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Discussion Starter #1
Theres a 2007 police interceptor (Crown Vic) in my local pick a part with the rear end still in it. After giving the wheels a few spins I noticed that there all posi. After looking it up online, wikipedia says they ll came with 3.55 gear 8.8. can those be swapped into my cat like how some guys have done with the explorers?
 

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Other than Crown Vic of that vintage has a coil-spring trailing arm Watts-link rear suspension and the Explorer is leaf spring... Of course you could use an Explorer leaf spring housing and use the Vic posi internals - but IIRC, after 2005 the Vics use 31-spline axles, so the posi is for a 31-spline, but the explorer axles are 28s, not to mention the difference in axle shaft lengths...
 

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Discussion Starter #3
when I looked up the car, the rear looked funny to me it had links going everywhere. I have access to a Ford only yard that has plenty of explorers and interceptors parts at my disposal, but at the cost of time and expense, it will be more worth my while to put that time and energy into buying a posi for my 9 inch unit and new housing and trinkets to make it work. I was hoping it would be something simple like change the u-joint and weld new spring perches.
 

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Explorer rearends are 31 spline. Use car-part.com and you'll find many choices from the LA area. Relatively easy swap if you have a grinder and a welder. PM me if you need specifics.
 

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For the sake of the group, the following was relayed in response to this topic:

I have not done an interceptor housing, but from what was discussed it sounds as though the Interceptor housing is an 8.8 with 31 spline axles. If so, for the purposes of the swap, it will be identical to swapping in an Explorer rear. Essentially you must grind off all the brackets and weld on the new perches.

I say new perches because the 31 spline axles are going to be 3.25" diameter as opposed to the 8" Cougar's 2-3/8" axle housings. You have 2 options at this point, you can either try and reuse the cougar perches by carefully cutting them off the 8" axle tubes, grinding them out so they sit flush around the 3-1/4" tubes and rewelding them, or you can get 2 new perches from a trailer supply or offroad supply store. I went with the 2nd option, but they only had perches for 3" housing, but it was fairly easy to get the extra 1/4".

When you weld on the perches you also have to match the pinion-angle. You also have 2 options here, you can either get an expensive pinion angle measuring tool, or you can use a couple concrete blocks and sit the 8" rear up so you can mark off the angle to match when you set the 8.8 on the perches (and then weld it once you match up the marks). I did it this way and the rear is in my car and it worked well. This method also allows you to even out the overall width diffence between the 8" and 8.8" by moving the perches out equally.

Lastly, if you are using the same transmission as before you will need to replace the yoke/u-joints. I am using a 4r70W transmission and an aluminum explorer driveshaft so I don't have to use these becuase I am not using the original driveshaft or transmission (different input spline count). If you are using the originals, I think you have to swap them for 1310/1330 combo u-joints. More info on this can be found here: http://forums.vintage-mustang.com/mod-custom-forum/621715-project-8-8-a.html


For some pics of an Explorer swap, go here and check out my posts (8,9, and 11). I have since completed it and can give you more details/pics if you need them.
http://www.mercurycougar.net/forums/showthread.php?53911-8.8-ford-explorer-rear-end-swap-advice
 

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Found this as well:

http://www.crownvic.net/ubbthreads/ubbthreads.php?ubb=showflat&Number=1646287&fpart=1

If the width is wheel mounting flange-to-flange, I would not use an Interceptor rearend becuase it is going to be way too wide (over 7" wider than a Cougar's). If the 65.6" he is referring to is outside wheel-to-wheel, then it would be fine. Something you will have to measure. Remember, the Explorer 8.8 is 59.5" which is wider than the 8". If it is 65.6" on Crown Vics (Intercepters are the same width), then you would have more than you could deal with, even with a crazy offset wheel.
 

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You know a bunch of the explorers came with an independent rear suspension, right?
If you're gonna do junkyard mods, why not put that in your car?
 

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Discussion Starter #9
@ Cougarshaman I'm not certain about the Explorer rear ends gear ratio and posi traction. I know for certain that every interceptor has a posi with 3.55 gears. I heard that Explorers had 3.73 which is too high for me without an AOD. I have a 9 inch I'm building up (gonna take another year), but would love to build something I can use now.

@ 67rynorod after welding on new perches, can I use my C4 yoke and driveshaft and just replace the pinion yoke (i think thats what its called) the rear of the current drive shaft that connects to the explorer rear end is different. Can I use the explorer connecting plate and a new u joint to connect it to my current drive shaft?
 

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Not all CVPIs got 3.55s. Some years were equipped with 3.27s. Not all are posi either! It was up to the department what 'package' they wanted. Some will have cruise control, some will have power seats... Then there is the street appearance package that made the car look more like a civvy Vic with color-keyed mirrors, no black rear facia, no spotlight... Still is a P71 though and not a P73 Vic or a P74 CVLX. BTW, P72 was taxi and P70 was the extended wheelbase version also used for taxi service.
 

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Discussion Starter #11
oh I understand, I thought that all of the interceptors had that package. The interceptors that are at the yard right now have posi 3.55 I checked.
 

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@cougarshaman
An IRS swap instead of a rear swap is like changing to EFI instead of changing out a carburetor. The amount of work, know-how and cost is not even remotely the same. Cool concept, but I don't think it benefits 67MercCat much. 1995-2001 are the Explorer live axle rears with discs. 2002-on are the IRS versions.

@67MercCat
Explorer rears came in 3.55, 3.73 and 4.10 gears, most are 3.73. All had limited slip. As I am not retaining the c4 I cannot comment on the length of the driveshaft but the mustang guys always have to have theirs shortened, something you will have to check or someone else will have to answer. I do know you have to replace the u-joints (specifics were in post #6) and other than this you can use your original driveshaft. As is stands, I actually still have my original driveshaft sitting around (offered it for free a couple months ago to anyone that wanted it). If you need a spare to mock up/modify and can make it to San Diego, you can have it if it helps.
 

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I understand it's a tougher swap, but he's already willing to weld and fabricate new perches just so he can have what is ostensibly no better than what the car came with from the factory. Still a live axles on leaf springs. A stock 8 or 9 inch will do everything an 8.8 can do and bolts right in. Swapping to an 8.8 seems like an inefficient use of resources.
Not that there's anything efficient about owning and working on old cars, so that's a nutty point to make.
Converting to an IRS from an Explorer, or anything else, is challenging from a fabrication perspective. I'll give you that. But, the benefits of a 4 wheel independent suspension on his car would be a real upgrade. If we're talking junkyard mods, I'm just suggesting he expand his perspective since he can probably get the entire rear clip for what would amount to the price per lb of scrap.
Back in the 80's, you couldn't throw a cat through a car show without scratching a car with a Jaguar rear setup. It's not impossible.
 

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Discussion Starter #15
@Cougarshaman thats a good point. I in fact already have a 9 inch that I'm building but I want to build in right though so its taking a little time. I'm just into experimenting a bit at this stage in my automotive exploits. I get kick out of taking something from the yard and making it work. A posi unit and decent gears for a little weekend welding sounds good to me. This pick a parts out here are incredibly cheap too (depends on which on you go to). $80 bucks worth of rubber burning fun can't be all that bad :)
 

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I understand it's a tougher swap, but he's already willing to weld and fabricate new perches just so he can have what is ostensibly no better than what the car came with from the factory. Still a live axles on leaf springs. A stock 8 or 9 inch will do everything an 8.8 can do and bolts right in. Swapping to an 8.8 seems like an inefficient use of resources.
Fabrication of perches is not required, as I explained they are purchased. Welding is not comparable to the type and difficulty associated with an IRS swap. And a 8.8 explorer, although still a live axle on leaf springs is better, stronger, cheaper and easier to work with than an 8, and a 31 spline 8.8 is the same to a 9. Disk brakes for a 9" are more expensive than the whole 8.8"with disc brakes included that you can find any day of the week less than 30 miles from any major city using car-part.com. Finding a 9¨ that bolts right in is going to take some searching, especially for one with disc brakes, posi, and the gears he is looking for. I think I have beat this to death enough, the important thing to note is I have been there, done that, documented it and posted it here. More info: http://www.fordmuscleforums.com/rear-end-articles/495110-31-spline-explorer-axle-swap-print.html

Converting to an IRS from an Explorer, or anything else, is challenging from a fabrication perspective.
Enough said, the original poster asked about a live axle, and what needed to be done. No offense to the poster, but the amount of skill, work, self research and finances required for this type of undocumented swap into a cougar does not suggest in any form or fashion that the suggestion is useful. I have already done the 8.8 and figured it out by myself and I would not try an IRS at the moment, I doubt the original poster wants to deal with the kinds of headaches involved. This is why I posted additional information for him to look into from someone that had done it. For the financial comparison, usually junkyards charge by the part, not by the pound and an entire IRS is going t be quite a bit more expensive than a rearend.

If we're talking junkyard mods, I'm just suggesting he expand his perspective since he can probably get the entire rear clip for what would amount to the price per lb of scrap. Back in the 80's, you couldn't throw a cat through a car show without scratching a car with a Jaguar rear setup. It's not impossible.
This is the second thread that I know of where you have tried to get someone to do an IRS. In my opinion, and you know what everyone says about opinions, these types of recommendations fall on deaf ears without having any information about how it is done, who has done it, how much it costs, and how well it worked. For argumentative purposes, my rebuttal to your proposals have offered more information about your proposal than you yourself did. It is not that your idea is that horrible it is just that it doesn´t fit the scenario, and if there is anything that car guys don´t need it is advise that makes projects spiral out of control.
 

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Actually, creativity is what makes hot rodding what it is. Well, that and the willingess to do things that other people haven't done.

Everyone has limits to what they can or will do because of budget, talent, or skill. Your limitations are not my limitations. And no one needs your permission or forgiveness to post ideas here. It's a forum. It's what we do here.
 
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