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What does "P1870" mean?
P1870 is the DTC (diagnostic trouble code) displayed by the computer when a compenent inside the transmission is slipping. If your SES (service engine soon) light is on, use a diagnostic tool to scan the code to verify this is the trouble code you are encountering.

What exactly is this problem, anyway?
90% of the time when our cars throw this code, the 1-2 upshift is slipping. If this is happening, it will be quite obvious. The 1-2 shift will no longer be smooth, it will delay a moment before slamming into gear. This happens when a valve body inside the 4L60E sees wear over time and starves the transmission for fluid. Essentially, the TCC (torque converter clutch) locks up. This problem should be dealt with immediately, as the slipping can cause metal shavings to circulate through the transmission and cause further damage.

What are my options to fix this problem?
1. What are my options to fix this problem? Before spending any money, check simple things first. Check your transmission fluid level. Low or dirty transmission fluid can often be the culprit. If the fluid looks clean and is full, fluid is most likely not the cause of your transmission slipping issue.
2. What are my options to fix this problem? If you are experienced in transmission work, check the adjustment on the intermediate band. If the intermediate band is incorrectly adjusted, this can cause slipping as well.
3. What are my options to fix this problem? Rebuild the transmission. Although the most expensive fix, a full transmission rebuild could be the best fix for you if your car is high mileage and you plan to keep it a lot longer. If you've got 150k on the transmission already and plan to keep it for another 100k, you will be needing a rebuild in the future anyway. Be sure to repair/replace that valve!
4. What are my options to fix this problem? Replace the transmission. You can usually find used transmissions for relatively cheap. Although this is often cheaper than rebuilding your transmission, be careful in selecting a used transmission. You could easily wind up with one that has the same problems as your current transmission.
5. What are my options to fix this problem? Install the TransGo shift kit made for the 4L60E. Now, I'm sure most of you are thinking, "How would performance parts help me in this situation?" Simple! The shift kit applies a lot more pressure to the band and other parts of the transmission, helping eliminate slipping. Part of the shift kit also repairs the part on the valve body that initiates the transmission slipping problem. This is ideal if your car is not high mileage or you wish to fix this problem without spending an arm and a leg. This is the most often used method for fixing a 4L60E with a P1870 code. See our various sponsors for more information on the TransGo shift kit!

I have chosen a fix, but I am addicted to modding my car... What else can I do?
So, you're addicted to modding? Great! There are various things you can do while fixing your P1870 code.
- If rebuilding the transmission, you can use high performance parts available through most transmission specialists.
- If replacing your transmission as a whole, there are various companies that offer fresh racing transmissions for street or strip use.
- If installing the TransGo shift kit, use the level 3 setting. This offers the best performance out of the package by applying the most pressure. This is also a good time to consider a corvette servo. This is another automatic transmission modification that applies more pressure. Best part is, it's cheap!
- No matter what method you use to fix your transmission, it is always a good time to consider a transmission cooler. Although a debatable performance modification, a transmission cooler will help prolong the life of your automatic transmission. Heat is deadly to automatic transmissions and a transmission cooler, available through many of our sponsors, can help prolong the life of your investment.

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