Hard 4-3 Downshift

[91gmblack]

Hi All,

My 91GM has 226,000 miles on it with the original engine and AOD tranny. Both U-joints were changed last year.
Tranny fluid is clean and full. All other shifts are fine. I change the tranny fluid and filter every 20,000 miles religiously.

On the highway, on a hill at 50+ mph, the tranny normally drops out of OD into 3rd, smoothly with no problem until now.
Now, this downshift is very hard. You feel the shudder quite noticeably. It still works, but it kicks you in the seat.

I just now put 2 bottles of red Lubegard to try to fix it.
Should i be looking at the tranny mount? Any thoughts are appreciated.

Note: Upshifting from 3rd to OD is still smooth, as are all other shifts.

Thanks,
91gmblack

[gadget73]

Mount is a good possibility. If the trans is moving around, it will make for rough shifting.

[91waggin]

This happened to me awhile back. I ended up taking it to a transmission shop because I don't know jack about automatics, but I remember it being a real simple fix. I seem to recall that the valve body had been damaged in some way.