Cold start rumble from engine or gearbox

hello everyone.

I'm in need of some advice.
My 2006 G2 Prius has from the day I bought it (2.5 years ago) had a cold start rumble the comes from up front.
It is getting worse.

This morning it was particularly bad.
It's not a misfire. That much I do know.
It sounds like a really bad thrust bearing noise that might be from a manual gearbox.

The thing is, it only happens at cold start.
It goes away very quickly. If the car is in P or N the noise does not happen. (Engine running)
If the car is in D, with the car not moving, the noise happens. (Engine running)
As soon as the break is released, the noise goes away. (Engine running or not)
Even if the car is moving at 1kmh, there is no rumbling bearing type noise.

This noise is NOT present if the car is in EV mode.

The above leads me (maybe erroneously) to thinking that the noise is in the gearbox.
not the engine.

I'm wondering if anyone here has had the same issue, and or knows what it is.
I'm trying to get a handle on what it's likely to cost me to put right.

I know that before too long I will need a replacement battery (HV)
And now possibly major engine or trans work too.....

Thanks in advance
Jason.

 

Thanks for the reply.

The car has 224k km on the clock

I don't have a full history for the car.
But the trans has not been serviced while I have owned it.

Is there a seperate trans dipstick to check fluid levels ?

Jason.

 

The car had 181k km when I purchased it.
I have done 43k km in the time I have owned it. Around 2.5 years so far.

I will have to look for that plug and the instructions for checking and changing fluids and filter.

Jason.

 

By brake released, I mean the foot brake. As soon as the car starts moving, the noise vanishes.

I should clarify. I'm not talking about the park brake or e brake as it's called in the USA. But the regular foot brake pedal.

In P or N, there is no noise.

Also, ambient temp plays a big part in the noise. Sunday morning when I went to work, it was around 9c and the noise was bad.

Today it was around 22c when I started the car to go to work. The noise was there, but not as bad.

I will try to get the fluid changed as soon as I can.

I will report back of the noise goes away after.

Jason.

 

Yeah. It's not the brake pump noise.
It's definitely a bearing type rumble.

I'll get the oil in the trans changed (probably overdue anyway)
and see if that makes the noise go away or somewhat reduced.


Seems odd to me that it's seems to be ambient temp related also.
The colder outside it is when started, the louder the noise is.
I've never heard it on a warm start either.

Jason.

 

As far as I know they are.
There's no odd noises at any another time.

I have had a thrust bearing fail in an old manual car I once owned.
That's the kind of noise I hear at cold start.

It's not a rhythmic kind of noise. Just a deep rumbling noise.


Jason.

 

I sure could try to capture it.

It doesn't last very long though.
By the time the engine is warm enough to shut off, the noise will be gone.

I'll try to record it over the next few days and see what happens.

Jason.

 

Just updating this thread.
The noise has only happened 1 time since the last post 2 weeks or more ago.
What ever it is, it can't be anything that major.

I will get the oil changed in the trans as soon as I can though.
That just makes sense.

I was not able to record the rumble when it did happen.

I did try, but the cam didn't capture it.

Jason.