tcr1016

I have a 97 GMC 1500 with a 5.7L (4L60E trans) with 150K miles on it. I keep getting a 1870 pending code, but no engine light goes on. It shifts hard from 1st to 2nd gear. No slipping. It only gets the code when driving alot in one day like 100 miles.

If I add tranny fluid it goes away for awhile. Tranny may have over a quart extra fluid, since I add some when it goes off. It also goes away if I hook up my scanner and clear the code.

I had my pump seal replaced about a year ago. What can it be that causes it? I tried changing the fluid and it still does it.

What is causing it, and how do I fix it??

Thanks

tymr287

The valve body is worn out.

tcr1016

Will it hurt the tranny if I don't fix it right now? Also is it ok if I have about a quart or 2 over filled in the tranny?

Jeff Collision

P1870 indicates that there is a slipping component in the transmission, and most often, it's the torque converter clutch that is slipping. This was a very common problem in these models. There is a bulletin from GM that talks about it, and the fix was to replace the valve body in the transmission. 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 applies. Install a control valve body with the revised TCC regulator and isolator valves.