ArkBird96

Hey guys, I've got a question. Is it better to let the car accelerate in 4th gear or make it downshift to 3rd? I've heard 4th is a weak gear and I'm trying to figure out what I should do. Car is stock. Thanks!

1lejohn

iTrader: (9)

The car should pull better in 3rd. I would down shift it into 3rd depending on what speed you are at.

ArkBird96

FYI, I'm not talking about manually downshifting here. That's a mistake IMO. I'm talking about when accelerating if it is better (from a transmission life standpoint) to let the car accelerate in OD or to get on it a bit more and make it go into 3rd?

FirstYrLS1Z

iTrader: (4)

when you're cruising at a steady rate,let's say on interstate,your selector is in 4th and torque convertor is in 'lockup mode',if you give it some gas to accelerate and the torque demand level reaches a point that the PCM is going to unlock the convertor and you'll be in 4th unlocked convertor mode. More gas and acceleration at some point will cause the PCM to shift to 3rd based upon what kind of acceleration you're asking for.
It knows when it's time to kickdown to 3rd so I wouldn't be concerned about trying to replace the PCM actions by thinking do I want to stay in 4th or a little more gas so it'll shift to 3rd.

mike13

iTrader: (27)

I think what your asking is will it hurt the transmission accelerating in 4th versus making the car downshift into 3rd? If that's the case it's a good question I've heard all kinds of things overdrive being weak but I don't know how much of it is true.

ArkBird96

^^^ Mike13 you're correct! That's exactly what I was asking but I wasn't sure how to explain it. FLT, Performabuilt, etc. any ideas?

slow67

iTrader: (2)

I'm pretty sure the 3-4 clutches are the weakest point of a stock 4L60E. They are on in both 3rd and 4th. It will however, put more strain on them in 4th as compared to 3rd.

PBA

Once the vehicle is in 4th gear, and you give it enough gas, so as to not have it downshift, you should be fine. The more throttle you give it, the higher the line pressure holding the 2-4 band. This will not hurt anything. If you want to make a 3-4 WOT shift, then that is a different story. Bringing on the 2-4 band will require a bigger feed hole in the separator plate, bigger boost valve, and changing the accumulation, or just adding a Sonnax 4th apply servo. Depending upon torque and horsepower, you might need both here.