Originally Posted by shuswapcruisers
Another poster is right... it sounds like tennis shoes are in there.
I have no experience with Litton Group dryers, but in my experience with Maytag and Whirlpool, worn drum rollers will typically result in a squeeking noise that gradually progresses into a squeeling noise. Not a rumbling noise.
There's a tool that you can buy at any place that sells automotive tools, and it's called a "mechanic's stethoscope", and will sell for anywhere between $15 and $200, depending on quality and where it was made. For diagnosing problems like this, you only need a cheapie. Basically, a mechanic's stethoscope looks much like a doctor's stethoscope, but it has a metal probe that you touch to various parts of a machine. Because vibrations of solid objects cause noises like squealing, squeeking and rumbling, when you touch the metal probe to the part of the machine that's making a noise, the probe will cause a metal diaphragm to move in the same way and that same noise will be heard much louder through the earphones. Thus, a $15 mechanic's stethoscope will allow you to pinpoint the source of the rumbling noise.
But, there's lots of things that could cause a rumbling noise in a dryer. The blower wheel rubbing against something that got into the blower housing, is one. A loose clothes lifter might make a rumbling noise. Dirt on the drum rollers might make a rumbling noise. I think your best bet would be to buy a $15 mechanic's stethoscope and try and locate the source of the noise with the machine in operation (being careful to keep hands and hair away from all moving parts).
If you get no further answers in this forum, go to Appliance repairs, Appliancehelp,
and click on the Q&A Section link. That web site is owned and operated by an appliance repair tech I met online and have known for a long time.