Got a new Fit, love it. But I hate been on the highway at 70 mp/h at nearly 4000 rpm. Is it possible to change the 5th gear or to modify the ratios to make it drive more smoothly on the highway?

I know Honda engines are made to last, but 4000 rpm days after days after weeks after years should make it wear faster... I plan to keep this baby for at least 15 years, so I was wondering...

Thanks

 

^ A very valid point, and one I've considered myself. Swapping in a new, taller 5th gear would obviously void the crap out of your warranty on the transmission, axles, and so forth. On the upside, it would reduce cruising RPM, which would, as you mentioned, reduce friction and fuel consumption on the highway, improving fuel economy and reducing engine wear. Now, for the tricky part...

Since there isn't a off-the-shelf taller 5th gear, you'd need to have one custom made. You have two options here- remove your Fit's transmission, and drop it off at a custom transmission shop, and have them custom make you a new 5th gear, which would take a few days, plus some testing in the car, OR, pick up a spare Fit transmission, and follow the same route, but without as much downtime. Either way, you are taking some risk, and putting a LOT of cash out there, not to mention down time.
On the other hand, IF you did this, I know I'd sure be interested in one As long as you don't go TOO tall, to where any hills would require a downshift to 4th, it should be a good idea. If you find a shop willing to try it, keep us posted! Mark W.

 

You can try to swap your 5th gear for a 5th or 6th gear from a CR-Z.

A Honda Fit 5th gear ratio is 0.727, and a CR-Z is .854 and .689 for 5th and 6th gear respectively in a manual transmission. I can't remember the formula to calculate the the exact RPM at 70 MPH ( its something like rpm = (gear ratio x final drive x ?) / (tire diameter). Of course your final drive ratio will change as well. Fifth gear is more reasonable to switch because 6th will drop the RPM down too much.

If you're switching 5th gear ratio to a higher one you're going to lose some acceleration. That's what 5th gear is good for in the Fit on the highway as it is already in a good power band to pass people or climb uphill without having to shift down to 4th.

 

a complete crz 6 speed would be sweet. a much easier way to reduce crusing rpm would be to go to a slightly taller tire

 

^ But will it physically fit, to both of these posts? The case is likely bigger, which would require new axleshafts, further increasing costs for custom shafts way beyond the cost of gas and even an eventual engine rebuild- no thanks Mark W.

 

Just checked on Majestic Honda's website- a whole trans, at their discount price, is $3,051 and change, plus tax and shipping- not really an economical solution At junkyards, they're only a grand or so cheaper, so still, not really feasible- Mark W.

 

I know for searching on google that some people talked about this, but if it isn't that easy to change the gears, is there any danger for the engine to run everyday at 4,000 RPM for years and years? I mean: Honda engines are tough, but I don't see the point of building a MT that shows 4,000RPM at 70 mph...

 

I read some where that the CR-Z's 5th gear is similar to most L-series, except with a 6th gear on top. One would have to compare the two to actually know for sure.

I know 4000 RPM sounds a lot at 70 MPH, but Honda built the engine so that it can put out as much power as it can for the 1.5 liter engine at high RPM. I find that the high RPM for each gear compensate for the lack of acceleration/torque for the higher gears in the little engine.

 

THIS. honda wasnt fucking around with they geared the transmission.

 

A few things of note:

• The 5MT is around 3500rpm and not 4000 at 70mph.
• The best swap for dropping the 5th gear noise would be the 5th gear from the 5AT as it is even lower than 6th on the CR-Z. This would require lots of shifting to 4th on any road other than the levelest roads. Even swapping in the CR-Z's 6th gear (which is higher than the 5AT 5th) would force you to downshift on any hill or a gust of wind.
• Moving to a taller tire and putting a taller 5th (or swapping in a 6th) would likely bog the engine/transmission down WAAAY too much unless you went with a super-light wheel/tire combo. The CRZ's Electric motor provides the torque to be able to handle a taller 6th. The fit has no torque.
• Long and short of it is the 5MT is geared just about right for the engine size and the majority of Driver Needs in the US. The reason the 5AT is taller is because it handles shifting for you. Dropping to 4th at every gust of wind is ok for the AT to do but would not be acceptable for someone rowing the gearbox. I bet we'd be having the opposite conversation if Honda geared 5th in the 5MT too tall.

~SB

 

It's also not good to lug a little low displacement engine at too low RPMs, which would be tempting for people with the MT to do to avoid frequent downshifts - i.e., wait till it really bogs down and you have no choice but to downshift. Honda may have it intentionally geared the MT a bit higher and avoided an overdrive gear specifically to benefit engine and drivetrain life.

 

Ok- gotta push the failboat out of the weeds here Umm, (modern) automatic transmission gears aren't the same as manual transmission gears. They are different in just about every way. You could never swap in a (modern) AT gear into a modern MT. Maybe you could swap in a 5th gear in that RATIO, but the physical gear would never work.

Next up, dropping in a SLIGHTLY taller 5th gear to drop the RPM's at 70 MPH to, say, 3,000 RPMs would not be too drastic of a move. I've build custom manual rebuildable transmissions in the past (I worked in NASCAR, I'm ashamed to say ), and while a NASCAR engine is NOTHING like a Fit, I've also built them for my own cars. I had a '98 Subaru where I swapped ratios- I went to a shorter 1st and 2nd, and a taller 5th- again, kept it moderation. I gained better acceleration down low, and lower RPM up top, plus a higher top speed- everybody wins

Also, you seem to be underestimating the L15A7- it has pretty good power and torque, especially for a 1,500 CC engine. If you dropped highway RPMs at 70 MPH to, as I mentioned, roughly 3K, you'd still be in the powerband for this engine. As I don't know the type of highways the OP is driving, I can't speak for big hills, but I'm sure that only the bigger hills would need a gear drop from this range. If the driver kept their momentum up coming up to the hill (momentum driving is something every small engine/small car driver should practice, since we don't have the power to compensate for momentary lapses like a bigger engined vehicle), they should be fine.

Also, people are proposing adding the 5th and 6th ratios from the CR-Z's trans like there's room in the Fit's trans case for them. Doubtful. Also, you'd likely need the entire shift linkage from that car adapted to this application. Or, swap in the entire transmission. Again, has anyone actually measured the sizing of the CR-Z trans case vs. the Fit's? I'd LOVE to hear that they're the same, as I'd LOVE a 6th gear. Using the OEM CR-Z gearing, at 60 MPH, you'd be at about 2,400 RPM, where the Fit still has a fair bit of torque. At 70 MPH, you'd be at just shy of 2,800 RPM, about 700 fewer than the OEM Fit MT. NOT a huge drop, and just about where you'd want it. Calculated with OEM Fit Sport size tires, and OEM CR-Z gears and final drive.

I'm NOT meaning to pick on you, dude, but there's some serious false knowledge going on. Call it forum knowledge. I'm speaking from REAL knowledge from REAL experience, not just stuff I've read on the internet. I've done the work, performed the mods, and seen the results on my OWN gas bills, top speed runs (on the racetrack/rally stages- NEVER on the street!), and at the strip, as well as going down the highway. Please believe when I say I wasn't meaning this as a personal attack, but as an attack on false knowledge- Mark W.

 

Thanks for the replies. Would it be expensive to replace the 5th gear with a slightly different one... if it changes anything to my warranty maybe it's not that much a good idea...

I make about 75/25 city/highway, but been on the highway at 4,000 rpm all the time for weeks and weeks... well feel strange... Got a Honda motorcycle which can handle that, but it's not the same, is it?

Thanks for the interesting thread

 

While I personally do prefer the gearing of the automatic transmission, there is nothing wrong with the approx. 3300 rpm that the manual Fit runs at 70 mph (except for a bit of noise). It is designed to tolerate this without excessive wear. Another data point for a high-revving Honda 4 cylinder engine is the S2000 (my much beloved Garage Queen, since 2002). That one runs about 3800 rpm in 6th gear at 70 mph, and has shown itself to be quite reliable. Engine failures occasionally occur from shifting errors, such as executing the intended 6-4 at 80 mph and achieving 6-2.

I would not worry about the gearing.

 

It would certainly be expensive to change out 5th. Figure in the $1000-2500 range for a custom gear, installation, and so forth. And it would sure as hell void the warranty on the transmission, and the rest of the driveline.
Again, yes, high RPMs is bad for friction and engine longevity, but if anyone can make a car engine that can surive that kind of abuse, it's sure as hell Honda Mark W.

 

Ouch! I was looking at some 6-speeds when I was shopping for the fit and having never driven one before, I was wondering if that ever happens. I really can't imagine making making such a disastrous shift on a 5-speed and after 20 consecutive years of driving one, I have not proven myself wrong...yet.

 

I've seen some people hit 2nd looking for 4th on the drag strip on 5MT's.

I watched an EG(?) hatch Honda on slicks do an endo while simultaneously windowing the block and explosive metallic diarrhea.

 

I think some people interpreting my post wrong. I'm recommending swapping the the Fit's 5th gear for a CR-Z's 5th gear, changing the ratio. The two gears can be the same size, and fit; but the amount of teeth on the gear is the only difference. If not the 6th gear may work.

Its impossible to add 6th gear to the Fit and make it a 6-speed transmission. Swapping the CR-Z tranny on to the Fit would not work either because of the IMA motor and bell housing.

Swapping 5th gear should be relatively easy as it sits at the end of the transmission, and accessible. It would be cheaper if one does it themselves.

 

There is no false knowledge here so I'm not sure where you are coming from. There are some serious assumptions coming from your end and it's probably my Mistake for not clarifying every last little item as I expect too much from too many... obviously... Hey... I'm an optimist!

I never said you could actually take the physical gear from the auto and put it into the manual. Anyone who would consider doing some sort of transmission gearing upgrade knows that the two transmissions are different but for those that will "armchair" upgrade, I should have clarified. the reference was more theoretical and in line with the fact that the 5AT has the best top gear of any of the L15 engines. even 6th gear in the CR-Z isn't as tall as 5th and the 6MT FIT RS also doesn't have a 6th that is much taller than 5th in the Sport 5MT. Want a 6th gear. Source a JDM RS Tranny. VOILA!

as for the Drop in RPM. In many vehicles, dropping from 3.5K to 3K isn't much but in the FIT, where noise suppression is limited in order to cut down on weight, the drop would be welcomed by MANY. Just listen to those who complain about the volume level in their 5MTs at 65mph vs those in the 5AT's that DON'T.

As for underestimating the L15... not so much. The L15 is very torquey... for a 1.5L engine. My HP Omnibook 900b laptop runs super fast... for a Pentium3 650 with 192MB of RAM. Perspective... The fit does not have the torque to support a tall 6th gear. Most 4Cyl hondas out there have a decent amount LESS torque than the competition... they REV higher (take my GS-R with the 8100rpm redline for example) The CR-Z with it's L series does have the ability to run a taller 6th with the extra torque from the IMA. The L15 Itself might be fine at 70mph running at 3K... on a Lighter vehicle with way less drag but just because the vehicle is in it's power band doesn't mean that other forces aren't at work. around 30mph, there is very little drag on the car so the "PowerBand" you speak of is fine and in theory, that would also be fine at 70 if there was not a huge amount of drag exerted on the vehicle. Add in a few hills and there is no way you'd maintain 70mph at 3krpm in the fit without seriously lightening the vehicle. Every Hill would require a shift for Most all drivers out there. I personally DO conserve momentum but Honda isn't planning these vehicles for you, or me. They build them for the Masses and those masses, especially here in the US, don't want to be bothered with having to learn these new techniques. Us here on FF are definitely NOT going to be the norm.

As for the "gotta push the failboat out of the weeds..." and ending with "Don't mean to pick on you dude..." That's like one of my staff members saying "Now I don't want to get John in trouble... BUT... He did blah blah blah..." It's the "I'm goign to be an ass yet make myself feel better by quantifying my 'intentions' in an ending sentence". oh... and "dude" went out with the 80's.

~dude

 

^ The CR-Z's 5th ratio is shorter than the Fit's, so that, again, would be counterproductive. Also, given the basic nature of the OP's question, I'd be very doubtful they would be up for swapping gear ratios, let alone the teardown involved! And, again, that's assuming the gearshafts are the same diameters (doubtful, but possible), and that the gears would physically fit inside the Fit's transmission case. Somewhat more likely, but again, a big unknown- Mark W.