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Vibration at 3rd gear 40-45mph

This is about a 1999 Honda CR-V. When it gets into the 3rd gear, if I cruise at about 40-45 mph (cruising meaning I don’t accelerate, just press the gas pedal as is. If I accelerate, vibration doesn’t happen), the whole car occasionally will vibrate. It doesn’t happen all the time. The vibration doesn’t happen in any other gears so cruising in the 4th gear has no problem. When it vibrates, I can let go of the gas pedal, it immediate stops vibration. Then I can press the petal again until it vibrates again at a later time. It has been like this for a couple of years. Is this a transmission problem? I brought the car to a shop and was told the transmission needs repair and they don’t do that. I didn’t go to another shop because the car is old and every diagnostic costs money. I am hoping someone here can tell me what the problem could be and have a sense whether it still worth it to repair.

Thanks!
BK

Have the tires checked for balance.

I installed a new set of tires and balanced them.

After about three months a vibration occurred.

When checking the balance, I found the left front tire was three ounces out of balance.

Lost a three ounce weight.

Tester

Thanks for the response. I have not checked, but because it directly relates to gas pedal (not pressing gas pedal vibration will not happen), I don’t think it is tire related. Also, going higher speed (>50) has no problem.

I think it is something between engine and transmission that has issues.

Could still be a tire balance. Certainly that is the first thing to check. While that is being done, have the wheel bearings and front end parts inspected.

If you want a cheap check, swap front and rear tires and see if things change.

Thanks. Tires had been rotated and the problem is still there. Might have been balanced as well.

Is this by chance all wheel drive?

Thanks. It is FWD.

As in Front wheel drive or Four wheel drive? When I see FWD I assume it means Front wheel drive.

Yes, it is 2WD or FWD, not AWD.

I don’t think this is tire related.

The speed is wrong. Tires are usually 50 to 70 mph, this is 40 to 45.

Tire vibrations would be there pretty much all the time regardless of gear and wouldn’t disappear when the throttle is applied.

I kind of think this would be U joints, but since this is a FWD, not an AWD, I’m going with CV joints - but I don’t particularly like that answer.

Side note: I’m struggling with the idea that someone drives at a steady 40 to 45 mph in 3rd gear. I’m wondering if the real problem is a drivability problem - engine or trans related. Need more info to sort out.

Thanks! I think you are on the right track (not that I know the answer, LOL). What will happen when I press the gas pedal?When the vibration happens, releasing the petal will stop it immediately. It seems to me that pressing the gas pedal will engage some gear (where the problem is, maybe the gear is wearing out) and releasing the pedal will avoid the symptom. The interesting thing is that this only happens in the third gear so it may relate to the transmission? Also, when accelerating, it doesn’t happen either, so it seems that the gear is a kind of loose but when engaged it will stay in working position until cruising (letting it loose).

pressing the gas pedal causes lots of changes in the driveline of the car. Gears, linkages, CV joints that were not under pressure suddenly see a change in pressure, which can change lots of things. In other words, the distribution of forces changes, by a large factor. This can cause the vibration you are seeing, or cause a vibration to lessen.

Vibration at certain speeds can be tied to resonant frequencies. When a small vibration changes frequency with speed, it can hit the resonant frequencies of something, a structure, a gear, a coupling, which causes the vibration to increase in magnitude.

Thanks. It feels more like a gear out sync than resonant. It can happen in any speed in the third gear, but most often between 40-45.

This is a front wheel drive conventional manual transmission configuration, right? If so I’m guessing a tire problem or an inner CV joint problem. One way to tell if it might be a tire problem is to get it up to a vibrating speed, then go a little faster, shift to neutral and coast back down through that speed. If the vibrations go away, unlikely to be a tire.

Actually, George, the opposite is true. Tire vibrations are largest when the tire rotational speed matches the wheel hop frequency.

The suspension is a Spring-Mass-Damper system and those have natural resonant frequencies - and for a suspension it’s called the Wheel Hop Frequency - because if you brake too hard (or accelerate too hard), the wheel will hop at that frequency.

In most light vehicles (cars and pickups), that occurs in the 50 to 70 mph range - and it is almost impossible to design it out (Physics!) An engine off/transmission neutral coastdown is the common test to see if a vibration problem is wheel end related (tires, wheels, and other rotating components, like brake rotors).

Thanks. I really don’t think this is tire related. Let me summarize the facts (I observed) here:

The vehicle has a 2 wheel drive, auto transmission.
The vibration never happens at any speed if I don’t press the gas pedal.
The vibration rarely happens at any speed if I accelerate.
The vibration mostly happens during cruising at 40-45mph.
The vibration always happens in third gear (don’t know if this is coincident).
It feels like the vibration is from a worn gear that could not properly engage another gear and it is loose and skid causing the vibration.
My trick to reduce the occurrence is to accelerate and then let go of gas pedal (at around 40-45mph), and then repeat the process. It rarely happens this way.

Can we narrow down the potential problem parts based on these clues?

Thanks!

You shouldn’t be in third gear when cruising at 45-50. Are you manually holding it in 3rd?

Insightful has a good question. I thought at first this was a manual trans by the 3rd gear reference. The Op says automatic so does this thing do this in drive?

Well, I think it is in the third gear because it (auto) shifted twice from idle. It may be more accurate to say that the speed is around 40-45 mph. This is the gear that is one below the highest driving gear (on highway). The last shift usually happens around 50 mph. I hope I made it clear this time :-).

Does your transmission have a manual setting?

Can you put it into 4th and drive at 40-45 and see if you get the vibration? Or force it to stay in 3rd and see if the vibration goes away at 50-55 ?