tcc shifting to early in 1st stage. - Third Generation F-Body Message Boards

49m · 02-13-2006, 10:15 AM

86 305 iroc 700r4
The car shifts fine while cold or under moderate to heavy accelerations. Once car is up to temp it will lock up tork convertor in over drive at low rpms. For example I come to a stop sign and stop when I take off under normal acceleration this is when it occurs. You can feel the car down shift to first correctly and it gos thru 1,2,3 then lock up and it will hit 4th around 42 mph correctly. To over come this I have to accelerate med to heavy. Tps is cal. correct. I have the gm shop manual but cannot seem to fine a good direction to go to next. Where should I start trouble shooting next? Thanks: 49m

sofakingdom · 02-13-2006, 10:40 AM

???

That's what it's supposed to do.

49m · 02-13-2006, 11:05 AM

There should be no convertor lock up before 42 mph. Maybe you do not under stand, It lugs the motor down just like skipping 2 gear.

305q_ta86 · 02-13-2006, 11:25 AM

I also think the way you described it sounds right. Or do you mean to say that it locks up at way under 42 mph when warm? Because otherwise, lugging the motor down is pretty much a side effect of fuel economy.

sofakingdom · 02-13-2006, 11:29 AM

No, I understand perfectly.

That's what it's supposed to do.

Now whether you think it could do something else and it would be better, or you just don't like it and wish it would do something else, that's a different matter.

But it sounds like it's doing exactly what GM thought it should do and made it to do.

49m · 02-13-2006, 11:31 AM

Funny thing I have Two off these cars and a 92 chevy truck with the same trans and they dont do it. Also this one did not do this when I first got the car.

sofakingdom · 02-13-2006, 11:33 AM

I don't think there's much I can do to help then.

It's supposed to do that.

49m · 02-13-2006, 12:45 PM

305q_ta has it right.
It is locking up way before 42mph only when the car is up to operating temp.

305q_ta86 · 02-13-2006, 01:23 PM

Ok, then now that we have that sorted out, the question is why is it locking up at really low spd when warm?

Well, what engine is it? lb9? That would mean it has a computer and is therefore nothing like my '86 trans am non cc lg4, but I would say you should check the vacuum hoses going to the vacuum lockup switch (uh, if you have one) and then the next question is have you done anything to the computer?

49m · 02-13-2006, 01:51 PM

lb9 is correct computor is stock.

ZZ28ZZ · 02-13-2006, 03:10 PM

Mine did that after I swapped the TPI/700r4 eng/tranny into my 82. There are speed limits on the prom for the min speed the converter can lock up. There's seperate settings for 3 gear and 4th gear. I set mine to 255 mph for 3rd gear and abt 45 mph for OD. This prevents the converter from ever locking in 3rd gear and the 45 mph for OD keeps the converter from locking at too low a speed and lugging the eng. I also did it to prevent the tranny from shifting from 3rd to OD while the converter was locked which I didn't like.

I think there is also a min coolant temp for torque conv lock-up. Can't remember for sure. It's been a while since I messed with that stuff.

I imagine you were looking for an easier fix, but this is the only way I know to address it without going to a toggle switch for the converter.

49m · 02-13-2006, 05:26 PM

thanks that is a option. Does anyone have the information on what inputs of the ecm effect the tcc controls. Such as tps and temp switchs ect.

Vader · 02-13-2006, 09:24 PM

The Emperor of the Ottoman, King of the Couch, Duke of the Davenport is correct. He just didn't elaborate.

The stock programming for an '86 LB9 with TH700-R4 will lock the converter as low as 13MPH under some conditions. There is/was a TSB regarding this, some other issues, and the proper repair for the "problem". The 1986 model year is the ONLY one with this problem.

Code:

PONTIAC			ROUGH IDLE, CHUGGLE, LOW SPEED.		Page:    1
86-6(GAS)-66									Issued: 10/17/86
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
1986 FIREBIRD VEHICLES WITH 5.0L LB9
TPI ENGINE (ENGINE CODE F)

New service calibrators (Ref: Called Mem-Cal In Shop Manual) have been
released for the 1986 Firebirds with the 5.OL TPI engine. These new
calibrators will address the following customer comments:

1.  "Rough Idle" on both hot and cold engine - the idle speed is raised to 650 
    plus or minus 50 RPM.

2.  "Chuggle or Shudder" at low speeds - torque converter clutch (TCC)
    engagement speed is raised to 41 MPH.

3.  "Hesitation" on light acceleration with a hot engine.

4.  "Cold Driveability" - New calibration eliminates light to moderate sag on 
    cold driveaway.

5.  "Service Engine Soon” Lights - Eliminates the following false Codes:

     A.   Code   32 - EGR System failure
     B.   Code   33 - Mass Airflow Sensor Voltage High
     C.   Code   34 - Mass Airflow Sensor Voltage Low
     D.   Code   43 - Electronic Spark Control
     E.   Code   44 - Lean Exhaust Indication

If normal engine diagnostics and repair do not correct the above conditions,
it will be necessary to replace the calibrator in the ECM.  Below is a listing
of the new calibrators and their usages.

ON AIR CONDITIONING (C-6O) FIREBIRDS

With  QYZ (P215/65 R 15/N 15" Tire) 		Use -  1228290  Calibrator
With  QAC (P235/60 VR 15N Tire)			Use -  1228291  Calibrator
With  QDZ (P245/50 VR 16N Tire)			Use -  1228291  Calibrator

ON NON-AIR CONDITIONING (C-41) FIREBIRDS

With  QYZ (P215/65 R 15/N 15" Tire)		Use -  1228292  Calibrator
With  QAC (P235/60 VR 15N Tire)			Use -  1228293  Calibrator
With  QDZ (P245/50 VR 16N Tire)			Use -  1228293  Calibrator

Use Applicable Labor Time and Operation Numbers.

1228291  Calibrator available $63.64 F.O.B. factory

The only sensor that affects this is the VSS for vehicle speed. The ECM does the rest by calculating engine load and shifting the TCC accordingly. The only real "fix" for this is to replace the defective programming. The factory upgrade calibration is better, but custom programming is far better yet.

49m · 02-14-2006, 01:25 PM

thanks for filling in between the lines.
The chip is avail. thru GM still.