how firm is too firm

[oldred95]

All I have is a vette 1-2 servo and I've raised the line pressure tables by roughly 50% over stock (stock saddeningly low) and I now have crisp firm shifts but when I really get on it the firmness almost seems too rough. It doesn't chirp the tires but it just feels like the drivetrain is absorbing a hell of a lot of shock when it shifts like that. Its almost like a shudder is sent through the truck. It kinda scares me, makes me think I might explode some planitarys in the transmission. This leads me to another question. If and when I install a higher stall converter will the converter act as more of a shock absorber then the stock converter?

[bigburb]

yes the TC will act as a absorber but only effectively under the rating of the tc, if you get a 2000 rpm stall it'll shift just as firm after 2000 as the stock one. the only purpose of getting a higher rpm stall is to get the motor into its power band more quickly, overall it is a less efficient convertor.

[oldred95]

Less efficient but a lot more fun. Do you think I should be worried about the firmness being too much? I was thinking of pulling some pressure during the shift and then leaving the line pressure as is so its still holding good while engaged. Then again I don't want it slipping to absorb the shock either.

[AlienTranz]

A real quick firm shift is good, but there's a fine line between a firm shift and a hard shift. If you are obtaining a firmer shift by just raising the pressure, usually you are getting a hard shift, which is not a good thing. It's kinda hard to explain what kind of shift is a good shift and what kind is a bad shift. I guess the best way to explain it is to compare B&M shift kit shifts to transgo shift kit shifts.
Some people think B&M shift kits are better because they give you a much harder shift than a transgo kit, and this is true... but it's a harder shift not a firmer shift. The reason it's not a good shift is because B&M doesn't take shift timing into consideration, so what you are feeling is clutch overlap which is why you get a hard bang when it shifts. Transgo will always raise pressure and compensate for the raise in pressure by adjusting the accumulation to try to obtain perfect shift timing where one clutch comes on at the exact same time another one comes off. I'm not sure if i'm really answering your question. I'm actually feeling the need to fix the 1-2 shift on the 700r4 and 4l60E I've been noticing that with a corvette servo and a shift kit, they feel great at full throttle shifts, but they seem to harsh under light throttle shifts at times. I've been playing around with it a little I think maybe leaving the factory cushion spring by itself, and maybe removing the snap ring that holds the cushion spring cover on might be the key to cushioning the shift on light throttle shifts. They used to tell you do that in the older transgo shift kits, then they went back to putting the clip in, but i'm going to try it the other way and see if I can perfect the 1-2 shift for light and full throttle without sacrificing at either end. If you want to try it let me know how it turns out, it's a simple in car adjustment if you can get to your servo easily.

[oldred95]

Can't the shift timing be changed in the tuning though? Seems like thats where I need to look at. But I get what your saying about the clutches not engaging/disengaging at the same time.

[AlienTranz]

You can change the shift timing with internal tuning. As far as with the ecm tuning you can only speed the shifts up and change the time at which the shift will occur, you won't be able to synchronize the tranny without doing some internal modifications. The best thing to do is get the sonnax servo release check valve installed under the seperator plate. This gets the band in check with the 3rd clutch coming on. I love the way it shifts from 2-3 and 3-2 after installing that part drilled to match the vette servo and vette servo installed. It's a cheap upgrade that can be easily installed while doing the shift kit, and it just adds to the shift kit, doesn't mess anything up. I still don't think the 1-2 shift is perfect once the band breaks in. I'm doing a 93 4l60e tommorow i'll tinker with the servo and see how it comes out.