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6930B Derek Dr. Fort Wayne, IN 46803Phone: 260-245-0352 Fax: 260-245-0358www.hoosierperformanceengineering. c om

C6 Corvette M/T Differential Strut Installation

InstructionsApplication:2005-2008 C6/LS2-LS3 Corvette with M/T and 2.5" or 3" exhaust.

Thank you for purchasing the HPE Differential Strut for the C6 Corvette! This product was successfully engineered by HPE to solve the problem of differential case fracture and/or transmission output shaft housing breakage caused by inherent driveline stresses present during high performance street driving, road racing, or drag racing. This kit increases the strength of that vulnerable attachment point of the transmission-to-differential to reduce the likelihood of fracture in that area that would otherwise cause complete transmission/differential failure. The entire kit only weighs approx. 17.1 lbs. (approx. the same weight as 2.5 gallons of gas) and is engineered to spread the stress loading during hard acceleration, over a greater area of the driveline architecture.

Kit Design Features:This design counteracts the natural upward "wrap-up" action of the RS driveline during hard acceleration by tying the transmission and differential together via adjustable strut rods. These steel strut rods provide a pre-load against this destructive wrap-up action that causes differential case fracture at the trans/diff mounting flange. In some severe cases, this fracture can also destroy the transmission output shaft.

The installation of this product provides added rigidity to the entire Corvette drivetrain as a whole, while the steel perimeter brackets mounted to the transmission and differential cases act as case "girdles" that provide additional strength in those areas also. These steel "girdle" brackets spread the driveline shock loads over a greater surface area; therefore decreasing differential mounting flange cracks, decreasing case distortion and increasing driveline durability. The differential bracket cross-strut rod counteracts any possible deflection between them by tying them together side-to-side. Each one of the two upper strut rods are secured to the trans./diff. brackets via heavy duty heim joints at both ends, where each rod works with the stock differential mounting legs by being independently adjustable to set a pre-load of the entire assembly.

Kit Packing List3-piece differential girdle bracket set2-piece transmission bell housing bracket set 2-piece main strut rod set2-piece right hand thread heim joint w/lock nuts 2-piece left hand thread heim joint w/lock nuts1-piece cross-strut rodTransmission bracket mounting bolts/washers Differential bracket mounting bolts/washers Cross strut rod bolts/washers2 aluminum Heim joint spacers

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Detailed installation instructions

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BEFORE YOU BEGIN-Please follow these instructions closely when installing this product and if you have any questions at all during the install, please call HPE to speak with someone who can answer the question for you. Also, be sure to support the vehicle evenly and safely with heavy-duty jack stands or a commercial vehicle lift before attempting this modification. If you do not feel you are mechanically inclined enough to perform this installation, please consult your local GM Service Technician or a trusted independent technician that's qualified to do the job. Finally, make sure the vehicle's battery is completely disconnected before attempting to install this product. Installation time is 2-4 hours on average.

Vehicle Disassembly/Preparation:1. Locate the rear transverse mounted mono-leaf spring that's located in the rear sub-frame area. (Fig.

1)2. Locate the rear ride height adjustment nuts on each end of each spring and count how many threads

are showing at its current adjustment. Write this information down, as you will need it for re-installation later. (Fig. 2)

3. Release the spring tension slowly by using a support jack under one side of the spring at a time, loosening and removing the adjustment nut until the thru bolt can be completely removed. Gently and slowly lower the jack until ALL of the tension has been completely removed from the spring end until it’s relaxed. Do the same procedure for both sides. (Fig. 3)

4. Remove the two upper and two lower anti-sway bar mounting straps fasteners on each side of the sub-frame and lower the anti-sway bar out of your way for now by swinging it down. (Fig. 4)

5. Remove the bolts that secure the over-axle exhaust pipes/mufflers to the main center section of the exhaust system. (Fig. 5)

6. Remove the muffler assembly from each side of the vehicle completely to allow for maximum clearance when installing the differential strut. (Fig. 6)

7. Locate the four rear sub-frame mounting nuts that secure the sub-frame to the vehicle chassis and loosen all four of them until 1 thread is showing on the end of the stud. This step will drop the rear sub-frame down approx. one inch to allow for maximum clearance when installing the differential strut. (Fig. 7 & 8)

*You should now have the vehicle ready for the differential strut installation.

Transmission Bracket Installation on Transmission/Torque Tube Flange:*These installation procedures were completed on a sample transmission/ differential assembly located outside of vehicle to better illustrate fitment procedures and to provide concise photos.

1. Locate passenger side of transmission mounting flange where it attaches to the torque tube and remove the two O.E. bolts in the 1 and 2 o'clock positions. You will discard these O.E. fasteners. (Fig. 9)

2. Remove the main wiring harness retaining clip from the stud on the upper mounting bolt and drill the original mounting hole out to 3/8" for re-installation with new differential strut bracket bolt. (Fig. 10)

3. Locate 12 large washers that are supplied in the kit and separate them into 4 stacks of 3 each. These will be used as spacers between the differential strut transmission bracket and the O.E. transmission flange. (Fig. 11)

4. Using an adhesive of your choice, secure the 3-washer pack together as shown: (Fig. 12 & 13)5. Set them aside to dry for installation later. (Fig. 14)6. Place 1 washer on the transmission bracket mounting bolt, pass it though the bracket, then through

the washer pack and finally install the pre-assembled bracket onto the transmission mounting flange. The final order of assembly for the transmission brackets should be: Supplied mounting bolt-washer-bracket-washer pack-transmission mounting flange. Tighten these bolts to 35 ft. lbs. (Fig. 15 – 17)

7. Perform steps 1-6 for the driver side of the transmission.*You should now be completed with the differential strut bracket installation on the transmission

flange and it should look like this: (Fig. 18 & 19)Differential Strut Bracket Installation on Differential Housing:

1. Locate the driver's side of the differential assy. (Fig. 20)2. Starting with the driver side, remove all the O.E. differential cover bolts required to fit the bracket

onto the differential. You will discard the O.E. bolts you've removed. (Fig 21)3. Install the driver side differential bracket as shown using the supplied bolts in the kit, making sure

to use a supplied washer under the head of the bolt. Torque the differential bracket bolts to 20 ft. lbs. (Fig. 22)

4. Now go to the passenger side of the differential. (Fig. 23)5. Remove the differential cover bolts required to fit the supplied bracket onto the differential. You will

discard these O.E. bolts. (Fig. 24)

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6. Install the differential strut bracket onto the driver side differential cover as shown and torque to 20 ft. lbs. (Fig. 25)

7. Install the differential bracket cross-rod (shortest of the three rods) between the two main upper differential brackets as shown using the supplied 1/4 x 20 bolts in the kit, making sure to use the supplied washer under the head of the bolt. (Fig. 26)

7. Torque each end to 12 ft. lbs. and all of the brackets, including the cross-rod. Now fully installed on the differential , it should look like this when finished: (Fig. 27)

*You should now have the differential strut mounting brackets securely mounted onto the differential case at this time.

Strut Rod installation:1. Locate the two main strut rods in your kit. You'll notice that they are of equal length and these

attach to the TOP of the differential strut kit with the machined rings facing the rear of the car.2. Your kit has 2 left handed thread heim joints w/matching jam nuts and 2 right handed thread

heim joints w/matching jam nuts. Install the appropriate jam nut onto the heim joint stud and screw them all the way on until the nut bottoms out on the stud as shown. Do this procedure for all 4 heim joints and studs until they look like this: (Fig. 29)

3. Each main strut rod has a right handed and a left handed thread machined into the ends of them for which you'll screw the appropriate heim joint stud into equally on both ends. (Fig. 30)

4. Position both main strut rods on your workbench so the machined rings are all on one end. These rings dictate which end is to face "rearward" or towards the rear of the car when they are installed. Be sure each upper strut rod is installed with the ring towards the rear of the car to insure proper installation. *FAILURE TO FOLLOW THIS STEP ACCURATELY **WILL** LEAD TO DIFFERENTIAL FAILURE!!!

5. There are 2 different length heim joint mounting bolts: (Fig. 32)-The 2 longest bolts are to be used in tandem with the provided aluminum spacers to secure the

2 rear Heim joints of the upper strut rod ends onto the differential bracket mounting holes as shown. Torque to 30 ft. lbs. (Fig. 33 & 34)

-The 2 shorter length bolts are to be used to secure the 2 front heim joints of all the strut rod ends onto the 2 transmission bracket mounting holes shown. Torque to 30 ft. lbs. (Fig. 35 & 36)

6. Make sure all 4 Heim joints are adjusted evenly out of the 4 strut rod ends as shown. *IF THEY ARE NOT, THEY WILL BIND WHEN PRE-LOADED AND THE DIFFERENTIAL STRUT KIT WILL NOT BE ADJUSTED PROPERLY, LEADING TO DIFFERENTIAL FAILURE. DO **NOT* * SKIP THIS CRITICAL STEP!!!!!!! (Fig. 37)

7. *You should now have the entire differential strut kit brackets, strut rods and mounting hardware securely mounted onto the differential/ transmission cases at this time and it should look like this: (Fig. 38 & 39)

Strut Rod Pre-Load Adjustment:*Please follow the pre-load adjustment instructions EXA C TLY as we describe here to avoid any

possible diff/trans. damage with this products Installation!1. Adjust the pre-load on all the main strut rods to a static ZERO-lash by turning each rod clockwise by

HAND until just snug then stop, making sure they are PULLING THE M SELVES TOGETHER as you tighten them.

2. The proper adjustment sequence is; Driver-upper first, Pass-upper second.3. After ZERO-lash is completed, tighten each respective main strut rod, in sequence, in ¼ turn

increments until 3/4 turn on each rod is reached and lock down with the jam nut on each heim joint stud. (Fig. 40)

4. Follow this step for both main strut rods, in the previously described sequence.5. DO NOT adjust preload rods tighter than 3/ 4 turn pa st ZERO-lash or differential

damage/ gear whine WILL occur. Once ZERO-lash has been c ompleted for each rod, DO NOT try to tighten rods eve n further past ZERO-lash as you proceed through the tightening sequence, even though the next rod in the pre-load sequence will "FEEL" loose before your adjustment sequence is complete. These steps are absolutely critical!!!!!

*You should now have the HPE Differential Strut completely installed and adjusted properly on your Corvette! Congratulations!!

Chassis Re-assembly- Follow the reverse pattern of outlined disassembly to re-assemble your vehicle successfully, paying

particular attention to installing the adjustment nuts on the rear leaf spring with the same number of

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threads showing before you started. You should have written this number down to refer back to as outlined in the disassembly procedures.

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