65 Mustang Rearend Upgrade

sinisterstang65 · Jul 12, 2010

I have a 8 inch rear end in my 65 stang. it currently has 3.55 gears, But first of all i was wondering if someone could tell me the main difference between a 8 inch and a 8.8 inch rearend? Bc the rear end we have, came with the car when we bought it 5 years ago,and have had engine, tranny, front end, and interior all redone ourselves. But we dont know for sure if it is a 8 inch or 8.8. So is there a way to figure out which one it is? Now to the main part, is there a certain year of the explorer that you can buy from a junk yard that can just bolt up, and just have to relocate the spring perches? We want 3.73 with Trac Lok, but i also rear you have to shorten the axles. We will stay with rear drum brakes bc it has all been rerouted already. But would this be wise to do, or just buy 373 gears and a detroit trutrac? Any advice is needed. thanks

2+2GT · Jul 12, 2010

That's easy. The 8" has a removable carrier, containing all the differential parts.

The 8.8 (which appeared much later on the Fox body) has an integral carrier, meaning the differential is assembled inside the axle housing, with only a removable sheetmetal cover for access.

Max Power · Jul 13, 2010

The 8.8 is also not a direct bolt in swap. I don't really see the huge benefits of making this conversion. It would be far easier to upgrade to a 9" if you are making serious power. If not, keep what you got.

65coupe408w · Jul 13, 2010

+1 8 inch has a removable carrier like a 9inch. 8.8 has a back cover that you have to remove to access all the parts.

if you plan on upgrading, go with a 9 inch and you will never have to worry about it. It is one of the best investments I made in my 65.

brianj5600 · Jul 13, 2010

I would not look past the 8.8 if you need to upgrade. There are quite a few people putting 8.8's in older Mustangs. If you have access to a welder and angle grinder it is not too difficult and they are very stout and very affordable. Forum searches don't allow for searching "8.8", but google will return results.

bocksta · Jul 13, 2010

I just finished researching this myself . I decided to go with a 9 inch housing (small bearing) that's a direct fit ,and a rebuilt 9 inch t-lock third member .You can reuse your 8" inch axles and brakes. Its about a grand if you do it that way .

With doing the explorer rear-end swap your going to get a high mileage used part (usually the cheapest) that's going to need to be narrowed ,brakes ,a new axle. Then you need to modify the spring perches or use the explorer perches and buy new rear shock's .
8.8 rear ---- 150.00 - 200.00
narrowing -- 150.00 --250.00
new short axle with bearing 150.00 (100.00 without bearing)
brakes ----- 75.00 ---- 100.00
your looking at between 550.00 and 700.00
and you bought a 100,000 mile limited slip rear-end that may need a rebuild . you wont know that until you start to drive it.

v8only · Jul 14, 2010

people like to downplay the 8.8

bottom line is it's the perfect width for 67+ or 65/66 with late 17" wheels

it's nearly as strong as the 9"

it can be had from a junkyard all day long for $150-250 with 31 spline axles, 373 gears, trak lok AND disc brakes! I searched forever for a 9" rear, and the only things that can be found are old pos 9" rears that cost 700+ that needs a complete overhaul and usually is open diff too

1. the explorer rear does not need to be shortened. having the pumpkin off center causes no issues for driveline angles, and only under the most extreme situations the driveshaft may contact the tunnel (which can be clearanced)

2. The trak lok is simple to rebuild on your own

3. These rear ends will go 100-200k miles easy and not need a rebuild.

i've got a 96 8.8 that i'm in the middle of finishing up. I paid $200 for it, another $20 for spring perches.....and a case of beer to my friend to weld it up.

that gets me a near indestructable rear with disc brakes and trak lok and 373 gearing for $250 out the door.

can't do that with a 9" period.

bocksta · Jul 14, 2010

The 8.8 will work without narrowing it ,but you need the late model wheels . If you don't already have them then you need to add that to the cost of doing the swap. The drive shaft doesn't bolt right up so that needs to be worked out also.
There's nothing wrong with the 8.8 swap . If you have the wheels then you can save some fabrication and money.

phutch11 · Jul 14, 2010

What are you planing to do with the car and how much power are you making?

If you aren't planing to drag race the car regularly the 8" should hold up fine.

Road race and normal cruising really isn't that hard on a rear end compared to drag racing and the 8" should do fine for both.

2+2GT · Jul 14, 2010

phutch11 said:
What are you planing to do with the car and how much power are you making?

If you aren't planing to drag race the car regularly the 8" should hold up fine.

Road race and normal cruising really isn't that hard on a rear end compared to drag racing and the 8" should do fine for both.

True. The 8" is nearly identical in design to the 9", and they even share some internal parts.

If you upgrade your 8" with stronger internals, such as Currie's 4-pinion Traction-Lok, it'll be stronger than some 9" rears.

palerider94 · Jul 14, 2010

+1 on 8". I ahve a 347 sroker with 8". Upgraded center to 3.44 trac loc. Not an issue.

jonfor · Jul 15, 2010

palerider94 said:
+1 on 8". I ahve a 347 sroker with 8". Upgraded center to 3.44 trac loc. Not an issue.

this is the way i would rather go because my car will not be used as a drag car. my target is around 275hp at the rear tires with mostly city driving. what was the basic cost of your upgrades and does it include new axles or gears too?

str8sicks197 · Apr 26, 2011

Resurrect this thread please! @V8only or anyone else who knows, are you saying I can bolt in a 95-01 explorer rear end in my 66 Stang with no modifications as long as I have late model 05-09 17" wheels? I know drive shaft will have to be shortened, but is that basically it? I don't have to mess around cutting the rear end, or removing rewelding spring perches?

DukeGnarley · Apr 26, 2011

the explorer rear end is 59-5/8" wide and the '65-'66 rear end is 57-1/4" wide. the wheels you will want will be '04 and older with the 5 on 4.5" pattern. I don't know about the spring perches, but those are easy enough to change.

DukeGnarley · Apr 26, 2011

also, all explorer rear ends are 31 spline, and some have trac loc differentials. I know some were 4.10, and i think others were in the 3.5 range. It may pay to look around a little while to get a trac loc one with the gear ratio you want, however the 4.10 ones will be hard to find since the jeep crowd hordes them. you will be looking for a '95+ rear end for the disc brakes.

iskwezm · Apr 26, 2011

most of them were 3.73's

str8sicks197 · Apr 26, 2011

Thanks DukeGnarley. I actually have some 17" 2006 mustang bullitt wheels laying around my garage, so if those would work that be awesome. If I gotta buy some wheel spacers or adapters that's no biggie either. I'm gonna start calling some junk yards and try and find this 8.8 explorer rear end with the 3.73 gears, disc brakes, and trac lock. If I only gotta change spring perches around? That be great! I'm a DIY guy as long as I don't have to start doing some serious fabricating to get it work. I'll pay someone few bucks if all I gotta do is weld the spring perches.

2jzpony · Jul 23, 2011

Will the 8 inch hold up with 450 rwhp for street use with a posi and 4:11 gears?

PoppyMod · Jul 23, 2011

2jzpony said:
Will the 8 inch hold up with 450 rwhp for street use with a posi and 4:11 gears?

Not, if you really hook!
However, it's the "RWTQ" not the RWHP that will twist it up.
So, you're making 450 RWHP, at what RPM are you making RWTQ and what is it?
Just asking?

Westmus · Jul 24, 2011

2jzpony said:
Will the 8 inch hold up with 450 rwhp for street use with a posi and 4:11 gears?

The Fordmuscle project car vent high 11s on a stock 8" (4.11) with a blown 331" and T5. At that level the splines on the stock axles began to twist and they opgraded to aftermarket 28" splines axles. But I think they said that with the 525rwhp from the 331" they could hear the 8" was crying for mercy and that a future update would be a 9".

I think that the shock loads from high rpm clutch dump and wheel hop is what mostly kills rear ends not engine power, especially if you got the traction from slicks. I bet some people will be able to kill a 9" with a factory stock 2-barrel 289".

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