Need information to replace rear diff

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Need information to replace rear diff

July 18, 2012, 01:38:39 PM

I bought my son his first car a couple months ago. It's a 1987 Mercury Cougar XR7. It's a 4 lug. I want to convert it to 5 lug. The problem is that I've seen a ton of information about the rear diff, but a lot of it seems confusing. Some say one thing is a perfect fit, but then others say that's wrong. Too long too short etc...

What I know: The tag on the diff housing is hard to read, but it's model V493B which as far as I can tell is a 2.73 Ratio with a 7.5 Gear Ring 28 spline (NL). I'm guessing the NL means Not limited slip? It has the 2 regular shocks then the 2 smaller stabilizer shocks.

What should I look for as an exact fit replacement? What's easiest to find? I'm willing to replace the entire rear or just the axle shafts. I just want to make sure I get the right parts so I can get this car looking/running good for my son. Any help is greatly appreciated.

Need information to replace rear diff

Reply #1 – July 18, 2012, 03:45:50 PM

Hey if you haven't seen this, it might help you out. http://www.coolcats.net/modifying/5lugrearaxleswap.html

Need information to replace rear diff

Reply #2 – July 18, 2012, 11:39:37 PM

Or you can find a couple of ranger/aerostars in Junk yard and pull both the long side axle's from both vehicles. Take those home slide those into your housing. Now if your doing this might want to upgrade to the bigger rear drums from the ranger. you would need that backing plates and all other part to make sure you aren't missing things. Sometimes its easiest to keep the housing you have.

hope that helps
Stuckman

Need information to replace rear diff

Reply #3 – July 19, 2012, 04:36:05 PM

Are you wanting to just convert to five lug with the Mark VII rotors up front and five lug drums in the rear or utalize the SN95 Mustang parts to upgrade the brakes and five lug? The first is pretty cheap but it limits your wheel selection to OEM style wheels. This is due to the larger opening needed in the center of the wheel because of the hub size on the front Fox style rotors. Frankly the brakes will still suck with this setup. If you switch over to the SN95 brakes it will cost more but they are safer and the wheel choices are almost unlimited.

To convert over to the SN95 brakes I would rummage the local car recyclers (salvage yards) for the following:

For the rear
1) A complete rear end (caliper to caliper) from a 94-98 GT Mustang. This will get you the larger 8.8 housing and a clutch style posi-track.

For the front
1) Spindles from a 94-95 V6 or GT Mustang are preferred due to the geometry issues with a stock k-member. 96-98 spindles can be used but may require a bumpsteer kit.
2) Rotors and hubs from a 94-04 V6 or GT Mustang. I checked the parts stores and they are the same part number for 10 years...whew, what the hell was Ford thinking??? Ha ha ha!
3) Calipers from a 99-04 v6 or GT Mustang. These are the twin 44mm piston PBR units that are far superior to the stock single piston units on the 94-98 cars. A slight modification to the will be required to the spindles to make them work (see Matt's site below).
4) Brake booster from a 94-98 V6 or GT Mustang (requires slotting the fire wall to install) or for a 93 Cobra Fox Mustang (direct bolt in but more expensive, have to buy new, and I would recommend highly)
5) Master Cylinder for a 85 Lincoln Town Car (SAE threads and a 1" bore). I believe all the Fox T-Birds and Cougars have SAE threads at the MC

Now there will be a couple things you are most likely going to want to buy new:
1) brake pads for front and rear
2) front soft lines from the calipers to the hard lines on the car
3) rear soft lines from the calipers to the hard lines on the rear end
4) soft line between the rear end and the hard line on the car
5) re-manufactured calipers - this one is optional but some people feel this is one of those things that should be new

With all of that said there is a fitting that will be required to get the right front soft line to bolt up to the hard line on the car. It is a Weatherhead fitting with part number 7828 which can be had at any local NAPA and sometimes at an OReilly's. Also, you can substitute the stock soft lines for SS braided units. Not 100% necessary for a street car but they are nice bling that actually serve a purpose. All of this can be found at this site:

http://home.comcast.net/~mjbobbitt/mustang/page1.html

I had this setup on my 93 Coupe but with a different MC as the threads on the fittings on that car are Metric and it stopped like a champ. I used the Performance Friction pads you can get at AutoZone but now I think you have to order them. They don't dust like a race pad but they do dust. The performance over the stock pads is definitely worth it. If you really want some nice pads get the Hawk HP's but not the HP+ as they dust horribly and for the street are not necessary.

Anyhow, its all on Matt's site and if you are patient and are willing to salvage yard hunt it can be done for $500 or less and you get five lug with some brakes that should have been installed on these cars from the get go.

Darren

Need information to replace rear diff

Reply #4 – July 19, 2012, 06:01:27 PM

The SN95 front flex hose mated to my hard lines without need for the adapter fitting. I DID need it for the Fox Stang GT/TC 11" brake setup I had before though..

Need information to replace rear diff

Reply #5 – July 19, 2012, 07:00:39 PM

You got me thinking about it and I went back and looked at the install on my 83 and by the pictures it appears I need an adapter on each side. I am going to have to confirm this as there may be an SAE to metric deal with our cars from 83-86 and 87-88 or something like that.

Darren

Need information to replace rear diff

Reply #6 – July 19, 2012, 07:31:21 PM

Not to get crazy here but never use an old axle that was rotated in X Direction then reverse it's direction. So obtaining 2 used axles from a ranger / aero is something not to do. reason being one will be driven in the reverse of it's break in and normal rotation status and it will fail!!!

Need information to replace rear diff

Reply #7 – July 19, 2012, 08:46:37 PM

If you find a 8.8 out of another bird or cat with 10" drum brakes and still want to do the 5lug swap but dont want to upgrade to discs throw some SN95 axels with the ABS exciters knocked off of them and 88 Grand marquis 10" drums TC spindles of GT mustangs have 11" rotors as do the mark VII's. nab some TC spindles and mrk VII rotors and reuse your calipers.

Like its been said before the SN95 front end parts are a little more desireable due to the center hub being more "shallow" you can run things with a flat face so to say but if you dont mind having center caps then thats probably the cheapest route

Need information to replace rear diff

Reply #8 – July 20, 2012, 08:54:36 AM

I ran the two Ranger axles in my Coupe for several years when I first converted to five lug and never broke an axle. I sold them to another guy who is still running them on his car today. There are hundreds of guys out there that have done the Ranger and Aerostar axle conversions and not broke an axle. Try to find a set in the salvage yards and that should tell you how many conversions have been done this way. While there may be some metallurgical change in the axle when broke in one way I just cannot see why you cannot run it the other direction. Its not like it has been cryogenically frozen or heat treated in a way that the engineers were looking to obtain a particular grain structure. That would almost be like saying don't go in reverse. Do some break? I would say yes but I would chalk it up to a set of ET Streets or slicks at the track but I always see those break at the beginning of the splines rather than at the bearing surface. I could be wrong but without a degreed metallurgist chiming in here I don't buy it.

Darren

Need information to replace rear diff

Reply #9 – July 20, 2012, 05:36:06 PM

Thanks for all the information. it's certainly narrowed my shopping list. Time to find some better stocked salvage yards. Thanks again.

Need information to replace rear diff

Reply #10 – July 21, 2012, 12:29:59 PM

Here's how I did my 5 lug rear:
TC 8.8 housing and differential (3.55 trak lok)
'97 Mustang GT axles with abs rings tapped off
Thunderbird Sport 10" drum backing plates
'88 Crown Vic drums.

Direct fit.

For the front, I simply used SN95 Stang stuff, also I used SN95 balljoints because I didn't want to piss around with a stack of washers for spacers (the Fox ball joints are too long for SN95 spindles..)

It's a done deal, car works fine and as should. :)

Need information to replace rear diff

Reply #11 – July 21, 2012, 01:30:22 PM

The TC housings are just about impossible to find anymore. Unless you are starting out with one I would just snag an SN95 rear and have disc brakes all the way around. The other thing with this is you can adapt the SN95 ABS into your car.

Darren

Need information to replace rear diff

Reply #12 – July 21, 2012, 01:32:12 PM

Darren this is a known fact. I work on over the road trucks and sand trucks for the town. Never reverse an axles direction once broken in in X direction. I am not saying this is a definate but it does take a set. Example torsion bars are the same way. years ago guys would find torsion bars that were not marked by the JY. If placed on the wrong side they would prematurely FAIL. A good JY guy would mark the side when disassembling. I just threw that in as a learning thing. You might be right but i would not take the chance with a C CLIP AXLE. NO NO NO NO NO ABSOLUTELY NOT!!! Just me could be wrong AGAIN!!

Need information to replace rear diff

Reply #13 – July 21, 2012, 07:15:47 PM

Well, the sn95 housing is the same as an '87-8 TC, so one COULD use it as I did mine with drums. Someone ought to mentio to the OP that if he goes rear discs he'll need to upgrade his master cylinder or learn to love a soft, spongy brake pedal.

Plus, remanned rear calipers are about 80 bucks apiece...I've got about 112 bucks into my rear drums, that's counting the purchase price of the axles and the new syn gear oil, and friction modifier. I reused my 7.5 rear's hard brake line, just had to "stretch" it ever so slightly to get it the fittings to match and thread into the wheel cylinders...

As far as the axles breaking, well, we'll see how that goes...it's been over 2 years since I bought mine....long since lost track of which one was right and left, lol.