Introduction
The 6-speed manual gearbox fitted to certain Hyundai and Kia models is commonly found across the 1.6 petrol engine variants.
Understanding which vehicles this gearbox relates to is important when diagnosing faults, sourcing replacements, or identifying whether a known issue applies to your specific vehicle.
This gearbox is part of a transmission family used across both Hyundai and Kia platforms, and is not the same unit found in the more widely discussed diesel models with higher gear synchromesh faults.
In this case, we identified both excessive bearing wear and a 2nd gear engagement issue.
It is important to note that while these faults were present together in this instance, we have also seen:
- Bearing wear occur independently
- 2nd gear grinding/pop-out faults occur independently
So at this stage, these should be treated as associated findings rather than a confirmed direct cause-and-effect failure.
Quick Symptoms
- Grinding when selecting 2nd gear
- 2nd gear popping back out under load
- Noise or vibration from the gearbox
- Inconsistent or weak gear engagement
- Internal movement visible once stripped
Q: Does this sound like worn synchromesh?
A: Yes, however, while grinding can be linked to synchro wear, gears popping out under load usually indicate a deeper issue.
Q: Is this a common Tucson issue?
A: No. This specific combination of faults is not something we see regularly, however this could be a period where age/mileage related issues start appearing.
What We Found
During inspection, two separate issues were identified:
- Excessive internal bearing wear. Complete failure is also common.
- A fault affecting 2nd gear engagement
Bearing wear can introduce internal movement within the gearbox, which affects alignment and load distribution.
Separately, 2nd gear grinding and pop-out typically indicate that the gear is not engaging or holding correctly under load.
While both were present in this case, it is not always possible to confirm that one directly caused the other without further component-level analysis.
Understanding Gear Pop-Out
For a gear to remain engaged, the gearbox relies on:
- Correct shaft alignment
- Full engagement of the gear and hub
- Correct part tolerances, to eliminate excessive movement.
If any of these are compromised, the gear may:
- Fail to fully engage
- Be forced back out under load
- Produce grinding during engagement
This is why gear pop-out faults are often linked to internal wear rather than just synchroniser issues.
Confirmed Vehicle Applications
Hyundai Tucson (TL / TLE)
- Engine: 1.6 GDi petrol
- Engine code: G4FD
- Transmission: 6-speed manual
- Drive type: Front wheel drive
- Approximate years: 2015 onwards
Kia Sportage (QL)
- Engine: 1.6 GDi petrol
- Engine code: G4FD
- Transmission: 6-speed manual
- Drive type: Front wheel drive
- Approximate years: 2016 onwards
Gearbox Identification Details
This transmission is typically identified as:
- 6-speed manual gearbox
- Used with 1.6 GDi petrol engines
- Front wheel drive configuration
- Common gearbox codes: ZG70 / ZG70KJ
At present, we have only seen this specific issue on the 1.6 petrol models fitted with the 6-speed manual gearbox.
This is a different transmission to the one commonly associated with the well-known Hyundai/Kia gearbox faults involving 3rd, 4th, 5th and 6th gear crunching, which are predominantly found on the 1.7 diesel variants.
Those more common faults are typically linked to synchromesh design flaw which has been replaced by the manufacturer with a revised design..
This case is different, both in terms of the gearbox design and the symptoms being experienced, so it should not be grouped in with the more widely documented Hyundai/Kia gearbox issues.
What Drivers Usually Report
Typical feedback from drivers includes:
- Grinding when selecting 2nd gear
- Gear engages but does not stay in
- Gear lever kicks back under load
- Noise or vibration from the gearbox
- Progressive worsening over time
Repair Requirements
This type of issue requires gearbox removal and strip-down inspection.
Typical repair work may include:
- Replacement of worn/failed bearings
- Inspection of gears and selector hubs
- Checking for wear caused by internal movement
- Re-establishing correct tolerances and alignment
External adjustments or clutch replacement alone will not resolve this type of fault.
Why Diagnosis Matters
Where multiple faults are present, it is important not to assume a single root cause.
Correct diagnosis ensures:
- All contributing factors are identified
- The correct components are replaced
- Repeat failures are avoided
Final Thoughts
This Hyundai/Kia gearbox fault highlights the importance of accurate diagnosis when dealing with grinding or gear pop-out issues.
While synchromesh wear is a common cause of gear crunching, faults affecting gear retention and internal movement require a deeper inspection.
In this case, both bearing wear and 2nd gear engagement issues were present, but should be considered as associated findings rather than a confirmed direct cause.
Eco Torque Contact Details
If your manual gearbox is grinding, popping out of gear or showing signs of internal wear, get in touch with our team for advice and repair options.
Eco Torque Ltd
Unit 1A Portland Industrial Estate
Hitchin Road
Arlesey
SG15 6SG
Telephone: 01462 835335
Email: info@eco-torque.co.uk
If you’ve experienced similar symptoms, leave a comment below with your vehicle details.
