MustangWorks.com : Ford Forums - View Single Post

Jeff Chambers · 05-07-2002, 06:40 AM

To measure the backlash, you need a dial indicator set up so that its tangent to the teeth of the ring gear. Adjust backlash by removing/adding shims to move the ring gear into the pinion (reduce backlash) or move the ring gear away from the pinion (increase backlash). You'll also need a micrometer so that you can measure the shim thickness so that you know where you're going. For example;

Left Shim/Right Shim/Backlash

.281/.245/0.000 (initially tight)
.276/.251/.005
.273/.254/.008 final

Actually since the gears are a hypoid shape a .003 change in shim won't net exactly a .003 change in backlash, but it will be close. The Helm manual has a table that provides the shim change needed to obtain a given backlash change. Don't forget that the main caps HAVE to go back on the same side that they came off and must have the arrows pointing outwards. With proper carrier bearing preload, the carrier should be hard to remove (i.e. gently pry it out). Too little preload and the carrier will move under load, too much and you'll fry the bearings pretty quick.

From the way it sounds, you probably don't have enough preload now on your pinion since you just snugged it up (was probably closer to correct the first time). You may be able to get things assembled without the proper pinion preload, but you'll probably wind up with premature bearing or gear failure. Without the proper preload, the pinion will move excessively under high load (launch/acceleration). The pinion will get sucked deeper into the mesh and end up moving side to side wearing out the bearings and possibly the gears. Better go back and preload it properly. Since you'll be crushing the sleeve further, you don't need to change the one you've got in there.

Check out my website for some detailed instructions on gear setup. I worked in the engineering lab at DANA's Spicer Axle Division during college and have probably setup up more than a hundred gearsets in everything from Jeeps to UPS trucks. I just swapped to 4.56's in my Mustang last week and did a 3.73 install in a kid's mustang over the weekend.

05-07-2002, 06:40 AM	#5
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	To measure the backlash, you need a dial indicator set up so that its tangent to the teeth of the ring gear. Adjust backlash by removing/adding shims to move the ring gear into the pinion (reduce backlash) or move the ring gear away from the pinion (increase backlash). You'll also need a micrometer so that you can measure the shim thickness so that you know where you're going. For example; Left Shim/Right Shim/Backlash .281/.245/0.000 (initially tight) .276/.251/.005 .273/.254/.008 final Actually since the gears are a hypoid shape a .003 change in shim won't net exactly a .003 change in backlash, but it will be close. The Helm manual has a table that provides the shim change needed to obtain a given backlash change. Don't forget that the main caps HAVE to go back on the same side that they came off and must have the arrows pointing outwards. With proper carrier bearing preload, the carrier should be hard to remove (i.e. gently pry it out). Too little preload and the carrier will move under load, too much and you'll fry the bearings pretty quick. From the way it sounds, you probably don't have enough preload now on your pinion since you just snugged it up (was probably closer to correct the first time). You may be able to get things assembled without the proper pinion preload, but you'll probably wind up with premature bearing or gear failure. Without the proper preload, the pinion will move excessively under high load (launch/acceleration). The pinion will get sucked deeper into the mesh and end up moving side to side wearing out the bearings and possibly the gears. Better go back and preload it properly. Since you'll be crushing the sleeve further, you don't need to change the one you've got in there. Check out my website for some detailed instructions on gear setup. I worked in the engineering lab at DANA's Spicer Axle Division during college and have probably setup up more than a hundred gearsets in everything from Jeeps to UPS trucks. I just swapped to 4.56's in my Mustang last week and did a 3.73 install in a kid's mustang over the weekend. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"