99 GMC K1500 old body, Transmission problem??

I have a 99 Sierra old body 4X4, 108,000+, that is acting up.

It is shifting HARD from 1st to 2nd and check engine light comes on.

The codes says transmission it slipping, but I am wondering if it is vacuum or electrical related.

If I stop and kill the engine, no problem for a while, but the vent damper will go nuts (open, close, open, close), then the transmision starts to shift hard again. If I leave the return air off, no problems, engine light goes out and runs smooth.

Ever heard of a problem like this? Help please.:confused:

I have a 1997 chevy p/u with a 4L60 transmission that is having the same exact proplems. I have found a site that says the problem could be in an external sensor. yet I canot locate these sensors, I do believe that this is what's causing the hard shifting problem. The site is www.usatransdoctor.com . If you can help me locate these sensors then please let me know. c s

I have a 1997 GMC K-1500 with the 4L60 tranny. It did the exact same things you are talking about. What you are looking at is a complete rebuild. Sorry guys no easy road here. Mine started acting up at less than 50000 miles. Finally asked around and was told the problem is very common for this tranny.

I have a 2000 c/k classic, same tranny, same problem. It is still under warranty however and I took it in. They diagnosed the problem as a tccp module. This module regulates the torque converter. It is inside the bell housing however. A complete rebuild is completely unneccessary. Sounds like somebody got screwed.:bandit:

Depends on exactly what the problem is. The 4L60e is computer controlled and there is a wide variety of things that can cause these problems. I've seen it be anything from the low and reverse clutches being burnt up to a simple shift solenoid to needing new valve bodies. It just depends as for sensors the 4L60e only has one external sensor everything else is inside the trans.

What is the code that's setting?? P1870 ?? That seems to be the most common one for late model 4L60E's. It's a generic code. Definition is "transmisson component slipping" Any time this code sets the computer goes to fail safe and raises line pressure. This causes the harsh shifts. More often than not, its caused by a worn bore in the valve body. Its controls torque converter lockup. The worn bore lets pressure bleed off and allows too much coverter slip.

I HAVE 2000 GMC 2500 4X4,HAVING THE SAME PROBLEM WITH THE HARD SHIFTING. I CAN SHUT THE ENGINE OFF AND IT WILL NOT SHIFT HARD FOR A WHILE. CODE SHOWS 1870. DOES ANYONE HAVE OR HAD ANY PROBLEMS SUCH AS THIS AND IF SO WHAT ACTIONS DID YOU HAVE TO TAKE TO CORRECT THIS? ANY HELP PLEASE. E-MAIL IS w4gfr@bellsouth.net thanks

I have a 1996 g.mc. with a 460E and when I am on the gas less than half way the tranny shifts fine, but when I get on it 3/4 throttle from 1st to 2nd, the engine drops down in r.p.m then 2 seconds later the tranny finially switches gears. Has anyone else heard of this before? Mike

ok yall on the 4L60E and the 4l60 to fix the 1870 code (torqe converter shipping) in the valve body the bore for the (pmw) valve has wear . i work @ a trans shop this is how we fix them you could replace the valve body but 50,000 miles later you will replace it again .on the pwm valve we put a larger sping and remove the old one witch this holds the valve close .it will have a frimer shift to it it will stop the valve from leaking down and it will not harm nothing yall try that and let me know ............tommie99

Help..........We changed the transmission fluid,filter and gasket now the our 1999 K1500 drive doesn't work correctly it acts like it is starting in 3rd.I shift thru the gears and they all work fine.What could it be

My 97 had same prob. Mine was shot but I have heard a few
people have luck with the bore kits when it wasn't too late.
For a couple days I had to keep pulling over and shut the truck
off for a minute to fix and would be OK until I went over 40MPH
again. There's lots of info on the web. Google the code.
$1600 for my rebuild & TC

I own a 1999 Chevrolet express van with the 4L60E transmission now its 120k miles but when was about 80k miles its started to abruptly shif up from 1st to 2nd gear, it happens when after a long ride over 50mph or a fast acceleration (full) when go back to lower speed and accelerates again its shift abruptly to the next gear either 1st to 2nd or 2nd to 3rd and at the begining of the problem the "service engine soon" lamp went on and from them numerous times i made checked with the dealer an at diferent shops but the problem persist because here in mexico they are not well trained according to gm mexico, in february after a long trip (1000 miles), in the way back the tranny burned up and overheated my radiator that broke up due this, I took it to the shop they changed the cluth, disc, belts inside of it (supposedly a kit that its sells to reapir a tranny) and the torque converter the problem dimished but not gone at all the light and the codes 161 and P1870 still go on. I visited other shop I was told to put a new valve or a valve presure regulator, It will fix the problem. Has anyone done any of this? Is this a good solution?

p1870 can be caused by the valve body bore for the tcc apply valve wearing out of round, this causes the tcc to slip when applied, this then boosts line pressure, a full scan with a trans function scanner is needed here before anything else is done, as it would be guess work. 161 is missing a number somewhere. BTW, start a new thread in the future when you see it is a month old, this one was about done. Stay here for now. BTW this has been going on for almost 9 months and it seems I have given you the same advice before and it keeps coming back, do what I said , lets cut if off until the diagnostics are done.