Jarred Hodges

My car is an 02 z28. before I put the converter in overdrive worked fine. I installed a 3600 stall and it works great in 1-3 but will not shift into overdrive now. I was wondering if anyone had any ideas

lt1-xjs

It has to be tuned for the converter.

jrzdude

iTrader: (4)

are you letting it warm up for a while? It takes about 10 minutes of driving around for mine to start working. I believe the trans fluid needs to be at a certain temperature for it to shift into OD

Jarred Hodges

I had it tuned and the trans is pretty much shot according to my tuner. we were riding in the car and the only way it would go into overdrive was if he used hp tuners and commanded it to, it would still not go into overdrive by itself. Also the 2nd to 3rd shift is kinda slow too. The trans should be pulled and gone through in a couple weeks

jimmyblue

iTrader: (11)

Small converters aggravate misfire detection (false
detects) and misfires will inhibit lockup. This may
-feel- like you're not going into OD if the converter
soaks up the RPM, as slip.

In HPTuners the TCC_Mode will show --3-- if it's
misfires holding off lockup.

You would hope that somebody who calls themself a
tuner and charges people money, would know how to
chase this kind of problem down.

It's easy for a clown to finish the job of ruining your
trans, that mods (esp. ghetto mods) may have started.
Maybe you want a different set of eyes on it.

01ssreda4

iTrader: (96)

JB is right, very common problem. Misfires = no OD per the PCM.

redtan

iTrader: (5)

That has nothing to do with it, the stock tune still commands 4th gear at a certain speed/tps position...so when getting to that point it will shift into 4th.

That is true about converter lockup, the trans fluid has to be above a certain temperature for it to happen. However, shifting into 4th has nothing to do with fluid temps...it can and will shift into all gears at any fluid temp.

I would tend to also thing that the transmission is shot...same thing happened to me when the common 3-4 clutch failure happened. Never had any problems with an aftermarket converter messing around with the missfires and/or shifting into 4th when the transmission was working properly.

mrvedit

I wonder if there is some mixup here in just what "Overdrive" means. Overdrive is defined as any trans gear ration below 1.00; therefore on the 4l60e, 4th gear (ratio 0.70) is Overdrive. TCC Lockup is independent, although it is typically only engaged in 4th gear when speed is above a programmed value and throttle is below a programmed value. The PCM will not engage TCC lockup if it detects various problems, including engine misfire (as jimmyblue stated).

If HP Tuners cannot command 4th gear, then there is a trans problem. It could be as simple as a problem in the servo. If the trans is working well in 2nd and 3rd gear, removal of the trans may not be necessary because internally 4th gear is a combination of 2nd and 3rd gears. In another recent thread where the OP did not have 4th gear, he took it to a trans shop which after first verifying the servo was OK, replaced the valve body to solve the problem.
There is no obvious reason why a converter change would give you this problem; it might just be a coincidence, or perhaps it stirred up some dirt which has lodged in the servo or valve body.