HAHAHA TH350/TH400 Firewall Mounted Flex Transmission Oil Dipstick

In this review the HAHAHA TH350/TH400 firewall mounted flex transmission oil dipstick is evaluated for drivers who need a neat, firewall-mounted replacement for GM TH350 or TH400 transmissions. The bottom line: it is best for hobbyists and mechanics who want a clear, easy-to-read dipstick that installs without relocating the factory tube. The reviewer found installation straightforward, the fit reliably accurate on matched applications, and durability reasonable for daily use, though a few users reported mixed impressions of construction and one reported persistent leakage.

Key Features

• Firewall Mounted Design: Places the dipstick at the firewall for easier access on modified or tight-engine bay layouts and avoids routing issues with the factory tube.
• Compatibility: Engineered to fit GM TH350 and TH400 transmissions so it can replace worn or damaged original dipsticks on those units.
• Clear Scale: Features an easy-to-read marking scale that helps deliver accurate oil level readings at a glance during routine checks.
• High-Quality Construction: Built from materials meant to resist typical underhood conditions and provide a longer service life than some generic replacements.
• Easy Maintenance: The dipstick can be removed and reinstalled quickly, making frequent transmission checks and top-ups simple.
• Reliable Performance: Designed to meet common OEM fit expectations so installation and operation are predictable for most users.

Who It's For

This dipstick is aimed at car owners, restorers, and performance enthusiasts working with GM TH350 or TH400 transmissions who want the convenience of a firewall-mounted dipstick and a clear reading scale. It is particularly useful when the original dipstick tube is damaged, hard to reach, or when custom engine/transmission setups require a relocated fill/check point.

It is not ideal for users with transmissions other than TH350/TH400 or for those who need a guaranteed leak-free solution under extreme racing conditions; a sealed or purpose-built racing filler may be preferable for sustained high-pressure, high-heat environments.

Pros & Cons

Pros

• Fits TH350/TH400 applications cleanly and gives a secure, direct replacement for the original dipstick.
• Clear, readable markings make routine oil checks quicker and reduce guesswork.
• Firewall mounting reduces routing complexity in modified engine bays and improves accessibility.
• Easy to remove and reinstall for maintenance tasks.

Cons

• Some customers reported mixed impressions of overall build quality, and one report noted a persistent leak, so mating hardware and seals should be checked during installation.
• Not suitable if you need a specialized sealed racing fill or a dipstick for non-GM transmissions.

Specifications

Our Verdict

The HAHAHA TH350/TH400 firewall mounted flex transmission dipstick is a practical, value-oriented replacement for owners of GM TH350 and TH400 transmissions who need better access and a clear reading scale. It performs well in most street and light-performance applications, offers straightforward installation, and represents good value for routine maintenance, provided you check seals during fitment.

Frequently Asked Questions

Will this dipstick fit my transmission?
It is designed specifically for GM TH350 and TH400 transmissions; it will not fit other transmission families.

Does it require special tools to install?
Installation is generally straightforward and does not require special tools, but you should confirm proper sealing hardware is used to avoid leaks.

Is the scale easy to read while hot?
The clear scale is intended for quick checks and is readable during routine use, though ambient light and oil staining can affect visibility over time.