Silverado Steve

I have a 1994 Silverado with the 4L60E tranny. It was just rebuilt and is not shifting correctly. It shifts at higher rpms than it should in all gears, but from first to second is really hard.

After reading several posts, I decided to start cleaning some of the ground connections. When I drove it the next day, it was shifting perfectly. Same thing the next morning. When I left work, it started shifting hard again.

The shift is much worse when starting out slowly. If I hit the gas hard from a stop, it shifts much smoother. My mechanic and I are both at a loss. Any ideas?

Allan In NE

Let me just throw some ideas at you. Is this the same reason that the transmission was rebuilt in the first place?

The number 1 offender when diagnosing a 4L60 or 4l60E transmission is a partially clogged fuel filter. If all shifts are late, that's the first place you want to look. Pull the filter down and blow thru it. If you encounter any resistance at all, that's your problem. Further, your "worked okay yesterday and shifts hard today" symptom is sure pointing in that direction.

Secondly (and if the fuel filter is clean), a banging 1-2 shift 'almost always' stems from issues at the 1-2 accumulator. Weak/broken/wrong accumulator spring, bad/wobbled out piston, wrong seal, or incorrect assembly. When assembled correctly, it should be very difficult to get the piston into it's bore.

Third: Force motor. They do go bad and especially so on a high mileage transmission.

Fouth: Dirty or bad TPS switch. The transmission needs to know exactly where that throttle is and what kind of a load is called for.

Lastly: Let's hope that a shift kit was not installed?

Just my 2¢ and some ideas for you to ponder,

Allan

Silverado Steve

Thanks, Allan.

The tranny was rebuilt because it was slipping badly, most notably in 2nd and reverse. I would have never thought of the fuel filter. I'll check that first. As for 2, 3, and 4 on your list, I hope my tranny guy would have looked at those. I will check with him.

Also, after posting yesterday, I took it out and tried manually running through the gears. Even though I had it in 1st, it shifted to second on its own. That doesn't seem right to me.

Steve

metalchevydeathtrap

i'm also having the same problems. cleaned the header ground on several occasions to end up with a hard shift a few starts later. i noticed lifting off the pedal around the time its supposed to shift helps.
I'm starting to believe my problem is coming from the O2 sensor that is missing since that changes fuel flow. not sure if it will change anything installing since i have no cat and my exhaust is 2 leaky flex pipes clamped to a junkyard Y pipe that's stuck to a cherry bomb
haven't done the fuel filter swap since the old one is rusted on even though i've had the replacement in my tool box along with the O2 sensor since i bought the truck.

good luck with your 350, sir

(update) recently discovered that any dirty positive wires will cause a hard shift as well. had to go through and clean most of the electrical components including the entire distributor, cable to the starter and such.