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Discussion Starter #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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what is a stak

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
 

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Discussion Starter #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.
 

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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.
 

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Just use a big nail and a hammer and make a divot in the valvebody like in the pictures.

Man, and don't take this wrong, but you need to work on your typing. I'm having a real hard time understanding you.
 

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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?
 

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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.
 

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i would tackle this mod but wut is LOCK UP?? i keep thinkin you meant to lock the tranny so it wont change gears. anybody wanna explain this to me like a 2 years old?
 

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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.
 

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i would tackle this mod but wut is LOCK UP?? i keep thinkin you meant to lock the tranny so it wont change gears. anybody wanna explain this to me like a 2 years old?
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.
 

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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
 

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Fix it right with the Sonnax kit. Once you're done, sell the reamer on ebay and recoup your costs.
 

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Does the Transgo kit need the reamer as well or just the sonnax kit? Don
 

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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.
 

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