mogaliciou

I was in the truck and stopped completely on an incline about 15-30 degrees. When I hit the gas. It was making some weird noise. Like a grind almost.

Anyone know what this could be? I have an 05 GX470 with 200k miles.

MrJason

Could be several things... wheel bearing, stuck caliper, differential, etc....

more details on on where noise is coming from in the car...

did you have the diff lock button pushed?

Is the 4H-4L fully engaged?

where you using DAC?

this would be helpful information.

mogaliciou

Not sounds like it’s coming somewhere from the front.

No to doc lock button.

4H-4L not fully engaged, it’s in neutral.

I wasn't using DAC, not sure what that is.

When driving, the car shifts smooth as butter. Brakes are smooth. I’m going to look up how to change out trans fluid just to be safe too.

MrJason

Wait.... you say the vehicle’s 4WD shifter is in neutral???

the GX470 is all the time 4WD... if the lower shifter is in neutral... no power is going to any wheel.

I would place the vehicle in neutral... shift into low... drive around for a 1/2mile(on back roads or an empty parking lot), then stop and lock the diff with the button by the seat heaters, drive about hundred yards, unlock the diff, drive another 100ft or so, and then shift back into neutral and place the lower shifter in 4H.
The try it out on the hills you mentioned and see if the noise is gone.

mogaliciou

Hmm. I thought the hi-Lo shifter had N in the middle. So basically H-N-Lo. I’m assuming it’s in either hi or lo? Sorry this is my first AWD car and not too sure. But I’m learning.

Ill do the things you said. I’m assuming for normal driving, I keep the 4wd shifter in high?

mrblister

Sounds like it could be motor mounts ?

chiph9

Worth trying low range for a little while. Stop the vehicle, put it in neutral, shift the transfer case into low, put it back in drive. Drive around a little bit.

However ... make sure you do NOT lock the center differential when on pavement! You will bind it up and could cause very expensive damage.

Also, when you gave it gas, did it move at all? Were you in D?

Chip H.

MrJason

Yes.. there is H-N-L... but it should stay in H unless you need the low range. That’s why it’s called a “all the time 4WD” vs an “AWD”.

I was suggesting you “exercise” the system. But like chip said... be careful when engaging systems. Its best to just be out on a dirt road or in an empty parking lot... and always be stopped with your foot firmly on the brake... and have the main gear shifter in Neutral before changing the 4WD from H to L.
“Exercising” the system could clear that noise right up.... and if it does, be sure to change your diff fluids.. maybe even a drain and fill on the ATF.

chiph9

I normally do a drain + fill on the transmission every 30k miles. I can't believe that Lexus believes in the "Sealed for Life" garbage.

I'll do a 4x4 service at the same time. Drain + fill the front and rear differentials, and the transfer case. And grease the zerk fittings on the propshafts.

Chip H.

MrJason

In the German world... most likely the same for all brands... but a trans or and power train part of the vehicle with a fluid that states “lifetime” fill... actually means 100,000 miles(or105k). At this point the service intervals start over.

It took me forever to get that answer and I had to go all the way up the ladder to a German audi engineer to get that answer.

I ran my Chevy Colorado and Dodge Charger, both, well over 300k and never changed the trans or diff fluids.
If they weren’t both wiped out by other drivers... I’d still be driving one of them today.

But my mileage is all interstate and over 60k a year. Hell... I didn’t put brake pads on either vehicle till over 150k. Just smooth sailing commutes to work.
But we also took the wife’s Audi(whichever lease i had her in at the time.. we’ve leased 3 now) everywhere other than my work commute.

But it with the GX470 I now have a small boat and like to take the family places on the weekend since it’s so comfortable and roomy.
So I’ll be much more diligent with the maintenance on things like the ATF and diff fluids on the GX470... I love this vehicle... the other 2 were just replaceable transportation. Lol

chiph9

The drain + fill on the transmission (not a flush) will get somewhere between 1/4 and 1/3 of the fluid out. And that's good enough for a vehicle approaching 180k

I had the internal filter changed on it about 150k and they said it came out clean.

Chip H.