Rear End with no tag how to ID

1970FordTK · Post by **1970FordTK** » Fri Apr 08, 2016 4:06 pm

I was given a what looks like a 8.8 rear end, it does not have an I.D. tag on it. The code on the front housing passenger side lower is F7TW-4025-A"C" or O its hard to tell. On the other side (drivers side) front lower housing is 19 is as much as I can make out. Along with 852B on a really faded sticker on the axle tube.
Anybody got any clue what ratio this thing is and/or a fairly easy way to figure it out?
Thanks.

colnago · Post by **colnago** » Fri Apr 08, 2016 5:15 pm

I read somewhere to put the tranny in Neutral, raise one wheel, rotate it, and count the number of revolutions of the driveshaft (or rotate the wheel until you get one rotation of the driveshaft). You might have to double the count, if it's Limited Slip (from what I've read), to account for the other wheel not turning.

I've never tried this myself, it's only what I've read, but it's free to try. Hopefully, someone else will chime in.

Joseph

two-bit · Post by **two-bit** » Fri Apr 08, 2016 8:09 pm

Sounds like an 8.8 with a '97 casting number. Pull the cover and look for the numbers. Should be stamped on the ring gear. It will be a combo number like: 41 10 or 40 13 or 45 11. Those are the number of teeth on the ring gear and the pinion.
Count the teeth on the ring gear and the pinion gear, then divide the ring gear tooth number by the pinion tooth number to find the ratio.
For example:
41 divided by 10 = a 4.10 ratio
40 divided by 13 = 3.08

and .....TADA ! no guess work. You know for sure.
Two-bit

1970FordTK · Post by **1970FordTK** » Sat Apr 09, 2016 8:43 am

Thanks folks, I'll do both of these just to see how well the "turn tire and watched marked shaft" method lines up with the numbers.

1970FordTK · Post by **1970FordTK** » Wed Apr 13, 2016 6:49 pm

Any body got an idea what the bolt thread size and lines per inch are for the drive shaft flange on a 8.8?

1970FordTK · Post by **1970FordTK** » Thu Apr 14, 2016 5:39 pm

Well at least I found out the bolt size for the flange the drive shaft mounts to. 12mmX1.75 25mm long.

1970FordTK · Post by **1970FordTK** » Fri Apr 29, 2016 2:26 pm

Got the rear opened and have more questions than answers now.
7 308 Ford E7TW AA 13 41

That is what is marked on the ring gear in order of how it was on the gear. Anybody got an idea what the heck I've got, cause something aint adding up to me?

HIO Silver · Post by **HIO Silver** » Fri Apr 29, 2016 10:10 pm

3.08 rear gear.....

1970FordTK · Post by **1970FordTK** » Sat Apr 30, 2016 10:01 pm

Thats what I kinda figured but when you divide 41 by 13 you get 3.15384615384615..............
and of course its an open dif on top of that. Gotta wonder what a shop will charge for a gear change on it.

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Rear End with no tag how to ID

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