Best TH350 shift kit

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Supercharged111

Comic Book Super Hero
Oct 25, 2019
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Colorado Springs, CO
i was a professional transmission rebuilder for over 40 years, i am retired now. i have made 100s 0f 350s shift how i wanted them to with no store-bought shift kit. tricks of the trade,,,,,,,,,,,,,,,,,

Well you're not in the trade anymore, and Captain Kangaroo says share. . .
 
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olskool

Apprentice
Sep 26, 2021
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well if the transmission is half worn out it will not be a good idea to shift kit it, my opinion, i only did them when i built them. but, to beef up a THM 350 without a box shift kit, i would remove 4 check balls. only put back the one in front of the modulator valve. i would open up the direct clutch and the intermittent clutch feed hole in the VB plate. i would remove the heavy 1-2 accumulator spring on the side of the transmission, i would remove the pressure regulator spring and put an old selector shaft seal on the stem of the PR valve, it fits perfect, and reinstall the spring, this puts more tension on the spring. i would remove the 3rd accumulator piston and spring "in the VB" and replace the spring with a weaker one, just strong enough to hold up the piston. i would remove the intermittent wave/cushion clutch steel and put a flat one in its place. do these actions if you want it to really hit hard! because it will have a hard shift.

if i were just going for a positive shift, i would drill the feed holes in the plate, and cut 2 coils off the heavy 1-2 accumulator spring. and i would put the seal/shim on the PR steam to put some tension on the spring, i would leave everything else alone.

these things i describe is not for the novice, so don't mess your transmission up! but for a very firm 1-2 shift and something easy to do, you can remove the 1-2 accumulator spring on the side of the transmission. usually, the O-ring that seals the cover is hard and needs to be replaced. to remove this cover, look on the side, there is a small hole you can put a pin punch or nail in and tap with a hammer, it will push the snap ring so you can pop it out. WARNING! if you do any of this and screw it up, do not blame me! just trying to answer a question and help,,,,,,,,,,,,,,,,,,,
 
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Supercharged111

Comic Book Super Hero
Oct 25, 2019
4,921
7,694
113
Colorado Springs, CO
well if the transmission is half worn out it will not be a good idea to shift kit it, my opinion, i only did them when i built them. but, to beef up a THM 350 without a box shift kit, i would remove 4 check balls. only put back the one in front of the modulator valve. i would open up the direct clutch and the intermittent clutch feed hole in the VB plate. i would remove the heavy 1-2 accumulator spring on the side of the transmission, i would remove the pressure regulator spring and put an old selector shaft seal on the stem of the PR valve, it fits perfect, and reinstall the spring, this puts more tension on the spring. i would remove the 3rd accumulator piston and spring "in the VB" and replace the spring with a weaker one, just strong enough to hold up the piston. i would remove the intermittent wave/cushion clutch steel and put a flat one in its place. this is if you want it to really hit hard! if i were just going for a positive shift, i would drill the feed holes in the plate, and cut 2 coils off the heavy 1-2 accumulator spring. and i would put the seal/shim on the PR steam to put some tension on the spring, i would leave everything else alone.

these things i describe is not for the novice, so don't mess your transmission up! but for a very firm 1-2 shift and something easy to do, you can remove the 1-2 accumulator spring on the side of the transmission. usually, the O-ring that seals the cover is hard and needs to be replaced. to remove this cover, look on the side, there is a small hole you can put a pin punch or nail in and tap with a hammer, it will push the snap ring so you can pop it out. WARNING! if you do any of this and screw it up, do not blame me! just trying to answer a question and help,,,,,,,,,,,,,,,,,,,

How far are you opening up those holes in the VB separator plate?
 

olskool

Apprentice
Sep 26, 2021
82
122
33
How far are you opening up those holes in the VB separator plate?
do you mean how big to drill the holes? i have a bit i use and i do not remember the size. i will have to look in my box, but the are not twice as big as factory, just under that. when i go to the shop i will get you that answer.
 
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