[blublood2045]

Since I replaced my stock gears on my '91 GT, (3.90's), I've noticed that my automatic transmission wants to shift early. Also, when it downshifts, it does so kinda' rough. should I be worried? I will take it in to have the shifting early problem taken care of, but should I be worried about the hard downshifts?...If anyone can help please do....Thank you in advance.

[TheBocSez]

Cant tell you about the shifting firmness, but as far as the early shifting, its a result of the gears.

Your AOD shift points are controlled by TV pressure. Since you have steeper gears now, you are reaching higher RPM's at lower MPH's. The higher RPM's are building line pressure and your car is shifting at a lower MPH.

With your stock gears 2.73 let say your car shifted from 1st to 2nd at 20mph which was 2000 rpm. Now with the 3.90, you are reaching 2000 rpm in 1st gear at 10 mph so your trans is shifting at the same RPM but at a lower MPH. Make sense?

All you can really do about it is install a shift kit that will allow you to tailor shift points, or get a different valvebody.

[blublood2045]

I am taking it to the mechanic soon to have the transmission serviced and readjust the valves. I am also changing the speedo gear to adjust the correct speed. I hope the hard downshifting stops then....
Thanks much for the help.

[84 predator mus]

a friend of mine had a similar problem with rough downshifts in his tbird with the aod. his ended up being the direct drive clutches being bad. it could also be the tv pressure is not set right. you either need a pressure guage or a block to set the cable right.