Upgrading the Ford 8-inch Differential
Powertrax Lockright Installation

Only recently have Ford vehicles come standard with some sort of traction device in the differential. Although traction-loks and Detroit Lockers were optional in the 60's and '70's, fact is majority of cars simply came with an open "peg-leg" differential. This was hardly adequate in keeping the wheels from spinning with the factory power levels, let alone the asphalt melting torque most of our engines are churning out these days.

We recently looked into getting some traction for our 8" equipped 1967 Mustang. If you don't already know, the 8" rearend is pretty much the stepbrother to the 9". Although it is very similar in design, and is fairly strong, it has been overlooked in the sense that there just aren't many cost effective options for upgrading an open 8" rearend. In fact the 8" has long been considered a "weak" rearend, yet what most people don't realize is that in stock form, most of the internals (spider gears, side gears, bearings) are the same pieces as the 9". In fact, not only will an 8" rearend hold up just fine behind the stoutest of 289 and 302's, it will save 100 lbs over a 9".

Anyway enough history... Powertrax Corporation has developed the Lockright differential not only for the 8", but the 8.8" and 9" Fords as well.The beauty of the Lockright is that it is a locking differential, which means in straight-line acceleration the axles are positively locked together and the wheels turns at the same rate. When turning the unit un-locks and differentiates torque to each wheel, so that the inside wheel turns slower than the wheel on the outside of the turn. Unlike a posi or traction lock differential, which operates on clutches which eventually wear out and slip, a locking differential provides a true mechanical lock-up of the two axles.

Since we were going to go through a complete rebuild of the tired 8" rear end, we opted to install a new set of 4.11 gears. Since we'll be installing a new ring and pinion we let West Coast Differentials in Sacramento, Ca handle the assembly. However you can install the Lockright in your garage in about half-a-day, so long as you are not changing the ring or pinion settings. The unit comes with detailed instructions which walk you through the installation.

Click for larger image!1) Our old and tired carrier (a.k.a third-member or pumpkin) is disassembled. Be sure to mark the bearing caps so you can identify which side they go back on, they have a wear pattern and thus are not interchangeable. Click for larger image!2) Once the bearing caps are removed the differential case can be lifted out of the carrier, and the ring-gear unbolted.. The differential is like a clamshell, Eric uses thin chisel to split the two halves.
Click for larger image!3) Here are the guts of the stock open differential; two side gears, one spider gear (the other one is in the other half of the shell) and the single cross shaft. The Lockright requires use of a hardened cross shaft. Test the stock shaft with a file; if it scratches or groves the shaft, replace it with a hardened piece.. Click for larger image!4) A press must be used to remove the pinion from the pinion housing, and also to remove the pinion bearing.
Click for larger image!5) The hard parts were cleaned in a solvent tank. Nothing like clean iron! Click for larger image!6) In this picture the side gear is placed on the Lockright supplied driver. It is critical that the height measure a minimum of 1.165 inch (not including the thrust washer.) Any less and the unit will not function properly. Ours did measure slightly less, so WCD replaced the worn side gears with new ones.
Click for larger image!7) On the left is a new side gear, with no wear on the teeth. On the right is the old gear with considerable wear. If you can't tell the difference from the photo, don't worry, the Lockright instructions come with detailed diagrams. Click for larger image!8) Reassembly of the case; place a thrust washer in the case, followed by a side gear, then the Lockright driver, and then the pinion shaft block...which is what you see in the larger half of the case in this picture.
Click for larger image!9) T he hardened pinion shaft is driven in between the two short shafts which come with the kit. Click for larger image!10) A closer view of the pinion shaft block with the long shaft between the two short shafts. Note the four holes in the driver; this is where the tiny springs and pins supplied with the kit go. Don't forget these or you'll have to pull it all apart again!
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