8.8 into 70 mustang driveshaft flange question

callys

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Jul 7, 2010

#1

• Jul 7, 2010

• #1

I just picked up a rebuilt 8.8 (new yukon axles, dif rebuilt) from a wrecked 97 cobra for $150

I am familiar with the 8.8 swap - welding on the spring perches, the width difference, etc, but one thing I did not see covered in most posts is the driveshaft flange.

The 8.8" has the new flat flange, my factory 9 inch has older 1350 style u-joint flange.

What is the best way to solve this problem? Leave the 8.8 alone and get a driveshaft made? I do not want to cut my original 70 driveshaft (Ill just store it). Even if I could bolt the 1350 u joint flange onto the 8.8 (guessing I cant), the stock driveshaft would still be too long.

How has everyone else tackled this? My car has the FMX...would it be possible to make a junkyard AOD driveshaft work with no modification?

 

callys

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#2

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Does anyone have measurements on this piece Ford 8.8 Pinion Yoke 1350 Series Forged 30 Spline

?

It looks shorter than the yoke on the 9" - which is what I would need, since the 8.8 sticks out more than the 9"

 

9

96 DOHC Cobra

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Jul 8, 2010

#3

• Jul 8, 2010

• #3

Don't know the answer to your question, but those yokes were used on a lot of Ford truck 8.8s. You should be able to find one in a junkyard and save yourself about $100.

 

D

D.Hearne

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south louisiana

Jul 8, 2010

#4

• Jul 8, 2010

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How long is your 70 driveshaft and how much shorter do you need it ? Measure the distance from the centers of the U joint holes

 

R

Red5oh

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Jul 8, 2010

#5

• Jul 8, 2010

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I took my junk 67 stock (two piece) driveshaft along with the driveshaft out of the 92 mustang that has the flat piece and had them make me a new one. I measured it properly and they made me a whole new on that fit like a glove. I think if you want to keep your original, the yoke should be easy to get for the FMX and the new model mustang one are a dime a dozen! I also think the entire driveshaft only cost me about 125.

 

brianj5600

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Sep 19, 2003

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Jul 8, 2010

#6

• Jul 8, 2010

• #6

You are taking out a 9" to put in an 8.8? I love my 8.8, but it replaced a 6 cylinder rear end. If I had a 9" I would have not considered an 8.8.

 

callys

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#7

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Brian going from a 3.00:1 open rear-end with 40 years on it with drum brakes to a 3.27 posi rear-end with disc brakes that puts 10-15 more hp to the ground (per car craft test) seemed like a no brainer for the cost

- 96 DOHC Cobra -

I will look for that flange at the local parts place...or at least go measure one

- D.Hearne -

The 70 driveshaft is pretty long (I think 51-52 inches). I would need it several inches shorter, maybe as much as 6. Would the 9" yoke swap into the 8.8 pinion though? I have a feeling the 9" pinion shaft is a metric size, or at least different than the 8.8" pinion shaft.

 

D

D.Hearne

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#8

• Jul 8, 2010

• #8

callys said:

Brian going from a 3.00:1 open rear-end with 40 years on it with drum brakes to a 3.27 posi rear-end with disc brakes that puts 10-15 more hp to the ground (per car craft test) seemed like a no brainer for the cost

- 96 DOHC Cobra -

I will look for that flange at the local parts place...or at least go measure one

- D.Hearne -

The 70 driveshaft is pretty long (I think 51-52 inches). I would need it several inches shorter, maybe as much as 6. Would the 9" yoke swap into the 8.8 pinion though? I have a feeling the 9" pinion shaft is a metric size, or at least different than the 8.8" pinion shaft.

Click to expand...

No way an 8.8 is 6" longer (in front) than a 9". And no, a 9" yoke doesn't fit an 8.8 pinion. You need the actual driveshaft measurements, not a guess here, for us to help. I would have kept the 9" too. The strength factor is more important than the alleged HP loss. Th e40 year old thing ? That's not even an issue here. They simply don't wear out unless they're abused or left disassembled and left to rust. A simple swapping of the chunk to one from a 4WD Bronco or pickup would have been an easier way to better gearing and traction loc. But if you want to sell the bare 9" housing, I have a friend who needs one. And there's hundreds of others who want one too.

 

callys

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Jul 8, 2010

#9

• Jul 8, 2010

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D. Hearne per my measurement, the 9" is about 8.5" from the center of the axle tube to the where the U-joint flange mounts (the flat area on the front of the pumpkin)

From the center of the 8.8 tube to where the flat flange mounts is about 9.5"

When I say about I mean give or take 1/8 of an inch on both.

However, the U-joint receiving flange is much large than the flat disc, it sticks out about 3 inches farther. So if I were to mount a flange of similar depth onto the 8.8" it would bring me to about 4 inches...2 short of 6. My apologies

My stock drive shaft is 50.5" from u-joint center to u-joint center, so I would need a drive shaft around 46.5" - I think 46" would also be fine, the stock one is very snug in the back of the FMX.

 

D

D.Hearne

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Jul 9, 2010

#10

• Jul 9, 2010

• #10

Ok, the Fox Body Stang shafts run anywhere from 45-46" long, ctr to ctr. The 2004 shaft I have in my 77 Comet is 45.75". Based on your measurements, that's what you need to make it work. Use your FMX yoke as is. If it doesn't fit the Fox Stang U joints, there are combination joints that will fit both, available at your local parts house.