Final wheel drive

Note: If you’re likely to change your rear diff liquid yourself, (or you intend on starting the diff up for support) before you let the fluid out, make certain the fill port could be opened. Nothing worse than letting fluid out and then having no way of getting new fluid back.
FWD final drives are very simple compared to RWD set-ups. Almost all FWD engines are transverse installed, which implies that rotational torque is created parallel to the direction that the wheels must rotate. There is no need to modify/pivot the path of rotation in the final drive. The final drive pinion gear will sit on the end of the output shaft. (multiple output shafts and pinion gears are feasible) The pinion equipment(s) will mesh with the final drive ring equipment. In almost all situations the pinion and band gear will have helical cut teeth just like the rest of the transmission/transaxle. The pinion equipment will be smaller sized and have a lower tooth count than the ring gear. This produces the final drive ratio. The band gear will drive the differential. (Differential operation will be explained in the differential section of this article) Rotational torque is delivered to the front tires through CV shafts. (CV shafts are generally referred to as axles)
An open differential is the most typical type of differential found in passenger vehicles today. It is usually a simple (cheap) design that uses 4 gears (occasionally 6), that are referred to as spider gears, to drive the axle shafts but also allow them to rotate at different speeds if required. “Spider gears” is a slang term that’s commonly used to describe all the differential gears. There are two various kinds of spider gears, the differential pinion gears and the axle part gears. The differential case (not casing) receives rotational torque through the ring equipment and uses it to operate a vehicle the differential pin. The differential pinion gears trip on this pin and are driven because of it. Rotational torpue can be then transferred to the axle part gears and out through the CV shafts/axle shafts to the tires. If the automobile is venturing in a straight line, there is no differential action and the differential pinion gears will simply drive the axle part gears. If the vehicle enters a turn, the outer wheel must rotate quicker than the inside wheel. The differential pinion gears will start to rotate as they drive the axle side gears, allowing the outer wheel to speed up and the within wheel to slow down. This design is effective provided that both of the driven wheels have traction. If one wheel doesn’t have enough traction, rotational torque will follow the path of least resistance and the wheel with small traction will spin while the wheel with traction will not rotate at all. Since the wheel with traction is not rotating, the automobile cannot move.
Limited-slide differentials limit the amount of differential actions allowed. If one wheel begins spinning excessively faster compared to the other (more so than durring normal cornering), an LSD will limit the acceleration difference. This is an advantage over a regular open differential style. If one drive wheel looses traction, the LSD actions allows the wheel with traction to obtain rotational torque and invite the vehicle to go. There are many different designs currently in use today. Some work better than others depending on the application.
Clutch style LSDs derive from a open up differential design. They have another clutch pack on each of the axle aspect gears or axle shafts inside the final drive casing. Clutch discs sit down between the axle shafts’ splines and the differential case. Half of the discs are splined to the axle shaft and the others are splined to the differential case. Friction material is used to split up the clutch discs. Springs place strain on the axle part gears which put strain on the clutch. If an axle shaft wants to spin faster or slower than the differential case, it must get over the clutch to do so. If one axle shaft tries to rotate quicker compared to the differential case then your other will try to rotate slower. Both clutches will withstand this step. As the speed difference increases, it turns into harder to get over the clutches. When the automobile is making a good turn at low swiftness (parking), the clutches offer little level of resistance. When one drive wheel looses traction and all the torque would go to that wheel, the clutches level of resistance becomes much more apparent and the wheel with traction will rotate at (near) the speed of the differential case. This type of differential will likely require a special type of liquid or some type of additive. If the fluid isn’t changed at the correct intervals, the clutches may become less effective. Leading to small to no LSD actions. Fluid change intervals vary between applications. There can be nothing wrong with this design, but keep in mind that they are only as strong as a plain open differential.
Solid/spool differentials are mostly found in drag racing. Solid differentials, like the name implies, are Final wheel drive completely solid and will not enable any difference in drive wheel rate. The drive wheels always rotate at the same rate, even in a switch. This is not an issue on a drag race vehicle as drag vehicles are driving in a directly line 99% of that time period. This may also be an edge for cars that are getting set-up for drifting. A welded differential is a normal open differential which has experienced the spider gears welded to make a solid differential. Solid differentials certainly are a great modification for vehicles made for track use. For street make use of, a LSD option would be advisable over a good differential. Every change a vehicle takes will cause the axles to wind-up and tire slippage. That is most obvious when driving through a gradual turn (parking). The effect is accelerated tire wear and also premature axle failing. One big benefit of the solid differential over the other styles is its strength. Since torque is applied directly to each axle, there is no spider gears, which will be the weak spot of open differentials.