8.8 to 9" conversion.

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Mar 8, 2005 | 02:45 PM

No_BS

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From: Southeastern PA

8.8 to 9" conversion.

i've found a few 9" rears at a local junk yard that I can get for under $50 and I was wondering what would bolt up, and what would have to be changed, expecially with the brakes, are any of the parts interchangable, and will the diffrent flange setup bolt right to my driveshaft or will I need something diffrent? Also, did the 9" come with 3.55 gears? Thanks.

Mar 8, 2005 | 03:23 PM

andym

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From: Bonita Springs FL

Brakes are different. Watch the lug pattern, mustang 9" axles came with 5 x 5" lug patterns.

Depending on what you're going to bolt into, it may not work at all. 92 & up trucks use a VSS. No 9" came with a VSS, and your speedo and electronic tranny depend on that signal. '91 & earlier and you'll be ok, but you'll still lose the rear ABS.

9" axles came with 3.50 gears, not 3.55 gears. If you have 3.55 now, then you have a 3.54 front, and that' VERY close to being incompatible with a 3.50. I would definately not run it on anything remotely close to a hard surface. Not even a dirt road.

Springs and shocks should bolt up, not sure about the pinion flange. Try searching the diff, trans, and axle forum. This comes up a lot there.

Mar 8, 2005 | 06:10 PM

f_ford_custom

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From: Noth Georgia

Why 9? The 8.8s are just as strong, and less friction. Best of all, you already have em.

Mar 8, 2005 | 08:28 PM

Mr. Finch

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Not to steel the forum or anything, but what is the advantage of having a 9" over an 8.8", or an 8.8" over a 9".

Mar 9, 2005 | 02:17 AM

aurgathor

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Joined: Aug 2004

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From: Lynnwood, WA

9" axles are a bit beefier and have an extra bearing, and that helps off-road.
"

Mar 9, 2005 | 07:22 AM

RTM

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Joined: Dec 2003

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From: Sunny Florida

The broncos and f150 trucks came with a 9 inch rear until around 85 or 86 so the 3.50 ratio is fine. Your not suppose to use 4X4 on any hard surface such as pavement, only slippery conditions.

The 8.8 in stock form is not as strong as a 9 inch. Why, the 9 inch an extra pinion bearing which provides a much better support to the pinion and the carrier itself has extra spider gears, again better support. Plus the 9 inch can break an axle and not have it fall out of the housing.

Can an 8.8 be built up, yes but in stock form you can not beat a 9 inch. IMO it is far stronger than an 8.8.

Almost 99% of the 4X4 trucks will have the 3.50 ratio. I have found the same gear ratio in vans and 2 wheel drive trucks but are a little harder to find. be careful because I have pulled 28 spline set ups from vans before. For a truck try to stay with the 31 spline set up.