I've got a 97 silverado with 111k that recently threw a P1870 code. After a bit of research, it seems this is a common 4L60 code and it was a problem in the valvebody that caused the computer to throw a converter slipping code. Seemed to be a easy fix by installing a transgo SK4L60 shift kit. Bought the kit and had the shop install it and picked it up this morning. It drove great all day, but after a bit of driving, it threw the 1870 code again. The shop had cleared it earlier. After driving some more, it would not down shift. When stopping at a light, I would have to pull it down to 2 manually and shift it on my own. Tried pulling it to 1, but it would still take off in 2. Wouldn't shift to 1 even if done manually. The transmission never had a lick of trouble, even when I dropped it off for the kit. The thing still works as far as shifting goes, but it has to be done manually. Is this a problem that the shop did, or is the trans. taking a dump?

 

The TG kit won't always fix the 1870. the Sonnax TCC Reg. kit is a much better solution. The Sonnax kit is a little more work, because the valve body has to be reamed first, then a new valve and sleeve are installed.
If the Sonnax valve doesn't fix it, then it could be an internal slip or a converter clutch. 1870's definition is "Internal Transmission Slip", although it's usually the TCC reg valve, I've seen other problems trigger it.

I'd atleast try having thre valve body fixed right, before condemning the transmission or converter. What condition was the fluid in when they worked on it? Did you have any black sediment in the pan? Can you actually feel the converter lock up when you drive it (before it kicks the 1870)? Does the transmission shift OK (before it kicks the 1870)?

Frank
CPT

 

The fluid was burnt. I had changed it roughly 12k miles ago and replaced the filter and it was good then. When I checked the dip stick, after the first code, it smelled bad and was dark. Noticeably burnt. Dipstick had some debris on it. Transmission shop said that the pan was realtivly clean. The code seems to come on when I hook my boat up and it tripped yesterday while coming to a stop light on decelaration. The transmission was doing great up til yesterday. Very smooth and responsive with the shift kit installed. It wasn't till a dragged my boat out and went about 15 miles that it threw the code and started giving me fits.

 

If the fluid smells burnt, you're probably looking at some internal transmission issues.

Frank
CPT

 

Just went outside to reset the code and releave myself from "limp mode" and decided to look underneath. My under carraige is covered in transmission fluid. This happened to me once before a long time when I put a little to much fluid in and pulled a load. I guess it built up pressure and forced it out the vent. I warmed the truck up a checked the fluid with the truck in neutral and there is WAY to much fluid in the tranny. I'd say it is roughly 2" over the hot/full line. "Could" this be a problem or am I just grasping for anything I can get..... BTW, fluid is coming from the vent.

 

Fluid will come out the vent for a couple reasons. Most common reason is the transmission over-heating. the other would be an internal pressure leak.
I can't figure out why you'd be over-full if you're leaking fluid, unless you've got a radiator problem. If the cooler, in the radiator leaks, you'll get coolant in the transmission. you might want to drop the pan and get a visual of the fluid, and check to see if it looks like a strawberry milkshake.

Frank
CPT

 

My guess is that there is way to much fluid in the case, coupled with high stress/heat causing it to over flow from the vent. On to another random test...... I cleared the code and went for a ride. It did fine for the most part, but it did get hung in second once at a stop sign and wouldn't kick down to first for the take off. I laid into the gas and it down shifted, ran up and chirped second like no ones business. When I got back to the drive way, I manually pulled it to first and goosed it, it jumped as it should. Then I manually put it in second, goosed it, and it just barely moved, as if it wouldn't go to 1. Put it in 3, it jumped as it should, and OD jumped as well. For some reason, when I put it in 2, it won't drop to 1, but all other gears will. Seems like something is fishy with 2nd gear......

 

Um...In trucks the 4L60E is designed to start out in 2ND gear when the gear selector is put in the manual 2ND range.

Frank
CPT