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On my 84, when i am cruising through town at about 25-35 mph, my auto trans shifts nicely through 1st to 2nd, then just bam! falls into third with a big rpm drop, but picks up fine and motors on. Like it misses a gear and just shifts into high. Any thoughts on this? I was told that my converter locks up too soon. I found a lockup delay kit on Ebay by Rostra that allows you to set the speed for the converter lockup. Has anyone had experience with this?
What you describe is the transmission shifting to 3rd too early, not a lockup problem. There's a set of mechanical weights you can adjust to delay the shifts in the governor on the side of the trans. Access to the cover can be troublesome, I've done it on a truck before, but not a Vette
Not sure about the 84, but on the later models that is a common problem and the cause is usually the lockup switch on the brake pedal (3 part switch) or if manual, same switch on the clutch.
They develop high resistance in the contacts for the switch and cause no lockup or drop out.
You can check lockup status on pin F.
A small LED indicator can be used to check if it is lockup causing RPM drop.
Lockup can activate from 2nd to 4th.
Get a scan tool to check for fault codes that may be affecting the shifting. It may also allow you to see the gear positions when you road test. Personally, I wouldn't modify anything until you verify that something isn't wrong. If you have no fault codes and are still stuck, get us the data read out from the scan tool, and collectively we'll figure it out.
Last edited by Mrvettenick; Feb 26, 2020 at 07:21 PM.
Get a scan tool to check for fault codes that may be affecting the shifting. It may also allow you to see the gear positions when you road test. Personally, I wouldn't modify anything until you verify that something isn't wrong. If you have no fault codes and are still stuck, get us the data read out from the scan tool, and collectively we'll figure it out.
Even a good code reader scan tool will not show that kind of data for lock up. A higher level scan tool is needed to show that kind of live information. A Tech 1 (or 2) will show when the switch is closed and the circuit is complete for the lock up signal. I'm sure there are other high level scan tools that will give that information as well.
Even a good code reader scan tool will not show that kind of data for lock up. A higher level scan tool is needed to show that kind of live information. A Tech 1 (or 2) will show when the switch is closed and the circuit is complete for the lock up signal. I'm sure there are other high level scan tools that will give that information as well.
Snap ON mt2500, or any SnapOn tool , That's just me. I have to see what';s going on before replacing /doing anything. TPS, Coolant, etc. Funny thing....You have to understand with converter lock up on the scan tool......it will only tell you if the ECM gave the command. That doesn't mean that it happened. A bad solenoid, or converter clutch could prevent that from happening. There;s a lot to see before doing anything IMHO.
Last edited by Mrvettenick; Feb 26, 2020 at 11:35 PM.
No scan tool of any caliber will show anything about the transmission in an 84-93 except the converter clutch commanded state. ON or OFF. Nothing else. The 84-93 is hydraulic only, no ECM controls, inputs or sensors regarding the transmission for anything except TCC command. There are also no DTC's associated with the TCC circuit in the 84-93.
Exactly. An easy way for the op to see if the torque converter is locking and causing his symptoms is to either pull the fuse or simply unplug it from the transmission. If the symptoms persist, look elsewhere for fault.
I don't agree with you people. Big question is....is it an transmission problem, or an engine problem. All we're doing is guessing. I don't understand why not taking a look at what's going on. Believe it or not, most tranny shops hook up a scanner before doing anything.
Well, my engine runs well and strong. Its just that long drop in rpm that bothers me. It picks up and gains speed well, and will downshift right after, when I am accelerating, but that dive into whatever higher gear is the bother. It makes sense to me that the converter lockup would pull the rpms down, and that moving that point to a point in fourth gear where the rpms are lower would smooth out that operation.
Oh and I have a scanner but it shows no codes at all
I'm not looking for codes. There are certain ECM criteria that determines engine AND transmission activity.
That's why I said to examine data, and to make sure that all of the basics are working the way they should. Is the ignition system working properly?
Is the fuel system working> What is your fuel pressure? Hey, I'm just trying to help. It's your car.
If you need help....just ask. I'll leave this thread to the others.
I have the bin files if you know someone with an eprom programmer.
The chips are 1k of a type that is 'impossible' to fine but you can use 4k eproms and repeat the data 4 times.
Actually the 4k chip ( 2732 if I remember ) has extra address pins that are something else on the stock chip. When using a 4k chip data will be read from the 3rd k if I remember.
Torque converter lockup delay
