98 Chev pickup transmission question

I've got a 98 Chev 1 ton dually w/ 454
Ocasionaly after towing, after I drop the boat, if I drive without towing, the trans will shift real hard, untill the truck is shut off and cools down..then its back to normal.
One trans shop said that 98-99 GM trucks had problems with the engine distributer wearing and screwing up the signal?? to the trans at right around my milage. Since he's turning away business, I tend to belive him. Has anyone else experienced this. The trans has always been serviced regular(just done) and has 90K miles on it.
Does anyone know a message board for Chev trucks info??
Thanks
Dan

More likely to be a problem with a worn valve body, or a valve body that is worn a little around the TCC apply piston. Do a search on about any GM vehicle site or google for P1870 and/or hard shifts

yeah my bet is on the shift solonoids, or tcc....