700R4 TCC Solenoid bad? (limited EFI content)

[mike mager]

Peter Gargano asked about his THM 700 R4:
(Complete message below.)

>At this point the transmission seemed to try to unlock and immediately lock 
>up again, causing an oscillation at about 3-5 Hz - only cure was to change 
>back to 3rd (from OD to D on shifter) until over the hill!
.
.
.
>All ideas greatly appreciated.


Peter, do you know the simple TCC test when you are driving?

(BTW, I'm sure that some ECU might try something different, but most respond 
to this.)

Cruising at a steady speed (90 KPH, or so) with the TCC locked, push the 
brake pedal just far enough to turn on the brake lights (but not pump the 
hydraulics);  there is the BOO (Brake On-Off) switch that will drop out the 
TCC - just cruise, and pedal down - up - down - up, and you should feel the 
TCC lock and unlock.

In the states, I don't know quite what the Commodore equates to, but most 
THM 700 R4s would cooperate.

HTH,
Mike


>From: Peter Gargano <peter at ntserver.techedge.com.au>
>Reply-To: gmecm at diy-efi.org
>To: gmecm at diy-efi.org
>Subject: 700R4 TCC Solenoid bad? (limited EFI content)
>Date: Wed, 15 Mar 2000 09:59:43 +1100
>
>My VN Commodore 3.8 V6 has a "Turbo Hydra-Matic 700R4" and has just
>one ECM connection - the TCC Solenoid (I'm sure this isn't news to most
>list members ;-) I had to look at my manual!...
>
>My wife mostly drives the VN to work in light traffic. I only get to drive 
>it
>when it's playing up, or on a long trip. Last weekend the car (apparently)
>had a problem with unlocking the TCC. When doing constant freeway speed 
>(say
>~ 70 mph) and coming to a hill, there would be a point when you'd expect
>the TCC to unlock to get a few more revs (and torque) to make it up the
>hill.  At this point the transmission seemed to try to unlock and 
>immediately
>lock up again, causing an oscillation at about 3-5 Hz - only cure was to 
>change
>back to 3rd (from OD to D on shifter) until over the hill!
>
>I swapped the ECU and this didn't make any difference - haven't had time to
>check anything else (wife has car!). I'll swap/check the TCC solenoid 
>tonight:
>
>It seems like the TCC solenoid may be pulling in and then almost 
>immediately
>letting go - is this common, or do I have a hydraulic (ie. auto trans) 
>fault?
>
>Note that this problem is not apparent when accelerating (fast or slow) up 
>in
>the gears, only when the motor/ECU/transmission senses a load that would 
>cause
>a downchange/TCC unlock condition.
>
>All ideas greatly appreciated.
>
>regards, PG
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