Forum Discussion

porkchop1221's avatar
porkchop1221
Explorer
Jun 25, 2013

GMC transmission issue

I'm not sure where to post this, but we have a 2012 GMC 3500 Sierra and a Cyclone 3010 5th wheel 35 foot toyhauler.

Lately we have been experiencing "clunking" when the transmission drops a gear, usually from 5th to 4th or something like that. It's more noticable when we have the RV hooked up but we can still feel it when we are at speed (60 mph+) and the auto tranny downshifts.

We brought it to the dealer who couldn't notice it nor could they find anything wrong with it. They reset the tranny (whatever that means) and told us when we tow we need to keep it under tow mode at all times.

What they did changed NOTHING and I'm not sure what the next step is....

Has anyone experienced this and have any suggestions?
Thank you.

27 Replies