no 4th, code 1870 ??
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From: Missouri
no 4th, code 1870 ?? For a while now my converter has been locking and unlocking in 4th at the slightest increase in throttle. At steady throttle it would stay locked most of the time, but it has progressively got worse. Today it was in and out, in and out then the check engine light came on and it lost overdrive. When I came to a stop then took off it was in some kinda limp mode. Made it home, let it sit about 30 minutes, then when I took off again it was OK except it still doesn't have 4th and the cel was still on. What could be wrong? (this is a 4l60e)
You have the notorius 4L60-E TCC Regulator bore wear. The torque converter clutch regulator valve is short and sliding back ad forth in the bore wears out the valve body. The resulting fluid leakage past the valve causes poor TCC apply which leads to slipping, and finally setting the slip code, P1870.
The transmission does not need to come out to fix it but the valve body does. You have three choices. I arranged them in the order I would do them to solve the problem.
1. Buy a TransGo shift kit. It comes with a redesigned TCC regulator valve that will cure the problem as long as the wear isn't too severe. (It has worked for me 3 out of 3 times with 3 trans)
2. Sonnax makes an oversized valve that requires reaming the bore in the valve body with their tool.
3. Buy a new Valve Body.
The Torque Converter fluid circuit is not related to the band and since you still have second gear I'm going to guess that overdrive was being prevented by the computer. Once the TCC regulator is fixed it should be good.
The transmission does not need to come out to fix it but the valve body does. You have three choices. I arranged them in the order I would do them to solve the problem.
1. Buy a TransGo shift kit. It comes with a redesigned TCC regulator valve that will cure the problem as long as the wear isn't too severe. (It has worked for me 3 out of 3 times with 3 trans)
2. Sonnax makes an oversized valve that requires reaming the bore in the valve body with their tool.
3. Buy a new Valve Body.
The Torque Converter fluid circuit is not related to the band and since you still have second gear I'm going to guess that overdrive was being prevented by the computer. Once the TCC regulator is fixed it should be good.
I had that code once..........about 2 days before the TC lock-up plate came apart!!!!!!!!
James B........wish I had known that info then.
Either way, it is a serious problem, you need to have checked out/fixed
James B........wish I had known that info then.
Either way, it is a serious problem, you need to have checked out/fixed
Launching!
Joined: Jun 2004
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From: Mooresville, NC
P1870 won't cause 4th gear to be inhibited unless its in "hot mode".
The P1870 code is a diagnostic which uses calculated TCC slip. Since 4th gear is applied shortly before the Converter is locked up, the PCM may perceive the slipping 4th gear as TCC slip.
I would install the TransGo kit, with Vette servo (if you don't already have) and use the "D" ring seals (will help with 4th gear). The TransGo kit will fix the problems with the TCC regulated apply valve issues that usually cause the 1870 code and may help the 4th gear if thats the problem.
The P1870 code is a diagnostic which uses calculated TCC slip. Since 4th gear is applied shortly before the Converter is locked up, the PCM may perceive the slipping 4th gear as TCC slip.
I would install the TransGo kit, with Vette servo (if you don't already have) and use the "D" ring seals (will help with 4th gear). The TransGo kit will fix the problems with the TCC regulated apply valve issues that usually cause the 1870 code and may help the 4th gear if thats the problem.
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OK, after I cleared the code it started working fine again (except for the in and out business that I am sure is that bore being worn. I haven't driven it more than a couple miles but I am convinced the tranny itself is fine.
I have another tranny that has a known good valve body so I took it out and cleaned it up real good today-If I get home from work in time tomorrow i am going to swap them out. This other VB already has the PWM mod so I am hoping for some good TCC action. I will post the results once the job is done.
I have another tranny that has a known good valve body so I took it out and cleaned it up real good today-If I get home from work in time tomorrow i am going to swap them out. This other VB already has the PWM mod so I am hoping for some good TCC action. I will post the results once the job is done.
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From: Missouri
Changed the VB last nite. It was raining harder than I ever saw it rain, so I couldn't tell much on the test drive. I made sure it was full of fluid, closed the hood and drove it 1 hour to work this morning. As soon as I got on the interstate I noticed it was doing the in and out converter thing. But it had 4th and at steady throttle all seemed well. Then about half way to work it lost 4th again and the converter unlocked for good. On my lunch break it started slipping really bad in low, to where it wont even take off. If I take off in manual second and shift to 3rd it works ok, but I really dont expect to make it home. Guess it is time for the trans to come out now !! This sux.
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11 Second Truck Club
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From: Missouri
So is this "Transgo Kit" the performance shift kit, or on of those "fix" kits that tranny shops use? I am in the process of rebuilding and trying to decide what to do on the valve body. I was quoted $168 for the bit to install the Sonnax valve. Dont wanna spend that much if I dont have to.
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From: Missouri
It already has a Level 10 shift kit, plus a hodge-podge of other mods-blocked pwm isolator valve, etc. I really don't need a performance shift kit. Is the Transgo valve available separately?
On The Tree
Joined: Jul 2003
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From: Wesley Chapel, FL
I have the Transgo shift kit in mine with an SY3500 and it started doing the lock/unlock on the interstate at about 70mph. It through the P1870 code. So does this mean I need a new valve body? 
I've got about 79k miles on it now. 
I've got about 79k miles on it now. 