Wolfmann

My dad has a bone stock '99 grand with 200k on it. At low speeds from 5-20 mph. It makes the noise only when under power or when the engine is under back pressure. We replaced the d35 wheel bearings just last week because we though the noise could be from 200k bearings but it didnt change anything. Could it be the transfer case, u-joints, front driveshaft, front wheel bearings? Also there is no vibrations felt while the noise is happening.

Wolfmann

Anyone have any idea?

JJCIII

Is it all wheel or 4 wheel drive? Most of the time a noise during acceleration is probably a ujoint. Need a few more details to be more help

Wolfmann

Its not the all wheel version, it has 2 wheel and its the 4.0. We were thinking of checking the u-joints but we havent yet, could it be the front driveshaft cv's?

JJCIII

So its only rear wheel drive? Im assuming its 4 wheel drive. Check u joints first my bet thats it

Wolfmann

Ok ill start at that

dave1123

I think he means it's Selectrac. It could be pinion bearings in the D35 rear end. 200K is about the right time. Spin it up on a lift and listen to the differential. Lock the trans in 1st gear and you should hear it pulsating as the power bounces between drive and coast. If the bearing are bad, that is. You may also be more able to locate the source of the sound better.

Wolfmann

Ok thats great ill try this out and see if that is the problem

Cnwxj

Does it go away in Neutral? May be the pump in the trans.

Wolfmann

No if your giving it gas then you let off it still does it even if you throw it in neutral

Wolfmann

It does shift pretty hard sometimes but i dont think the noise is from the trans, it could be ill try the other stuff first

Cnwxj

Hope it's something simple.

dave1123

The pump in the trans is still running in neutral. It doesn't in park.

Wolfmann

Found the problem, it was the pinion barring. Thanks for the help guys

JJCIII

Nice that was my second guess