The factory rearend is removed from under the Formula, and the disc-brake backing plates are relocated to the new rearend. Before inserting the Yukon axles into the housing, they are compared side by side with the factory offerings. The Yukon alloy axles are made of 1541H steel and are approximately 20-25 percent stronger than the factory offerings. Added strength comes from the increased levels of manganese in the 1541H configuration (versus the factory 1040 or 1050 steel), while computer-controlled hardening ensures a consistent metal grain structure, free of the imperfections that can lead to stress-induced failures. Note that the Yukon axle splines are cut longer and the diameter of the axle shaft is consistent, unlike the factory axles.
Before installing the axles,...
Before installing the axles, a new set of GM wheel studs is inserted into the axles and properly seated with the aid of a hammer. Had the Formula been intended for extensive drag racing, longer aftermarket wheel studs are a nice choice for additional safety.
The Yukon axles are inserted...
The Yukon axles are inserted into the axle tubes and carefully slid toward the differential. Once they are pushed in all the way, new C-clips are installed on the axle ends, and the cross-shaft that positively locates the axles in the differential is tapped into position.
Rather than installing the...
Rather than installing the factory steel differential cover, a replacement cover from TA Performance was sourced from Randy's Ring & Pinion. The TA cover is a heavy-duty cast-aluminum piece that is much stronger than the factory unit. In addition to the overall quality, it includes a 11/42-inch NPT fill plug on top and a 11/44-inch NPT drain plug on the bottom.
RECOMMENDED TOOLS AND RESOURCES
. Standard socket set
. Allen wrench set
. GM Kent-Moore differential service tool
. OTC race driver
. Prybar or large screwdriver
. GM service manual for 7.625-inch rearend
CRASH, BANG, BOOM-FIVE STEPS TO BLOW UP YOUR REAR
As the corollary to last issue's "Five Steps to a Stronger Rearend," here are some sure-fire methods guaranteed to shorten the life of your rearend, along with time-proven solutions:
Clutch-dumping-A manual transmission introduces significantly more driveline shock than an automatic transmission. Rev the engine up and dump the clutch and see how long the 10-bolt lasts (assuming your clutch holds).
Solution: If you must rev your LS1 to get it into the sweet spot to launch, go straight to a 12-bolt or Ford 9-inch.
Drag slicks or sticky drag radials-Enhanced traction from sticky rear tires transfers the power to the pavement, thereby placing additional pressure on the rearend to hold together.
Solution: Weld axle tubes, aftermarket axles, and TA differential cover.
Wheelhop-Six-speed-equipped Birds are especially susceptible to wheelhop, which causes the housing to distort and the ring to start creeping up the pinion.
Solution: Aftermarket torque arm, TA differential cover.
Addiction to deep gears-Although the 3.23 or 3.42 gears are nice, you can't live without 3.73 or 4.11 gears in order to accelerate even faster. The lower gear ratios put additional pressure on the housing, ring, and pinion, stressing the components.
Solution: Weld axle tubes, aftermarket axles, TA differential, and Eaton posi (drag racing only).
Poor service-The rearend fluid is designed to be replaced per the factory service intervals. If a rearend is starting to make noise or a gear change is in your plans, stay away from the corner service station or other service professionals that don't have extensive experience or the proper tools to set up your 10-bolt correctly.
Solution: Use a professional drivetrain specialist to set up and service your rearend.
RECOMMENDED PARTS AND SUPPLIES
. (1) Yukon rearend installation kit (YK GM7.5-B, retail $138.21)
. (2) Yukon axle bearings (PN AK1563, retail $15.20 each)
. (2) Yukon axle seals (PN 8660S, retail $2.68 each)
. (2) Yukon axles (PN YAG 26059962, retail $175)
. (1) Yukon 3.42-ratio ring-and-pinion set (PN GM 7.5-342, retail $196.35)
. (1) Eaton limited-slip differential (PN EAT19599, retail $541.04)
. (1) TA differential cover (PN YPT3-GM7.5, retail $148.11)
. (1) TA stud kit for differential cover (PN 1815, retail $24.99)
. (2) Qts. 80W90 gear oil (GM PN 88900329, retail $6.47 each)
. (1) Bottle GM limited-slip additive (GM PN 1052358, retail $7.65)
. (10) GM wheel studs (PN 955595178, retail $4.13 each)