I have been having some problems with the trans in my 1999 Suburban K1500 (4L60E). I've been having the ocasional hard shifts between 1-2 for a couple of months. Yesterday, I noticed some hesitation shifting from 1-2 under full throttle. I'm not sure if I would call it slipping or not. From a stop at full throttle, it would accelerate fine until 4000-5000 rpm and would then sort of hang up and not shift. It didn't feel like the rpm's were climbing without acceleration, just sort of like it lost power. I know I need to replace the fuel pump and filter, so I'm wondering if that's a potential cause. Once I let off the accelerator, it shifted to 2nd. I did this a couple of times, each time with the same result. Today I ran the codes and came up with 1810 (trans fluid pressure valve position switch circuit) and 1870 (trans component slipping). The 1870 didn't surprise me, but the 1810 has me a little worried. I cleared the codes out of the computer, and now it seems to shift like it used to. I've got 100,000 miles on the truck, so I know a trans rebuild is coming soon, but I'm hoping to get a couple more months out of this so I can get the money together. I'm planing to replace the trans fluid and filter tomorrow. Any ideas other ideas or advice?

 

A bad pump or fuel filter can cause what you are describing.

 

I have a 2001 blazer with a 4l60E transmission I have the exact same problems with the shifting and RPM as you described and I changed out the pump witch was dead along with fuel pressure regulator high pressure return line and the fuel filter I still have the same problems but all that had to go anyways i bought it used check the shift solenoids in your transmission i cant get them in tell tomorrow will check back on here and let you know how it went
segamaster

 

RESULTS on this...poss same issue!!