My dryer runs good and heats fine, but for some strange reason after it is on for a few minutes I get this strange smell almost like some dead animal. I have taken lint tube off back and made sure it is clean, I have taken heat element out to make sure it is good and no broken coils. I also replaced vent hose with a new one. I took front off and inspected underneath and around motor and tub I could find nothing. This is very strange it does it with heat on or on just air dry. I know this is a strange request but can you help?

Unplug the unit and disconnect it from the vent system.
Now try a run.
If it now runs without the smell odds are the vent system needs checking/cleaning.
Be sure to check that the louvers on the outside of the house open correctly.

If you do not want any lint in the house.
Take a pair of pantyhose.
Put one leg into the other and then attach this to the dryer's vent.
Leave enough room so the pantyhose can balloon out like a windsock.

Note: The above is not recommended for gas dryers due to carbon monoxide concerns.

If the smell is still there.

Is there a sewer trap in the same area as the dryer?
If yes then is there water in the trap.
You did not say if it was possible that an animal got into the dryer and died, so I am assuming that this is unlikely.
My thought for the above is that the dryer is pulling air out of the sewer when on.

If it is a possibility that an animal did get into the unit, then you will have to take the unit apart and see what is causing the smell.