Hello Everyone,
I drive a 2003 Pontiac Vibe GT (6 speed Manual) and I have noticed that when im in 6th gear going highway speeds, I have an RPM of about 3K. For this model I feel this value is high and im worried about engine wear and fuel economy. I’m not sure about the other gears, but from my knowledge of other cars in the same weight category, less horsepower and 4-speed automatic gearbox, my car should not have such high RPM.
Thanks for the help
Don’t worry about it. The shorter gearing allows a less-torquey engine to accelerate faster, and high RPMs at highway speeds is the tradeoff.
My old Honda CRX Si was geared to run at 3000 RPM at 100 km/hr (62 mph). I did a lot of freeway driving at 75-80 mph, running at 3500 RPM or so. I put 175,000 miles on that engine and could have gotten another 100k if the body hadn’t rusted out. After 15 years, the engine ran like new.
Just take care of the engine, change the oil and filter regularly. You could get 200-300k miles out of the engine if you maintained it well. Problem is, most people don’t. And your engine is already 10 years old. Most of the wear damage is already done by whoever failed to change the oil regularly enough in those 10 years, or ran low on oil, or used the wrong oil viscosity, etc. Whether it turns 2500 RPM or 3000 RPM on the highway is largely irrelevant.
On my 89 Mustang GT 5.0 at 70 mph I turn about 2300-2400 rpm in 5th gear, ( a .69 to one ratio overdrive ) in 4th maybe around 3200 ( guessing )( 1 to 1 ratio ) as it red lines at 6000 rpm doing 120 mph in 4th and the over speed govenor shuts the engine down at 6250 rpm ( like running out of fuel ) to prevent engine damage. It all depends on the final ratio of the tallest gear in the tranny and the ratio after the tranny to the drive wheels. All cars are different as far as gear ratios go… If I were to change my final rear ratio lets say to 4.11 to one from a stock 3.08 , I might turn over 3200 rpm at 70 mph in 5th. Nothing to worry about as you did not give a specific speed and rpm. This was done on a oval racetrack as I do not do this on public roads. After hitting 130 in 5th it got to scary for me, but was fun during this one time run. Just do not tell my insurance company.
The specs show a final drive ratio of 4:53 and combined with a near square 4 cylinder engine and comparatively low torque the RPMs sound about right to me.
The RPMs of one car at a certain speed can’t be compared to various other makes and models.
Does this higher RPM seem excessive because of what you previously drove? That is a common malady.
My Lincoln turns 1700 RPM at 65 MPH. When I drove my daughter’s Mitsubishi it was turning near 3k and sounded like it was screaming in comparison. No harm, no foul; just a matter of perception and jesmed is right, no need to worry.
I’ve driven an older Camaro with a TH350 transmission (auto, 3 speed, no OD) and that V-8 engine was turning over 3k at highway speeds with a 3:42 rear axle. It also sounded like it was howling after being used to the Lincoln.
the 4spd auto version has a 3.0 ratio and the 4spd awd, 5sp man, and 6sp man all have about a 4.0 ratio. actually the last 3 all have within 1/10 of each other. why GM has 4 different ratios? i know about the performance aspect of hi/lo gear ratios but the very close ratio of the last 3 is a mystery.
The gt motor is 180hp while the non-gt motor is 140 or so. I assume torque is similar since displacement is same. If u do a lot of highway driving, the gt model will use more fuel.
The Vibe GT has the Toyota 2zz-ge engine.
This is a high revving engine with an 8400 rpm redline.
3000 rpm is easy-going for this engine.
It has essentially no more torque (due to essentially the same displacement) than the 1zz-fe engine used in the base Vibe (and my 2006 Matrix).
The difference between 130hp (1zz) vs 180hp (2zz) is almost all due to the higher revs.
The manufacturer assumes people buy the optional engine for the peppier response at legal speeds, so they gear it accordingly.
It is possible to get a 6-speed transmission with taller gearing if you ever need to replace/rebuild it, that’s what I’ll get if I ever need to replace mine (5-speeds have a reputation for weak bearings).
@jesmed is right on all accounts. There is nothing cut and dry about rpm and cruising as far as final drive ratios are concerned. If the car motor has a good reliability record and is meant to easily run at higher rpms regardless, it will be fine. You should be more concerned about noise intrusion. Slower running motors may be quieter.
If you’re turning 2300-2400 RPM in 5th gear then you don’t have the stock 3.08 gears. 3.08 gears with a T-5 and the stock 225/60/R15 tires, will yield a speed of about 85ish MPH at 2400 RPM in 5th gear. 3.73’s would put you at about 70 MPH at 2400 RPM though.
It can be deceptive comparing differential gear ratios of one car make with another. The final drive ratio which compares both the final transmission and differential ratio is more realistic. It makes sense comparing cars from the same manufacturer with the same transmission but not otherwise.
For example, an axle differential ratio greater then 4.00 may be perfectly acceptable for cruising when combined with a low enough numerically “over drive” final transmission gear ratio. That’s why going from a 4 speed to a 6 or six speed transmission may or may not give you give you the results you want for cruising. Using a 6 speed with a close ratio gears but with the same final drive as the 4 speed it replaces is a wash for cruising except that it gives you better passing gear options.
So just look at your speed at comparable cruising rpm for simplified help in comparing two makes and don’t let the the gear ratios confuse you.
What speed are talking about? My Versa 6-speed revs 3000 at around 65 MPH. A bit short for my taste, but it works. Some cars that I’ve driven, including my Versa, I wish the gear ratios were more evenly spaced. They seem to put a bit of distance between 1st and 2nd, then 2nd and 3rd are a bit closer together, then 3rd, 4th, 5th, and 6th are ridiculously close. On the hills here in Pittsburgh, the reach from 1st to 2nd is kind of a pain in the butt.
Wow! Thank you everyone for your insight and responses. I really appreciate all of the input.
I’ll stop worrying about rev values so much and drive accordingly. To answer the concerns about the state of the car, it was previously owned by a good friend who moved away. I know he kept it in immaculate condition, but I couldn’t ask him about any of my concerns because he is unreachable.
Thank you everyone again, I really appreciate how in-depth the answers were.
My 2010 KIA Forte SX 2.4L 6spd manual has an interesting solution. It has a 2 speed axel ratio. 4.10 in gears 1-2 and 3.10 in gears 3-6. The axel shifts automatically and is seamless. It turns about 1,900 RPM in top gear at 60mph.