Note: If you’re likely to change your back diff fluid yourself, (or you intend on opening the diff up for assistance) before you let the fluid out, make sure the fill port could be opened. Absolutely nothing worse than letting fluid out and having no way to getting new fluid back in.
FWD final drives are extremely simple compared to RWD set-ups. Virtually all FWD engines are transverse installed, which means that rotational torque is created parallel to the direction that the tires must rotate. There is no need to alter/pivot the direction of rotation in the ultimate drive. The final drive pinion equipment will sit on the end of the result shaft. (multiple output shafts and pinion gears are feasible) The pinion gear(s) will mesh with the final drive ring gear. In almost all instances the pinion and ring gear could have helical cut the teeth just like the rest of the transmission/transaxle. The pinion gear will be smaller and have a lower tooth count compared to the ring gear. This produces the final drive ratio. The ring gear will drive the differential. (Differential procedure will be described in the differential portion of this article) Rotational torque is delivered to the front wheels Final wheel drive through CV shafts. (CV shafts are commonly referred to as axles)
An open up differential is the most typical type of differential found in passenger cars and trucks today. It is certainly a simple (cheap) design that uses 4 gears (sometimes 6), that are referred to as spider gears, to operate a vehicle the axle shafts but also allow them to rotate at different speeds if required. “Spider gears” is definitely a slang term that is commonly used to describe all the differential gears. There are two different types of spider gears, the differential pinion gears and the axle side gears. The differential case (not casing) receives rotational torque through the ring gear and uses it to drive the differential pin. The differential pinion gears trip upon this pin and are driven because of it. Rotational torpue can be then transferred to the axle aspect gears and out through the CV shafts/axle shafts to the wheels. If the automobile is travelling in a straight line, there is no differential action and the differential pinion gears only will drive the axle side gears. If the vehicle enters a switch, the outer wheel must rotate quicker compared to the inside wheel. The differential pinion gears will begin to rotate because they drive the axle side gears, allowing the outer wheel to increase and the within wheel to decelerate. This design works well provided that both of the driven wheels have got traction. If one wheel does not have enough traction, rotational torque will follow the road 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 vehicle cannot move.
Limited-slip differentials limit the quantity of differential action allowed. If one wheel begins spinning excessively faster than the other (way more than durring normal cornering), an LSD will limit the velocity difference. This is an advantage over a normal open differential design. If one drive wheel looses traction, the LSD actions allows the wheel with traction to get rotational torque and allow the vehicle to go. There are several different designs currently in use today. Some are better than others based on the application.
Clutch style LSDs are based on a open differential design. They have another clutch pack on each of the axle aspect gears or axle shafts inside the final drive housing. Clutch discs sit 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 put pressure on the axle side gears which put strain on the clutch. If an axle shaft really wants to spin quicker or slower than the differential case, it must get over the clutch to take action. If one axle shaft attempts to rotate faster than the differential case then the other will attempt to rotate slower. Both clutches will withstand this action. As the velocity difference increases, it becomes harder to get over the clutches. When the vehicle is making a tight turn at low swiftness (parking), the clutches provide little resistance. When one drive wheel looses traction and all of the torque goes to that wheel, the clutches level of resistance becomes a lot more obvious and the wheel with traction will rotate at (near) the rate of the differential case. This type of differential will most likely require a special type of fluid or some form of additive. If the liquid isn’t changed at the correct intervals, the clutches may become less effective. Resulting in little to no LSD action. Fluid change intervals differ between applications. There is definitely nothing incorrect with this style, but remember that they are just as strong as an ordinary open differential.
Solid/spool differentials are mostly used in drag racing. Solid differentials, like the name implies, are totally solid and will not allow any difference in drive wheel swiftness. The drive wheels always rotate at the same speed, even in a switch. This is not an issue on a drag competition vehicle as drag vehicles are traveling in a directly line 99% of the time. This may also be an edge for vehicles that are getting set-up for drifting. A welded differential is a regular open differential which has had the spider gears welded to create a solid differential. Solid differentials certainly are a fine modification for vehicles created for track use. For street use, a LSD option will be advisable over a solid differential. Every switch a vehicle takes may cause the axles to wind-up and tire slippage. This is most noticeable when generating through a slow turn (parking). The result is accelerated tire put on as well as premature axle failing. One big benefit of the solid differential over the other styles is its power. Since torque is applied directly to each axle, there is absolutely no spider gears, which will be the weak point of open differentials.