my truck today and found the code just as you said, including the fact that the 3 was hidden under the bolt head. There was another tag that said EHP Oil only. What type of oil is this? I want to replace all the oils to include the transmission with synthetics, so is this just another designator for Hypoid gear oil?
One last question for now, how can I find out what kind of Automatic transmission this truck has, ie is there a specific code I should look for?
Thanks again, hopefully I can be as helpful as you all have been.
One last question for now, how can I find out what kind of Automatic transmission this truck has, ie is there a specific code I should look for?
Thanks again, hopefully I can be as helpful as you all have been.
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Joined: Dec 2001
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From: Louisville,Ky.
The tranny code in the door is probably a U. It is a 4R70W tranny, same as in the Mustangs. Use only Mercon V in the tranny if that is the tranny that you have. Others can cause major problems. The rearends come with synthetic fluid in them. 75w90 I think.
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