Specializing in the 3g CSM
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PostPosted: Wed Dec 31, 1969 7:00 pm 
CSM Expert
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Joined: Sat Nov 03, 2001 7:00 pm
Posts: 2191
Location: SoCal and Wisconsin
I ordered a B&M Tranny LSD insert and installed it into my 1990 Turbo DSM transmission. This is what the unit looks like, and easily fits in the palm of my hand.

Take off the end case cover by unbolting the 12mm bolts
exposing the 5th gear and intermediate shaft and these two large 36mm nuts. Remove those three bolts near the endcase as well. Hold onto the springs and ball bearings that are inside the holes. It may be easier to loosen the 36mm nuts with the transmission in the car. Either way, shove a penny in between the two large gears and you should be able to loosen the nuts with a breaker bar. Impact tools work as well. Put the car in gear to loosen the taller gears nut.

With these off, you should be able to tap the center shafts while GENTLY prying the gears up and off of the shafts. Be careful or else you will chip the gear. Pop the little tapered pin out of the 5th gear shift fork and pull the shift fork off of the transmission with the entire gear assembly. Dont forget how this goes back together. It is recommended that you use a gear puller on the intermediate shaft gear, but it can be done without. Once you remove the gears you should now be able to take off the case. Unbolt all of the 14mm bolts holding the case to the bellhousing and lift slowly. You should see something like this inside

You don't need to mess with the main shafts or any of the gears. You should be able to pull the diff out, which is the large gear in the right hand side of the first picture.

You need to pop off the 8 19mm bolts holding the ring gear on the diff. By shoving some bolts inbetween the gears, I was able to loosen them.


I suggest using air tools. These need to be torqued back down to 86ft/lbs and its suggested to use red loctite. You need to take the bolts off to pop out the little pin that holds the large pin in the diff.


With the gear removed, you can easily pound the pin out (towards me) It is tapered and only comes out one way. Pull the big pin out

and drop the LSD insert in between the spider gears. Put the big pin back through the diff and put the tapered pin back in as well. The LSD is shipped with two little pins on each side and a plate. The plate holds the LSD together, because it is sprung with 1,300lb springs. Take off these little plates and pins once it is inside the diff. Drop the diff back into the transmission, reassemble the transmission and re-install in the vehicle.

My car now has NO torque steer. I can basically hold onto the wheel with one finger. The car leaves two nice patches of rubber :) The front end does not "float" at all under wheelspin. The front end feels "planted" and "heavy". I was getting some wheelhop in 1st gear. I didn't try launching yet though.

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