Why do some trucks not have synchronizers?

[CarolineRose]

Some trucks do not have synchronizers due to cost considerations. Here is an introduction to synchronizers: 1. Classification and structure: Synchronizers come in various forms such as constant pressure type, inertial type, and self-energizing type. Currently, the inertial type synchronizer is widely used. It mainly consists of a coupling sleeve and a synchronizer lock ring, and its characteristic is achieving synchronization through friction. 2. Constant pressure type synchronizer: A spline hub 1 is installed between the first shaft gear 2 and the gear 4, which is loosely fitted on the second shaft 5. The spline hub is slidingly connected to the second shaft and the coupling sleeve 3 through its internal and external splines. By moving the coupling sleeve to the left or right, its internal spline gear ring can engage with the gear ring of gear 2 or gear 4, thereby engaging the direct drive or second gear.

[AsherLee]

Having driven trucks for over 20 years, I know this topic best. The main reason trucks don't have synchronizers is to save costs and ensure durability. Think about it - trucks run long distances hauling heavy loads every day. If they were equipped with synchronizers, maintenance costs would increase significantly. These components wear out easily with heavy use, while experienced truck drivers are accustomed to double-clutching for gear shifts - with practice, it's even faster than using synchronizers. Moreover, the low-grade transmissions used in trucks are inherently robust. Their simpler structure actually makes them more reliable, especially when operating on rough construction sites. Imagine if the transmission failed while climbing a slope with a full load - that would cause serious delays. We veteran drivers all know that omitting synchronizers can actually extend transmission life by several years.

[LaylaRose]

I've been repairing trucks for almost ten years, and I've found that the non-synchronizer design is actually quite reasonable. Truck transmissions have to withstand extremely high torque, and installing synchronizers can actually make gears more prone to damage under heavy loads. Moreover, synchronizer repairs are particularly troublesome, with expensive parts and long labor hours. It's better to teach drivers the double-clutching technique, using engine speed control for smooth gear shifts, which actually makes the transmission more durable. Many logistics companies have done the math—the added cost of synchronizers outweighs the fuel savings, making them simply not worth it. Heavy-duty trucks operate in harsh road conditions year-round, where simplicity and reliability are king. In our repair shop, we dread working on trucks with synchronizers the most—their failure rates are at least 30% higher than regular ones.

[FelixMarie]

I think the fundamental reason why trucks don't need synchronizers is due to their different usage environments. Cars driving daily in urban areas require frequent gear shifts, making synchronizers practical. However, trucks mainly cruise on highways with far fewer gear changes. Moreover, truck drivers are professionally trained, and double-clutching is a mandatory skill. Last time I went on a long-distance trip with my dad, I saw how incredibly smooth his gear-shifting technique was—matching engine speed and gear position perfectly—even smoother than my automatic transmission. Synchronizers are particularly prone to overheating and damage when climbing hills with heavy loads, and a truck breaking down halfway would be a major accident. Some newer truck models do come with synchronizers now, but they cost tens of thousands more, and veteran drivers all say it's unnecessary.