[Bull Dog]

Bull Dog’s HCH Transmission Swap Anthology

While I was down in Southern California this winter, I purchased a 2005 Honda Civic Hybrid 5-speed manual transmission from a nearby wrecking yard. Scott (KLR3CYL) and I rebuilt it with all new bearings and seals and afterward, we installed it into my 2006 Insight.

Since then, I have driven over 4,500 miles with the HCH transmission in my 2006 Insight. Along the way, I promised several people that I would write about my thoughts and observations related to the swap. This one is for you guys.

Driving experience & Gearing
The HCH Transmission shifts nicer. This is likely due to the large weight mounted on the end of the shift lever. It adds inertia to your inputs and helps dampen the effort required to move between gears.

The main claim to fame of the HCH transmission is it’s 3.6 final drive ratio. Compared to the Insight’s 3.208 final drive, the HCH is 12.2% lower geared overall. It is important to note that both transmissions have the same gear ratios for 1st (3.462) and 5th (0.711). In those gears, the final drive is the sole difference.

Time for a couple of charts and graphs.

You can click on the images below to access the original quality, high resolution versions which are better suited for printing.





I really like that the HCH’s lower geared final drive makes starting from a stop easier. Less clutch slippage is required to get going. The Insight transmission would need a 3.885 first gear to be equivalent the HCH first.

The more evenly spaced gear ratios on the HCH trans means that the next gear, up or down, is never too far away.

Random note: In my 2006 with the HCH transmission, the upshift light does not illuminate in 5th gear. Note: This may not be true for your car. I know of a 2002 Insight with an HCH swap, where the light does illuminate.

 

[Bull Dog]

Lean Burn
Both my 2005 and 2006 Insights will not lean burn above 2,650 RPM. It appears to be a limit coded into the ECU. As an aside, this isn’t the case with all Insights. I’ve driven a model year 2000 Insight that would happily lean burn to at least 2,800 RPM. But for me, 2,600 RPM is the upper limit of what I can reasonably expect to maintain lean burn at.

When this 2,650 engine RPM threshold is met, my Insights will refuse to re-enter lean burn for a period of time afterward unless engine RPMs drop significantly, or the ECU detects a gear change.
5th gear at 2,650 RPM in the HCH transmission is ~69 MPH. This isn’t an issue on level ground as I rarely drive over 65 MPH. However, on downgrades it is all too easy to accidentally exceed 2,650 RPM, and it can be nuisance to get lean burn back.

VSS Problems
The HCH vehicle speed sensor or VSS is not geared the same as the Insight. The HCH speed sensor will cause the speedo to read 7.6% too fast. This means that when the cluster says 70, you will be actually traveling 65 MPH.

2007-2008 Fit sensor on the left. 2003-2005 HCH sensor on the right.

If you want to get close with an OEM part, you can install a speed sensor from a 2007-2008 Fit. Then your speedo will read only 2.2% fast. This means that when the cluster says 70, you will be really be traveling about 68.5 MPH.

For me, this is still too much error. If I decide to leave the HCH transmission in my car long term, I will pursue some kind of VSS calibration method.

According to the counting I did: The Insight’s speedometer drive gear has 27 teeth and the VSS has 23. The HCH speedometer drive gear has 24 teeth and the HCH VSS has 19. The Fit VSS has 20 teeth.


Fitment Issues

HCH input shaft on the left. Insight on the right.

The shoulder on the HCH mainshaft/input shaft will need to be machined down to make room for the pilot bearing.

Insight Transmission Above

HCH Transmission Below

The Insight and HCH transmissions share the same bolt pattern for the driver’s side motor mount. Despite this, there are a few issues that still need addressing. Unlike the Insight transmission which uses two M10 studs and one M10 bolt, the HCH trans uses two M12 studs and one M10 bolt.

It will be necessary to acquire two M12 Flange bolts.

Update: A better solution. The three mounting holes are M10 threaded on both transmissions. This means you can remove the HCH studs and replace them with ones from your Insight transmission. A pair of stout pliers or a couple of nuts jammed together should do the trick to remove them.

 

[Bull Dog]

Fitment Issues Continued

Update: This step is not necessary if you transfer the mounting studs as outlined above.

However, if you do want to use the HCH mounting studs, then it will be necessary to acquire two M12 Flange nuts. I recommend I recommend Honda part# (94050-120800).

The M12 stud has a flared section that won’t fit in the hole on the rear side of the Insight motor mount bracket. It will be necessary to partially clearance the hole with a 14mm or 9/16in drill bit.

Side note: The Insight’s rear motor mount bracket will bolt to the HCH transmission with no issues.

The reverse switch on the HCH transmission is not in the same location as it is on the Insight trans. In order to make the plug reach, it will be necessary to extend the wiring. I got lucky. My HCH transmission came with an extra plug and wiring that I was able to use to extend the OEM harness without cutting it.

The rear air box support bracket is secured with two bolts to the to the top of the shift tower on the Insight transmission. The HCH transmission is missing the second bolt hole. It’s not ideal, but using one bolt to anchor the bracket seems to be working on my car.

The IMA System Works
I wasn’t entirely sure if the IMA system would work properly with a different transmission. I’m happy to report that it does. (And yes, I missed Sigma Project's post back in December where he said it does.)

There are some occasional oddities where the car will refuse to regen. The most frequent occurrence of this is when I shift into to 5th gear at around 38-40 MPH with little or no throttle while letting the clutch out. When it happens, the car will refuse to regen even when pressing on the brake pedal. I haven’t extensively tested this, as I will usually just downshift to 4th or 3rd instead.

 

[Bull Dog]

Parts Interchangeability

Despite the fact that you can pretty much bolt an HCH transmission up to an Insight, there are enough differences inside, that only some things are swappable.

The 3rd and 4th gear sets can be swapped. 5th gear can too, but there is no point as they are the same 0.711 ratio.

Countershaft & Ring Gear: While the overall length of the countershaft and the diameter of the splined sections are the same, the pinion is not. This is expected as the pinion and ring gear are part of a matched set. You can’t change one without the other. Nevertheless, the countershaft does physically fit inside an Insight transmission case.

The HCH ring gear is held to the carrier with ten bolts. The Insight’s ring gear uses only eight bolts but still in a 10-bolt circle.

This naturally begs the question, “Can you bolt an HCH ring gear to an Insight carrier?”

Update: The answer is yes. You can put an Insight ring and pinion into an HCH transmission, and you can put an HCH ring and pinion into an Insight transmission. It is important to note that HCH and Insight countershafts have different inner bore diameters.

If you swap them, you must also change the countershaft oiler, or "Oil Guide" as Honda calls it.

HCH Oil Guide 21103-PLW-000
Insight Oil Guide 21103-PHR-000



A non-exhaustive list of parts that can definitely not be swapped.

Mainshaft: The HCH mainshaft is longer and the teeth for reverse are cut in the opposite location as on the Insight mainshaft.

Reverse Idler: Except for the number of teeth, the HCH reverse idler is completely different and is actuated in the opposite direction compared to the Insight one.

Edit: 2019/10/22 Updated post with new information.

 

[Bull Dog]

A non-exhaustive list of parts that can definitely not be swapped - continued

(Carrier - The subassembly that houses the spider gears as well as retains the axles. It is sometimes referred to as a Differential Case or Ring Gear Carrier. This unit transfers the motion from the ring gear to the axle shafts.)

Carrier: While the HCH and Insight carriers both accept axles with the same spline count and seal diameter, the similarity ends there.

Insight carrier bearing inner diameter above…

…HCH below

HCH carrier bearings are bigger. The HCH carrier uses bearings with a 40mm inside diameter, and on an Insight, they are 35mm. This also affects overall bearing diameter which is 80mm for the HCH and 72 mm for an Insight.

Speedometer Drive Gear: The carrier bearing difference also affects the nylon gear that drives the speed sensor. An Insight’s speedometer drive gear has an inside diameter of 35mm. This quite obviously won’t fit over the HCH’s 40mm diameter carrier. The outside diameter of the HCH speedometer drive gear is also larger and has fewer teeth compared to the Insight.

Speed Sensor (VSS): The gear on the Insight’s speed sensor is larger than the HCH speed sensor. Because of this, the Insight’s VSS will not mesh with the HCH’s speedometer drive gear…and even if it could, it still wouldn’t read accurately

 

[Bull Dog]

Mass and Weight

The HCH transmission weighs 9.3 pounds more than an Insight transmission. It’s remarkable how Honda was able to make the Insight transmission over 12% lighter than a regular Civic transmission from that era.

While rebuilding the HCH transmission, I found it fascinating to compare the HCH transmission with the Insight transmission and observe some of the ways Honda saved weight with the Insight transmission. For example, the Insight transmission case is thinner. The Insight transmission’s shift fork shafts are hollow while in the HCH transmission they are solid. The Insight’s reverse gear was lightened, specifically for the Insight. The Insight ring gear has extra holes drilled in it. The shift lever weight present on most front wheel drive Honda manual transmissions was omitted. The list goes on…even the Shift Arm Cover shows evidence it was lightened compared to the HCH one.


Would I recommend it?
If you are running your car gas only, the combination of the more evenly spaced gear ratios and the 12.2% lower geared final drive should be a welcome improvement.

For me, the equation is different as I intend to keep my IMA system working. I love the 12% lower first gear. I like that the gears are more evenly spaced and closer together. On the other hand, I have come to realize that I am not in love with the 12% lower 5th gear and the VSS issue.

It would seem that something between the Insight’s 5th and the HCH’s 5th might be in order…but that’s a story for another time.

 

[hondarider90]

Running bypassed I'm very happy with mine. The car bypassed always struggled insanely at altitude going up hills and it's now got a fighting chance if I'm willing to push it over 4k rpms. Even with headlights on I haven't found a huge issue with the battery getting run down on 5 to 10 minute dc-dc shutdowns while climbing so I'm not too worried yet. The hills are steep enough I could bump start it in reverse if it ever did die on me.

 

[davenm]

Thanks for the write-up, and well done!

Having driven Bull Dog's car with the HCH transmission, I was impressed enough to buy one of these transmissions and begin planning for a trip to Scott's for the swap in one of my cars.

 

[retepsnikrep]

Nice Writeup

Interesting and useful addition to the knowledge base and archive..

 

[tryingbe]

I solved the VSS issue a while back using an Arduino Uno.

Contact me if you want to pursuit that route.

 

[Mattl92]

Or an off the shelf device to correct the speedo would work just fine:

https://www.jaycar.us/corrector-speedo-module/p/AA0376

 

[tervic]

Bull dog - great write up with detailed pics, thanks!

I detected a hint of mods to come - I'm looking forward to more!

 

[retepsnikrep]

I solved the VSS issue a while back using an Arduino Uno.

Contact me if you want to pursuit that route.

Have you published the details on here?
Can you do so?

A pic solution would be easy as well.

 

[minor4326]

great documentation.

 

[eq1]

Nice thread. Thanks...

 

[hastincg]

Fitment Issues

HCH input shaft on the left. Insight on the right.

The shoulder on the HCH mainshaft/input shaft will need to be machined down to make room for the pilot bearing.

This pilot bearing is listed on rockauto as a fit for both the civic hybrid and the insight: NATIONAL 102CC Bore=0.5906", Outer Diameter=1.2598", Width=0.3543"

Is machining down the shoulder absolutely necessary?

 

[Bull Dog]

Yes. Even though the pilot bearing is the same, it isn't located in the same position in the flywheel.

 

[Sigma Projects]

Yes. Even though the pilot bearing is the same, it isn't located in the same position in the flywheel.

This is why I'm curious how a HCH flywheel would fit.

Btw awesome write up! Btw curious how you got your calculation for the speed difference of the VSS of the Fit vs 1G?

 

[Bull Dog]

The math is based on teeth counts of the drive/driven speedo gears.

According to the counting I did: The Insight’s speedometer drive gear has 27 teeth and the VSS has 23. The HCH speedometer drive gear has 24 teeth and the HCH VSS has 19. The Fit VSS has 20 teeth.

 

[Sigma Projects]

The math is based on teeth counts of the drive/driven speedo gears.

Right right, I blame lack of sleep for my lack in logic.