Shutter and jerking

when i drive my car it starts to shutter when speeding up or slowing down in the 40-60 mph range. Upon slowing down is shakes like the front wheel is going to come off…checked it is ok. Just came out of shop for that same thing where they charged me 1100.00 for 300.00 in parts at the dealership. checked oil,tran fluid, fuel injector cleaner. Thinking its tranny. any thoughts?

they charged me 1100.00 for 300.00 in parts

Could you provide some more information? What parts would be a good place to start. What else might they have done.

It would also be nice to know what make model and year of car and if it has automatic or manual transmission etc.