MYY6S and MYY5T gearbox assemblies are two mainstream manual transmission models widely used in ISUZU light and medium-duty trucks (such as N-Series, NPR, NQR, and NLR). As core powertrain components, their differences directly affect vehicle performance, load capacity, fuel efficiency, and adaptability to working conditions. This industry guide comprehensively compares the two gearboxes from parameters, structural design, application scenarios, and replacement considerations to help professionals in the truck parts industry, fleet managers, and maintenance personnel make accurate selections and judgments.
1. Core Parameter Comparison (Key Differences)
The fundamental differences between MYY6S and MYY5T lie in gear configuration, torque-bearing capacity, speed ratio range, and weight, which determine their respective application boundaries. The following table details the core parameter differences:
|
Comparison Dimension |
MYY5T Gearbox Assy |
MYY6S Gearbox Assy |
Impact of Differences |
|---|---|---|---|
|
Gear Configuration |
5 Forward Gears + 1 Reverse Gear (Manual only) |
6 Forward Gears + 1 Reverse Gear (Manual / AMT Optional) |
MYY6S has more refined speed ratios, enabling smoother shifting and better adaptation to complex road conditions. |
|
Rated Input Torque |
Approx. 225–250 Nm (23–25.5 kgf·m) |
Approx. 420–450 Nm (42.8–45.9 kgf·m) |
MYY6S has stronger torque-bearing capacity, suitable for high-horsepower engines and heavy-load scenarios. |
|
Speed Ratio Range |
Approx. 0.721–5.979 (Top speed ratio of 5th gear: 0.721) |
Approx. 0.759–5.979 (Top speed ratio of 6th gear: 0.759) |
MYY6S has better low-speed torque performance and more fuel-efficient at high speeds; MYY5T is more straightforward for basic transportation. |
|
Housing Material & Weight |
Aluminum alloy (Net weight: approx. 115 kg) |
Full aluminum alloy lightweight design (Net weight: approx. 83 kg) |
MYY6S is lighter, reducing the overall weight of the vehicle and improving load-carrying efficiency. |
|
Shift Control Mode |
Pure mechanical H-type shifting (Full synchronizer) |
Mechanical shifting / AMT (Automated Manual Transmission) optional (with E/P mode and A/M switch) |
AMT version of MYY6S reduces driver fatigue, suitable for long-distance and frequent shifting scenarios. |
|
Applicable Engines |
ISUZU 4HF1 / 4HG1 / 4HE1 / 4JH1 (Medium and low horsepower: 100–150 HP) |
ISUZU 4JJ1 / 4HK1 / 6HK1 / 6HH1 (High horsepower: 180–300 HP) |
Engine matching is the core factor for gearbox selection; mismatching will lead to reduced performance and shortened service life. |
|
Typical OE Numbers |
8-97350621-0, 8-97350622-0 |
8-97350623-0, 8-97350624-0 (AMT version) |
OE numbers help distinguish models and ensure accurate replacement of parts. |
2. Number of Gears (Speed Configuration)
| Model | Number of Forward Gears | Transmission Type |
|---|---|---|
| MYY6S | 6 forward + 1 reverse | Manual / Synchromesh |
| MYY5T | 5 forward + 1 reverse | Manual / Synchromesh |
The most obvious difference:
MYY6S is a 6-speed gearbox.
MYY5T is a 5-speed gearbox.
This makes the MYY6S suitable for applications requiring closer gear ratios, better fuel economy at highway speeds, and smoother climbing on varied terrain.
3. Application Scenario Differences (Key for Selection)
The selection of MYY5T and MYY6S is mainly based on the vehicle's load capacity, engine horsepower, and operating conditions. The following is a detailed analysis of their applicable scenarios:
MYY5T Gearbox Assy /Transmission
It is mainly suitable for light-duty ISUZU trucks with medium and low horsepower, such as ISUZU NPR, NKR (light-duty version), and ELF 100P/600P. Typical application scenarios include:
- Urban distribution and short-distance transportation (such as grocery delivery, express delivery, and light cargo transportation);
- Light-load operations with stable load (load capacity ≤ 5 tons);
- Simple road conditions (urban roads, paved roads), no frequent heavy-load starting or climbing;
- Users who pursue low purchase cost and simple maintenance (fewer parts, lower failure rate, and easier maintenance).
- OE NO. : 8-97350621-0 8-97373919-0
- Truck Model Fit for : ISUZU NHR/NKR/NPR/NQR/NRR
- Engine Model Fit for : 4HE1 4HF1 4HG1 4HH1 4HK1
MYY6S Gearbox Assy /Transmission
It is mainly suitable for medium-duty ISUZU trucks with high horsepower, such as ISUZU NQR, FVR, and 700P. Typical application scenarios include:
- Long-distance transportation and heavy-load transportation (load capacity 5–10 tons, such as bulk cargo, container transportation);
- Complex road conditions (mountain roads, rural dirt roads) that require frequent shifting, heavy-load starting, and climbing;
- Fleet operations that pursue fuel efficiency and driver comfort (AMT version reduces shifting fatigue);
- Special-purpose vehicle modifications (such as refrigerated trucks, small tank trucks) that require stable power output and long-term operation.
- OE NO.1701010-ME25A; 8-98067680-1; 8-98067680-0; 8-98067656-0,1701010ME25A; 8980676800; 8980676560; 8980676801
- Truck Model Fit for:ISUZU NHR; NLR; NMR; NPR; NQR
- Engine Model Fit for:4HF1; 4HG1; 4HK1; 4JJ1
4. Key Considerations for Replacement and Selection
When replacing or selecting MYY6S and MYY5T gearbox assemblies, the following points must be noted to avoid mismatching and potential safety hazards:
1.Engine Matching First: The gearbox must match the engine's horsepower and torque. For example, installing MYY5T on a high-horsepower engine (such as 4HK1) will lead to insufficient torque bearing capacity, resulting in gearbox damage; installing MYY6S on a low-horsepower engine will cause waste of performance and increased fuel consumption.
2.Check OE Number: The OE number is the most accurate basis for distinguishing models. Even if the appearance is similar, different OE numbers may have differences in internal structure and mounting size, so it is necessary to confirm the OE number of the original gearbox before replacement.
3.Mounting and Transmission Shaft Adaptation: As mentioned earlier, the mounting brackets and transmission shaft lengths of MYY5T and MYY6S are different. Direct replacement will cause installation difficulties and unstable power transmission; corresponding modifications to the bracket and transmission shaft are required if necessary.
4.Consider Operating Conditions: For short-distance light load, MYY5T is more cost-effective; for long-distance heavy load and complex road conditions, MYY6S is more reliable and fuel-efficient. Blindly pursuing more gears will increase purchase and maintenance costs.
5.Maintenance Differences: MYY5T has fewer parts and simpler maintenance, and the maintenance cost is lower; MYY6S (especially the AMT version) has more complex electronic components and higher maintenance requirements, requiring professional maintenance personnel and special tools.
5. Summary
In summary, MYY5T and MYY6S gearbox assemblies are designed for different application scenarios: MYY5T is a cost-effective choice for light-load, short-distance, and low-horsepower ISUZU trucks, focusing on reliability and simplicity; MYY6S is a high-performance option for heavy-load, long-distance, and high-horsepower trucks, with advantages in torque bearing, speed ratio refinement, and comfort.
For professionals in the truck parts industry, accurately grasping the differences between the two models can help provide more professional product recommendations and technical support for customers; for fleet managers and truck owners, selecting the appropriate gearbox according to their own operating conditions can effectively improve transportation efficiency, reduce operating costs, and extend the service life of the vehicle powertrain.
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