3 Link Rear Axle, Disc Brakes,
and stuff.

 I was going to call this 'let's drop the big one now'. It's the last big project I wanted to do to the car. It turned out bigger than I thought.

  During the years I owned the Mustang, probably every component had been re-built or changed except the rear axle, which had been left pretty much stock. Just some urethane bushings, stiffer springs and shocks. The stock Mustang four link geometry was still in effect. This arrangement tends to fight itself and bind up, leading to weird handling.

 The aftermarket seems to have settled on one of two cures. Replacing the upper two links with either a Torque Arm, or a single Upper Link to make a 3-Link. There are also other systems, such as a Satchell Link, or the good old 4-links straight back from the frame. Most types also need a panhard rod, or such, to locate the rearend sideways under the car.
 The cheapest 3-link is simply to remove one upper arm. People call this the PM3L, The Poor Mans 3 Link.
Some people call a torque arm a three link. I say a three link has pivots at both ends and is above the axle center line.
 I knew others had built all of these, and debated with myself one way or the other which one to chose. Any would probably do the job, and so came to the result that there is no right or wrong.

 Looking at it from a practical viewpoint, the torque arm can be installed totally under the car, while the 3rd link requires the temporary gutting of the rear seat area. (some kits require permanent removal of the rear seat.) When completed the 3rd link is up out of the way, but is near the floorpan, while the torque arm hangs down under the axle and crowds the exhaust. The 3rd Link is much lighter than most Torque Arms. But the Three Link is also close to the brake line, while the Torque Arm isn't.

 In the 2005 Mustang Ford changed the rear to a three link. I decided that maybe they knew something I didn't so finally picked that type. I had the goals of:
  -proper geometry,
  -lack of noise and vibration,
  -packaging under the rear seat.

 In addition the entire axle would be swapped and the stock nine inch drum brakes would be replaced with newer style discs during the operation.

Suspension page first, then brakes on another page.

 Step One: Build a fence. This is so the garage could be emptied, and the interior of the car gutted, and all the stuff hidden from the passerby.

 The cut-off tops of the fence posts would also be handy to rest the car on because I wanted it as high off the floor as possible.

The neighbors liked it too because it hid their patio from the alley.



 Moving on...

 The third link bracket was made on an 8.8 that was rebuilt and sitting on the garage floor.
  I wanted the link as low as possible to avoid contact with the floor, and yet as long as possible, so a piece of angle plate was used as the basis.
  First the axle bushings were pressed out with washers, tubing, and threaded rod. Aluminium inserts were made on the lathe and tapped in.
 1x1 inch square tube connected to the angle, and three tabs were bolted to the top of the rear cover. The top edge of the cover had to be cut off flat to do this.
 The mount for the link was added directly over the pinion. This makes it slightly offset to the passenger side of the axle. My tape measure location of the pinion is; Drivers side 2ft 3 1/2in, Pass. side 2ft 2 1/2 in.. 1 inch difference.

   Here is a finished picture. Hard to see it with the fresh gloss black paint.

 Easy to see the three rear tabs. The bad point of welding these on is that the adapter must be lifted to remove the rear cover. But how often do you do that.



  Here is another pic after after several months of dust.

  The center tabs are 1/8th, and then doubled up with a washer. Later a thick rod was welded to the edge. I thought a pic was taken but apparently not.

  Lastly the angle was triangulated with flat plate and it was finish welded. Between the tabs a smaller piece triangulated at the back as well.
  Do as much welding as possible in place. Mine twisted and needed to be hammered back into alignment.

  These brakes lines were removed later.


 I'm not the greatest weldor, but the brand of wire that was in the machine was giving me problems. I've written right on the machine not to use it again.




 The entire axle had to be replaced before the third link could be installed. I took it apart in pieces after draining. Old gear oil stinks.

  While it was out I did several 'might as wells'. It is much easier without an axle in the way.

 The torque boxes were welded up and a plate added across the bottom. I used a bottle jack to snug it up, and the car lifted off the wood blocks without the plate bending. Strong enough.

  I got sick of looking at the rust after this. (although the 500W halogen makes it look worse.) I cleaned up the loose stuff with power tools and used a touch-up gun to spray a few coats of anti-rust black on everything.



 The lower arms and springs were given a bath in the rust removal solution. The urethane bushings were removed for this. The rear center bushings were very rusted, and even after cleaning looked more like archeological artifacts than car parts.

 Looking around the garage two tubes were found that fit together, and the outer one was aluminium. The inner piece was knurled slightly, lubed with anti-seize, and pushed into the outer with a vise.

   The axle was put together outside the car. To move it into positon by myself it was put on a board and slid across the floor with my legs. Under the car each end was raised on boards until a jack could get under it.

 After it was raised I realized the new axle brackets had not been drilled out to 1/2 inch. While doing that it fell off the jack and I had to start again.



 Yes, I had a panhard bar with a four link before I knew it was a bad thing. I even had urethane bushings for a while before I went back to rubber on top.
 Now the bar seemed like it might rub on the new rear cover. So the bracket was cut off and moved back as much as possible before re-welding. Should just clear now.

 You can see this bracket has been re-worked several times before.

 The axle end has this little bracket bolted to the lower axle bracket. It was sturdy enough before so it was re-used. In fact when the urethane caused a bind it was the panhard that bent not the tab.
 It is made from 1x1 cut and welded at an angle to point straight back. The end has another threaded tube sleeved in. Tubes are tacked into the bolt holes as well.
 The two side bolts are from the McStrut of an escort or something. The small heads are needed to clear the stock arm bushing.

  An angular piece was welded to the axle bracket to stiffen it up.

  The panhard has ends made from shock eyes. Urethane bushings are used. The one at the frame has an inner bushing with a 1/2 in bolt, while the axle has a 5/8 bolt, because it is held by one side in single shear.



  Before working on the 3rd link the axle had to be in position. So everything was bolted up and the car was raised lightly off the wooden blocks to put the weight on the axle.

  To adjust the pinion angle and hold the axle in place without the upper arms this link was used. It is a rear toe link from a Dodge Intrepid. I was going to use it as the 3rd link, but thought it might be a bit spindly. Too long as is but perfect for this job however.

 There are many sites with info on setting pinion angle and they are all different, and often contradictory. I used a pdf from Steeda, which was at least straight-forward. Two degrees down.

  I was curious to test drive the car using this as a 3rd link, but nothing else was hooked up. One of you will have to try that.

  Finally I could start the project. After two weeks of this and that the rear seat area was cleared out and a cut was made in the floor.

  All the bracketry was going to be welded in. But when trial fits were made I realized there were no truly flat surfaces in the car. To weld in pieces would require cutting somewhere.

  While eyeballing things with a 1x1 inch tube, it was set on bolts turned into the seat belt holes. A thought ocurred that the tube could be used and bolted on. And if the rear was bolted in it didn't make sense to weld the front half. So it became a bolt-on project. Kind of a production prototype.

  The only pic I have was somehow made small with no backup.



   Here is the tip of the 3rd link peeking through the hole in the floor. I had made the link extra long, so I believed. But the end was right around the center line of the finished bolt hole.

 This is the only shot of the bare piece. As it turned out the hole is almost the finished size. Three holes have also been drilled above the area for 3/8 bolts.

 At this point nothing else had been made yet. The entire project was 'do one step, then figure out the next one'. Without coming to dead end.

 The link is made from a 1x1 square tube, rubber bushings from a Mustang rack and pinion, and a thick walled tube that happened to be around. The center tube was from the old Energy Suspension urethane upper links. It all fit tightly, and had to be rubber hammered together.

  Seemed pretty tough. And stiffer bushings are available as replacements if needed. I think the stiffness goes; mustang, taurus, aviator, urethane.

  Welding this piece was the only part that worried me. If it breaks, major chaos. I vee'd the metal, did a pass, ground it lightly, sandblasted it, and did wider passes twice more. This finally made me totally confident in the finished piece.



   Here's the axle end. The pieces were put together to mock it up, then the next day they wouldn't come apart and the hammer started to damage the center bushing. So they were painted in place.

 The rubber bushing was belt sanded down to the width of the center tube. The grooves were filled with marine white grease before final installation.

  I was surprised by the length, thinking it would be 8 to 10 inches. Finished size was 13 1/4 center to center. Hey ladies, CHECK OUT MY 13 INCH MEMBER!!


  The tops of the muffler hanger pockets were cut off earlier. Now flat metal was welded in. Nice job. Last task of the day. Should have photochopped it to make it look pretty.

 The undercoat on the other side kept catching fire.




  The assembly is shaping up. Two tubes have been welded to the square tube over the seat belt holes. (newer mustangs have bolts on the floor.) Longer bolts are used to hold the assembly in tight for every step. These tubes will also allow the seat belts to be re-installed in the same place.

 Two tabs are located near each end right over the frame flanges.

 The finished areas were painted ford engine blue. Didn't think of painting the axle piece this color until it was installed.

  The top piece is cut from 3/16 inch plate. Four 7/16 holes were drilled before it was tacked in place. An angle finder was used to ensure the plate was the same angle as the car.
 Location was a guess-timation, with the seat above and the driveshaft below, keeping the angle of the link in mind.

  A piece of angle is welded to the top with plugs and stitches. Three 3/8 are welded in.

 The finished 3rd link is trying to get into the shot.




 The side pieces are 1/8th plate.

  Strips of 1/2 were laying around so that's what was used. Holes were drilled before they were twisted into shape and tack welded. Their backs were bent up simply to close off the box from the outside.
 All three sides were tacked in before it was finished off the car and de-splattered.

 Getting there. Notice the rear of the plate is level with the tube, so any bracket can slide over it if needed.

 The front piece happened to be made of 3/16, which came in handy later.






   The bottom plate was tack welded to the top before the holes were drilled. This way I knew they would align without doing precise calculation. The down side is that they may only fit together one way.

 All the pieces are made from the same 3/16 plate cutoff that was bought from a metal shop.

  To assemble the bracket properly, the bottom plate was bolted to the top plate, while the sides were bolted to the 3rd link. With the axle raised to put weight on it, and the pinion angle set, the link was held up and the sides were tack welded to the top.
 Then finish weld and paint.

 While drilling holes for the 3/16 rivets I noticed how thin the sheetmetal was. I thought this might cause vibration and fatigue over time. So an extension with four bolt holes was added along the spine to the crossmember. I wanted to use two smaller tubes but this is what I had, and I had to stick two scraps together to get it.

My Three Link has a Torque Arm!



   Now we're getting somewhere. Looks better painted.
 The floor was covered with spraycan truck bed liner and the 'T-Bar' ford engine blue.

 There are 9 bolts, 8 self tapping screws, and 16 rivets holding it to the car. It's not going to tear out anytime soon. I almost forgot to weld in the four top bolts before painting.

 The width of the crosspiece was three feet. Then I widened it to reach the inner fenders. Then I realized there was nothing there with any real strength, and it was hard to get in and out of the car, so it was cut back down. When measured again, it was three feet.

 The piece on the passenger side is rust repair. The spring bracket is behind there, and gunk built up between the pieces and rotted out.

 Bigger Pic.

   3/16 rivets circle the box. Bathroom caulk was added as a seal before final assembly.

 The seatbelts are re-installed with 3/8 Fine thread bolts and thick washers. Teflon tape was wrapped around the tube to prevent rattles.

 The sheetmetal had a few cuts from the AngryGrinder that had to be welded up.

 Bigger Pic.



 Underneath, the bracket is installed.

While building it, somehow I forgot that a bolt had to be installed. It just barely fit, after it was cut exactly to length.

 The white around the edges is caulk, while the white in the middle is white marine grease.

 The black on the link is overspray from undercoating. That bedliner stuff is impossible to get off. MY 13 INCH MEMBER HAS BLACK SPOTS ON IT!!

  Bigger Pic.

 Getting on with my life...

 I stuck the camera up above the axle and straightened out the shots in Photoshop. This one is approximately level.

 There's the bracket with the rod welded to the edge. Looks nicer. Should have welded it in solid, but I went thru 3 lb. of wire as is and my eyes are throbbing. The welding had to be arranged for only a certain amount each day.

 The bracket in the background is from the old Rancho adjustable sway bar kit.

Bigger Pic.



 On the frame, you can see there is only a finger width of space over the link, but it is near the front pivot. The back would probably hit the floor first.
 The five bolts ring the link for strength, and there is a stock crossmember right above made from sheetmetal. Later mustangs don't have the giant seatbelt washers there, and the sheetmetal is slightly changed, but the idea would still work.

The bracket bolts are long enough to drop the bracket with a spacer. Of course the holes would have to be slotted to keep the same pinion angle. As is, the driveshaft is five fingers below.

 The top of the axle mount is also about five fingers from the floor, while the axles' rubber snubbers have a hand width.

Bigger Pic.

 A shot of all the bottom bolts. The front ones have a strip of plate that conforms to the floorpan.




  Here is the rear seat bottom test fitted. The metal brace at the rear will have to be altered before it falls totally into place.

 The seat back should fit the same as before, but I'm kind of burnt out right now. Lots of upgrades on the car this year. It feels as if I worked on it more than it was driven.

  The Intrepid link was removed easily and the axle didn't collapse. So far so good.

 Next re-install the sway bar kit. The entire thing was taken off, de-rusted, and painted.
  Years ago Rancho sold adjustable sway bars for cars. The one shortcoming was the rod ends were too small. They soon crapped out, and the design made it difficult to add bigger ones. Luckily my kit also came with dogbones with urethane bushings.




   Of eight bushings only one went bad. Pretty good after all this time. A replacement was turned using a front swaybar link bushing. It had to be cut slowly or else the urethane squirmed away from the cutter.

 The old one was probably that color once.

 The sway bar installed. Big U-bolts hold it the axle. These bolts were rubbing on the tailpipes before so they were moved inwards.

 Teflon tape was wrapped under the bushings. They say this makes it more slippery and prevents wear. I had previously tapped them for grease fittings .

The bar is one inch with adjustable ends. The ends were cut down years ago as they hit the frame.

  Third Link Project completed. But before a drive; brakes.


   The first few drives revealed a clunk, so the relocated bump stops were cut, but it didn't help. Now I think it is the panhard bar hitting the frame bracket.

 Using various suspension programs on the Web the anti-squat came in at somewhere over 100%, which I found hard to believe. I was thinking it would be about 60%.
  So out came the pencil and paper and a scale ruler. It was hard to find web info of CofG height for a mustang . If 16in in then Anti-squat was 65%, if 18 then 60%. But the web programs kept disagreeing with that.

 One program also said at 1in movement the axle has no RC shift or Toe-In Gain. Cool. But that program also said I had 143% A/S. Another said it was 122%, with very slight RC and toe change.


   Finally I realized that the drawings I based my design on were flawed. Here is the same basic drawing that was in many Steve Smith stock car type books. I have altered it on the left hand side.
 It says Antisquat is at 'A', directly under the CG. But everyone else says it is at the intersection of the Force Vector, and the front axle centerline, aa compared to CG Height. Even the text mentions CGH, not CG.

 You can see the difference. At 'A' is is about 40% A/S, compared to about 120% at the front axle.

 I wonder how many people were screwed up by this drawing over the years? You might think that because they used this drawing again and again, Someone Might Have CHECKED THE FREAKING MATH ON THE THING!!!

On the other hand, several of these books said 'not to use over 50% A/S', but they were the ones with the bad drawing. If they are re-calculated the other way, their examples are over 100%. So I'm not so far off after all.

Here are some programs I downloaded.

http://www.performancetrends.com/SuspAnzr.htm A Demo. I used the 99mustang file for some numbers, then glued them into the 3 link file found in Vehicle Specs. It says I have 141% A/S.

http://mysite.verizon.net/triaged/files/3LinkV1.0bBETA.zip It says I have 121% A/S. Same numbers used.


Here's an article on how the calculate CG Height, if you have car scales.


I found a program for Torque Arms at;


 Using the rather common 48 inch arm the A/S is 162%. Also very high, yet these type are widely used.

  EVM sells a 3 link, and states it "...allows for adjustment of the anti-squat from 90% - 105%.".
  Steedas' 5 link blurb says "...geometry lets you choose between 65% and 98% anti-squat ".
 Lateral Dynamics 3 link "..the nominal A/S is about 70%....there are six possible settings for any given ride height."


  My own measurements using pencil, paper, and a scale ruler came up with: 115.27% A/S, IC 41in. at 8in. from the ground, at half a tank of gas. [assuming 18in CGH.]

 So my conclusion is, drive it more and see how theory compares to direct experience. I have driven it on the highway and around town, but only in the snow.

 If I do need to alter the amount of A/S, then there is room at the axle bracket. The center can come forward and down, as the photo chopped pics shows.

 Then the frame bracket can be altered, or my member can be shortened an inch.


   In January unusually warm weather moved in for a week. I used the time to revise the bracketry on the rearend.

 The clunk had to be dealt with at least. If both tires hit a big bump at the same time you had to grit your teeth as it felt like someone hit the chassis with a sledgehammer.
 After checking it over, the only sign was a small line at the front of the link, right where I said there was a finger width of space between it and the center of the 'T' frame. That wasn't enough space after all.

 Lowering the rear pivot seemed like a cure for both the AS and the clunk.
  The link was shortened, as I didn't want to put it deeper into the tunnel, as it would clunk worse. The frame sheetmetal was ground a bit higher as well.
  The axle bracket was removed and the center cut out. Then two 3/16" plates were bolted to the link and the bracket re-installed.
When the rearend was originally centered the bracket was off by 3/16, so this was now perfect to overlap the new pieces on the bracket.
  The plates were tack welded in place and finished outside.

  You can see the old hole still in place.

  The paint was cleaned off with a cute little sandblasting pistol that looked like a paintball gun, with the sand going into a top hopper. Fifteen bucks.


  I could only get two blurry pictures before the batteries went dead. This digital eats them like candy.
 The bracket was painted a nice blue and then I scraped the crap out of it getting it in, as it warped slightly.

 The weight off the car is on the axle here but the suspension is not compressed.

 I roughly calculate AS at between 80 and 100%. And there's no big clunk. White grease was placed on the top of the link and axle to see if it transfers to the frame or not.

  The next day the weather was back in the deep freeze.

  But still there was a thump. Different than before though. So when the weather gave me another break I looked again.

 No grease had transferred. But I saw was the shock bracket was bent. This had happened before but I thought the floor jack had bent it when the axle was lifted, and so straightened it out and carried on.

 Now it became obvious that it was hitting the sway bar bracket as the axle moved upwards. I had installed the bolt with the nut to the inside and never looked at it closely again.

So the bolt was flipped, the bracket trimmed down, and the head thinned down to be sure.

Goes to show how you can over complicate something. I was examining the 3rd link and forgot the simple things.


   Cut to; A few months later. Still winter.
However there has been some warm weather with clear roads. Accelerating from a stop it is weird to not feel the rear squat down. It doesn't feel fast, until you notice traffic is a block back.  

 Understeer is definitely reduced. On a few freeway ramps where I used to tug on the steering hard I now almost hit the inner curb. This surprised me. Without the stock bind the 'spring rate' should be lower, which would increase understeer. However, high A/S increases oversteer. So they cancel each other nicely. (they say high A/S is why certain cars are liked by drifters.)


   I jacked up the car to fiddle with the spring spacer and noticed the chassis seems to be stiffer than before. When jacked like this the opposite tire used to stay on the ground.

 The 'T' shape fastened to the frame must have tightened up the back half of the car.


 Once the wheel was off I discovered the extra flex the axle now has

. Usually with the quadra-bind to remove the spring you need to remove the lower control arm rear bolt and lower the arm with a jack.

  Now when I undid the shock bolt and aftermarket sway bar, the spring fell out on its' own. All three links and panhard still attached.



  Updated. Finally got around to putting the rear seat back in. The back fit after adjusting the bolts all the way up. It still touches the bar a bit, but a firm pull makes it clear. [I forgot the cross bar angles up a bit. My calculations assumed it was level.]

  Actually I finished over a month ago. A tree fell in the front yard and I took some pictures of it. A week later, where the funk is the camera? It had disappeared. I must have left it in the front yard.

  The Canon A460 was 'free' from my credit card company. Luckily I had enough points on a different card to get another one. This time a Sony Cybershot. It took over a month to get here.
 The controls aren't as intuitive as the canon, but the pics are better, except the super-macro.

 The old cable was a dollar store replacement item. This one is Fifty bucks from Sony!! Are you freaking kidding me?!

 The seat bottom had to be altered. The center of the frame was replaced with a rod. It was bent to clear and welded in after some eye-balling and guessing. Then the stock frame was cut out. I had better pics in the old camera.
  The strange paint color is green primer, bought from a hardware that was closing down.

  A big square of sponge was cut out where it fits over the 3 link box. Anyone who sits there would have a sore butt.

  The seats are real factory leather. The hog rings were removed and the cover was stretched out and protected from weld splatter.


 Finished. Sweet Jesus.

  Actually it was a easy project, now that it's over.

  The one annoyance is a random clunk from the spring areas. I think the axle can move so freely the springs pop out of their seats on big bumps.

  It's a much better set-up than stock. But then almost anything is.