What size thread is a C5 shift knob?
Typically, the C5 Corvette's manual shift knob uses a 5/16-18 UNF thread. However, variations exist by year and with aftermarket knobs, so it's best to verify for your specific car.
Understanding the thread size on a C5 shift knob
Knowing the exact thread size is essential when replacing or upgrading the shift knob on a C5 Corvette. The numbers can vary depending on production year and whether the knob is a factory part or an aftermarket insert.
Stock versus aftermarket variations
While many C5s use the 5/16-18 UNF size, some cars—especially with aftermarket parts—may employ different adapters or knob sizes. The exact size can vary by production year, and some aftermarket knobs rely on adapters to fit the lever.
Before you purchase a new knob or adapter, use the following verification methods to confirm the correct size for your vehicle.
- Inspect labeling or part numbers on the knob or lever tip, which might indicate the correct thread size.
- Measure the threaded portion’s diameter with calipers to determine whether you’re dealing with about 5/16" (0.3125 in) or a larger size such as 3/8" (0.375 in).
- Use a thread pitch gauge to identify the TPI (threads per inch). Try common sizes such as 5/16-18 UNF, 5/16-24 UNC, and 3/8-16 UNF to see which threads cleanly without cross-threading.
- Consult the dealership, GM service bulletin, or the parts catalog for your specific model year to confirm the correct size.
Conclusion: The majority of stock C5 shifters use 5/16-18 UNF, but always verify on your vehicle before buying an aftermarket knob.
Replacement options and adapters
If you plan to upgrade or switch the look of your shift knob, here are common paths and what they require.
- Direct replacement knob designed for 5/16-18 UNF threads, which matches the typical C5 stock size.
- Adapter kits to convert to 3/8-16 UNF or other thread standards, enabling fitment of knobs with different bases.
- Knobs using a set-screw or threaded insert that can be secured to the shift lever with an included adapter or insert.
Note: When using adapters, ensure the overall length and weight are appropriate to avoid interference with shifting or head clearance.
Summary
The most common thread size for a C5 shift knob is 5/16-18 UNF, but variations exist. Always verify on your specific vehicle or with the knob manufacturer before purchasing replacements, and consider whether an adapter is needed for aftermarket options.
