88gunmetalgta

iTrader: (1)

I don't seem to be getting any TC lockup as I'm driving around. $6E mask.

I noticed one flag in the datastream called "overdrive requested" and in all my logs, its always false.

Is this just a function for the manual trannsmissions? or is this TCC?

Note there is also a 4th gear flag, and this one seems to be working right in my logs. Previously I had a loose connection at the transmission, but if the other inputs are reading right (park/nuetral, 2nd gear, 3rd, etc) I would guess it isn't the case this time.

I'm off to compare the table values between the ARAP and the factory bin.



*EDIT
The tables were different, but not by much. I matched the ARAP tables to the $32b tables. It didn't help.

Turns out, "OD request" is yes anytime "4th gear" is false.
"1st gear" is always false
"3rd gear" is always true
Hmm, maybe it is the wiring harness connector....

RBob

iTrader: (1)

The overdrive requested may be for the y-body 4+1 stick tranny. It had an automatic overdrive unit in the tailshaft run by the ECM.

There isn't a 1st or 3rd gear switch in our 700R4's. There is the 4th gear switch which is used by the ECM to switch between two sets of lockup tables. Usually higher lock MPH and MPH vs TPS when in 4th gear.

If the switch status is correct then no need to change it. There is an option flag for NO/NC on that switch.

There is also a brake pedal switch that breaks power to the TCC when depressed. The ECM grounds the other end of the TCC solenoid to activate it. This wire may also be at pin F of the ALDL connecter.

Should be at +12 volts with the TCC unlocked and foot off the brake pedal. Then near ground when the ECM locks the TCC. Can also ground this pin to force the TCC to lock. May even be able to hear the solenoid click with key-on, engine-off.

RBob.

Orr89RocZ

iTrader: (20)

What converter you running again? its very noticeable to get lockup on higher stalled converters.

Theres only a few constants needed for TCC control as mentioned above, high gear and low gear lock/unlock constants at high speed and low speed.

Theres also a unlock prevention threshold where it will force the converter to lock up at WOT at any MPH you choose. Comes in handle for dyno tuning and sometimes at the track to gain ET/MPH although i never gained by locking it.

88gunmetalgta

iTrader: (1)

I have an unknown brand 2500 stall put in when my trans was rebuilt last summer.
I had lockup before the car was parked, and my memory of how it behaved is pretty good.

However, it seems like there are some significant differences between the $32b and $6e handle TCC lockup. Maybe I'm just missing the signs, since I've never driven an L98 'vette! It does seem to cruise at 60mph and 2000 rpm, which was the same as before the swap, but I never notice it unlock when I roll on the throttle, and when I let off the throttle, the rpms immediately drop.

I did have some trouble with my brake light switch, and I don't remember checking transmission fluid levels since I refilled it after I found the bad seal on the dipstick tube. Time to go back and check the basics.

Thanks for the clarification on those points RBob.

There are a pile of scalars available, with names like "low speed limit for low speed lock to unlock transition" They're a little bit cryptic. Seems to me they just provide a TCC window of operation.

88gunmetalgta

iTrader: (1)

Followup:
I finally remembered this problem when I was working on my car.

First thing I checked was the brake pedal switch, and sure enough it wasn't adjusted right.

Another example of why you have to check everything else before you second guess the ECM.