1986 Vette TCC Engagement Speed

[Joseph A.]

Hi Everyone,

I have 1986 Corvette, Automatic Transmission, G92 High Performance Gear Ratio:(3:07). The Torque Converter Clutch is engaging @ approx 65-67 MPH. This seems a little high to me. Does anybody know the correct MPH TCC should engage. I have a GM shop manual but it does not tell you the specfic parameters about TCC Lockup. I just replaced my ECM And PROM with the latest revision applicable to this car. The part number for the PROM is 1227944 and the ECM is 88999194. I had a problem up until two weeks ago with TCC engaging in reverse and first gear with the car at operating temperature. The transmission was rebuilt about two years ago and doesn't even have a thousand miles on it. We test the electrical side first and everything checked out okay. So we decided to pull the pan and drop the valvebody. Once we drop the valvebody and got it to the bench we checked all the valves to make sure they were not stuck and to make sure all the steel balls were there, all that checked out okay. So we decided the transmission had to come back out. So we but the lower end back together so I could drive home and then we could decide when were going to pull it back out. When we reinstalled the valve body we used all new GM gaskets and a new TCC switch from GM. Well once it was all but back we filled it up and ran the car through gears. We let the car warm up because the only time it would stall was when it was hot. We but the car in reverse at 200 and it did not stall. I don't have a clue what we did or how it got fixed but its fixed. I wanted to give a history of the problems i'm having with TCC. Could we have messed something and fixed the reverse problem and caused a problem with TCC engagement speed. I thought a computer would fix the problem, because TCC engagement is controled by the ECM.

Any help would be appreciated.

Joe

[Wayne W.]

Re: 1986 Vette TCC Engagement Speed

Wow, Sounds like you have had a time with this one. The TCC should lock up much sooner than that. There are a lot of factors that determine just what that number might be. The computer, the governor, The TV cable adjustment etc. My bet is that the TV cable is not adjusted correctly.

[Joseph A.]

Re: 1986 Vette TCC Engagement Speed

Wayne:

The TV Cable is a new GM cable and its adjusted to the specfication in the GM Shop manual for my 86. Also I was told that the ECM controls when the lockup of the converter happens. The computer is new. The governer was inspected when the transmission was rebuilt and checked out okay. Like I said, I really don't know why the lockup of the converter happens 65-67 MPH.

Joe

[Oliver G.]

Re: 1986 Vette TCC Engagement Speed

HI Joe,

The TCC engages around 45mph in my totally original low mileage convertible.

Many years ago, 1986 comes to mind, I did install an aftermarket chip which raised the TCC engagement into an area similiar to yours. That chip was quickly removed as I did not care for the change in the car's personality.

If the TV cable is properly adjusted, I would suspect the new PROM you installed.

[Joseph A.]

Re: 1986 Vette TCC Engagement Speed

oliver, after we fixed the problem with the car stalling out in reverse hot and tcc engaging when its in reverse and first gear. We test drove the vechile and came to the conclusion that the ECM and PROM needs to be replaced.Also my neighbor the guy who has been helping my fix everything is a service manager at a car dealership. He told me he was going to look for recalls on 86 corvettes and we came up with the following recall that applied to my problem with tcc engaging to high. Recall# 86-657-106. Two things were happing that made us replace the computer and the recall that was issued by GM to install a new prom and ecm. 1. the upshift for best fuel economy light as coming on and second the tcc engaged at 65-67 MPH. After we replaced the prom and ecm nothing changed. The upshift light still comes on and the tcc still engages at 65-67 MPH. So thats the story. What I would like to know from you if you would be so kind is to try to get that number of your prom. The number on my new prom from GM is part number 1227944. Also there is a number on top of the prom. The number on mine is 7944.

Any help would be greatly appreciated

Joe

[Oliver G.]

Re: 1986 Vette TCC Engagement Speed

Hi Joe,

The PROM presently in my '86 convertible, auto trans, 2.73 axle ratio is the factory PROM. The Code number is 9653BUJ The build date of the car is 07/86.

The Part Number for this PROM is 16059649

I see your Part Number is most likely a supercession and I cannot cross that over to the orignial Part Number. The Code is also most likely assigned to the superceded Part Number - because I cannot find a 7944 code on any 86 including export models.

The Part Number for the original ECM is 1227165. The good news is there is only one Part Number for 1986 models.

Not sure how much help this info will be - but as I stated in my original post - my lockup is in approx 45 MPH with light throttle. YOu are absolutely positive that the TV cable adjustment is correct - and the cable is connected internally in the transmission.....?