Name that knock...

[TCapelle]

Have been tooling around in the 109 NADA and have notice a knock.

It sounds rotational (I thought maybe a u-joint) but when the vehicle is parked and try to twist the drive shaft and there is no slop or movement.

It seems to be coming from the rear but it feels like the whole drive shaft front and rear has play or this "knock" in it.

Any ideas or 1st things to check without taking anything it apart?

PS- I had a horrible nightmare my wife told me I had to sell my 2 series rovers and buy a minivan......

[mechman]

Is the knock steady or occasional? Only when moving, or there when running stationary? Only under heavy load, or there when cruising on level ground?

I'd put it up on jack stands at all four corners, under the axles, and have a buddy run it through the gears as I walked around it and listened for the sound.

There are so many ways these trucks can make noise...

Mech

[TCapelle]

Hi Mech

The knock is when driving not idling so it sounds like drivetrain not engine

No scrapping like brakes-doesn't sound like a wheel bearing ...

It is present while driving at low or higher speed (i use that term loosley :)

It will make the knock and slow down until the truck comes to a stop- so I would label it as pretty continuous...

Keep the ideas coming...

[mechman]

Okeydoke, sounds like you're right. Now, does the frequency of the knock (how fast it is) change with speed (get faster the faster you go) or with RPMs (the higher you rev the engine, the faster it gets)? Does it change frequency when you shift gears?

If it just knocks faster the more quickly you move, it is likely a problem PAST your transmission, perhaps a u-joint or pinion bearing going bad. Get under your truck and do a push-pull test on your drive shaft, see if it moves either up and down or side to side. If it's OK, it shouldn't. Try putting your rear up on jack stands (that just doesn't sound right...), drop the transfer case into neutral and try moving your tires up and down (bad bearing, but your symptoms don't sound right for that) and try moving your drive shaft around, checking for looseness at the u-joints and at both ends. Check your drive shaft for small shiny spots as well - you may have lost a balancing weight. Give the shaft a spin and listen to your transfer case, too. You could have a worn bearing or broken tooth in there.

If the knock changes speed with engine RPMs, the problem is either in your engine or transmission (like a worn lay shaft bearing, for instance).

If you don't find anything in the back, jack up the front axle and check the front drive shaft, u-joints, etc. Then check your front half shafts - the u-joints inside the swivels might be going bad. Fun repair, that...

Mech