Install of Friction-Type LSD into B15 Transmission

In order to ensure that I get the best traction possible (as traction will likely be a problem), I have installed a friction-type LSD into my B15 transmission. My transmission already had a viscous limited slip differential (VLSD) from the factory and installing the friction-type is pretty much just going the extra mile. The following write-up outlines how to go about this install.

The friction type limited slip greatly improves traction in front wheel drive vehicles and is quite affordable (usually ~$200). The part itself (pictured below) is a small assembly of two metal disc plates which hold tension on the differential side gears with the help of four small springs. In VLSD equipped transmissions, this complements and improves upon the viscous limited slip while in open diff equipped transmissions, this basically converts the diff to a limited slip. In cornering and braking, the friction type performs like a disc-type limited slip while in straight line acceleration, it acts as a locking diff (like posi-traction). The friction type limited slip can be purchased with different spring rates which correlate to different degrees of effectiveness (e.g. the "street" and "drag" versions). The street version has a lower spring rate and the drag version has a higher rate.

The transmission used in this write-up is a B15 with a viscous limited slip differential (locking diff), but the friction type limited slip can also be installed into the open differential (non-locking diff) and the process is virtually identical to the one described here save for some differences in the stock differential.

I would like to make mention of something first off. This install is not very difficult for people who are mechanically inclined and have had experience tearing apart transmissions and/or motors. If you have never taken apart a transmission before or are clueless as to how they work, I would not recommend doing this by yourself. You would be best off either doing this under the guidance of an experienced technician or having someone else do it for you. That being said, I'd like to start with a list of necessary tools for this install. If you do not have all of these tools, do not attempt to do this install. Here they are:

Tools Needed:
-Ratchet with metric socket set or metric wrenches (specifically 10mm, 12mm, and 14mm)
-Flat head screwdrivers
-Large phillips head screwdriver
-Ball-peen hammer
-Rubber mallet
-3/32" and 5/32" pin punches
-Telescoping or pen style magnet
-Standard snap ring pliers
-Lock ring pliers (You will need either the special transmission variety available through Matco tools, or a normal pair that you can grind down, I'll explain why later)
-Regular pliers (preferably two pairs)
-Impact wrench with 14mm socket

Begin by placing the transmission in a convenient work location like a work bench or some other out-of-the-way place where it will not be in the way of anything but can easily be worked on. There are a few things during this install that may force the process to go a lot longer than planned, so decide on your work location accordingly. Before placing the transmission on its bell housing, grab a shirt, towel, rag, or something else to lay the axle seal on. This will help prevent the seal from getting torn up while you work on the transmission. In the picture below, I have a folded shirt, and as a matter of fact, it happens to be an MC Hammer "Please Hammer Don't Hurt 'Em World Tour" shirt but any old shirt will do.

Once the tranny is on its bellhousing, the first order of business is to remove the five 10mm bolts to the main shaft rear bearing cover pictured below. After removing the bolts and cover, group them together in a convenient location so as not to lose anything.

Next, remove the six 10mm bolts and the reverse idler gear cover pictured below. This is the only instance where you come across an actual gasket, so be careful not to damage it and it can be re-used. Again, group the cover and bolts together off to the side so as not to lose anything.

Next we will remove the reverse idler gear. Begin by removing the retaining shaft's snap ring which is pictured below. Then thread one of the idler gear cover bolts into the threaded hole in the top of the shaft. Simply pull the retaining shaft out of the case by the threaded bolt.

After that, the reverse idler gear comes right out of the case. Take note of the orientation of the gear because it is not straight cut like typical reverse gears. Be careful when pulling it out, there are some loose pieces that can easily fall out (two thrust washers as well as a bearing). Set the gear aside with its loose parts so as not to lose anything.

Next, remove the lock ring from the main shaft rear bearing with a pair of standard snap ring pliers. Place it with the cover that was removed earlier.

Next, remove the two 14mm check plugs pictured below. Inside each sleeve will be a small spring as well as a check ball. Remove these parts with either a telescoping or pen style magnet and set them aside where they will not be lost!

Next, remove the 12mm bolts holding the case and bell housing together. Group them to the side somewhere so as not to lose any.

You are now ready to remove the case!

Once all the bolts are removed, you must carefully separate the case from the bell housing. I started by placing the handle end of a rubber mallet on the bottom side of the protruding part of the case pictured below, and then I tapped it with a ball-peen hammer until there was ample room to get a flat head screwdriver in between the bell housing and the case. At that point, I worked my way around until they were sufficiently separated. Once free, the case just lifts straight off with no adjustment necessary (if you've ever taken apart a B13/B14 tranny, this will seem weird because of the way that you have to work the case off of those).

The picture below is what your transmission will look like without the case on it.

Remove the green plastic parts and set them aside (first note their orientation). Now it is time to remove the shifter rods so that you can remove the gear stacks and get that diff out! Begin by removing the check plug pictured below. Then pull back (it is not necessary to remove) the spring, check pin, and check ball that hold tension on the input shaft's shifter rod (which by the way is responsible for engaging 3rd and 4th gears). The use of a telescoping or pen style magnet will most likely be necessary to pull back the check ball.

Now here comes the hardest part of the whole job. The shifter fork on this shifter rod is held in place by two lock rings. These lock rings are positioned in a small recess and because they don't have typical snap ring nipples on them, they are extremely tricky to remove. I searched Sears, Advance Auto Parts, Autozone, and even some local tool shops, but nowhere could I find the right style lock ring pliers to remove these rings--and I know what you're thinking, but standard snap ring pliers will not work. As it turns out, Matco tools sells the appropriate set of pliers for this job, but they are $25.00. Not wanting to pay this, I simply ground down a pair of my own lock ring pliers. You basically just need them to be able to fit in the recess in order to remove the lock ring. After some considerable grinding, I was ready to remove the rings.

What I did was basically position the pliers on the ring and heftily push forward with the pliers while very lightly (and that is the key to not slipping off the ring) opening them. I did this until the ring was just slightly off of the shifter rod since it is extremely difficult to take it fully off with the pliers. At that point, I popped it the rest of the way off with a flat head screwdriver. Keep in mind that these are pretty high tension lock rings despite their size so be careful to hold on to it while prying it off so that it doesn't fly off somewhere. This particular shifter fork has two rings that require removal.

Next remove the roll pin from the bracket pictured below. It is a two pieced roll pin, the inner of which requires a 3/32" punch and the outer of which requires a 5/32" punch.

You are now ready to remove that shifter rod. You will need to pull it up and out of its seat so that you can pull the shifter fork laterally off of its coupling sleeve. This will not come easily. I clamped on to the upper part of the rod with a pair of regular pliers and pulled up until the rod came out and I'd suggest this method as it is nearly impossible to remove it with only your hands. Once the rod is removed, I'd suggest storing it in a ziplock bag with its lock rings and roll pin until it comes time to re-install it.

Its now time to remove the next shifter rod (which by the way is responsible for engaging 5th and reverse). First, using your magnet, remove the check plunger and check ball that hold tension on the rod. Next, the lower bracket has two of the tricky lock rings to be removed. After that, there are two of the two piece roll pins to be removed. You can pull the shifter rod out with its brackets but the shifter fork cannot be removed until the final shifter rod is removed. Store this rod the same way the first was stored (i.e. with all of its small parts).

The final shifter rod is responsible for engaging 1st and 2nd. Removal of the final shift rod is pretty easy (because there are no lock rings!). First, remove with your magnet the two check balls that hold tension on the rod. Next, there are two of the two piece roll pins to be removed. After they are out, simply remove the rod the same way that the others were removed. Once it is out, the shift fork from rod #2 can be removed.

At this point, you only have two gear stacks and the diff left to be removed. The gear stacks will simultaneously pull out with great ease. Be careful during removal so as not to damage any bearings. Store these gear stacks away in a safe place (now might be a good time to send them out for cryo-treating if you were considering it). After the gear stacks are out, the diff simply lifts right out of the case and you're left with what is pictured below.

Now it is time to install the friction type limited slip into your diff assembly. First, using an impact wrench with a 14mm socket, remove all of the final drive gear retaining bolts.

Pull the final drive gear off of the assembly. You will see two screws holding the viscous fluid housing together with the pinion shaft/gear housing. Remove those two screws with a large screwdriver. They will be pretty tight but not too tight to take off by hand, just be careful not to strip the heads and use a torque driver if necessary to loosen them (I didn't have to and you probably won't).

After removing the screws, separate the two housings and set the viscous fluid housing off to the side. What you need to do is run the pinion shaft through the friction type limited slip. To do this is simple. There is one roll pin (5/32") holding the pinion shaft in place that you will first remove. Once removed, simply pull the pinion shaft out slightly and place the friction type limited slip in the housing. Run the pinion shaft through it and re-install the roll pin that you removed.

After you have pinned the pinion shaft back into place, bolt together the viscous fluid housing and the pinion shaft/gear housing with the two screws that hold them together. Next, re-install the final drive gear onto the assembly with the impact wrench. Using whatever works best for you (two pairs of pliers or pliers and flat head screwdriver), remove the two horseshoe pins from the sides of the friction type limited slip to allow the springs to decompress.

There you have it! The only thing left is re-assembly of the transmission which is the exact opposite of disassembly. Be careful to ensure that all part orientations are correct and that all small parts get installed back in their proper places.

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