Alright guys. In my T/A I have a FLT Level 4 and a Yank SS4000. Been running great and not a issue once since I put this combo in back in Feb of this year. I've put about 8k on it since then. Twice on a drive back from Frisco, TX back in March the lock up just unlocked while cruising at 80. Each time it happened I just backed down to 70 for a couple minutes and then it locked up again. Back in July I had the same thing happen on a 2 hour drive back to Arkansas, again I was running 80-85 when it did it. I backed off for just a minute or two and it locked up again. Did not do that again the rest of the trip or on the return trip home. Been just fine since then. I went ahead and had my tuner go over all the tables/files and everything was fine, I.E there was no way that my TPS % was close enough to cause it to unlock those times and I was not pulling a grade etc. It had not unlocked while cruising down the interstate until last month when it did it again. Repeat same secenario. All is well until last week. Friday night I finally hit the track. Made two n/a runs. I decide to make a n2o pass. I have sprayed this car 3 times on the dyno and twice on the street. The street runs were just through 2nd gear and I only let it shift into 3rd one time. On the bottle pass at the track I don't hit the juice until about 80ft out and 50ft before the finish I'm on the limiter.

Monday morning it wouldn't lock up on the way to work. Let the car sit from 8am until 1pm and I go take it for a spin, it locks up just fine, go back and let it sit until 6:30 when I leave. Whole way home you'd have never known anything was wrong, locked up like it always has. Tuesday morning on the way to work and home it never acted up, was perfect. Wed. morning I drive to work, won't lock up, BUT it throws a P1870. Clear the code drive again, no lock up, but doesn't throw the code. Drive it a couple times that afternoon, still no lock up and no codes. Drive it home Wed night, still nothing. I have to drive it(10min drive) Thursday morning, still no lock up and or codes. I have the pan pulled to change the filter and fluid and also look for any clues. Nothing, fluid looks great, but there is what seems to be some very, very small pieces of clutch material in there, mechanic says nothing out of the ordinary for a fresh trans. Drive it back to the store, no lock up, code pops up again (P1870). Clear it and drive around the block again, nothing. So Friday I have my tuner take a ride so we can command lock up. We get nothing. Car shifts fine, goes thru all 4 gears as it should, all parameters are met for lock up. I've changed plug wires, plugs, triple checked the brake switch, wiring, vss is working as it should. Still no lock up. I did not replace the TCC solenoid yet is all I haven't done. I pulled the trans and the converter is now back at Yank to be inspected. I've checked the fluid with it sitting on the bench and I can't find any debris in it and there wasn't any in the old filter. O-ring on the shaft of the trans is also mint, looks brand new still.

Is there something I'm over looking?
Should I go ahead and send the trans back to FLT and have them go through it? Help me guys if you can think of anything else to look for.

 

General Motors Informative
GM service bulletin about code p1870 - GM service bulliten about code P1870
Posted By: NJBOB on 2/28/2006

Location: Collingswood, NJ

This GM service bulliten might apply to your vehicle:

TSB # 01-07-30-023A
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body)
1996 Buick Roadmaster
1996 Cadillac Fleetwood
1999-2000 Cadillac Escalade
1996-2000 Chevrolet Camaro, Corvette
1996-2000 Pontiac Firebird
1996-2000 Chevrolet and GMC Light Duty Truck Models
1996-2000 Oldsmobile Bravada
with 4L60-E Automatic Transmission (RPO M30)
Built Prior to January 15, 1999 (Julian Date 9015)
This bulletin is being revised to update the Parts Information

Please discard Corporate Bulletin Number 01-07-30-023 (Section 07 -- Transmission/Transaxle).
Condition
Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated.
Diagnosis
Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs.
The scan tool may show a DTC P1870 set as a history code.
A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93°C (200°F).
Cause
The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply

Important
DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code.
When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result.
This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle).

When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code.
When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL).
Correction
Install a control valve body with the revised TCC regulator and isolator valves. These valves are used in all transmissions produced after January 15, 1999 (Julian Date 9015), and all of the service parts currently available through GMSPO contain revised TCC regulator and isolator valves.

Important
If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body.

Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears).
The torque converter is not blue or overheated.
The transmission fluid is not burned or has no burned odor.
The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments

 

Immature P1870 can inhibit lockup for the remainder of
a key-on cycle but you need multiple to set the code.

I had similar (worse) behavior on my TCI Streetfighter.
The short term solution was to bump up the line pressure
at light load. At the time I jacked the force motor table
to do this, bringing 0% current down to 900mA. The
PCM commands 0% line at cruise and stock pressure
can be too light for a small diameter clutch. I've seen
an occassional complaint from SS series converter folks
in this vein.

There are line pressure adders for locked-TCC that
are available in some OSes. That would be a cleaner
way to go. But the modified force motor table has been
OK for me, for 20-30Kmiles now.

 

something is stuck. rev it up to 3000 rpm in neutral, and with your foot still on the gas, shift it to drive a couple times...that should clear up any issues

 

And scatter parts everywhere.

 

Thank you sir. I'll pass this along to my tuner once I get the trans. back in.

 

misfires will make it unlock but usually throw a code and can be felt plus you could still command it to lock up if that were the case so scratch that.

 

Now if this "Level 4" trans is vacuum modulated, the
tuning angle may not help (though you should still
make TCC PWM be 99% all the time). Don't know if
there's a "****" in vac-mod setups that can raise the
minimum line pressure at high vacuum.

 

I have the same thing going on... did you ever find out anything helpful?

 

I sure did. It was the converter clutch itself. Was burnt.