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1870 Fix - 4L60E "TCC Mod" 95/6 -> 94 also fixes P1870

43K views 25 replies 11 participants last post by  roger55 
#1 · (Edited by Moderator)
Got a P1870 in your '96?

(Updated 10/1/2019 by Sherlock9c1 because the old "stake or block the valve" method would balloon the converter and wear the crankshaft thrust bearing.)

Why? In 1995, GM added a second control solenoid to the 4L60E Torque Converter Clutch (TCC) to allow them to better control the way the torque converter clutch lockup felt. The original on-off solenoid still enables lockup, and the new solenoid (the "apply" solenoid) controls a slide valve in the valvebody via "pulse-width modulation" (PWM)- what that means is that the solenoid is turned on and off rapidly but the time "on" and the time "off" are varied like a fuel injector (like "duty cycle") to control the amount of fluid released by the solenoid, and this controls lockup. Smooth shifts are easier on the drivetrain with little loss in performance.
That said, the valvebody valve acted upon by the PWM solenoid tended to wear the bore and cause problems. GM techs figured out that if the valve was staked in the full-open position, the code would go away. The downside of that fix was that now the torque converter becomes pressurized with transmission line pressure, which can go as high as 250psi at times. In a properly functioning 4L60E, lockup pressure should really be around 100psi or so. Given the size of the torque converter, this much higher pressure can physically distort the case of the converter and cause other problems.
Sonnax developed a repair kit for this, which includes improved valves and a special sleeve which not only eliminates future bore wear, but improves the valve structure themselves. It is P/N 77754 (pay attention as there are suffixes for the different aspects of this fix)).
One thing to note is that you will have to remove the valvebody and also purchase a reamer tool which is not cheap (~$85). You can always sell this tool on ebay once your done, or charge four friends $20 each and fix theirs while you're at it, then you're back to zero.
 
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#4 ·
u mention that i can stak the pwmin a 95 0r 96 4l60 tranny and put it in a 94 it seems pretty easy too, but how exactly do i get the spring to not move out when i replace the pan
sherlock9c1 is the user to posted this fix, i just saved it after the forum crash... you may want to pm him.
 
#5 · (Edited)
google "stake" - all you're trying to do is just lock the valve in place. You can do it any way you want; take the valve out and replace the spring with a screw that's the right length, doesn't matter (just leave some room for fluid to flow in the bore).

But the easiest way is just to move the valve with a small screwdriver, then whack the sides of the valve bore with a pointy-tipped punch so the metal mushrooms out and locks the valve in place. You can see it in the picture.
 
#8 ·
Would there be any reason the valve would not move?

I'm getting an 1870 code, Shane mentioned he might have missed staking it. Pulled the pan and sure enough no stake. I cant get the valve to move towards the outside of the valve body at all. It also seems like the TC is locking up randomly at idle and low speeds.

Now that I have the pan pulled, I cant get a hold of anyone at CPT for advise. Anyone?
 
#10 ·
Been trying 336-294-8100 with no luck.... Slapped it back together and issues still. After it warms up, putting it in drive at an idle stalls the engine. At slow speeds it feels like it's dragging the engine when I coast when it's hot. It seems fine when it's cold, happens after I've been driving 10-15 miles. No CEL yet, no fun when it's a daily driver.
 
#15 ·
Lockup referrs to the torque converter (TC). Think of a TC as two halves of a grapefruit - one half is attached to the engine, the other half is attached to the trans. The halves spin in fluid. The engine turns it's side and the drag in the fluid spins the other side. Since there is no hard mechanical connection between the two sides, the shifts feel softer and happen without any mechanical fuss, such that you would get with shifting a manual without disengaging the clutch. Lockup happens when at a somewhat predetermined speed (normally approaching highway speed in top gear), the two halves of the grapefruit grab together and act more like a conventional clutch. It reduces the drag in the drivetrain at highway speed and gives better fuel economy as a result.

This is oversimplified and maybe not totally correct, but you should get the basic idea. Lots more and better info on the internets.
 
#14 ·
Just got the code. Thanks Wolf/Sherlock for the fix.

It's running a little hotter since the code too. Used to NEVER go over 1/4 even on the hottest days, now it creeps up over 3/8 pretty consistant, got up to 1/2 once. Not whining, but that's just a big delta that's coincidental with the code and wondering if connected.

This is with rebuilt original '96 tranny with many upgrade parts and 3,000 Edge. I did the full Transgo kit too - but still got the code.
 
#16 ·
can't see the pictures

any chance the pictures could be reposted on this stake mod. I am going to do it to my 95 4l60e and wanted to be sure I have the valve in the right spot before i do it..

thanks,
Dan C.

1972 Buick GS imposter with a 95 lt1 and 4l60e.. still in the retro modding stage.:D
 
#19 ·
Be careful what you're referring to. The Transgo 4L60E-HD2 kit does not need a reamer. The Sonnax 4L60E-HP-01 kit (a fantastic kit) doesn't either. Sonnax makes a new valve and reamer separately that fixes the leaky bore.
 
#20 ·
#21 · (Edited)
Sorry I didn't see this earlier. For what that auction is selling, You might as well just get the 4L60E-HP-01 kit from Sonnax. It has all those parts and is better engineered. The boost valve alone is definitely worth the difference.
 
#22 ·
...

Finally, if you're putting a '95 or '96 transmission in a '94 vehicle, the '94 electrical system doesn't have provisions to control the PWM solenoid and so you will have no lockup at all if you leave it as-is.

1. Leave PWM solenoid INSTALLED - very important.

2. On the valve directly to the right of the PWM solenoid – push that valve all the way towards the outside of the valvebody. That is to the left in all the pictures here. I used a small pick on the spring to force the valve out.

3. Then, hold the valve in position and stake it into place on both sides. I've shown one side but both sides of the same valve should be staked to guarrantee it doesn't move under pressure.

That’ll lock down your PWM function and it’ll function like a regular lockup. No PCM reprogramming required.
Hi. I need some help here. I stumbled upon your information and realized I need to make this mod.

I have an LT1 engine and transmission out of a 1996 Impala SS installed in my 1983 El Camino Choo Choo SS.
But, I'm controlling it with an ECM out of a 1994 Firebird. I had Fuel Injection Specialties make a custom harness for me as I didn't get a harness with the engine or ECM.

I bought this engine/transmission new (factory takeout supposedly) in 1997 and installed it in the El Camino that same year. I've only driven it 20K miles since then. But it looks like those 20K miles have been driven with the torque converter not locking up according to your information. Almost all of those miles have been around town but I've taken 200 mile trips maybe 6 or 7 times.
I'm hoping I haven't damaged anything. However, the transmission still seems fine and has never set an 1870 code.
But, I did one of those 200 mile trips just last week and noticed for the first time that there was a slight odor of hot transmission fluid after pulling the car into the garage and shutting it down. I didn't notice this on the previous trips I took but maybe I didn't immediately put it in the garage like I did this time.

Now that I've found this thread, I'd like to make the necessary modification I need. You refer to pictures you've posted but I don't see any. Where can I get those?

Can I do this job by just removing the pan? Or, do I have to remove the valve body too?

Roger
 
#23 ·
Roger, most of those guys don't come on here much anymore....we've kind of moved over to facebook. But, we've got a really, really good 4l60e guy right here in town...JD over at Ernst Automotive on S Bell Street is really smart and won't mind helping. He's built several for me and a lot of the other racers in the area.
 
#24 ·
Thanks. Good to know. I may need him on this.

I did get a PM from sherlock9c1 and he said if I got a kit from Sonnax and installed it, that would take care of my issue.

Pretty sure he was referring to the Performance Pack that they sell. I downloaded and studied the instructions but I'm not quite clear on it all. JD might help me there.

I'm also unclear about whether the Performance Pack can be installed with the transmission in the car. I think it can but not sure. In any case, I may not tackle this job until spring. I've got a lot of things on the table right now. At the very least it will need my full attention. The only thing I've done internally to an automatic is install a shift kit in a Turbo 350 and that's been about 40 years ago.
 
#25 ·
You can do it in the car but getting access to the servo on the passenger side is tough with the factory B-body catalytic converter. There might be a part or two that require transmission removal and disassembly to install (the pump slide spring comes to mind), but they are not mandatory to install.
 
#26 ·
Well after a year and a couple of months of putting this off and barely driving the car at all, I just got this done and wanted to thank you. It worked great! My '96 tranny is now working perfectly with the '94 ECM.

I decided to do it with the transmission in the car. It worked out just fine. I pulled the valve body, put in the new Sonnax TCC valve and installed the plug in the separator plate. I decided to not use any of the other parts in the Sonnax Performance Pack kit except I did install the 8 plastic check balls it came with.

I did a complete flush of the fluid and I just test drove it and now I can feel it shift 4 times. So the TC is locking up now!
 
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