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Ford Explorer 8.8 Rear in 1972 Plymouth Duster/Demon/Dart Sp
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Author:  Leaning Dusty [ Mon Feb 27, 2017 7:45 am ]
Post subject:  Ford Explorer 8.8 Rear in 1972 Plymouth Duster/Demon/Dart Sp
Hi folks,

I'm a long-time reader, but a first time poster, so be gentle. haha

I am well aware of the countless threads on "Ford 8.8s" in our cars, however I have a few very specific questions that relate to the wider Duster/Demon/Dart Sport 2-door cars which all share the same wide rear quarter panels that look like they have enough room to run considerable rubber without the need for mini-tubs... feels like there should be a way to run a wider rear axle, too.

Here are the specifics:
- 1999 Ford Explorer 8.8" 3.73 lock-up rear axle, complete with disc brakes
- 1972 Plymouth Duster with the factory 7.25"

I am aware of needing to move spring perches out, however the one thing I have not really seen answered in any kind of detail is on the offset of rear differential.

Will the stock Ford Explorer 8.8 fit into my car without needing to shorten the long side? What is the point of re-centering the rear differential (I mean it works in Mustangs and Explorers with the offset, right)? Is there any performance benefit what-so-ever to going through the hassle of having the differential centered?

Here are a few specs for the Ford Explorer rear: http://www.therangerstation.com/tech_li ... r8_8.shtml

If anybody is wondering why I don't use a 8.25" or 8.75" from a Mopar, it's simply due to cost ($250 for a tested strong Ford rear with locker vs $800-$2,000 for an untested Mopar that needs a rebuild at minimum) the fact that I bought this thing for a very specific "budget" build which is getting bigger valves, cam, among a ton of other upgrades, and already running a set of split headers, a 4-barrel carb, and digital ignition. I'm shooting for 250-300hp with a little witch craft, and intend to drive the car this way for a year or two, but ultimately planning to swap the carb to EFI and a turbo... I need this rear to last in-order to still be considered a "budget" build for me. ;)

I have a front power disc brake conversion, some upgraded rotors/pads for the rear, some 5-bolt Vision Wheel 143 15" rims (F: 15x7 4.25" B.S., R: 15x8 4.5" B.S.), and set of Cooper Cobra GT 255/60-15 tires for the rear and some sort of (I think) 225 for the front... who cares about the front, though? :lol:

I will also create a separate topic in relation to my transmission build, so if you are an A904 guru, please offer any input you can muster into that also. Thank you all! :D
Author:  sandy in BC [ Mon Feb 27, 2017 9:58 am ]
Post subject: 
The unnarrowed Explorer 8.8 will be too wide for your car.

The offset pumkin on the 8.8 lines up with the transfer case on the Explorer.

You can put a stock width 8.8 in your car....but you wont be able to put on those wide tires. They wont go past the axles .

I have 265/75/15 tires on 8" rims on my Desoto courtesy a narrowed rear axle......and its still a squeeze.
Author:  Leaning Dusty [ Mon Feb 27, 2017 10:20 am ]
Post subject: 
Quote:
The unnarrowed Explorer 8.8 will be too wide for your car.

The offset pumkin on the 8.8 lines up with the transfer case on the Explorer.

You can put a stock width 8.8 in your car....but you wont be able to put on those wide tires. They wont go past the axles .

I have 265/75/15 tires on 8" rims on my Desoto courtesy a narrowed rear axle......and its still a squeeze.
Honestly, I completely forgot about the transfer case situation. :oops:

Would having my drive shaft (which would have to be cut and used with a Moog U-joint conversion as-is) at a slant potentially damage something?

I have a feeling that I won't be able to get around this without crawling underneath the car and measuring everything, but about how wide would you say your car is from inner-fender to inner-fender? I know that the Duster/Demon/Dart Sport is substantially wider in the back than the standard Dart or all of the earlier Valiants. I'm just saying, the stock 14" wheels are sooooo far in the fender well currently.

With 'measuring' aside, would you recommend just replacing the long side with another short side/axle and call it a day?

Thank you for your input! :)
Author:  sandy in BC [ Mon Feb 27, 2017 10:33 am ]
Post subject: 
The shortened 8.8 ends up the same width as the axle you have now.
Author:  DusterIdiot [ Mon Feb 27, 2017 6:16 pm ]
Post subject:  Sort of...
Quote:
I know that the Duster/Demon/Dart Sport is substantially wider in the back than the standard Dart or all of the earlier Valiants.
They aren't any wider in the back that the comparative sedan, in fact the 1973-1976 rear axle assemblies flange to flange are slightly narrower than the previous versions to allow for a slightly wider brake pad and drum set....

That being said, the fastback "29" series of bodies have a slightly wider swell to the well and allow for a little more room than the sedan for a slightly fatter tire... but if the leafs are sunk or the trunk has a spare slant six in it, the wells will only take the same max tread as the sedan... if the vehicle is at proper stance and not carrying an engine block in the trunk you can just get a 10" wide tire in the rear wells without modifying the trunk pan/wheel wells....

FYI.
Author:  Leaning Dusty [ Mon Feb 27, 2017 10:09 pm ]
Post subject:  Re: Sort of...
Quote:
Quote:
I know that the Duster/Demon/Dart Sport is substantially wider in the back than the standard Dart or all of the earlier Valiants.
They aren't any wider in the back that the comparative sedan, in fact the 1973-1976 rear axle assemblies flange to flange are slightly narrower than the previous versions to allow for a slightly wider brake pad and drum set....

That being said, the fastback "29" series of bodies have a slightly wider swell to the well and allow for a little more room than the sedan for a slightly fatter tire... but if the leafs are sunk or the trunk has a spare slant six in it, the wells will only take the same max tread as the sedan... if the vehicle is at proper stance and not carrying an engine block in the trunk you can just get a 10" wide tire in the rear wells without modifying the trunk pan/wheel wells....

FYI.
Good to know, thanks!

To be fair, mine is a 1972.

... and no, not planning to carry around spare engines in the back lol. I would love the idea of adding a trailer hitch for a small trailer, though.

The springs seem fine, but I did have to replace the bushings recently, along with some KYB sport shocks all the way around for good measure.

Cutting the rear tubes and getting some axles (or just the one) it is then. :wink:

EDIT: In case anybody else is interested, the original post that made me think a Ford Explorer 8.8 will work in the rear of a Duster/Demon/Dart GT is this one: http://www.slantsix.org/forum/viewtopic ... t=ford+8+8

It appears that it will!.. IF you are willing to mess around with wheel backspacing and sacrifice some tire in the back, you can pretty much just stick it right in without shortening the driver's side axle... but that's not really an option for me, since I already bought meaty rear rims with 255/60R15 tires and don't want anything rubbing. I figure the minuscule extra cost of cutting one tube on one side and getting another used or new OE-style passenger-side axle for the driver's side is relatively low compared to the value you will get out of something that allows you to get more traction from wider tires, while also being centered and looking stock-ish. :wink:
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