Odd 4L60e 1-2 shift issue...

I have a 1996 OBDII car.

Car has a 3000 RPM Edge Racing converter in it. Trans was rebuilt with a Pro-Built "Pro-Street" rebuild kit, and has been converted to vacuum modulation.

From a dead stop, if I nail the throttle, it spins the rear tires, gets to a point and shifts into 2nd, then about 1/2 to 1 second later it drops back to 1st, then a second or two after that it goes back to 2nd.

I'm thinking it's a tuning issue, but does anyone with any experience with A4 transmissions think that it would be anything else?

Make sure you don't have a leak in the vacuum line. Mine was setup this way but the vacuum line burnt on the header and caused shifting problems. You could also have a problem where the governor wants to shift at a different point than the PCM.

Go to www.fastchip.com on compuer problems, and talk to Ed Wright. This transmission does not use a governor.

Go to www.fastchip.com on compuer problems, and talk to Ed Wright. This transmission does not use a governor.

LOL!! That was a wild guess. I'm not a tranny guy. But I would suspect a vacuum leak since I had a similar problem. I might also suspect a bad shift solenoid or loose wiring to the solenoid but it should have been replaced when it was rebuilt.

I'm going to check/replace the vacuum tubing to the trans, as I think you may be on to something.

I do my own PCM tuning, and this isn't the standard "stall wall" issue that some run into. If the vacuum tube doesn't fix it, I'll try tuning changes.

I replaced the thin vacuum line that was included with the modulator conversion tonight. The spring was missing from the bottom two inches of the hose, plus most of the hose was SUPER soft, hours after the car had cooled off. The included hose just didn't like the heat of the exhaust system I guess, and although I didn't get within 4" of it, it was just too much I guess. That and the clear hose had collapsed around the spring, and where there wasn't any spring, it had collapsed totally.

I replaced it with 40" of hard brake like with flares on the ends. I also purchased 4 feet of 1/4" ID fuel/emissions hose rated for 50 psi. This hose was a snug fit over the flares on the hard line, as well as the fittings on the trans and tee in the brake booster hose. I routed the hard line from the brake booster, down and behind the stock heat shield where the brake lines run up, then back to about where the trans crossmember is. From there I converted to the rubber line and moved between the hard lines and floor, over the trans and to the other side where I connected to the modulator.

I didn't get to drive the car tonight, but hopefully that will take care of the problem for me.

Yep, sounds like the same problem I had. Let us know how it turns out.

The new vacuum line did not solve the problem.

The shifting is better, but it's still doing the 1-2-1-2 shuffle.

I'm going to look at the tune now.

The new vacuum line did not solve the problem.

The shifting is better, but it's still doing the 1-2-1-2 shuffle.

I'm going to look at the tune now.

Aw dang. I hate when I think I've got an issue licked and it's still there. :(

I think it's in the tune. I've been looking at the shifting tables, and it is really looking like it's in the tune. There's only 4 MPH difference between the 1-2 and 2-1 shifts. When I took my 2.73 stock tune and converted it for the 3.42s, there's a 15 MPH difference.

Loaded a new tune, with the converter shiftpoints in place of the others that I was running, and it doesn't shuffle back and forth. So it appears that I got it taken care of.

I'm glad you got it figured out.