[trlinde]

Ran accross this before, sombody said it had to do with a part in the transmission that had warped.
my 96 sl1 started doing it at arounf only 140, and only when hot. Chand the fluid and filter and it eased up a bit. Put it in Nutral and then tap the gas, it'll shift without the thud then.
Now at just over 230K 3rd tensioner, 2nd alternator, 2nd set of plugs and 3rd battery, still going.