327_TPI_77_Maro

iTrader: (8)

Hi guys, I found out the other day that different application 700R4s (carb vs EFI) will have a different # of pressure switches in the valve body, to bypass TCC lockup depending on pressure.

IE for older applications without an ECU low speed TCC lockup control, pressure switch(es) in the VB performed the low speed TCC lockup limitation.

Does anyone have a diagram for how many pressure switches the VB of a TPI car should have? The trans I'm using is a 1986, but it was being used in an early 90s Suburban before I got it. I assume it has the correct pressure switch setup in the VB for TCC lockup using the '165 6E computer, but I want to make sure before I hook it up.

Thanks!

Steve

327_TPI_77_Maro

iTrader: (8)

Here is what I am talking about:

http://www.iotech.no/corvette/technical/700r4/

This page, towards the bottom, describes how, for example, a 1987 Caprice has two pressure switches, a 4-3 downshift switch in series with the TCC solenoid, and also a normally closed 4th gear switch.



Also for example, a 1988 TPI corvette has only the NC 4th gear switch. The TCC solenoid is wired direct to the ECU for full control.

I assume the 1989 '165 6E setup I am using should get a trans with only the NC 4th gear switch, and no other siwtches in series with the TCC solenoid, since all TCC is fully ECU controlled, right? I am 99% sure my 1986 700R4 had a bunch of other switches in series with the TCC. I will have to drop the pan and bypass them if that is the case.


The TCC does not lock at all with no plug hooked up to the trans, so at least I know it is not a hydraulic TCC locking trans. That would be very bad.

Thanks guys!

Apeiron

Even with the 4-3 pulse switch, the TCC is still fully ECM controlled. The 4-3 switch is in the 4th gear exhaust circuit to unlock the TCC only during a downshift from 4th to 3rd to prevent the shift from being too hard.

327_TPI_77_Maro

iTrader: (8)

So should I leave the 4-3 switch in? I burn my own chips so I can adjust the factory TCC tables to suit me. Thanks very much by the way, for chiming in. I can definitely use the help from someone who knows the 700R4 a lot better than me

I will show you a pic of my valve body when I get home in an hour. I think it may have actually had THREE switches. One was 4th gear switch, the other must have been 4-3, and I am not sure about the third switch. It is not a hydraulic lockup TCC, it is still ECU commanded. Any idea what a third mystery switch would be for?

Apeiron

Is it original to the car?

RBob

iTrader: (1)

The third switch may be the temperature switch. It is mounted on the VB, but not in a pressure port. It forces the TCC to lock when the fluid temperature goes over a set limit.

RBob.

327_TPI_77_Maro

iTrader: (8)

Gotcha, thanks.

However, here is a picture of my valve body when I had it apart. Notice that I actually have FOUR switches. Yikes! That's a lot of switches. What are they all for?

gapimpin

here is a good link i found looking for the same thing...
http://www.technicalevolution.com/700inst.htm

RBob

iTrader: (1)

You got switches. . .

The top right one is the 4th gear switch.

The next one down (on the riser) is the 4-3 downshft pulse switch.

The other two are most likely the TCC signal and 3rd apply switches. This is what is shown in the circuit drawings. Do not know which switch is which.

If that is what they are: the TCC signal line has pressure in 2nd, 3rd, and 4th. No pressure in 1st or reverse. This is the feed to the TCC solenoid, not to the TCC itself.

The 3rd apply line has pressure in both 3rd & 4th gear.

Between the 3 main switches you can tell if the transmission is in 1st/reverse, then each of the other gears.

RBob.

327_TPI_77_Maro

iTrader: (8)

Okay Rbob, since I am using a 1989 6E ECU and I am burning my own chips, which (if any) switches should I eliminate? I don't want switches over-riding what the ECU is doing, because I want to be able to make changes to the TCC routine in my own tunes.

I assume I can remove at least some of the switches, since this trans was from a TBI truck I think.

RBob

iTrader: (1)

At a minimum the $6E code uses the hi-gear switch (4th). It can be NO or NC, option word selectable. Changes the TCC lock/unlock tables vs MPG & TPS%

Not sure if $6E does an unlock on a 4-3 downshft. Or, if it is desired.

Otherwise the other two switchs, AFAIK, as not used.

RBob.

327_TPI_77_Maro

iTrader: (8)

Thanks! I'll go probe my trans to see if the 4th gear switch is NC or NO, and then set my tune up accordingly. I want it to unlock on the 4-3 downshift. I guess the only way for me to find out is run the TCC solenoid with no solenoids, and see if it does the 4-3 unlock. If not, I'll drop the pan and add that switch back in series.

norcalz28

iTrader: (13)

Old thread I know, but I was wondering if the ECM controls the TCC, what provides the ECM with the data it needs to control the TCC? I ask because the moment my speedo cable is inop, which inturn is not driving the VSS. I looked at several wiring diagrams and do not see the vss having anything to do with the tcc, but, one would think that it could control or at least signal the ecm right?!?! If someone could clear this up for me, I'd appreciate it. I'm just worried about toasting the converter if the tcc is not working properly due to no speed signal. This is a ProBuilt 700R4 very low miles and a vig 2400 stall, trans cooler installed. Thanks guys

Will