Installing subframe spacers is an easy mod that will eliminate the wheel hop present in the 240sx. However, it is necessary to place your car on jack stands before beginning. Furthermore, you will need to loosen, but not remove the lug nuts on your rear wheels before lifting as these wheels will be removed once the car is in the air.
There are several companies making subframe spacers for the 240sx. They can be ordered in anodized blue/red or steel.
Locate the subframe mounting points
The subframe has four mounting points that hold the subframe to the chassis of your 240sx. These are cylindrical mounts with a rubber bushing that are retained to the chassis by a nut and collar on the rear mounts and a nut and 2 bolts with a collar/bracket on the front mounts.
This diagram shows the 4 subframe mounts circled in red. ( fullsize )
This image shows the front, driver’s side mount where the subframe connects. Note the 2 additional mount points on this bracket.
The rear, driver’s side subframe mount.
Loosen and lower the subframe
First, place the hydraulic jack under the rear differential and raise the jack until it is supporting the rear subframe. However, make sure that the jack is not lifting the rear of the car off the jack stands. There is a fine balance to keep here and things will become unstable if you lift the rear off the stands. Now remove the 2 lower collars from the rear mounts by removing their single nut. Proceed to the front and remove the 2 collar/brackets by removing the bolts and nuts. Very, very slowly begin to lower the hydraulic jack. You will notice that the subframe will begin to lower. Take extreme care to not drop the subframe by lowering its mounts past their guide posts. Once the subframe has lowered about 3/4″ inch lock the jack. The upper subframe collars (the slotted ones) will now slide onto the posts above the four subframe mounts. With the upper collars on, slowly raise the subframe with the hydraulic jack to its starting position, once again taking care not to raise it to the point that the rear lifts off of the jack stands.
The hydraulic jack in position under the rear differential.
The upper collar sliding into position.
Another image showing the upper subframe collar sliding between the subframe and body of the 240sx.
Install the lower spacers
With the subframe back into the raised position, the lower spacers (the ones without slots) are placed on top of the factory collars and then the factory collars are reinstalled. (For clarification, the order of your subframe mounts will now be: factory collar (or collar/bracket on the front), lower subframe spacer, factory mount and upper subframe spacer.) Next, make sure everything is tightened and slowly release the tension from the hydraulic jack to ensure that the subframe does not move. Once satisfied, reinstall your wheels and snug the lug nuts. Now lower your car from the jack stands and fully tighten your lug nuts once the car is on the ground. Finally, check the subframe nuts and bolts one last time and ensure that everything is tightened down.
Install the lower spacer on top of the factory collar.
The front collars are mounted in the same manner as the rear.
The subframe spacer properly installed on one of the rear mounts.