Rear Axle ID question

mjhaltom · Post by **mjhaltom** » Fri Mar 16, 2007 4:21 pm

The metal tag on my rear diff says: WDM-U 1AA 3 70 87 302A. Can you guys tell me what I have (gearing etc.) It originally backed up a 240 and a 3.03 but now will be behind a 390 and a T-18. What kind or performance am I looking at (MPG, RPMs at highway speed, pulling ability, etc.) Thanks in advance.

Big D's 69 · Post by **Big D's 69** » Fri Mar 16, 2007 4:30 pm

Your gear ratio will be in your vin tag. It will tell you what it originally come with. Decipher it on this link http://www.fordification.com/data-1971.htm

68F250 · Post by **68F250** » Fri Mar 16, 2007 5:34 pm

I think I read a 3:70 ratio in there.

Can't calculate the speed/rpm without knowing your tire size.

71 LONG BED · Post by **71 LONG BED** » Fri Mar 16, 2007 7:24 pm

Here is a link to some info.

hookman · Post by **hookman** » Sun Mar 18, 2007 6:55 pm

Hello everybody, Just got my donor truck which is a 73 short box. Can anybody identify the rear by the #s on the tag. WDH-AC 21 B 3.25 9 311 A or 4 cant make it out to good? may want to use it in my 72 explorer 360 auto not sure thank you.

Post by **FORDification** » Sun Mar 18, 2007 7:35 pm

hookman wrote:Hello everybody, Just got my donor truck which is a 73 short box. Can anybody identify the rear by the #s on the tag. WDH-AC 21 B 3.25 9 311 A or 4 cant make it out to good? may want to use it in my 72 explorer 360 auto not sure thank you.

That rearend is a non-locker (open) unit with 3.25 gears. However, putting a '73-up differential into a '72-older truck isn't a bolt-on affair. These rearends are 4" wider and the spring pads on the housing are also spread apart a similar amount. If you're up to relocating the spring pads, though, it'll be a good swap, since it'll bring the rear wheels out to to properly track behind the front wheels. It'll also give you the 31-spline axles, compared to the 28-spline of our trucks.

hookman · Post by **hookman** » Sun Mar 18, 2007 7:50 pm

I'll be using the disc frontend out of the 73 for a disc swap into the 72. should i consider the rear swap as well? 360 auto with 3.25 any better than the 300 in there now?

Post by **FORDification** » Sun Mar 18, 2007 9:01 pm

hookman wrote:I'll be using the disc frontend out of the 73 for a disc swap into the 72. should i consider the rear swap as well? 360 auto with 3.25 any better than the 300 in there now?

Not enough difference to warrant the time and hassle of converting it.

hookman · Post by **hookman** » Mon Mar 19, 2007 7:47 pm

I guess i'll just leave it in the 73 till i need it then thank you.

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Rear Axle ID question

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