Drivetrain shudder?

[Stuntzombie]

Hi all. I recently came into possession of a 2005 Pontiac Vibe Automatic with around 145,000 miles on it. It's been great so far, there's just one issue I've noticed. Sometimes if I accelerate slowly, between 40-50 mph I'll feel a shudder before it kicks into overdrive, then the vibration disappears. It almost feels like going over a rumble strip. It doesn't seem to do it when I accelerate briskly. I've checked the transmission fluid level, and it appears to be spot on. Tire pressures are all good, and the tires are all somewhat new. Other than that, the car drives great.

Any suggestions on what it could be? I was planning on doing a filter change in the next week or so, but now I'm worried I might have some bigger issues to worry about.

[tpollauf]

Welcome to GenVibe. I can't comment on your current issue as I've only ever owned "stick shift" cars, including my 2009 Vibe GT I'm sure others here who have a similar Vibe can help you out!

[vibrologist]

I have an '05 with fewer miles and automatic transmission. I never had your problem, so I am guessing.

First: these transmissions don't have a filter, they only have a wire grid to keep bigger junks back.
I am guessing: your transmission was not serviced on schedule or it was serviced with the wrong fluid. This happens easily because a lot of service folks think of the Vibe as any other GM product. You need Toyota T-IV or equivalent.
Since you don't know what is in there I would replace the fluid. Drop the pan, clean it out, put the pan back with a new gasket, add new fluid. Drive a week or so, then drain the fluid again using the drain plug and fill again with Toyota T-IV, obviously.
If you click on the link in the signature and scroll down near the end you will find my description of the process.

I hope that fixes it. Even if it costs about $80 it will be worth a try.

[Derf]

When in neutral does the engine idle and rev smoothly? On a flat road, What RPM is the engine at before shifting into overdrive?

[Stuntzombie]

I believe the engine idles around 900-1000 rpm in neutral.
There's a little vibration in neutral, and it accelerates smoothly.

On a flat road, it shifts into overdrive around 2700-2500 rpm. I'm going by memory, but I can't remember seeing it get over 3000.

[vibrologist]

something else: check if the PCM recall has been done on your car.

[ehoff121]

Welcome to genvibe!

If you gently accelerate, you'll feel the downshift around 35-40mph, which some have described as "lugging", but would be a low rumble until you got to 45+mph. If it's really intense, you might need to clean out a few things that may have been neglected over the years.

Are you inclined to wrench on your car? You'll want to make sure your Throttle body, Idle Air Control Valve (IACV)[EDIT: 2005-2008 FWD Base and 2006 AWD are drive by wire and do not have IACV. Thanks, Ian. 2003-2005 AWD and 2003-2006 GT do have an IACV], and Mass Airflow sensor (MAF) are clean of carbon deposits/dirt and may want to change the intake manifold gasket. All of these could be done in a few hours (you need to take the throttle body off to change the manifold gasket, anyway).

Re: the tranny fluid, color and odor are as important as level- did it look red/clean or dark brown? Smell burnt?

Also, the spark plugs should have been changed at 100k.

[SeattleJeremy]

Our Automatic V6 Passat does the same thing when the revs are low (around 1200-1500rpm in top gear at 55mph), and the accelerator is pressed slightly. Every time I've experienced it I've either backed off the throttle to stop the shudder, or pressed harder which forced a downshift. Our car has more than 140k miles, and the performance isn't as good as it use to be.

The best explanation I've been able to come up with is: The programming for the Engine/Transmission was setup to keep it in the highest gear possible for good fuel economy. When the engine was new it had enough power to conduct that specific Speed/Gear/Accelerator-input request. However, it's performance is now below the spec needed to conduct that combination, and it shudders as a result.

Solution: Add more power (via maintenance or repairs) or add more throttle input.

[Stuntzombie]

Hey everyone, thanks for the responses. Sorry I didn't reply sooner, things got busy around here with getting married and all.

Ehoff and Seattlejeremy, those sound kind of like what I'm experiencing. Ill also work on the various maintenance issues and see if that helps.

[lannvouivre]

Idle Air Control Valve (IACV)

The 2005+ 1ZZ engines are drive by wire and don't have/need an IAC, so skip this step unless you have a GT.

If you clean the MAF, only use MAF sensor cleaner on it. It's very delicate and sensitive.

[ehoff121]

Hey everyone, thanks for the responses. Sorry I didn't reply sooner, things got busy around here with getting married and all.

Ehoff and Seattlejeremy, those sound kind of like what I'm experiencing. Ill also work on the various maintenance issues and see if that helps.

Congrats on the nuptials!

Search the forums for the maintenance on all of these items- there are walk-throughs with pictures for most.