What happened if the shell had to go through some the exterior attachments (muffler, muffler shield, air cleaner,,,,)?
The same thing that would happen to any other shell? A somewhat disingenuous question...
I'm not saying that the story of an M8 killing a Tiger I from behind at short range is likely.
I'm just stating that there is enough evidence to conclude that it is indeed theoretically possible for a shot from an M8 to penetrate the rear of a Tiger I.
This is from a wartime report from the 7th Armored Division while in Belgium in December of 1944 - quoted in the US Army Armor School publication 'The Battle of St. Vith, Belgium, 17-23 December, 1944 - An Historical Example of Armor in Defence', page 31:
"While northern and eastern flanks had been heavily engaged, the northeastern sector (Troop A, 87th Cavalry Reconnaissance Squadron; Company A, 38th Armored Infantry Batallion; Troop B, 87th Cavalry Recconnaisance Squadron) had been rather quiet. The only excitement there had been was when an M8 armored car from B Troop destroyed a Tiger tank. The armored car had been in a concealed position at right angles to run along a trail in front of the main line of resistance.
As the tank passed the armored car, the M8 slipped out of position and started up the trail behind the Tiger, accelerating in an attempt to close. At the same moment the German tank commander saw the M8, and started traversing his gun to bear on the armored car. It was a race between the Americans who were attempting to close so that their 37-mm would be effective in the Tiger’s thin rear armor, and the Germans who were desperately striving to bring their 88 to bear.
Rapidly, the M8 had closed to 25 yards, and quickly pumped in three rounds; the lumbering Tiger stopped and shuddered; there was a muffled explosion, followed by flames which bellowed out of the turret and engine ports, after which the armored car returned to its position."
There is a footnote reference stating the action was reported to Major Donald P. Boyer, Jr., S3, 38th Armored Infantry Batttalion, by Captain W. H. Anstey (commanding Company A, 38th Armored Infantry Batttalion) who witnessed the engagement.
The same account is also found, word for word, including the footnote, in the 7th Armoured Divisions WW2 history 'From the Beaches to the Baltic' on page 86.
Amazing what you can find on the internet...