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Fixing a chipped Pinion Gear

Some gear sets get chipped or nicked during the manufacturing process or during shipping. In most cases these blemishes are outside the contact pattern, and they can be removed with a few minutes of careful polishing.

First thing is to determine if the nick is in the pattern. If this isn’t obvious by looking at the gear, you can install the set into the housing and run a quick pattern check. When you have determined that the chip or nick is clear of the pattern, use a medium grit 3M disk to polish out the nick. This is necessary to prevent any jagged edges from coming into contact with the gear under load and possibly causing damage.

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Ford 9" - Fixing a damaged side adjuster

If you do a fair amount of differentials the odds are pretty good that you have come across a spun carrier bearing or two in you time. Most people think that this means you need to hunt for a new housing or drop out but that’s not the case in most instances. There are two different fixes for this problem depending on what style of housing your working on.

It’s very common to find a Ford 9” that has a side adjuster with a grove warn into it from the carrier bearing race, the fix for this is very simple and takes just a few minutes. Using a 1 1/2”wide, fine flat file lay the adjuster flat on the bench then lay the file flat onto the adjuster and file the entire adjuster until the ridge is gone.

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Ford 9" - Getting a ring to clear pilot housing

A very common problem when installing low gear ratios in a Ford 9” is that as the ring gear gets thicker the toe of the gear hits the pilot bearing housing leaving you with only two options, grind the gear, or the housing. We prefer grinding the gear, the problem with grinding on the pilot housing is it tends to make it thin and weak making it prone to cracking. By grinding the gear you have no sacrifice in strength and it takes less time. Some OE Ford gears as well as a small few aftermarket gear manufactures chamfer their gears from the factory to minimize the possibility of additional grinding being necessary during installation.

Here is a picture of the best method we have found to clearance a 9” ring gear to clear the drop out case. CAUTION it is very easy to over heat the gear while grinding it with a bench top grinder, so be patient and only take as much as necessary. Clearing the pilot by 1/16” is more than enough clearance. After you have removed the necessary material, remove any burs with a 3M pad and thoroughly clean the gear before installation.

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Getting a cross pin shaft to clear a thick gear

In many cases it is necessary to grind one or more teeth on a ring gear in order to reinstall the cross pin in many c-clip style rearends. In most cases this will not interfere with the contact pattern of the gear or decrease the strength in any way as long as it is done properly. In some rare instances you may need to grind as much as ¼ of one or two teeth away. Although we have seen vehicles run with half of a ring gear or pinion tooth missing, we do NOT recommend pushing your luck that far. However, we have no problem running a gear-set in our own vehicles with 1/4 of tooth ground off of the toe or 1/8th of the heel of one or two of the ring gear teeth.

Gear grinding should always be done on the bench top, not while gear is installed. This is to avoid getting metal and other contaminants into the housing or differential carrier. In most cases you will only need to grind about 1/8” off the corner of the tooth. After the desired amount of material is removed, you need to use a medium grit 3M disk to round the edges and remove any burrs. Be sure to clean a gear thoroughly before you reinstall it into the housing.

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Properly setting preload with side adjusters

There are several types of rear ends that use a threaded side adjuster be it a single adjuster or one on both sides of carrier. The most commonly known rears with this type of carrier adjustment are the Chrysler 7.25-8.25-8.75-9.25, Ford 9”, GM 8.25” IFS, Suzuki Samurai, & Toyota. The GM 9.5” is a little different than most as one side uses shims but the other side is the threaded adjuster.

Randy’s has tools that work with a 1/2” drive ratchet or breaker bar that work much better than beating the heck out of the adjuster with a punch & hammer. These side adjuster tools are priced starting at $29.00.

Most people are reluctant to really crank on these adjusters to preload the carrier bearings. It is perfectly normal to have 150-200 ft lbs of torque on the side adjusters. It is very important to obtain good preload to avoid damage to your differential. At Randy’s, our service shop uses a 1/2” breaker bar, as shown in illustration 1A. The reason we do this is because as you accelerate, the pinion wants to make the ring gear deflect. The more power, the more it will tend deflect. Housings always flex, some more than others, depending on whether it’s stock or an aftermarket nodular. If you put a lot of preload on the carrier bearings it also preloads the housing. Since the housing is already flexed, it is not likely to flex even more causing the ring gear to move away from the pinion resulting in broken teeth.

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Tight Yoke Installation

In many cases when installing new yokes on Ford 10.25”and 10.5” as well as some other differentials, it can be difficult to get the yoke over the pinion splines. The fact is, many pinion splines have a slight “twist” to them (which controls rotational “slop”), but the Ford 10.25” & 10.5” pinion splines have a slightly tighter fit than most. As a result, they make it difficult to get a new yoke over the pinion splines, and it’s an even bigger challenge when installing a new yoke over a new pinion gear.

The solution? There really isn’t one, you’ve just got to use good old-fashioned force. Generally, it’s a two person job. One technician holds the pinion in the backside of the housing, while the other cradles a brass punch in the yoke and use a dead blow mallet to drive the yoke into place (See Pic). Keep striking the yoke until the pinion nut threads are exposed enough to get a few turns of the pinion nut on the pinion, then use an impact gun to get the yoke seated. (Be careful to make sure to have enough pinion thread showing to ensure you won’t strip the threads off the pinion.) It sounds rough, we know…but it’s the only way to get the job done.

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