Ford 9 inch

Ford 9 inch

The most popular rear end around is no doubt the Ford 9 inch unit, it is used by restorers, street rodders and racers alike, regardless of what brand of car the axle is going in. Many custom made axle housings for the GMH boys utilize the 9 inch Ford, even though they hate to admit it. Ford used the axle from around the 1957 model year right up until the early 1980’s
. A small bearing housing can be differentiated from a large bearing housing by the size of the nuts and thread used to retain the brake backing plates to the housing, the small bearing housings use 9/16 socket size nuts with 3/8” fine thread, while the larger bearing use 11/16” socket size and 7/16” fine thread. From rear of car look for a large center hump in middle of backside center section (post 66 models), in general a round appearance, it is a 9”.See photo above.
From front side look at the bottom two center retaining nuts, if a socket cannot access them to remove, only a wrench, then it is a 9” .
The C7AW-E case seems to have been the standard case in use for quite sometime, have found them with date codes up to 1981.Other standard cases encountered: C1AW-4025-C,C4AW-4025-A
The case of course most desirable is the N case, first used on the 427 Galaxies around 64I believe. They are most often found behind the later 428CJ and 429CJ cars Here are two nine inch ring gears side by side, one from a 3.00 ratio (thinner gear), the other from a 3.50 ratio (thicker).An easy way to spot a nice ratio after a while is by visual id.-the thicker the gear the better the performance ratio, thinner the gear= less performance, more fuel economy and better highway performance.

up one tire if you have an open diff, or both tires if you have a working posi or locking differential. Rotate the tire one full revolution for posis and lockers and 2 full revolutions for open diffs. Carefully count the number of full revolutions the driveshaft makes. This is your gear ratio. In other words, if the drive shaft turns 3 ¾ turns, you probably have a 3.73 gear ratio. Turning the tire for twice the number of full revolutions and dividing the drive shaft revolutions by two will give you a more accurate reading.Put the transmission in neutral and jack up both tires. Turn one tire. If the other tire spins the opposite direction you have an open differential, and if it spins the same direction you have a posi or a locker.

A limited slip differential typically uses some form of clutches that bind up the differential, providing traction to the both tires . Clutch packs may also wear with time and require replacement Limited slip units require a special gear oil additive and may chatter when turning.. Lower ratios are generally desirable when going off-road. Higher ratios are better for freeway driving since they run at lower RPM’s and offer better fuel economy.

PERFORM A REFERENCE CHECK ON BACKLASH AND A PATTERN CHECK ON DRIVE AND COAST. THIS WILL GIVE YOU A GOOD IDEA OF WHAT BACKLASH YOU WILL NEED AND WHAT THE GEAR PATTERNS LOOK LIKE UPON RE-ASSEMBLY
MAKE SURE DIAL INDICATOR IS EXTREMELY RIGID, OR RESULTS WILL BE SKEWED. ENSURE DIAL POINTER IS SET SO IT TOUCHES THE TOP OF ONE GEAR TOOTH AND IS TANGENT TO THE OUTER ARC OF RING GEAR TEETH. HOLD PINION FLANGE SOLID AND ROTATE RING GEAR BACK AND FORTH, ENSURING PINION/FLANGE DOES NOT MOVE. PLAY SHOULD BE EVIDENT AND THE AMOUNT OF BACK AND FORTH PLAY IS CALLED BACKLASH. IT SHOULD BE AROUND .008 TO .012 INCHES.
PAINT ALL RING GEAR TEETH, BOTH SIDES, WITH GEAR MARKING COMPOUND (USUALLY A WHITE TYPE OF GREASE). PUT FORCE ON RING GEAR IN EITHER DIRECTION (SMALL RUBBER PAD PRESSED AGAINST RING GEAR TEETH WORKS WELL FOR THIS). SPIN PINION/FLANGE BACK AND FORTH, 10 OR 15 TIMES, ENSURING 5 OR 8 RING GEAR TEETH MESH WITH PINION GEAR TEETH. RELEASE FORCE ON RING GEAR AND ROTATE IT TO A POINT WHERE PREVIOUSLY MESHED TEETH (PATTERN IN GREASE) CAN BE SEEN. PATTERN SHOULD LOOK LIKE CORRECT MESH PATTERN IN DIAGRAM BELOW.

REPEAT PROCEDURE, FORCING RING GEAR IN OPPOSITE DIRECTION. CHECK PATTERN AGAIN. BOTH PATTERNS SHOULD BE IN CENTER OF TOOTH AND NOT RUNNING OFF THE EDGE OF ANY TEETH. PATTERN CAN BE CHECKED AT VARIOUS LOCATIONS ON RING GEAR TO ENSURE PATTERNS ARE THE SAME OVER ENTIRE RING GEAR. DOING THIS WILL ALSO ENSURE RING GEAR IS SEATED CORRECTLY ON DIFFERENTIAL AND RUNOUT ON RING GEAR IS ACCEPTABLE.
REMOVE DIAL INDICATOR IF INSTALLED AND LOOSEN 4 CARRIER BEARING CAP BOLTS. MAKE SURE BEARINGS CAPS ARE MARKED IN SOME WAY SO THEY ARE INSTALLED AS THEY CAME OUT. THEY ARE NOT INTERCHANGEABLE. REMOVE CARRIER BEARING CAPS. REMOVE DIFFERENTIAL/RING GEAR,
.
REMOVE PINION ASSEMBLY. CARE SHOULD BE EXERCISED TO PREVENT DAMAGE TO RUBBER O-RING ON PINION ASSEMBLY. ENSURE METAL SHIM(S) BETWEEN MAIN CASING AND PINION RETAINER ARE ACCOUNTED FOR AND NOT DAMAGED. SLIDE PINION OUT OF RETAINER (MAY NEED TO BE PRESSED OUT) AND PRY OFF PINION SEAL ON END OF RETAINER.
PRESS OFF AND REPLACE REMAINING PINION BEARING. REPLACE BEARING RACES ON BOTH SIDES OF PINION RETAINER. REINSTALL PINION INTO RETAINER .
INSTALL NEW CRUSH COLLAR ON PINION . INSTALL REMAINING PINION BEARING, PINION FLANGE, AND NEW PINION NUT. HOLDING PINION FLANGE WITH VERY LARGE ADJUSTABLE WRENCH, TORQUE NUT TO 175 FT-LBS. ENSURE ROTATIONAL FORCE OF PINION GEAR DOES NOT EXCEED 5-8 IN-LBS FOR NEW BEARINGS OR 8 IN-LBS FOR USED BEARINGS. IT IS BEST TO CHECK ROTATIONAL FORCE OFTEN WHILE TORQUEING, AS THE ROTATIONAL FORCE WILL GIVE YOU A BETTER INDICATION OF PINION BEARING PRE-LOAD THAN THE PINION NUT TORQUE. TORQUING CLOSE TO, BUT NOT EXACTLY TO, THE SPECIFIED TORQUE MAY BE REQUIRED IF ROTATIONAL FORCE LIMIT HAS BEEN REACHED.
REMOVE AND REPLACE EXTRA SMALLER PINION BEARING FROM MAIN CASE. RETAINING RING CAN BE PRIED OUT AND USUALLY REUSED IF NOT DESTROYED. ENSURE CASING AROUND THIS BEARING IS NOT CRACKED IT IS A COMMON PROBLEM, ESPECIALLY AFTER HARD USE. IF IT IS CRACKED, YOU MAY WANT TO CONSIDER UPGRADING TO A NODULAR CASE AND/OR A PINION HOUSING THAT ACCEPTS LARGER BEARINGS.
Internally the number of clutch disc and plates differs between the equa loc and trac loc spools, the equa loc having only 3 fiber plates and 4 steel with one large belveder spring applying force.The trac loc unit utilizes 4 fiber plates and 5 steel plates, with 4 smaller springs applying force.Both equa lock and trac loc units were available in 2 pin and 4 pin varieties, in either 28 spline or 31 spline versions.The four pin 31 spline unit would be more commonly found as a trac loc piece. The four pin being the heavier duty unit utilizing 4 spider gears vs just two in the two pin variety a four pin variety will have actually just 3 pins and a two pin will in reality just have 1 pin- the number of spider gears is actually what is being referred to.Shown below are the internals of a four pin equa loc, note the five “fingers” on the steel clutch plates-the tiny circular tabs on outer edge- (trac loc units will have only 4).
Ford used either 28 spline or 31 spline axle shafts with the nine inch, the eight inch came only in 28 spline, as did the majority of nine inch car applications. For the most part eight inch and nine inch car axle shafts will interchange between housings of the same width, spline count and bearing size A method to identify 28 spline axle shafts can be by looking at the center brake hub area, a rectangular slot in the center will indicate 28 spline axles. The 31 spline axle shafts will have a different appearance, with one small center chamfer and two outer holes in the center hub, however, 28 spline shafts can also appear like this to, so it does not always indicate 31 spline shafts

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