If you find yourself always having transmission problems, you may want to consider whether or not your driving habits and operator mistakes are contributing to the faulty transmissions. That way, you can possibility avoid future problems after your transmission is repaired. Here are a few questions to ask yourself. 

Were the tires the same size all around? 

The transmission, differentials, transfer case, drive shafts, and other driveline parts can become damaged if the tires are different sizes, such as if you drive on a spare tire for more than the recommended distance, which is usually just 50–70 miles. When it comes to 4WD vehicles, it is important to never put your vehicle in 4WD if you have a small-sized spare tire on the vehicle, because doing so could damage the differentials, and that could lead to the transfer case and/or the entire driveline being affected and damaged. This is the reason you see full-sized spare tires on most Jeeps and other 4WD vehicles.

This is because the role of the differentials is to control how the wheels spin. When you turn the vehicle, the inside wheel does not spin as much as the outside tire. The outside tire needs to spin more in order for the outside wheel to travel a greater distance than the inside tire. When one tire is a different size, the gears inside the differential can get confused. The differential is connected to the transfer case by the drive shafts. The transfer case is basically the middle-man between the differential and the transmission. Due to how the driveline is all connected, a confused differential can damage your transmission.

Have you driven through a flooded roadway?

The engine, transmission, and other mechanical parts are warm or hot after driving for several minutes. If you drive on a flooded road, the cool water could easily splash up onto your vehicle's mechanical parts. Depending on the depth of the water and the height of your vehicle, some mechanical parts could be submerged in a flood. The extreme and sudden temperature difference between the cool water and the warm or hot mechanical components could have damaged your transmission.

Also, water may have gotten inside the engine, transmission, and/or drive train. If so, the water could have diluted the fluids in the various components, which would cause the fluids to be ineffective. For example, the job of the transmission fluid is to keep the transmission and driveline cool as well as lubricated. If mixed with water, the transmission fluid would be ineffective in cooling and lubricating the transmission. 

Did you regularly ride the clutch and/or drive aggressively? 

It's highly likely that you rode the clutch and/or drove your manual 4WD aggressively at some point. That's part of the fun of having a manual 4WD, although doing these things too much can damage your transmission if they are done on a regular basis. When you drive, do you have the clutch engaged when you are not shifting gears or braking? This is called riding the clutch and should be avoided. Riding the clutch causes the pressure plates to graze the flywheel, which means setting yourself up for clutch failure. 

Driving aggressively, such as allowing the engine to reach high RPMs before shifting gears, can cause the transmission to wear out sooner. When the gears are changed aggressively, the metal components can get shaved down due to the abnormal friction involved. These metal shavings end up in the transmission fluid, which can cause it to become ineffective and damage the transmission. If you cannot avoid driving aggressively, it may be a good idea to schedule transmission flushes on a more regular basis than what your vehicle's owner's manual recommends.