Today’s tech tip is courtesy of Fran Schmit of the Minnesota club and originally appeared in the Feb 2007 issue of the CORSA Communique magazine.
This procedure solves a difficulty with installation of the powertrain, which requires doing what I tell you before you begin to remove it. I was reminded recently of this when reading a CORSA article about how much trouble someone was having re-installing their late model drivetrain.
A late model with its drivetrain out has its rear wheels hanging down a mile. When you want to re-install the drivetrain you can’t get the strut rods back onto the differential housing. The shop manual is of little help as it says, “support torque arm so that spring is compressed to be near curb height” which is exactly and perfectly true. However, nobody ever told us how to do that.
So I was just like everyone else and did it my own way, which didn’t work. For many years I asked around for advice on this issue and always got some well-intentioned but no-good answer. I tried a multitude of devices to accomplish that curb-height condition; some of them turned out to be pretty dangerous and I was lucky to have survived messing around with a compressed spring that was not properly “contained.”
My solution: while the car is sitting normally on its wheels, the spring is properly compressed. Before removing the drivetrain, replace each rear shock with a short non-stretchable piece so the wheel can’t hang down when the vehicle is raised up.
When I finally hit upon this workable scheme I made a pair for our local mechanic to use in his shop. If you have a late model you should make a pair of these now before you need them.
I use two 20″ Iong pieces of 1/2″ threaded rod bent and welded into an eye-bolt configuration, as shown in the photo. Each threaded end is fitted with some washers and a nut. With the vehicle at curb height, remove the shock absorber and poke the straight end of the device up through the top mounting hole, secure the eye onto the shock lower end bolt, put the washer/nut on the top end of the device and spin the nut down to where the shock’s top nut went.
Make certain that you spin that nut down when the vehicle is sitting at curb height. Do this on both sides. No need to double nut it or to put on a rubber bushing as you’re not going to drive it anywhere.
When you raise the vehicle the wheels will go up with the car and remain there waiting “up” for you till the job is done.
At re-install time, after the drivetrain is bolted in, the strut rods slip into place, either end first, with ease, and bolt onto the wheel and to the diff with no problem.
Safety Warning: A compressed suspension spring contains considerable force that can be dangerous if released unexpectedly. The shock absorber mounting points must be in good condition, and the holding rods must be of strong material and properly fabricated.
Have any stories about installation of LM powertrains? Any tips or tricks to share? Hit the comment button and let us know!
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