My GF recently picked up a "new" 2007 Fit Sport 5MT in silver to match my Insight, and I've fallen in love with the car. I could probably go on and on about its virtues, but you're all already aware of them. I have some serious car envy, and my only gripe is how very short 5th gear is. I did a bit of searching before deciding to register and ask, but has anyone ever produced a taller 5th gear for these cars? Or, if not, where would be a good place to have one made? I know eventually we'll have to do an ISB or clutch or something, and figure that would be a good time to tear apart the gearbox and do the swap if I can find a replacement. Price isn't a huge concern so long as it's not unreasonably expensive. I would do a few hundred, but definitely not approaching a thousand for a gear.

Some relevant and fun bits:
The GD is only 2" longer than Honda's tiny G1 Insight, 7" taller, and no wider. If you count the mirrors it's actually a hair less wide.
The GD weighs ~33% more, but has ~50% more horsepower and torque at the same RPM.
In 5th gear, the Insight cruises along at a very relaxed 2700rpm at 80mph, just below VTEC engagement, compared with with Fit's ~3750rpm - 40% higher at the same speed!

I understand many people don't like to need more than 1 gear at highway speeds for any reason, but frankly it makes sense to me to have a quieter and more relaxed drive, higher fuel economy and reduced engine wear, in exchange for needing to shift down to 4th for particularly steep hills or passing. I'm thinking 3400-3600rpm would be "about right", which would mean I'm looking for a ~0.647-0.689. Interestingly, 0.689 is the exact gearing of the CR-Z's 6th gear, though I don't imagine they're interchangeable. If it were my daily driver I'd be tempted to go even taller.

Anyhow, a couple of pictures for visiting my thread:

 

Re: Engine wear: When people are getting over 300k miles out of these cars as-is, I wouldn't be concerned about engine wear as a consideration.

You could check the other generation Fits and see if the transmission is the same/similar and, if so, if the gear ratios are different. That, or check out the most recent generation and research whether a swap is feasible (it's a 6-speed manual).

Personally, I wouldn't bother. If you can find the parts, you're looking at a good deal of work for the benefit of a marginally-quieter interior and marginally-better fuel economy in a vehicle built to be more of a street runabout than a highway cruiser.

 

Thanks for your feedback!


After looking over things very carefully, I think the guts of an HCH1 gearbox should be a direct swap, sans differential. I believe the Insight's gears are also interchangeable. Here's a chart of increasingly tall ratios, leaving out a few possible combinations with the JDM final drive:

RPM at 70mph:
Fit 5th, USDM Fit FD: 3250rpm
HCH1 5th, USDM Fit FD: 3050rpm
HCH1 5th, JDM Fit FD: 2920rpm
Fit 5th, HCH1 FD: 2735rpm
HCH1 5th, HCH1 FD: 2565rpm
Fit 5th, Insight FD: 2440rpm
HCH1 5th, Insight FD: 2285rpm

Fit 5th gear: 0.757
Insight or HCH1 5th gear: 0.710
Fit FD: 4.294
HCH1 FD: 3.600
Insight FD: 3.208

Swapping the final drive would affect the other gears, but all of these cars have identical first gears and the Fit has better power to weight, so starting in first in the Fit would be little different than it already is in these others. I think the Fit's 1st is a bit of a granny anyway.

Considering how many Civic Hybrids there are in junkyards, and how the HCH1's final drive would affect the other gears less, I'm inclined to use an HCH FD and 5th gear, good for a roughly 700rpm drop at 70mph, and likely good for at least 5mpg at cruising speeds. I might consider the JDM Fit's 4.1 FD if I can find one cheap, but I won't hold my breath.

I doubt I'll tear apart the transmission just to swap gears, but if I have it out for other work, I don't see why I shouldn't. If I'm going to ever bother with a clutch, I'd likely replace all of the bearings in the transmission anyway, while I have it off.

 

Good information, but I think it's worth noting that the other two you are looking at have electric motors that provide substantially more torque off idle than the Fit.

All of the performance shops back in the day went the opposite direction with the GD Fit. They offered lower gears sets and steeper FD's to try to get it spinning even faster. You're looking to make it lazier at accelerating. Not sure that's a great idea.

For reference, the Insight and Civic Hybrid have 123 lb/ft torque available at 1000 rpm. The GD Fit has 105 lb/ft and it doesn't peak until 4800 rpm.

While I would like a lower cruising rpm, I think Honda chose the Fit's gearing because of the lack of torque and overall anemic performance. Lugging the motor is much more damaging than rpm. Owners have found that the ECM is opening the throttle body significantly already at highway speeds in order to compensate for load. You may not move your foot, but the drive by wire system is opening it anyway. Just think how much extra load it would have with even less gear and less rpm.

Even with the current gearing, it's 1500 rpm shy of peak torque going down the highway. That's not a good thing! I wouldn't want to make it worse.

 

Thanks for your feedback!

Granted. The Fit's engine has a pretty darn flat torque "curve" down to nearly 1000rpm though, I'm not thinking of going as low as the Insight, and it weighs a good 2-300lbs less than the HCH.

At the very least, I might swap to the JDM final drive and Civic Hybrid's 5th, and bring down cruising RPM a bit without affecting 1-4 very much. Honda's low-rpm engines are some of their longest-lived, spinning it faster has empirically shown to wear them out faster. Higher revving engines typically end up burning oil and have worn rings, or top-end failure.

Lugging is basically a non-issue in modern fuel injected engines. Doubly so because the Fit, HCH and Insight have an offset crankshaft. You're not pounding the bearings at low RPM, and even predetonation is significantly less dangerous because the geometry of the stroke is entirely different from older symmetrical designs. Insight engines typically last 4-600,000 miles and actually tend to last longer when "lugged" - their eventual deaths are usually the result of valvetrain failures (wear due to RPM), not crank bearings.

The Truly Amazing Honda Fit/Jazz



I'd also like to add that the S2000's peak torque is at 7,500rpm. I certainly would not want to cruise at 7500rpm. Volumetric efficiency is generally highest at peak torque, but volumetric efficiency is just how much air you can stuff into a cylinder. It has little to do with overall efficiency. Friction goes up exponentially with RPM, and friction = wear. The G1 Insight's lowest BSFC (basically best fuel economy) happens at 2000RPM, despite peak torque happening at 4,800rpm:

 

if you find a solution to this, I'm in. I do 2 round trips at 80 mph of 300 miles each way per month... and its one of my only complaints about the car.

 

Did you own a British car in the past? I say this because they're much more attention-seeking than a Honda and might've primed you to expect much more work than is necessary. For example, you mentioned that you'd replace all the bearings in the transmission if it needed a clutch, which is utterly mystifying to me. If you just want the experience, by all means go hog wild, but otherwise that is overkill overkill (so overkill as to be overkill on overkill). :P

 

My Insight was close to rolling past 300k. The engine still didn't burn oil and had great compression. It was close to needing its first clutch. There's a design flaw in the syncros that requires removing locking tabs from the syncros (they develop a burr which causes them not to engage), and I needed to pull the transmission apart anyway to get to those. It's good practice to do throw-out and input shaft bearing (these often fail before this point) when you have the transmission out, and I figured with how cheap bearings are, I'd do the rest anyway along with the clutch and syncro fix, and engine rear main seal while I was there. Tearing apart a transmission isn't hard and nothing is particularly expensive, it just takes some time. The biggest hassle is getting it out of the car and I paid a shop to do this. Comparatively, everything else was pennies. Seems wise to do inexpensive but potentially critical labor while you have access to it?

I'm hoping to keep this Fit on the road for a few hundred thousand more miles, so I'm not going to neglect little things.

 

I still think you're going overkill considering people have been going 300-400k without anything but coilpacks/tires/oil/trans-fluid/valve adjustments, but it sounds like you enjoy getting deep into transmissions so more power to you!

Since you're going to be in there anyway, have you considered adding an LSD? I know Quaife makes one for our cars and it would not only make the car more fun, but I could see it helping out in bad weather too considering you're up there in New England.

 

I hadn't considered an LSD, but that sounds like a decent idea. It's probably a helical LSD (?), and my understanding of those is that if one wheel has no traction, it's not going to help. You'll still get one wheel spinning freely, they act like open differentials unless both wheels can get at least a little bite.

I'll look into it, thanks.

 

I have a Quaife differential and complete larger diameter clutch masters kit here to install in our Fit. Will report how it is once installed. I will change the carrier bearings and seals while at it, but will probably leave the rest alone. At near 200k miles, it still feels good. Don't want to break anything not broken.

 

Please take pictures GAFIT (or Ecky, if you do go that route)!

 

Wow - didn't know there were LSD options? Any chance it fits on a GE 5AT??! :P

 

Not a chance.

 

Ecky, love your data presented and would love to see you or someone try a different 5th gear/FD combo with desired outcomes and report back your experience for the end result.

I've also been for a long time, wondering what solution there was to "fix" the 07/08 Fit's hwy cruising gearing. 80mph (flow-of traffic where I live) at 4000rpm for me... would love to drop it by 500 or more rpm and see a quieter cabin... and better mpg as a theoretical. And 1st is definitely a granny gear, revving out at 10mph. If I lived in mountains... perhaps 5MT stock is optimal.

I like the idea of swapping the FD gear, and will probably have a clutch job in the next 40k mi, which would be the right time to swap the FD.

 

I'll absolutely report back when I have to do the clutch.