Honda Civic Manual Transmission Fluid Amsoil Synchromesh Upgrade: Eliminating Third Gear Grind
You know that sinking feeling when you go for third gear and instead of a smooth snick, you get that awful crunching sound—the one that makes you cringe and wonder if you’re slowly destroying your transmission.
If you’ve owned a manual Honda Civic for any length of time, you might have experienced this. Maybe it’s that notchy 2nd gear on a cold morning, or the dreaded 3rd gear grind that seems to happen at the worst possible moment. The good news? You might not need a transmission rebuild. There’s a simpler fix that’s been making the rounds in Honda communities, and it involves a fluid swap with a product called Amsoil Synchromesh.
TL;DR
The Amsoil Synchromesh Manual Transmission Fluid upgrade is a popular fix for rough shifting and gear grinding in Honda Civics. Many owners report that switching from factory Honda MTF to Amsoil makes their transmission feel smoother, reduces notchy shifting, and sometimes even eliminates gear pop-out issues entirely. The upgrade involves a simple drain and fill procedure, though some owners note mixed results—especially in cold weather or after extended use. At roughly $20 for two quarts, it’s a cheap and easy DIY fix worth trying before considering more expensive transmission work.
Key Takeaways
- Amsoil Synchromesh is specifically designed to help manual transmissions shift more smoothly, and many Civic owners report it eliminates the 3rd gear grind.
- The product is compatible with a wide range of Honda Civics, from the 8th generation Si to the latest 11th generation models.
- The fluid change is a straightforward DIY job: drain the old fluid, fill with Amsoil, and that’s it.
- Experiences vary—many owners love it, but some report it feels great initially then gets notchy again, or that it performs poorly in cold weather.
- If Amsoil doesn’t fix your grinding, the problem might be worn synchros or a damaged transmission, which requires more serious work.
Understanding the Third Gear Grind Problem
Why Does It Happen?
The third gear grind in manual Honda transmissions is a well-documented issue, especially in earlier Civic Si models. It’s often caused by a combination of factors: the factory transmission fluid breaks down over time, and the synchros (the parts that help gears mesh smoothly) simply can’t keep up under hard driving.
Italics: The 8th generation Civic Si (2006-2011) is notorious for this problem, and there was actually a Technical Service Bulletin (TSB) from Honda addressing it.
Some owners have even had their entire transmissions rebuilt under warranty back in the day, though that’s no longer an option for most cars today.
How the Fluid Upgrade Helps
The theory is simple: Honda’s factory MTF (Manual Transmission Fluid) is a thinner fluid designed for fuel economy. Amsoil Synchromesh is a heavier, more robust fluid that provides better lubrication for the synchros. This extra “cushion” helps the synchros grab more effectively, resulting in smoother shifts and less grinding.
As one longtime Civic owner put it after switching to Amsoil, “After many tests involving various shifts, engine temperature, rpms, speeds, hills or not the conclusion is that the AMSOIL MTF fluid 100% fixed my shifting problem… Even when the car was cold it shifted great. No notchy crap at all. I am 100% sold.”
The Amsoil Synchromesh Upgrade: Step-by-Step
What You’ll Need
- 2 bottles of Amsoil Synchromesh Manual Transmission Fluid (the Civic typically takes about 1.5 to 1.7 quarts, so 2 bottles is plenty).
- 17mm wrench or socket.
- 3/8″ ratchet (for the drain plug).
- Funnel with a long hose (for easy filling).
- Drain pan (to catch the old fluid).
- New crush washers for the drain and fill bolts (highly recommended).
Step 1: Drain the Old Fluid
- Get the car level. Park your Civic on a flat, level surface. This ensures you drain all the old fluid and fill it to the correct level.
- Locate the drain and fill plugs. They’re on the transmission housing, usually on the driver’s side.
- Open the fill plug first. This is a critical step—you want to make sure you can open the fill plug before you drain all the fluid. If it’s seized, you’ll be stuck with an empty transmission.
- Drain the fluid. Place your drain pan under the drain plug, remove it with the 3/8″ ratchet, and let the old fluid flow out.
- Replace the drain plug. Install the drain plug with a new crush washer and tighten it to 29 ft/lbs of torque if you have a torque wrench.
Step 2: Fill with Amsoil Synchromesh
- Fill through the fill plug. Use your funnel and hose to fill the transmission through the fill plug hole. Pour slowly until fluid starts to trickle back out—that means it’s at the correct level.
- Wait for the excess to drain. Once the fluid is level with the fill hole, let any excess drip out, then install the fill plug with a new crush washer. Tighten it to 33 ft/lbs.
“A Honda interior isn’t just a place to sit; it’s a practical workspace, a family hub, and a command center. The thoughtful layout isn’t just about comfort; it’s about making every drive—from school drop-offs to cross-country trips—feel effortless.”
Real-World Results: What Owners Are Saying
The Success Stories
Many Honda owners report excellent results with the Amsoil Synchromesh upgrade. Here’s a snapshot of what they’re saying:
- Immediate Improvement: “I changed my MT fluid with Honda oem for a few times. I then switched to the Amsoil and there was no longer 1st gear pop outs.” (Verified Amsoil Customer)
- Smooth as Butter: “The only MTF I use. The best butter for your gears.” (Verified Unity Performance Customer)
- Fixed the Grind: “It fixed my grinding in my transmission for RSX Type S… it shifts like butter now.” (Verified Amsoil Customer)
- Long-Term Confidence: “Original owner of 2008 Honda Civic SI and made the change to AMSOIL synthetic at the first… interval. 16 years later and still a daily driver with zero issues.” (Verified Amsoil Customer)
The Not-So-Positive Experiences
However, it’s not a universal fix. Some owners have reported mixed results:
- Temporary Fix: “After a couple weeks however it feels like it did before Synchromesh.” (11th Gen Civic Owner)
- Cold Weather Issues: “I’ve noticed that there is much more crunch and force needed when shifting when cold. Improves a lot once everything is hot.” (11th Gen Civic Owner)
- Gritty Feeling: One reviewer even said Amsoil “made my transmission very gritty and on the verge of grinding my gears. I would not recommend this over oem fluids.” (Verified Amsoil Customer)
When Fluid Isn’t the Answer
If you try the Amsoil Synchromesh upgrade and your 3rd gear still grinds, it’s likely that your synchros are physically worn out or damaged. At that point, you’re looking at a more serious repair.
“It’s almost never the synchro. Usually a bent fork from idiots power shifting and then the hub/slider gets worn out.” (Honda-Tech User)
In those cases, it’s best to consult a professional transmission specialist or consider a used transmission swap.
Comparison Table: Manual Transmission Fluid Options
| Fluid Type | Best For | Installation Difficulty | Key Material | Price Range |
|---|---|---|---|---|
| Amsoil Synchromesh | Notchy shifting, gear grind | Easy (DIY) | Full Synthetic | ~$20/quart |
| Honda OEM MTF | Standard daily driving | Easy (DIY) | Mineral/Synthetic Blend | ~$15-20/quart |
| Pennzoil Synchromesh | Worn transmissions, value | Easy (DIY) | Mostly Mineral Oil | ~$10-15/quart |
| Red Line MTL | Improved cold-weather shifts | Easy (DIY) | Full Synthetic | ~$18-25/quart |
Chart: Reported Success Rate of Amsoil Synchromesh for Gear Grind
FAQs
What is the Amsoil Synchromesh fluid upgrade for Honda Civic?
It’s a popular modification where owners replace the factory Honda MTF with Amsoil Synchromesh fluid to improve shifting feel and reduce gear grinding, especially in third gear.
Will Amsoil Synchromesh fix my Civic’s 3rd gear grind?
Many owners report that it eliminates or significantly reduces the 3rd gear grind, but results vary. It’s a cheap and easy fix to try before considering more expensive transmission repairs.
How much transmission fluid does a Honda Civic take?
A Civic manual transmission typically takes about 1.5 to 1.7 quarts when doing a fluid change, so you’ll need two bottles of fluid.
How do I change the transmission fluid in my Honda Civic?
The process is straightforward: drain the old fluid from the drain plug, reinstall the plug, then fill through the fill plug until fluid starts to seep back out.
Is Amsoil Synchromesh better than Honda OEM MTF?
Many users prefer Amsoil for its improved shifting performance, especially in older or worn transmissions, but some report that it feels better initially then reverts to normal, or that it performs poorly in cold weather.
How often should I change my manual transmission fluid?
If you use Amsoil and do a lot of spirited driving or occasional track days, replace it every 15,000 miles. For regular daily driving, every 25,000 miles is recommended.
Have you tried the Amsoil Synchromesh upgrade in your Honda? Did it fix your gear grind? Drop your experience in the comments below!
For further reading on Honda Civic transmission maintenance and fluids:
