sirmike68

I have a 1987 with an automatic transmission. What I have noticed is the tranny is jumping back and forth in/out of overdrive when I'm at highway speeds. Pressing and holding the break while at speed keeps it from shifting up or disables the TCC from locking up. It will also jump around if it is cruise control.

I have done the test with a "test light" where it is connected from ALDL terminal "F" to ground and the light is "on" and the TCC solenoid is disengaged. I also raised it on my lift and ran it up to 70 mph with test light still hooked up to terminal "F". I noticed that the light would stay "on" up to about 45 mph then when it would lockup the light would be "off" which makes sense because it is locked-up but then the test light would randomly blink on/off. All while I'm holding the speed steady. What do I check for now? I do not have a scan tool, only a test light. Any tricks or tips is appreciated. THX

I also swapped the PROM back to the factory one to see if anything would change and it reacts exactly the same.

aklim

Have you tried adjusting the detent cable?

http://www.cpttransmission.com/tech_tvcable.htm

383vett

Are you saying it is shifting between 3rd and 4th (overdrive) or is it a converter lockup issue?

sirmike68

It is a lockup issue.

sirmike68

I have not done anything with the TV cable.

Also while running the car on the lift i tried to engage the cruise control. When i did the car reved right up then backed right off just like as if i was pumping the gas until inturned it off. It does control nicely while on the road, maybe being on the lift free wheeling is not something its setup for.

sirmike68

I was looking at the TV cable and noticed this kink in it. I assume this kink could be causing my problems. When I change this cable out is there anything else I should replace while I have things opened up?

sirmike68

Thanks for the replies. Since I already have the TV cable ordered and it is kinked up I'll change it out. I don't have access to a scanner and driving the car in the snow is not an option. Ha! So I'll start looking into VSS, MAF, and TPS and wiring.

gerardvg

The early C4 had the torque converter lock up at too low a speed, the usual fix is replace the chip with a performance one that has the higher speed TCC lockup. That improves drivability a whole lot.

(An added benefit of any Power Chip is there-programming of torque converter lock-up. Power Chip delays the lock-up until high gear which significantly improves driveability.)

https://www.corvettecentral.com/c4-8...m%26count%3d72

sirmike68

Update now that its summer and I can finally drive around I believe I have found my problem. I bought a scan tool this winter and ran the car on the hoist for a while collecting some data. I could see the TCC lockup signal engage/disengage as it should so everything electrically seamed normal. The next test I did was to pull the electrical connector for the TCC off the tranny and go for a drive. Low and behold with the TCC wiring unhooked everything ran smooth as silk all the way through the gears. Now I think I can safely assume that the issue is with the TCC solenoid and that I should replace it.

confab

The easiest thing to check and one of the most overlooked is the brake switch..

65Z01

Where did you find an OBD 1 scan tool? Does it have a Monitor Mode?