Ok my Auto transmission has been havin some trouble downshifting. When it tries to the whole truck shakes and bucks until if finally slams down. So today I took into the tranny shop to have them look at it. After the guy took it for a spin he said there is nothing wrong with the tranny and that the motor needs a tune up. My question is how does the engine needing a tuneup affect downshifting

 

I don't know how/if the issues are related. I think the computer would use information from the engine and transmission to decide when/if to shift, etc. So, if the engine was stuttering, maybe this could cause the transmission to act funny.

Did you ask the guy how the engine needing a tuneup affects the transmission? If so, what did he say?

 

He said the engine had a slight miss and wasnt making enough power to shift properly

 

That sounds like a reasonable explanation.
Maybe a tuneup is in order, if it helps, great, if not, then at least your engine will be running better.

 

If it has a miss it differently needs to be took care of as dewman said, if nothing else to help on the fuel mileage.

But I’m completely buying into it having that big of effect on the transmission especially since the transmission shifts electrically not from hydraulic pressure. Now if the converter was not up to par,the shift solenoids were sticking or the speed sensor is going bad along with a miss that would be a different story. But that’s just my opinion and I may be wrong.

But I would tune it up first to see if that was it. And keep us informed on the outcome.

 

My 97 does that to idk why but my motor seized so it's not really a problem any more

 

check your codes too and see what comes up