Driveline / transmission "thump" in the snow with AWD

[spta97]

Not sure if this is a problem, but there were a couple times when driving in the snow this weekend that I would hear and feel a thump. It mostly seemed to happen when I was going from dry to snow covered pavement and my most likely explination is that it was the AWD kicking in.

I believe my transmission is fine and I just had it power flushed over the summer. However I don't know if I should be doing any maintenance on my AWD. On dry or wet pavement I have never had this happen - only in the snow.

Is this normal or should I be worried? Also, is there a good way to test the AWD to make sure it is working the way it is supposed to? I wasn't too crazy about the slipping and sliding but I could feel the fronts kicking in so it seems that it is working. I don't know if it should be like the "wheels that slip to the wheels that grip" thing.

 

[Glacier991]

I'm guessing your notion is correct. I'll let others confirm....but I'd not fret.

 

[TPLYNCH]

I believe there is a viscous? clutch in the AWD system that is always engaged, normally sending 35% power front, 65% rear at all times. The system will adjust and add more power to the front in slippery conditions via further engagement of the clutch. Not sure, but could be a problem with that clutch. Have no recollection of harsh engagements like you describe with the AWD. This was more common with the AUTO 4x4.

If the AWD transfercase has fluid, check the level to start....

 

[Jester1994]

I have a 97 AWD and have not experienced any kind of thumps or noises when dealing with mine hte last 2 winters. Mine has always been flawless transferring power around and I would know since I love to spin the tires all the time in the snow and do donuts. I have never had any kind of bump, noise or thump doing donuts, hitting the gas hard to make the tires spin, and that would work the AWD system pretty hard. Just take a look at the video link in my signature and that'll give you a hint.

Check your tranny fluid, make sure your tires pressures are even in the front and even in the rear. and also listen to when this bump happens. This could be a far fetched idea, but when some Explorers drive onto packed snow, worn shocks seem to "thump" or make a noise/vibration since it is basically like hitting a little bump, just a thought.

You could bring your Explorer to an opne parking lot during he next storm and play around with it, and have some one watch your wheels as you hit the gas, they obviosuly should all be spinning, but if something is really worng, maybe you can find out by troubleshooting and starting from there.

 

[spta97]

I just took the X to an unplowed parking lot yesterday - wow that was fun Anyway, I was not able to reproduce the noise I encountered over the weekend. I'm thinking that perhaps it was just the tire grabbing dry pavement after slipping on the packed snow. I was going about 40 miles per hour and I'm figuring the thump was the tire spinning and getting traction right away. I'll keep an eye on it report back if any more problems.

Thanks for all the replies!