All,This Saturday two of us here in the Dallas, TX area did the Eibach Install on my A/C. In the interest of posterity, here are the instructions on how we did it including pictures.
Props: 
To Guitarist982 for knocking this out with me, taking notes, pictures, and throwing his weight behind the effort when brute force was necessary.
Notes: These instructions are for the Altima Coupe 3.5. Although the variations between the 3.5 and the 2.5 are minimal, these instructions may not be entirely accurate for the 2.5. Guitarist and I will be working on his 3.5 Sedan next week. If there is any variation in the process I’ll post them here.
I highly recommend doing the fronts together first then the backs together first, if you run out of time you don't want half your car lowered on one side and not the other. 
Disclaimer: These instructions represent my experiences, they neither represent a manufactures recommendation nor do I warrant them as being perfect or absolutely accurate. Use them at your own risk, I will not take responsibility for your success or failure in executing this mod on your own. Carefully weigh your decision to do this as there are a significant number of steps and a number of dangers if done without the correct tools. If you have any concern what-so-ever, have a professional do this work. Mechanical experience is a necessity. (Note: I worked on cars for 3+ years while in college). MAKE SURE TO READ AND FOLLOW THE EIBACH INSTRUCTIONS BEFORE PROCEEDING, THEY ARE PRETTY POOR, BUT WHAT LITTLE THEY GIVE YOU NEED TO KNOW.
OK, now for the fun part: 
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Preparation:
A) Tools: The following tools will be needed and are highly recommended:
1) 4 - Jack Stands, 1 Ton minimum
2) 2 Ton Floor Jack
3) Air Compressor (If you chose to use a Impact Gun/Wrench) - Highly Recommended
4) Impact Gun/Wrench - Highly Recommended
5) Impact Sockets (13mm - 24mm Sockets)
6) Open Ended Wrenches (13mm - 22mm)
7) Rubber Mallet (Or other Type Hammer if you're brave)
8) Break Away Bar (This is essentially a 1/2 Inch Socket Drive on the end of a long metal bar)
9) 3 Feet of 1/2 Inch rope
10) Spring Compressors (McPherson Type)
11) Pry Bar (Handle of the floor jack did this function for myself)
Note, The Compressor, Impact Gun/Wrench and Spring Compressors can be rented at your local AutoZone or such auto shop. Here in Dallas I rented only the spring compressors, had the rest of the equipment, rental is free from O'Reillys.
B) Raise the Car: I raised the entire car up about a foot on all four corners. To each their own, if you plan to do fronts then backs and only raise one side at a time, make sure to chock the wheels.
C) Wheels: Pull wheels off the car, you can't do this with them on, period. Tip: Rotate your tires if you’re due for a rotation. Make sure if yours are uni-directional you rotate them on the same side of the car.
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Front Spring Replacement: This is the hardest part of the effort. The fact that we have struts means we have to really work hard to change out the springs.
Step One: Front Strut Extraction
A) Break Loose the upper strut mount bolts (#1's - Picture 1) inside of the engine compartment using a 13mm socket wrench and a 13mm open ended wrench. The bolt closest to the wind shield can't accommodate a socket. There are three, you only need to break them loose and move the a quarter turn. There is a forth bolt that is closest to the center of the car, this bolt does not need to be loosened. Do not remove these bolts, they will give you support from above as you work on the lower strut assembly.
Picture 1 :
B) Using an 18mm Socket, break loose the Strut Master Bolt (#2 - Picture 1 - This is the bolt in the center that is silver/goldish in color). Only break it loose, DO NOT REMOVE! You will strip the threads of the strut if you do and likely will have to buy a new strut. Breaking this bolt loose now helps because the strut is held in position by the mount bolts, if you try to do it later when the strut is off of the car it's much harder, but not impossible.
Moving down into the wheel well, there are 4 key points of action (See Picture 2)
- Brake Line and Retaining Clip (#4 - Picture 2)
- Wheel Sensor Wire (I think it's for ABS/TPMS/VDC) (#2 - Picture 2)
- Lower Strut Bolts (#3 - Picture 2)
- Control Arm (Attached to Sway Bar) (#1 - Picture2)
Picture 2:
Here are a couple other angles with the noted items from above:
Picture 3 - Left Side of Strut Assembly & Picture 4 - Right Side of Strut Assembly:
Picture 5 - Control Arm Mount to Strut including Nut:
C) Use the floor jack to support the Brake Assembly before the next steps.
D) Using a pair of pliers remove the brake line retaining-clip from the strut.
E) With your fingers, remove the Wheel Sensor Wire Grommets from both sides of the strut.
F) Using a 21mm Socket Wrench, the break away bar with a 21mm socket and/or an open ended 21mm socket wrench undo the 2 lower strut bolts.
G) Using an 18mm Socket remove the Control Arm Bolt from the strut. Push the control arm toward the engine compartment and to the side. (Picture 6)
Picture 6:
H) With all of the above items complete, take the brake assembly, pulling away from the car apart from the lower strut mount. Shift it to the side (I pushed it toward the front of the car). (See Picture 7)
Picture 7:
I) While supporting the strut from below, loosen the upper strut mounting bolts (inside the engine bay) and remove the strut from the wheel well. You can do this by hand since you broke these bolts loose earlier. (See Picture 8 for removed strut assembly)
Picture 8:
Step Two: Remove and Replace the Strut Spring
A) Attach the spring compressor to the spring, try to get them as far on the opposite side of the spring as possible. (NOTE: The pictures enclosed show me using a McPherson style compressor, you need to have one of these to do the front springs) (Picture 9).
Picture 9:
B) Tighten the spring compressors in an alternating fashion until the spring shrinks to produce a small gap between the spring and the strut platforms (Picture 10)
Picture 10:
C) Undo the Strut Master Bolt, take is all the way off. Once off, the stut will literally fall apart. Take the spring off. Make sure to take a good look at the strut and it's components, you'll need to be able to reassemble the entire set later (Picture 11).
Picture 11:
D) Alternating between the spring compressors, remove them from the OEM Spring (Picture 12).
Picture 12:
Picture of OEM and Eibach Springs next to each other:
E) Take the strut dust boot off of the strut, inside the boot you will find the Bump Stop that needs to be trimmed per the Eibach Instructions. The bump stop is made of a rubber compound, cutting it down can be done with a box cutter, a hacksaw, or anything in between. DO NOT cut this while it is on the strut, you could score the smooth surface of the shock and damage it. The recommended cut down by Eibach is 25mm. Measure twice, cut once. (No Picture)
F) Reassemble the lower strut components is the correct order (Starting from below, Lower Strut Assembly, Bump Stop, Dust Boot.)
G) Attach the spring compressors to your new Eibach Springs. Placement is key as the spring in its uncompressed state actually leans off-center from the strut (Picture 13). We found that the best place to mount the compressors were (starting at the top) 360 degrees (1 full circle) (Picture 14 - #6) from the start of the top of the spring and the next 135 degrees further down (Picture 14 - #7). Place the lower hooks at the lowest point of the spring possible except for the bottom of the coil as you'll never get it off if it is all the way down.
Picture 13:
Picture 14:
H) Alternating between spring compressors, compress the spring. NOTE: Keep the spring on the strut assembly while doing this, as you tighten the spring your goal is to have the spring centered so you can reattach the upper strut housing. IMPORTANT! Make sure the rubber spring seat and the spring are in position. The rubber seat is formed to the contours of the lower strut base and the spring, all three must fit together (Picture 15 - #5).
Picture 15:
I) Once compressed you should be able to place the upper spring support and the upper strut plate back into position.
J) First hand tighten the strut master bolt, once you abve tightened it by hand as far as you can, complete the tightening job using an impact wrench. NOTE: This bolt must be tight. Your goal is to tighten the bolt flush. Do not over tighten, you can adjust later if there is a little gap.
K) Release the spring compressors in an alternating fashion till they come off of the spring.
Picture 16: Final Product - Strut Assembly with new Spring:
Step Three: Replace the Strut (This part is easy, reverse the items in Step One Above):
A) Attach Strut to Upper Strut Mount Point with three bolts. Hand tighten + 1/2 turn with a wrench.
B) Reattach the control arm mount point. (Tighten Well)
C) Reattach the brake assembly to the lower strut mount points. (Tighten Well)
D) Reattach the sensor wire grommets on both sides of the strut. (With Fingers)
E) Reattach the brake line with the OEM Retaining clip (Small tap with a hammer will knock this in place.
Step 4: Repeat Steps 1 - 3 for the other side of the car.
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Rear Spring Replacement: The rear spring replacement is a lot easier than the front. First of all, you don't need the compressors to get the job done, just a good floor jack. Other tools needed include: Break Away Bar, Appropriate sockets/open ended wrench, rope, impact gun).
Step 1: Remove OEM Spring
A) Place the floor jack under the lower spring arm and pump till contact is made. Increase support with an additional 1/2 pump of the jack (Picture 17).
Picture 17:
B) Tie the rope around the upper control arm and onto the spring, use a square knot. Just in case the spring pops out, it will keep it from bouncing around. (Picture 18 & 19)
Picture 18 & 19:
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C) Using the appropriate open ended wrench and Socket wrench break loose the bolt that attaches the Brake Assembly to the lower Spring arm. Set nut aside. (Picture 20 - #9 & 21)
Picture 20 & 21:
D) Using a combination of the socket wrench and impact wrench, remove the bolt. NOTE: This step takes a leap of faith, this bolt is really tight and at an awkward angle. Taking it out is tough. You need to adjust the floor jack to get the least resistance possible then remove it. I used a pry bar to torque the lower spring arm into the right position during removal and reassembly. It can be done, but it will seem like it can't. Having a friend with you at this moment is a good thing (Picture 20 & 21).
E) Using the floor jack release the spring slowly. NOTE: Sometimes the lower spring arm won't fall down, you may have to give it a push. I gave it a good kick and it released. (Picture 22).
Picture 22:
F) Untie and remove the old spring.
Picture of OEM and New Spring together:
Step 2: Replace and reassemble:
A) Take the new spring, make sure it aligns with the OEM Lower Rubber Mount. While holding the spring, use the floor jack to raise it back up into position. Continue to raise the lower spring arm till the mount point we detached in step D above is in position.
B) Re-Insert Bolt removed in step D. NOTE: This is the hard part also, due to the awkward angle the bolt won't go in freely. Focus on first aligning the entry point (From the rear of the car) to get the bolt into the attachment point. Then using a pry bar, torque the lower spring arm and insert the bolt the rest of the way. Two people are better than one here. Once back in, attach the nut and tighten.
Step 3: Repeat Steps 1 - 2 for the other side.
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There you go. Short of replacing your wheels and cleaning up, you're done.
NOTE: Once you've lowered the car back to the earth, check your Strut Master Bolts to see that they are tight. My Passenger side one was a little loose, the weight of the car when returned to the strut cleared that up pretty quick. Tighten and then drive, listen for any odd sounds which may indicate something went wrong.
Use these instructions at your own risk. Just want to share my experiences with others. 
-- Wind
Modified by windhaven at 9:30 AM 3/11/2008
Windhaven (Mod List At: http://forums.altimas.org/zerothread/352514)
I want to see what those Modas look like with the drop.
... Yeah, there are some things that Iwill try to do myself... and this aint one of them!!!! Great write up fellas!!!!
