Note: If you’re going to change your back diff liquid yourself, (or you plan on starting the diff up for support) before you let the fluid out, make certain the fill port can be opened. Absolutely nothing worse than letting fluid out and having no way to getting new fluid back in.
FWD last drives are very simple in comparison to RWD set-ups. Virtually all FWD engines are transverse mounted, which means that rotational torque is established parallel to the direction that the tires must rotate. There is no need to modify/pivot the direction of rotation in the ultimate drive. The ultimate drive pinion equipment will sit on the finish of the output shaft. (multiple output shafts and pinion gears are possible) The pinion equipment(s) will mesh with the ultimate drive ring equipment. In almost all situations the pinion and band gear will have helical cut tooth just like the remaining transmission/transaxle. The pinion gear will be smaller and have a lower tooth count compared to the ring equipment. This produces the ultimate drive ratio. The ring gear will drive the differential. (Differential operation will be explained in the differential portion of this content) Rotational torque is delivered to the front tires through CV shafts. (CV shafts are generally referred to as axles)
An open up differential is the most typical type of differential within passenger cars and trucks today. It is usually a simple (cheap) design that uses 4 gears (sometimes 6), that are known as spider gears, to drive the axle shafts but also permit them to rotate at different speeds if necessary. “Spider gears” can be a slang term that is commonly used to spell it out all the differential gears. There are two various kinds of spider gears, the differential pinion gears and the axle side gears. The differential case (not casing) receives rotational torque through the band gear and uses it to drive the differential pin. The differential pinion gears ride on this pin and so are driven because of it. Rotational torpue is then transferred to the axle side gears and out through the CV shafts/axle shafts to the tires. If the automobile is travelling in a straight line, there is absolutely no differential action and the differential pinion gears will simply drive the axle part gears. If the vehicle enters a convert, the external wheel must rotate quicker compared to the inside wheel. The differential pinion gears will begin to rotate because they drive the axle aspect gears, allowing the external wheel to speed up and the within wheel to decelerate. This design works well provided that both of the powered wheels have got traction. If one wheel does not have enough traction, rotational torque will observe the path of least resistance and the wheel with small traction will spin as the wheel with traction will not rotate at all. Because the wheel with traction isn’t rotating, the vehicle cannot move.
Limited-slip differentials limit the quantity 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 benefit over a regular open differential style. If one drive wheel looses traction, the LSD actions will allow the wheel with traction to obtain rotational torque and invite the vehicle to go. There are several different designs currently in use today. Some are better than others depending on the application.
Final wheel drive clutch style LSDs are based on a open up differential design. They have another clutch pack on each one of the axle side gears or axle shafts within the final drive housing. Clutch discs sit down between the axle shafts’ splines and the differential case. Half of the discs are splined to the axle shaft and others are splined to the differential case. Friction material is used to split up the clutch discs. Springs put pressure on the axle aspect gears which put strain on the clutch. If an axle shaft really wants to spin faster or slower than the differential case, it must overcome the clutch to do so. If one axle shaft tries to rotate quicker compared to the differential case then your other will attempt to rotate slower. Both clutches will resist this step. As the speed difference increases, it becomes harder to overcome the clutches. When the vehicle is making a good turn at low speed (parking), the clutches offer little resistance. When one drive wheel looses traction and all the torque goes to that wheel, the clutches resistance becomes much more apparent and the wheel with traction will rotate at (close to) the acceleration of the differential case. This type of differential will most likely need a special type of liquid or some form of additive. If the liquid isn’t changed at the proper intervals, the clutches may become less effective. Resulting in small to no LSD actions. Fluid change intervals vary between applications. There is usually nothing wrong with this design, but keep in mind that they are only as strong as an ordinary open differential.
Solid/spool differentials are mostly used in drag racing. Solid differentials, just like 
the name implies, are totally solid and will not really enable any difference in drive wheel speed. The drive wheels usually rotate at the same swiftness, even in a convert. This is not a concern on a drag race vehicle as drag vehicles are traveling in a directly line 99% of the time. This may also be an advantage for vehicles that are getting set-up for drifting. A welded differential is a regular open differential that has got the spider gears welded to create a solid differential. Solid differentials certainly are a fine modification for vehicles designed for track use. As for street make use of, a LSD option would be advisable over a solid differential. Every change a vehicle takes will cause the axles to wind-up and tire slippage. That is most apparent when generating through a slow turn (parking). The result is accelerated tire use and also premature axle failure. One big benefit of the solid differential over the other types is its strength. Since torque is used right to each axle, there is no spider gears, which will be the weak point of open differentials.
