The rear differential was dropped off at the driveline shop for a rebuild.  They made quick work of the dis-assembly and inspection process.  Unfortunately they immediately noticed that the housing had a crack.  I later learned that this is not all that uncommon with the standard  versions of the Ford 9″ rear end.  Ford used a housing made of nodular iron on their differentials used behind their higher performance engines such as the 428 Cobra Jet or the Boss 429 to resist this cracking problem.   But mine was cast iron and needed to be replaced.  Val did some quick checking on the Web and found a complete differential, rebuilt and ready to go.  That lead failed to pan out as it was built for 31 spline axles and my car had 28 spline axles.  Next he located a used housing on Craigslist.  There are also several vendors that sell new housings that are much stronger than the stock original.  In the end he found somebody that he knew in the local Mustang club who had one for sale.  He picked it up and dropped it off at the driveline shop so that they could continue with the rebuild.

***Update***

Several weeks later the differential is still in the driveline shop. First Val had to order the clutches and metal washers to repair the traction lock.  Then there was a mix up regarding who is ordering the rebuild kit.  Val ordered that as well and delivered it to the rebuild shop.  The person performing the rebuild was unavailable for a few days due to a family emergency.  When he returned to work he spent some time trying to get a good gear mesh pattern on the ring and pinion, only to discover that the ring and pinion needed to be replaced.  So Val ordered a new ring and pinion.  It’s been almost another week since I last heard the bad news about the ring and pinion.  Hopefully the differential is almost complete.

In the mean time Val has been working on some rust repair as well as cleaning and repainting the rear end housing.  He sent me some pictures which I am posting below.

Cleaned differential housing

Painted housing, axles, brake drums, and backing plates.

Rusted trunk drop off

Repaired trunk drop off

Rusted rear floor cut out

Patched rear floor

***Update 2***
I heard from Val and the differential is back from the driveline shop. That means that next week he will finish up the rear end rebuild and move on to the clutch, subframe connectors, and the brake power booster. If all goes as planned the car should be completed in about one more week. I’ve got my fingers and toes crossed, but I won’t be shocked if if ends up taking two weeks instead of one.

Here are some additional pictures of the rebuilt and painted differential

Rebuilt and installed differential

Cleaned and painted brake backing plate (rear view)

Cleaned and painted brake backing plate (front view)

My car was in the shop being worked on, but I was not doing much more than ordering parts, cleaning , and painting some of the old interior parts.  I had also recovered some of the seat cushions so I wasn’t completely idle.  But I wasn’t particularly involved with the mechanical work being done.  That was about to change as I had the opportunity to spend a day at the shop my car was at and help with some of the work being done.

I made the drive out to the shop which took about an hour and a half.  Once I arrived we got right to work.  First Val showed me a fixture he had welded together that mounted in a floor jack and was designed to hold the rear differential securely so it wouldn’t roll around while being lowered out of the car.  It was a pretty clever idea and we would have the opportunity to test it out that day, as the first job was removing the rear end. After admiring the fixture we got to work removing the rear end.  Or more accurately, Val got to work removing the rear end and I got to work observing and helping whenever he needed an extra set of hands.  That wasn’t very often as he is used to working by himself.

The first order of business was to remove the rear differential housing.  Val made quick work of disconnecting the brake hoses and the parking brake cables.  Next up was the U-bolts that hold the differential housing to the rear leaf springs.  These were a mismatched set of too long and short parts that will probably end up being replaced.  An air powered impact gun got these off without too much drama.  The rear shackles were next on the list.  They were fairly rusted and did resist being removed.  The exhaust system was in the way, but since it is scheduled to be replaced The tail pipes were sacrificed to make some additional room around the rear shackles.  With quite a bit of persuasion the rear shackles came off.  We were then able to remove the differential housing from the car.  It was pretty well caked up with 45 years of leaking fluid, mud, dirt, and road salt.

Next Val showed me how to remove the differential from the housing.  The first step was to drain as much fluid out of the housing the we could by removing the filler plug and turning the housing so that the filler was pointing down into a drain pan.  Now he could proceed with removing the differential.  This involved disconnecting the brake lines from the wheel cylinders.  Then he unbolted the rear axle retainers and used a slide hammer to remove the rear axles on each side.  After removing the nuts and copper washers that hold the differential to the housing he was able to remove the differential from the housing.

Here was the part where I had the opportunity to get my hands dirty.  Somebody needed to scrape away the 45 years of caked on dirt, and that person was going to be me.  After about 30 minutes with a putty knife and a small scraper I had chiseled away the majority of the caked on gunk and you could actually see the differential again.In the mean time, Val had been working on unbolting the front leaf spring bushing so that we could remove the rear leaf springs.  I had a new set of springs that we wanted to install when the new differential went in.

Unfortunately the front bushing were firmly rusted into place.  The first bolt had snapped cleanly off.  A sledge hammer and punch couldn’t dislodge the bolt.  Val turned to an air chisel which also failed to make the bolts come out of the bushing.  Finally Val resorted to the Sawzall to cut the bolt out of the bushing.  After some maneuvering and a few choice words the leaf spring came free.  One spring down, one to go.

The second spring started out being a bit more cooperative, which ended up making it more difficult to remove.  The nut on the spring eye bolt came off without snapping the bolt.  Unfortunately the second spring bolt was as rusted just as firmly into place as the first.  This meant that Val had to use the Sawzall to cut both ends of the bolt off.  That meant that this side required twice as much cutting as the first one.  But in the end the spring did come out.  That marked the end of the rear differential and spring removal job.

It was too late in the day to tackle the transmission which was next on the agenda.  Instead, Val offered to show me how to install the outer door handles and locks. The previous shop that had worked on the car had installed a set of metal rods that extended up out of the door handle holes so that the door could be operated without the door handles and locks in place.  These rods always snagged on my clothing and cut into your hands when opening the door.  I had a bag of parts with the original handle and lock parts.  It was easy to identify which side of the car the door handles fit on.  The door locks were trickier because there was nothing on them to identify which side they fit on.  We took an educated guess which ended up being wrong.  Val demonstrated on the driver’s side door by installing the door handle and lock.  After a bit of adjustment everything appeared to be working and it was my turn to do the passenger side door.

I got the door  handle installed and with a bit of adjustment it was working fine.  Now it was time to move onto the door lock.  I dropped it into place and connected it, but the rods inside the door seemed to be interfering with the door handle rods.  Turning the key to lock and unlock the door resulted in a limited range of motion where the key would only turn one quarter turn.  After some head scratching and experimentation we determined that the door locks were installed on the wrong side of the car.  After we switched the lock mechanisms to the opposite sides the passenger door worked fine and the driver’s side door required some tweaking of the rod inside the door to get a fuller range of motion.  In the end both doors were working fine.

After that work was done for the day.  Val showed me some rusty spots on the car that he planned to tackle.  There was nothing major and were areas where most Mustangs of that vintage have issues with rust.  He also showed me that he had a new power brake booster to install.  One recommendation he made was to install sub-frame connectors to try and regain some of the chassis stiffness that had been lost over time with all the patching that was done to the floor pans.  I agreed and he will order and install a set of the connectors.  After that I made the long drive home.  That was enough dirty hands for one day.

Val contacted me to let me know that the steering and brakes were working fairly well and that he had test driven the car.  The ride was rather stiff and he wanted me to drive it myself and see what I thought.  He also wanted to hear my thoughts regarding the car’s ride height.  If we were addressing the ride by replacing springs that would be the best time to address ride height as well.  Val noted that the rear springs have an issue with spring wrap up on hard acceleration.  This came as no surprise to me as spring wrap up has been an issue with this car since I have owned it.  I already had a new set of springs ready for Val to install.

I looked my schedule over and chose a day to make the trip out to Val’s garage, which is about a 1.5 hour drive from my house.  After finishing with my appointments for the day I made the drive.  It ended up taking 2 hours because there was a traffic accident that stalled traffic for about 20 minutes.  By the time I arrived I was hot, sweaty, and tired.  Val was in the process of aligning the front end for the test drive.  The rims on my wheels were so bent up that he had temporarily installed another set of front wheels so he could get a fairly accurate alignment.  He told me that the camber on my car was way off.  Somebody had set the toe-in on the car without setting the camber.  This resulted in one tie rod shortened about as far as it could go and the other lengthened an equal amount.  He straightened out the alignment and installed my wheels back on the car.  He started the engine and backed the car out of his garage for me to test drive.

The first thing I noticed is that the steering wheel was a bit too close to my stomach.  Seems like I’ve gained a few pounds over the years.  Val had also warned me that the clutch was chattering and would need to be replaced.  I started the car forward and the clutch chattered like crazy.  It was hard to get a balance between not stalling the car and moving forward without shaking me to death.  But we were off.  The engine ran pretty well.  Val had fixed some vacuum leaks, and had warned me that the power brake booster sounded like it had a leak as well.  I could hear what sounded like the booster leaking a bit.  Looks like I will need a new booster as well.

I approached a cross street and tapped the brakes to stop.  Wow, those brakes are really sensitive.  The car had no problem stopping, but it required an extremely light touch on the brakes.  Time to turn on to the cross street.  Since the car has manual steering I knew my arms would be getting a workout.  There was a bit of play in the steering but it didn’t wander around.  I got a bit of speed up to see how the car was riding.  I didn’t want to go too fast as there were people walking around the neighborhood.  The street was fairly smooth so I couldn’t get a good feel for how stiff the ride really was.  And since the car has no interior there were all kinds of squeaks and rattles.  Since the car didn’t have much gas in it I headed back to the shop.

When I returned Val asked me how the car drove.  My response was that it was not that great and that I couldn’t believe I used to drive the car like that.  My answer was really more in response to the chattering clutch, touchy brakes, whistling brake booster and all the squeaks and rattles than to how the car drove.  I think that after Val has made some progress I will try another test drive and try to look past the squeaks and rattles.  I think I was just overwhelmed and tired from the long ride out to the shop.

After my test drive Val and I looked underneath the car for rust.  There was a strange hole cut in the frame that neither of us could explain.  Val pointed out a few areas that would require patching.  The exhaust system was rusted and would need to be replaced, which I was aware of.  We decided to install the springs I provided and address the ride height after the car had a full interior installed, as that would affect the ride height anyway.  Val agreed to look the car over some more and prepare an itemized estimate of what needed to be repaired and approximately how much it would cost.  I went ahead and ordered an exhaust system and new exhaust tips in the mean time.  Progress is being made, but there’s still a ways to go before I get the car back.