85 rear axle swap from 8 inch to 9 inch

P51Mustang · 12-05-2005, 09:53 PM

Put a 351W in my 85 mustang. More horsepower now. Would now like to change the rear axle to a 9 inch. Seen online a stronger diff case for 8 inch. But I think I would just as soon change the complete rear diff, axles and housing. Can this be done? If so, what vehicle axle should I be looking for? Seen on the forum that an explorer axle would bolt up. I didn't know that axle would even fit. That makes me think that something should work. Can anyone help?

82 GT · 12-07-2005, 04:29 PM

A much easier swap would get an 8.8 rear from an '87-93 5.0 mustang. It's a direct bolt in and very strong.
As far as the explorer rears you've read about....the carriers inside the explorer rears are 31 spline, which bolts into the 8.8 pumpkin. You can't use the explorer exles because they are different lengths; you would need a set of aftermarket 31 spline axles.
Doing a 9 inch rear swap is a little more involved but not impossible. They sell 9 inch rears already setup for the foxbody mustangs with any gear ratio you want but cost around $600-$700 dollars.

~The Jester~ · 12-07-2005, 08:35 PM

Yeah! What Brian said!

For "simplicity" sake, a much easier swap is the 8.8" Just for the record that '85 has a 7.5" in her, not an 8".

Get a rear out of an '86 + GT, a set of Strange 31 spline axles, and a center section from an Explorer. Don't get much better than that, I ran a 1.48 sec 60' time with this exact setup.

A 9" can be done, but an 8.8" is MUCH easier to do!

P51Mustang · 12-08-2005, 01:02 AM

Great info. I will start looking around. If the rear diff is working good for you, then it should work for me. With the info you just gave me, I guess I will stay light on the throttle for a little while longer. No need to be Found On Road Dead. Its better to be First On Race Day. Is there any year of explorer diff to look for? Or is it, the newer the better. Guess I can measure the axle length that I get with the newer rear axle and find some stronger axle shafts. I know I will be asking more question in the future. Will keep you updated with my progress. Thanks for the tips.

The Need For Speed

12-05-2005, 09:53 PM	#1
P51Mustang Not to old to drive a Mustang Join Date: Apr 2005 Location: Portland Oregon Posts: 3	85 rear axle swap from 8 inch to 9 inch Put a 351W in my 85 mustang. More horsepower now. Would now like to change the rear axle to a 9 inch. Seen online a stronger diff case for 8 inch. But I think I would just as soon change the complete rear diff, axles and housing. Can this be done? If so, what vehicle axle should I be looking for? Seen on the forum that an explorer axle would bolt up. I didn't know that axle would even fit. That makes me think that something should work. Can anyone help? __________________ Best Regards, P51Mustang

12-07-2005, 04:29 PM	#2
82 GT Import Slayer Join Date: May 1999 Posts: 2,241	Re: 85 rear axle swap from 8 inch to 9 inch A much easier swap would get an 8.8 rear from an '87-93 5.0 mustang. It's a direct bolt in and very strong. As far as the explorer rears you've read about....the carriers inside the explorer rears are 31 spline, which bolts into the 8.8 pumpkin. You can't use the explorer exles because they are different lengths; you would need a set of aftermarket 31 spline axles. Doing a 9 inch rear swap is a little more involved but not impossible. They sell 9 inch rears already setup for the foxbody mustangs with any gear ratio you want but cost around $600-$700 dollars. __________________ '82 GT 351W (.060)Comp Cams 274* Extreme Energy cam, ported & polished heads w/ 1.94/1.60 valves 10.3:1 flat top pistons,stealth intake, Mallory dizzy,Holley 750dp carb, BBK shorties,Flowmaster exhaust,C-4 with 3700 stall converter, B&M pro shifter,8.8 rear, 4:10's, subframes, electric fan, powermaster alternator, 4 core radiator.

12-07-2005, 08:35 PM	#3
~The Jester~ Rat Killer Join Date: Aug 2002 Location: Cold ass Ohio Posts: 1,143	Re: 85 rear axle swap from 8 inch to 9 inch Yeah! What Brian said! For "simplicity" sake, a much easier swap is the 8.8" Just for the record that '85 has a 7.5" in her, not an 8". Get a rear out of an '86 + GT, a set of Strange 31 spline axles, and a center section from an Explorer. Don't get much better than that, I ran a 1.48 sec 60' time with this exact setup. A 9" can be done, but an 8.8" is MUCH easier to do! __________________ d-Con Racing "Nothing fancy, just 347 inches of RAT POISON!" MICE need not apply.....

12-08-2005, 01:02 AM	#4
P51Mustang Not to old to drive a Mustang Join Date: Apr 2005 Location: Portland Oregon Posts: 3	Re: 85 rear axle swap from 8 inch to 9 inch Great info. I will start looking around. If the rear diff is working good for you, then it should work for me. With the info you just gave me, I guess I will stay light on the throttle for a little while longer. No need to be Found On Road Dead. Its better to be First On Race Day. Is there any year of explorer diff to look for? Or is it, the newer the better. Guess I can measure the axle length that I get with the newer rear axle and find some stronger axle shafts. I know I will be asking more question in the future. Will keep you updated with my progress. Thanks for the tips. The Need For Speed __________________ Best Regards, P51Mustang

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