TH350 shift firmness

[BrentBTK]

I've got about 70 miles on my new motor install. SBC 385/409 HP/Tq mated to a TH350. Final gear ratio with my tires is about 3.21 I also replaced the torque converter with a 17-2100 RPM stall based on Blueprints recommendation. What I have noticed, is it seemed to shift much firmer before the swap. The shifts now are very soft. Is that related to the converter change? Anything simple I can do to firm things up a bit?

[tdangle]

I would think it may be the torque converter. At what RPM are you comparing shifts at? if just cruising you probably would have softer shifts, at full throttle I would not think there would be much difference. make sure you have the kick down rod adjusted correctly

[leftybass209]

I wouldn't ever describe a TH350 as having a firm shift, even from the factory, unless it's had a shift kit installed, or during kickdown operation. At light and part throttle, I always described them as soft to slightly crisp.

Terms are vague though, so it helps to describe exactly what's happening with the shift sometimes over text.

Now, my 700r4, that's a firm shift, with slightly a lunge from 1st to 2nd. Completely different feel than the TH350, and i WOULD absolutely describe it as firm, lol

[BrentBTK]

Originally Posted by leftybass209

I haven't ever known a TH350 to shift firm unless it's had a shift kit installed, or during kickdown operation. At light and part throttle, they are soft to slightly crisp.

I certainly wouldn't have called the shifts "hard" before, but they are significantly softer now.

[Steeveedee]

You won't fry a 350 as quickly as a 200 or 700 if the detent cable isn't right, but you're not doing it any favors, either.

[BrentBTK]

Originally Posted by Steeveedee

You won't fry a 350 as quickly as a 200 or 700 if the detent cable isn't right, but you're not doing it any favors, either.

Could you elaborate? I'm not a trans guy. I assume you mean the kickdown cable? Isn't the purpose of it to downshift the trans under full throttle when vacuum isn't available? How does that not being adjusted affect reliability or firmness of the shifts? If I manually shift into 2nd under acceleration, aren't I doing the same thing? I appreciate the advice, I just don't know what I don't know.

[BrentBTK]

Originally Posted by tdangle

I would think it may be the torque converter. At what RPM are you comparing shifts at? if just cruising you probably would have softer shifts, at full throttle I would not think there would be much difference. make sure you have the kick down rod adjusted correctly

I still have to get the kickdown properly adjusted. Shifting across the board is just softer. Even if I run it up to around 3500RPM and shift manually, they are very gentle. Easy acceleration, hard, no real difference in firmness. I haven't gotten into it too hard as the motor is brand new.

[Accelo]

Any time one goes up, with the torque converter stall, you will go down in perceived shift firmness. Higher stalls have more slip.

High stall converters will not immediately drag the engine rpm down like a low stall. More slip is designed into the system. You will get used to it.
You may help the situation by firming up the shift. It will make difference but not a significant difference.

The motor indeed has different vacuum characteristics. In all likelihood it is less vacuum and that would equate to harder shifts not softer.
Only change, to the transmission, was the converter. Shift timing is unchanged. Logic dictates it's converter related.
Cheers