this is very dangerous, and in my case the car would stall instead of "shudder"; it would only "shudder" when I could catch it and play w/ the brake enuff to keep it from stalling. I got pretty good at that. It's a sign of torque lock-up; the car is not properly downshifting in overdrive.

Tranny definitely needs to be replaced or rebuilt.

My advice:

If he drives aggressively or is into racing, follow my previous advice: rebuild w/ performace upgrades.

If not, get a brand new tranny installed at a reputable Mazda dealership. It will cost more than a rebuild, but should be more reliable and should have less hassle at the dealership if something goes wrong w/ the new one. Try to find somebody that works in a Mazda Parts Dept, and get it at cost (or a little more than cost).

DO NOT take it to a place like Cottmon's or All Tune Transmissions. You have been warned. I currently have to take a certain shop to court to get back @ $3000 for an improperly installed transmission.

Make sure whoever installs it also installs a brand new transmission cooler. This is a must.

Good luck. Let me know if you need to know anything else.