8.8 vs 9inch rear end

[cazsper]

When it comes time to rebuild the rear end in my car, should I go with the 9 inch or consider a modern 8.8? My car has the 9 inch now but I also have an 8.8 housing in storage so obtaining the housing isn't a factor. I know the 8.8 will be strong enough for the power i'm planning so it comes down to is one better than the other if you are making moderate power (450ish)? I heard the 8.8 is more efficient (not sure how) and I have heard one is much heavier than the other. Thanks....

Mike

 

[Tubo]

Can You?? One of the systems to up grade for swapping in a Coyote drive train is the rear. The 73 currently has an 8" 3.25. I've recently found out that a 99-04 Mustang 8.8 rear axle is 62.25 in flange to flange(some resources quote 61.6125). The 71-73 mustang rear axle is 61.5. Stick a 99-04 axle in a 71-73, you have an extra 3/8" on either side which is purdy much within allowable tolerances. (folks have been sticking Lincoln Versailles/Granada rears in 65-66 Mustangs fer years and thats with an +.5" per-side) Using after market wheels?? Difference is easily changed with off set.

How?? I have a set of 200 Mustang 8.8, 28 spline axles and Trac-loc diff, soon as I can find a carrier, I'll do the swap. Essentially grind off all spring perch & swa-bar mounts and relocate leaf spring mounts for the 71-73 with reset pinion angle

Why use an 8.8 in a 71-73?? For the average hobbyist, prolly easiest/cheapest way to get; lighter rear axle, Disc Brakes readily available range of gear ratios, & Stronger Diff w/LSD (Limited Slip Differential - Posi/Posi-track is a GM term. Rather universally understood, however inappropriate to apply to a Ford unit) 8.8 is a close copy of a GM 12 Bolt, stronger than a 8", and with 31 spline axles almost as strong as a 9", larger pinion shaft is better than a 9's weak point. Now most (some do have 31 spline) 99-04 Mustang 8.8's use 28 spline diffs, same as 70's 9" rears. So, compared to a 8" the 8.8 is superior alternative; lighter & stronger, has disc brakes, prolly cheaper than rebuilding (How good are your scavenging skills??) Compared to a 9" close to equal strength, will have Disc brakes, and is lighter, means better handling. Worth replacing a Good 9" with No, cheaper than rebuilding a 9" Wellll possibly. Unless one of the 8.8 advantage reasons is particularly strong for you, Rebuilding the 9" is prolly Best.

August HRM has a Ford 8.8 Scrounger's Guide page112

 

[71Rustang]

Hello,don't fix something that is not broken ,stay with the 9 inch

C

 

[RacerX]

Stay with the 9" much easier to change gears, upgrade, basically anything over the 8.8".

The pinion angle into the ring gear has less drag on the 8.8" vs the 9", but my opinion is if you already have the 9", keep it.

 

[cazsper]

Thanks everyone. I appreciate it.

 

[IA Rider]

The 9" has an extra bearing on the back side of the pinion gear making it stronger but it adds resistance turning the extra bearing taking more power. I went from an 8.8 to a 9" on my 83 mustang and don't notice a difference. Either unit would be a good choice. Wich ever one is easier? or cheaper? Flip a coin?

 

[nosdelacruz]

9 inch for life!! There's a reason chevy guys use it for everything

 

[cazsper]

Well it sounds like the 9" is the way to go. "They" made it sound like I would lose much more power to the wheels by using it over the 8.8. One thing u did consider was using a torque arm. It would be much easier with the 8.8.

 

[midlife]

The 9 inch rear end is that standard rear end used in NASCAR for all of their vehicles. The local NASCAR shop here (before they moved to NC) allowed our Mustang Club in for a visit. There was one wall that had at least 40 rear chunks hanging on the wall, each with slightly different gear ratios for the various tracks. They had a jig to straighten out all of the housings as well. The 9 inch Ford rear end is considered the best mass produced rear end for reliability and durability...ever!

 

[droptop73]

Here's some interesting reading.

http://www.carcraft.com/techarticles/ccrp_0806_chevy_chevelle_rear_axle_swap/

In my quest for overall performance and efficiency I'll be removing the 9" and going to an 8.8 in my car. There's gotta be a reason that Ford is not using 1950's 9" technology in modern Mustangs... unless you're looking at the CobraJet racecars.

 

[turtle5353]

I am running a 8.8 in my mustang and really like it. I had an 8" with open 3.05 gears. I got my 8.8 out of a 2005 or 2006 Sport trac explorer. I liked it because I got 373 gears posi and disc brakes all in one shot. And its all parts that can be bought at any auto parts store. Definitely a good upgrade.

 

[Go Time]

I am running a 8.8 in my mustang and really like it. I had an 8" with open 3.05 gears. I got my 8.8 out of a 2005 or 2006 Sport trac explorer. I liked it because I got 373 gears posi and disc brakes all in one shot. And its all parts that can be bought at any auto parts store. Definitely a good upgrade.

Im planning on this 8.8 explorer rear end upgrade as well because of your suggestions in the past turtle, I really like the Idea and the cost

BUT if money were no issue here is my choice

http://www.streetortrack.com/Street-or-Track-Full-Floating-9-Rear-End-System-pr-24538.html

Id would love to pair it up with their 3 link system

http://www.streetortrack.com/Street-or-Track-Rear-Bilstein-3-Link-Coilover-System-pr-24572.html

it has a really cool axel retaining system. But in Realville money is an issue or should I say obstacle, so Im going to do the explorer rear end....for now anyway

 

[turtle5353]

I am running a 8.8 in my mustang and really like it. I had an 8" with open 3.05 gears. I got my 8.8 out of a 2005 or 2006 Sport trac explorer. I liked it because I got 373 gears posi and disc brakes all in one shot. And its all parts that can be bought at any auto parts store. Definitely a good upgrade.

Im planning on this 8.8 explorer rear end upgrade as well because of your suggestions in the past turtle, I really like the Idea and the cost

BUT if money were no issue here is my choice

http://www.streetortrack.com/Street-or-Track-Full-Floating-9-Rear-End-System-pr-24538.html

Id would love to pair it up with their 3 link system

http://www.streetortrack.com/Street-or-Track-Rear-Bilstein-3-Link-Coilover-System-pr-24572.html

it has a really cool axel retaining system. But in Realville money is an issue or should I say obstacle, so Im going to do the explorer rear end....for now anyway

That's definitely a nice setup. But like you said money is usually an obstacle for most of us! And my 8.8 was free from a buddy of mine that worked at a ford garage. I also like the idea of going into any parts store and being able to buy calipers, rotors, and pads right off the shelf. I even used the stock sport trac brake lines.