TH350 harsh shifting
 

My TH350 is shifting hard, and I'd like to know what I can do to "smooth" it out? Its almost a neck snapper when shifting into 2nd and 3rd. Fluid is full, and the vacuum modulator is about a year old. The number on the pan indicates its a 1978, hooked to a 283.
Thanks

Re: TH350 harsh shifting
 

T350 Harsh upshifts ?
Most likely its something common to both upshifts 1st to 2nd and 2nd to 3rd...

simple items to check first:
Check vac at the modulator, if vac is OK, remove modulator and check modulator valve inside the case, use a needle nose pliers to grip onto the end of the modulator valve and move the valve in and out of the bore, sticky ?

If the modulator checks out OK, the gov would be next to check out......

Remove gov cover and pull the gov out of the case....hold the gov upright with gear pointing towards the sky, squeeze the weights towards the center of gov....you should see the gov valve move inside the gov. or grip the weights in one hand and shake back and forth, you should feel the gov valve move.... Check the colors of the gov springs...

Detent cable connected correctly ?

Please provide some history of this trans, been rebuilt ? Did it just start upshifting harshly...any engine work lately ?

check these items and we can go on from here....good luck.

Re: TH350 harsh shifting
 

Possibly has a "shift kit" in it and the check balls in the valve body have been removed as well.

Gary

Re: TH350 harsh shifting
 

As I re-read the OP, it indicated the modulator was replaced a year ago, so its not a fresh build and if it had a "SHIFT KIT" installed, the vehicle has been driven awhile with some harsh shifting.... Another suggestion is to pull the cover off the accumulator and see it the spring is broke.... this is on the passenger side of the trans (cooler lines/dipstick side).... remove the snap ring with a small punch that fits into the hole where the snap ring sits....pull snap ring and cover...cover has an o-ring, spring is next....

Re: TH350 harsh shifting
 

Thanks for the replies. As far as history of the trans: I had it put in in 1999, replacing the Power glide my Suburban came with. I'm not sure if it was rebuilt, or just freshened up. It:s been shifting hard for awhile now. I'm just concerned the hard shifts will affect my U-Joints. I have 3 new ones, just finding time to replace them as it's my only vehicle so can't take it down right now. The fluid looks pretty good. Red)clear and not burnt. Kickdown cable is hooked up as it's supposed to be. I will check the other items as mentioned and get back to you all. It may be awhile as my days off are Weds and Sat and I'm having issues with my post op knee.