Having 2-3 shift overlap - Thinking of switching from 4.2 apply lever to 3.8 - Any Other Thoughts?

This is one of my favorite torqueflite topics. As we all know the 727 historically can get stuck in two gears at once on the 2-3 shift and cause a bind or overlap.

We go to great lengths on our transmission builds to achieve a clean, quick and firm (not harsh) 2-3 shift. There are a lot of variables involved and we really need to know more details, such as valve body manufacturer and build date, a line pressure reading, etc. Servo design and spring rate, type and quantity of 3rd gear return springs, lever ratio, clutch pack clearance and valve body design all play a part in how the transmission will operate.

So we need to ask ourselves, what causes a bind, or overlap opposed to shift flare?
A bind or overlap on the 2-3 shift is caused by the high gear clutch applying before the 2nd gear band is fully released. Of course, the opposite of that would be a flare on the 2-3 shift which is caused by the 2nd gear band releasing before the high gear clutch is fully applied.

So, with an overlap condition decreasing the number of high gear return springs will make the overlap more amplified as you are now speeding up 3rd gear clutch apply. The more springs installed, the slower the clutch will apply. The idea with all 15 springs, in a high pressure manual valve body or trans brake application is to delay the 3rd gear clutch from coming on slightly, as to not have the bind or overlap. Also, in a trans brake application they are used to get the high gear clutch off quicker upon trans brake release.

A numerically higher lever ratio will apply the 2nd gear band quicker (1-2 shift), but it will take longer for it to come off, or release the band (2-3 shift). So, to answer your question, yes going to a 3.8 lever "may" help your 2-3 overlap condition.

We typically use a stiffer 2nd gear servo spring to get the band off quicker to prevent 2-3 shift overlap. I'd agree with RJ in ditching the (red) sonnax servo in favor of something better, with a stiffer spring.

With a high quality high pressure reverse manual valve body you typically:
- Block the accumulator piston
- Use 15 return springs in the 3rd gear clutch
- Use a modified or billet 2nd gear servo with a stiffer spring
- Use a billet low/reverse piston with a stiffer spring and thicker billet retainer (the factory stamped retainer can and will blow out of the case and the OEM piston can break and/or flip in the bore).

Hope this helps...