Freshly rebuilt trans question.

I just got my 96 Roady wagon back from AAmco, with a fresh trans rebuild. Apparently they have a facility in Texas that rebuilds transmissions, and it has the ability to bench test them more thoroughly than a local shop. Subsequently they offer a much better warranty-3 year, 200,000 miles. Anyway, when I picked it up, it had a harder 1-2 shift than I liked. I was told that they replaced the shift tension spring a lighter weight one. That fixed the problem, and it now shifts very smoothly. Can anyone tell me what a shift tension spring is? No one was available to talk to me when I picked the car up, and that explanation was with the paperwork I got when I picked it up. Thanks.

There is a shift solenoid that comes from a Corvette that makes the 1-2 shift much "harder". It has a different spring than the "stock" one. I assume the spring is the main culprit in that difference.

Is that a big deal to replace? Did the trans need to come out to do it? The shop left me a voice mail stating exactly what you said-the trans had a Corvette spring, and they changed it for a lighter one. I never had a hard 1-2 shift until the trans was replaced. The voice mail indicated that my car came with that spring, and they thought I wanted that hard shift. But, I never changed it during the 100,000 miles I put on it. Wouldn't that spring have been replaced during the rebuild process? I'm just trying to figure out if the shop is lying to me about the problem. It was under warranty anyway, but I just want to know. Thanks Fred.

There is another spring in the accumulator that can cause a real slam shift if left out. Your softer shift may be because of wear and tear on the trans, so you might not have felt the strong shift.

Does the trans need to come out to make the repair? Is it a simple repair?

The above issues do not require the trans to be removed.

Thanks Fred.

Fred Kiehl wrote:

There is a shift solenoid that comes from a Corvette that makes the 1-2 shift much "harder". It has a different spring than the "stock" one. I assume the spring is the main culprit in that difference.

Just a clarification - the 'shift solenoid' is identical across all 4L60Es. Shift A and Shift B solenoids is what GM refers to them as. The "Corvette Servo" is really just a servo piston with a smaller inner diameter, making the servo piston apply area larger. This applies the 2-4 band for 2nd gear. You can see the different sizes available here. The servo piston is easy to change but not with the transmission in the car; B-bodies have the passenger side catalytic converter right in the way, so that has to be removed to change a servo piston.

What the shop likely did was change out the spring in the 2nd gear accumulator housing. All you have to do is drop the pan and filter, three 10mm bolts, and you can change the shift feel. The accumulator piston has 2nd gear oil on one side, and accumulator oil (basically a hydraulic spring) on the other.  Springs that go in the housing under the piston control how much the piston can expand due to accumulator oil. Stiffer springs inside the housing allow less accumulation. On the flip side, if you put a spring between the piston and the case, the spring will work against 2nd gear oil and stiffen the shift. There is an accumulator valve/spring that regulates how fast accumulator oil can leave the area between the piston and the case; Transgo sells a stiffer spring, Sonnax shims the existing one. Both work fine. You can see some of that in my Impala trans build here (post #120). Do be aware that if the springs aren't right, the piston can bottom out in the bore, and you get a slide-bump shift at certain throttle positions. Not a fatal flaw, just an annoyance to fix.