Original Authors: Trent Tilton and Rob Shisler
- Transmission seals kit
- Shifter rebuild kit
- New six- or eight-bolt guibo with new nuts and bolts
- Center bearing
- Exhaust flex-sealing ring
- Clutch kit (including e21 323 throwout bearing)
- New copper exhaust downpipe nuts (3 of them)
- Downpipe gasket
- Slave cylinder
- Slave cylinder extension hose
- New set of flywheel/pressure plate bolts
We are working on getting part numbers for all these parts.
Probably one of the most "transforming" bits of work you can do to an '02 is to remove the standard Getrag 232 four-speed transmission and convert the car to accept a G-245 five speed overdrive transmission from the later '80-83 e21 320i.
The overall operation is not that difficult, although it may seem daunting at first. It is a task that can be done by someone with basic mechanical skills in their driveway (although it is preferable to do it on a level surface). For this article, Trent used a kit he got from Dave Varco at www.2002parts.com. Dave is a great guy, and the kit was complete with all the parts listed above without the need to do any fabrication. There are other suppliers who provide kits, or you can make your own kit, but Trent chose Varco's kit because it is complete, priced right, and he happens to be a friend of Trent's. Rob, on the other hand used a DIY setup he pulled from an already-converted parts car, adding some of his own modifications (more on this later).
In terms of sourcing a good candidate five speed tranny, the best bet is to just head off to a local boneyard. There are no guarantees with a junkyard tranny, but when compared to the cost of a rebuilt one (at least $600-800 in parts and tools to rebuild yourself or at least twice to 3x that for a pro-built box.) Reputable '02 shops will sell you a known good box for around $350, but Trent chose to roll the dice on a boneyard tranny. He found one at a local yard on a "Half Price Day" for only $75. Even if it is junk, and he has to try again, I'm still saving a little bread for the trade-off of uncertainty and hassle of swapping in a second five-speed, but only if needed.
Check to make sure that the seals on your boneyard box are not "ovalized" as this is transferred into the metal housings. This will make it impossible to change the seals with out the new ones leaking. When you get the "new" tranny home, clean it thoroughly with your favorite solvent or degreaser, and order a complete seals kit for it from your favorite parts vendor.
You will also want to get a shifter rebuild kit ordered, as well as a new guibo and center bearing. In addition, you will need a new exhaust flex-sealing ring, clutch kit, e21 323 throwout bearing, new copper downpipe nuts, gasket, and possibly a new speedo cable, slave cylinder, and slave cylinder extension hose. [unfortunately, we do not have these part numbers right now, but a call to a knowledgeable parts house should give you the right parts. -Rob]
It might also be a good idea to use new guibo nuts and bolts, as these can be subjected to some flexing and metal fatigue over the years. A new set of large flywheel bolts (the ones that hold the flywheel to the crank) is also recommended, but make sure you get the right kind for the size of your flywheel (either 215mm or 228mm).
Drain the tranny with a 17mm hex tool or with one you made out of an old VW or similar lug bolt with a nut welded on the other end or a pair of nuts jammed together.
You will definitely want to change all the seals on the tranny itself. The fact is they tend to leak after so many years. This includes the rear main seal which requires a thin wall 30mm socket (use an impact wrench to air it off -- or have a shop do it) and change out the seal with a seal puller (or just have the shop do it).
Be very careful with the new seals. Put a thin layer of RTV on the outside and some moly grease on the inside edge for starter lubrication. When refilling it, there are a few options. Some prefer the standard GL-4 (non-hypoid) gear oil while others prefer synthetic gear oil like Redline MTL.
There is some controversy over synthetics, but rest assured MTL is a good choice, especially if you've gone to the trouble of using new seals. Even ATF can be used with good results. Be aware that some have reported new leaks with synthetics because they can actually clean out gunk that might have been stopping or slowing down leaking spots. Either way, fill the tranny to the point where it begins to come out of the fill hole, then put the plug back in. (Do this with the car or transmission leveled.
This is also a good time to rebuild the shifter linkage. All the plastic washers and joints should be replaced. (Check the FAQ Index for this one.) Remember to put back in the exact number in the exact location. This will give your shifter a nice tight feeling. These parts are shared on most BMWs and a good independent shop or dealer should stock them.
In terms of the conversion itself, the first thing you need to do is SAFELY elevate the car and put it on jackstands. Ideally you would pick a flat hard surface in a level location (such as inside your garage). If this is unavailable you can do it in the driveway, but make sure the e-brake is on (and working) and/or you have securely chocked up the rear wheels. Start by putting a 2x4 across the cradle of your floor jack to spread the weight a little and lift the car at the center of the front subframe. If you are on a soft surface (NOT RECOMMENDED!), use thick plywood or equivalent to keep the jack and stands from digging into the surface. Place the a couple more 2x4s on top of the stands and then position them under the stamped steel frame rails attached to the front floors of the car. Then, if you are on a flat surface, you can raise the rear of the car in similar fashion, placing the stands under each end of the rear subframe, just next to the mounts. Make sure the whole thing is rock-steady before crawling underneath! Use good quality stands and/or ramps because cheap ones can collapse! Remember: Safety First!
Once the car is safely in the air, the first thing to attack is the exhaust system. There are three bolts at the bottom of the exhaust downpipe that will allow you to move the exhaust out of the way. When you remove the down pipe from the manifold, you will need a new gasket. Trent didn't need to totally remove his because it is a custom job that runs under his rear subframe, but on stock cars you will need the room. If your downpipe nuts are rusted on try soaking them with Liquid Wrench and/or blasting them with a torch. If they are REALLY bad, you might need to cut the nuts off (ouch!) with a Dremel or similar tool. Then remove the four Guibo nuts and bolts. Remember to note their direction for reinstallation. Then remove the four bolts that bolt the driveshaft to the differential. Next, remove the two 13mm bolts that hold the center bearing to the tunnel. Watch your head because at this time the driveshaft might fall on it! Next, remove the bolts that hold the transmission to the engine block. Don't forget the stamped metal shield at the bottom of the bell housing, otherwise the tranny wont slide off the flywheel/clutch assembly. Support the rear of the transmission with a jackstand, and then remove the bolts holding the tranny crossmember to the tunnel. Having an assistant at this point is very handy. Next, unhook the linkage at the bottom of the shifter. Finally, carefully slide the tranny off and let it thud to the ground. (Maybe put a stack of magazines under it just to avoid chipping the garage floor-the tranny itself is resaleable if the synchros are still good. Or there is always fleaBay!)
Next, remove the old clutch/pressure plate by removing the bolts holding them to the flywheel. You may also want to have the flywheel resurfaced at a machine shop, while you're in there replacing things. Make sure the shop knows to put a .020" "step" on the perimeter of the flywheel so that the pressure plate holds the clutch tight and centered with the intended amount of pressure. While the flywheel is being done, test fit the new tranny to the engine to determine how much and exactly where you need to clearance the tunnel for the slave cylinder. In most cases, a couple good whacks with a big hammer (try to use a non-marring "dead-blow" version) will move the sheet metal enough to make room for the new slave cylinder. Remember that motors move around during spirited driving, so a little "elbow room" is needed. Some kits (like the one from Varco) recommend that you put the slave on after the tranny is already in the car, but the opposite actually appears to be the easier way to do it. Make sure the bleeder valve is pointing down when you install the new slave!
At this point we recommend that you make or buy a tranny cradle for your floor jack. It will make your life a hell of a lot easier during the next stage of the conversion. One way is to take a piece of 2x6 wood and then screw or nail a couple of pieces of angle-cut 2x2 on each edge to create a kind of V shape that will steady the tranny enough for you to jack it into position. It is also very helpful to have a friend man the jack while you guide the tranny itself into position.
The five speed tranny is exactly 3.6" longer than the four speed it is replacing, which means we need to move the crossmember mounting tabs back in the tunnel exactly that amount. You will also need to shorten the driveshaft by this amount, or buy a kit with a shortened driveshaft in it. The Varco kit I used came with a new set of bolt-on tabs for moving the crossmember and also the shortened driveshaft. You can also cut the mounting tabs out of a donor car (e21 or 02 - it doesn't matter), then grind the tunnel metal off them and then either weld or bolt them to the tunnel in the correct spot. Remember that the elevation is as important as how far back you place the new tabs. To place the tabs with bolts, bolt the transmission to the motor with a couple of bolts and then attach the driveshaft by just snugging up a couple of those bolts too. Put a level on the bottom of the driveshaft on each side of the center bearing to make sure the angles are the same and the transmission is not positioned too high or too low. Take your time at this point because it is critical Drill the holes and bolt the brackets up.
Another way to solve the move-the-mounting-tabs problem is to do what Rob did and make a set of rails from some 1" angle iron from a hardware store (or old bedframe) and cut them to fit between the original four-speed mounting tabs and the center bearing mounting tabs further back in the tunnel. Then the cross member just attaches to the rails in the correct spot, while the elevation is just about spot-on perfect just by attaching the cross member directly to the bottom of the rails. If you need to, you can adjust the rear of the tranny down by using some big washers in between the crossmember and the rails, or even up with a little by stacking a (big) washer or two on top of the rubber tranny mount itself.
In Trent's case, drilling the holes for the new mounting tabs required pulling back the carpet inside and obviously drilling new holes in the tunnel. The rail method eliminates this alteration of the car's sheetmetal but requires more fabrication of the rails themselves from blank angle iron, as well as some grinding for clearancing the speedo cable. You may also need a little more hammering on the tunnel where the rails run from original crossmember mounting points and the center bearing mounts. Finally, the rails will not hit the original tabs "square" due to the change in elevation from original tranny mounts to center bearing mounts, but this is curable by either cutting the "L" of the angle iron to allow it to bend to fit, or just by tightening the bolts down really hard to force the mounting tabs to bend a little to meet the rails squarely. Its your call on what to do here, but since part of the point of the rail method is to avoid altering the car too much, Rob recommends bending the rails themselves.
Once everything is fitted correctly, disassemble everything and remount the flywheel and clutch. The flywheel bolts must be changed with new ones and then torqued to 75 lb.ft. Use a small amount of red locktite on the threads just for luck. Don't put too much because it affects the torque number you need to use due to its lubricating effect during installation. If your new clutch kit didn't come with a centering tool, you can cut the old input shaft off the four speed box and use that. Center the clutch, then carefully bring the new tranny into position. Spin the output flange while engaging the clutch splines to make it easier to engage them. Once all lined up, the tranny should just slide home and fit tight against the block. If it wont slide all the way home, pull it off and check for something in the way or not aligned correctly and try again.
After the transmission is bolted up, it is time to just finish up all the little things. The new speedo cable, wire up the reverse lights, bolt the driveshaft back up, re-install the shifter, put the carpet back (if needed), then take for test drive!
If you have any questions don't hesitate to post them to the Forum. Trent would like to thank his dad for his help, and Dave @ www.2002parts.com for the kit and great advice!