rear differential ratio
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rear differential ratio
1979 Ford F100 (I think)
VIN f10gnfc1748
Numbers from metal tag on rear end:
S800A
47884K03
Axle code on data plate on door : 11 J
I have done a search on this forum and cannot find anything on these numbers for the rear differential.
3 Speed on the column. I belive this is the original transmission and rear end. Any info would be greatly appreciated on decoding the rear end.
Fresh rebuilt 351W (my first Ford in alot of years) engine runs good but the rear end seems geared way to high. Cannot get nothing but a chirp out of the rear tires (235/75/15).
Once again, any info or additional web sites to help decode this would greatly be appreciated. If this is in the wrong spot or there is not enough info hang with me and remeber I am new and learning this site.
Thanks in advance
KenZ28
VIN f10gnfc1748
Numbers from metal tag on rear end:
S800A
47884K03
Axle code on data plate on door : 11 J
I have done a search on this forum and cannot find anything on these numbers for the rear differential.
3 Speed on the column. I belive this is the original transmission and rear end. Any info would be greatly appreciated on decoding the rear end.
Fresh rebuilt 351W (my first Ford in alot of years) engine runs good but the rear end seems geared way to high. Cannot get nothing but a chirp out of the rear tires (235/75/15).
Once again, any info or additional web sites to help decode this would greatly be appreciated. If this is in the wrong spot or there is not enough info hang with me and remeber I am new and learning this site.
Thanks in advance
KenZ28
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Joined: May 2003
Posts: 1,525
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The S800A is the model of the transmission that you would need to order parts.
There is a number missing from your second line that is under the bolt head.
The 47 is part of the ratio, the 88 is for an 8.8 ring gear, the 4K03 is build date information. Your first number "47" may be wrong, I have never seen a Ford rear end that was 2.47 or 3.47 but there is a 3.27. Pull the bolt out and clean the tag to see what it is.
There is a number missing from your second line that is under the bolt head.
The 47 is part of the ratio, the 88 is for an 8.8 ring gear, the 4K03 is build date information. Your first number "47" may be wrong, I have never seen a Ford rear end that was 2.47 or 3.47 but there is a 3.27. Pull the bolt out and clean the tag to see what it is.
Fleet Owner
Joined: Aug 2005
Posts: 23,667
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From: Easton,Ks
Originally Posted by kenz28
I will pull it this afternoon when I get off from work. Thanks for the Info. Do you happen to have any info on the
Axle Code: 11 J
Thanks.
Kenz28
Axle Code: 11 J
Thanks.
Kenz28
11 in 1978 was 2.72 NL 3750 Ford
J= Power Steering
G in the VIN was 8-302 2BC
There was not an 11 in 1979
It was made on Oct. 03 1974 OR Oct. 03 1984 and is a 8.8 Rear End.
The S800A is not a good number, you need to look closer at it. This number will tell what trucks & years it was in, ratio, and Mfg. Plant.
You need to look closer at the tag on the rear end. The missing places are:
S800A ????
47?? 88 4K03
Last edited by subford; Dec 15, 2005 at 08:12 AM.
Post Fiend
Joined: Mar 2002
Posts: 19,402
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From: Bonita Springs FL
Does it have five lugs?
If yes: Does it have a removeable rear inspection cover? In other words, are there bolts around the differential case that you can see from the rear? If no, it's a Ford 9" axle.
If yes: Is there a fill plug in the cover? If yes, it's a Dana 44 (yes, they were put in a few trucks in the late 70's) If no, it's a Ford 8.8 axle.
If yes: Does it have a removeable rear inspection cover? In other words, are there bolts around the differential case that you can see from the rear? If no, it's a Ford 9" axle.
If yes: Is there a fill plug in the cover? If yes, it's a Dana 44 (yes, they were put in a few trucks in the late 70's) If no, it's a Ford 8.8 axle.
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Yes,
5 lugs appears to 5 X 5.5
Removeable back plate with no drain plug.
Thanks, the more info the better.
Kenz28
5 lugs appears to 5 X 5.5
Removeable back plate with no drain plug.
Thanks, the more info the better.
Kenz28
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Post Fiend
Joined: Mar 2002
Posts: 19,402
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From: Bonita Springs FL
Interesting. The door plate tag will therefore be of no use at all to you. Ford didn't put that axle in anything until 1983, so we know a previous owner made the swap.
There should be a tag held on by one of the bolts for the rear cover. It will have the original ratio stamped on it. Look closely, because the first number is usually partially obscured by the bolt itself and most people miss it.
Or you can pull the cover off and count ring and pinion teeth. You can also jack the rear wheels off the ground. Turn the driveshaft by hand until the wheels make one complete revolution. The number of times the driveshaft spins is the ratio. 3 1/2 times = 3.55:1 gear ratio.
There should be a tag held on by one of the bolts for the rear cover. It will have the original ratio stamped on it. Look closely, because the first number is usually partially obscured by the bolt itself and most people miss it.
Or you can pull the cover off and count ring and pinion teeth. You can also jack the rear wheels off the ground. Turn the driveshaft by hand until the wheels make one complete revolution. The number of times the driveshaft spins is the ratio. 3 1/2 times = 3.55:1 gear ratio.
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The VIN # F10GNFC1748
As I decoded this everything was correct except for the axle code of 11 J.
I will look at the tag again this afternoon when I get off from work. In the post from SUBFORD it is indicated they used this code in 77 and 78 but not in 79. That post also stated that the rearend was made in either 74 or 84. If it is a 74 or 84 model what would the code be?
I am thinking the data plate is correct and that someone has changed the rear end.
All my decoding came from a link off of this site to another site where all I did was key in all the numbers and it decoded them for me. All the numbers equalled everything on the truck except the axle code.
Thanks, you guys are really great.
Kenz28
As I decoded this everything was correct except for the axle code of 11 J.
I will look at the tag again this afternoon when I get off from work. In the post from SUBFORD it is indicated they used this code in 77 and 78 but not in 79. That post also stated that the rearend was made in either 74 or 84. If it is a 74 or 84 model what would the code be?
I am thinking the data plate is correct and that someone has changed the rear end.
All my decoding came from a link off of this site to another site where all I did was key in all the numbers and it decoded them for me. All the numbers equalled everything on the truck except the axle code.
Thanks, you guys are really great.
Kenz28
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
It can't be a 1974, Ford came out with the 8.8" axle in 1983. So it's most likely from a 1984 truck.
That's what I said. 
Originally Posted by kenz28
I am thinking the data plate is correct and that someone has changed the rear end.
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Thanks andym,
Did not get to look last night, (honey do list came up). But I will be pulling tags and numbers this weekend and looking. Are there anymore numbers that I might expose or things that would indicate anything of importance, I will be doing a complete brake job on the rear this week end.
Thanks in advance
KenZ28
Did not get to look last night, (honey do list came up). But I will be pulling tags and numbers this weekend and looking. Are there anymore numbers that I might expose or things that would indicate anything of importance, I will be doing a complete brake job on the rear this week end.
Thanks in advance
KenZ28
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I will remove the bolt that holds the tag on to see any hidden numbers. Just thought there might be some more info I could find out when I take the rear brakes apart. I just hope the brake shoes I bought will fit, because I bought the ones for a 79 Ford. If they don't, oh well, another trip to the parts store.
Kenz28
Kenz28
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OKay guys here we go,
Pulled the tag off of the 79 and it reads as follows:
S800a
247884k03
Cover on the rear side of the rear end.
So I figure this is a 2:47 to 1 rear axle ratio.
I have a complete 76 Pick up a parts truck. The rear end has no tag on it that I could find. It appears to be a 9" rear end. No rear cover on the rear side of the rear end. All the bolts are on the front side. There is a fill plug approximately half to three quarters the way up on the front side and the pinion gear appears to go into the lower half/bottom of the rear chunk. It has an automatic transmission in it.
The VIN Number off of the 76 (I think it is a 76):
F25YCR91396
Axle Code: is 38 J
Can anyone decode this and are the rear ends completely interchangeable even if one is a three speed on the column (1979 project truck) and one is an automatic (1976 donor truck). Would the drive shaft hook to the pinion gear of the rear end out of the automatic truck
Thanks for all the help so far and sorry my post are a little slow between.
Thanks again,
KenZ28
Pulled the tag off of the 79 and it reads as follows:
S800a
247884k03
Cover on the rear side of the rear end.
So I figure this is a 2:47 to 1 rear axle ratio.
I have a complete 76 Pick up a parts truck. The rear end has no tag on it that I could find. It appears to be a 9" rear end. No rear cover on the rear side of the rear end. All the bolts are on the front side. There is a fill plug approximately half to three quarters the way up on the front side and the pinion gear appears to go into the lower half/bottom of the rear chunk. It has an automatic transmission in it.
The VIN Number off of the 76 (I think it is a 76):
F25YCR91396
Axle Code: is 38 J
Can anyone decode this and are the rear ends completely interchangeable even if one is a three speed on the column (1979 project truck) and one is an automatic (1976 donor truck). Would the drive shaft hook to the pinion gear of the rear end out of the automatic truck
Thanks for all the help so far and sorry my post are a little slow between.
Thanks again,
KenZ28
Last edited by kenz28; Dec 18, 2005 at 01:55 PM.