1870 Trouble Code Valve Body Replacement

Moderators: If I've covered something that has been covered better somewhere else, then please delete this thread.

I realize that there have been dozens of threads regarding this problem, and there have been quite a few replies as to how to diagnose and deal with this problem, but I have'nt found anyone posting pictures of how to go about it. I had the problem, bought a replacement valve body control, and took pictures of the process of replaceing it. I'm not sure I did it right, cause my mechanic friend wasn't availabe to help, but hopefully this might help other people with this situation. To qualify, I have a 1996 Chevy Blazer, 4 door, 4X4. You'll probably want to replace the oil filter at the same time, and it should come with a new gasket for the oil pan.

The first advantage I had was access to a hoist. This could be done on blocks, but would be fairly messy and awkward. Once the truck is up in the air, the oil pan will be visible between the exhaust pipe of the exhaust and the transmission cross member. See Picture 1.

Thumbnail Image

The bolts are all 13mm but the two holding the brace for the cable from the transfer case, which are 10mm. One of these is very difficult to get to, but if you have access to a wrench with a wratchet end, it will save your knuckles a lot of skin. There has been many post on how to drain and drop the pan, so I'll be brief. Remove all the bolts except those on the corners. then loosen one corner (I picked the right front because it had the most room) as much as possible before it comes out. Then loosen the other corners slightly to tip the pan to the one corner. This will be very messy so have a pan ready to catch the oil. Once you have drained as much oil as possible, gently remove the pan the rest of the way, and drain the rest of the oil. Its a good idea to check the magnet on the bottom of the pan for debris. If there is a lot of debris there, then likely the problem is bigger than just the valve body.

Thumbnail Image

Now the oil filter should be visible. It just pulls straight down. Once the filter is out of the way, the valve body will be visible. Picture 2 shows the valve body with the electrical connections circled in yellow unplugged. The solenoid circled in red should probably be removed first, just to make things easier. I removed it last, and it was a bit awkward. Be careful to watch the pin underneath it. Its held in by vacuum, and it released on be after a couple of minutes, fell in the oil pan and scared the crap out of me. It can be reinserted by simply pushing it upward. It will stay in place once you push it up.

Thumbnail Image

See picture 3. Most of the bolts holding the valve body up are 10mm sockets, 47.5mm in length, but there are 3 10mm bolts that are about 60mm long, shown in picture 4 coloured in blue. The bolts coloured in yellow are 8mm sockets, 54.4mm in length. Its extremely important to make sure that these bolts are returned to the proper position. Placing a bolt longer than 47.5mm in the position circled in red will cause the sun shell to be jammed. There are 2 short bolts (Picture 4) on the passenger side.

Thumbnail Image

Be careful lowering the valve body. There are 7 check balls that sit on top of the valve body, and if you tip it too much they will fall out. Picture 1 shows the check ball placements. I just placed the two valve bodies beside each other and moved them from one to the other.

Thumbnail Image


Thumbnail Image

Picture 2 shows the plate holding the separator plate up. There are 3 bolts on it. You probably could remove this plate before the valve body, but I elected to leave it till last because there is one check ball that rests on top of the separator plate.

Thumbnail Image

Picture 3 shows the placement of the checkball on top of the separator plate. Note that the correct placement is the one with the red arrow. Where the ball is circled in yellow is not the right spot. I bumped it off, and put it back in the wrong spot. I figured it out because it won't fit there, and I rechecked my diagrams. You should have new top and bottom gaskets for the valve body before you put it back on. I put it back on with the plate first, then the solinoid.


Thumbnail Image

Picture 4 shows the linkage that needs to be connected before the valve body is mounted. Once this is connected, mount the valve body with the bolts. Be sure to put them back in the correct places! After all the bolts are in place, reconnect the electrical plugs, and put the new oil filter back in. If the seal is still good, the new one isn't necessary, but you should check it carefully. The last picture shows everything reassembled. Its probably a good idea to prime the gasket for the oil pan with a little new oil before you put it on with the oil pan. Make sure to put the bolts on with the proper torque.

Once everything is back together, fill the transmission with new oil. Make sure to check the oil level again after driving for a while to make sure everything is proper.

Hope this helps!

quote:

The solenoid circled in red should probably be removed first, just to make things easier.

That should be the 1-2 Accumulator, and it should be part of the valve body. Put yes, it has a big spring in it and can stick to the plate via suction. You didn't hit your head and were wearing safety glasses right?  
 

quote:

You probably could remove this plate before the valve body, but I elected to leave it till last because there is one check ball that rests on top of the separator plate.

One ball to find is much easier then 7. I prefer to drop the plate with the lower valve body, unless you dont need to remove it. I also highly recommend you put something on the floor so you cna put the valve body in it immediately, and make it big enough that the sides of the box are taller then the valve body. There is good news, you don't need all those checkballs. certain mods call for the removal of them and the latest veriosn of the ATSG manual will give you all the info about the checkballs and which ones to keep. I highly recommned using vaseline to haold the balls in place unpon reasembly.

And  at the big red shower. Two words, drain plug. Install one while you got the pan off.


Sorry, just having a little fun. Excellent write up so far. Keep it up. You are doing a good job.

What was accomplished with this repair?  Did you replace the valve body with the updated valve body or did you ream the TCC isolator and/or regulator valves?

I have created a new post in the DIY section with the book diagnosis of P1870 and the TSB noting the updated valve body as well as a link to a manufacturer that sells the reaming kit for these valves.

Sorry if I forgot to specify why I did this. I was having the typical 1-2 hard shifts after driving for more than half an hour, and it was setting the code P1870 - Transmission component slipping. I replaced the valve body with a rebuilt one using the new TCC isolator and regulator valves. I didn't do the reaming myself.

Thanks for the tips. Hopefully I'll never need them again, but maybe someone else will. As you can tell, I'm not a mechanic, nor do I have a ton of mechanical experience. I'm just hoping that I can help others out. I searched the forum and found lots of info on how to diagnose the problem, for which I am very grateful. The problem is that I found very little on how to actually do the repairs. If my search was inadequate and the information already exists, I offer my most sincere and humble apologies for double posting.

No worries man!  Its always good to have pictures of  an open tranny.  I helped a fellow member install a shift kit in his truck a long while ago and that required the same work.  In the write up we didn't speak to the bolt lengths and such.

I try not to do write ups on tranny service work. I'll post up tips on how not to screw up a fluid change, and did a write up on how to remoce one, but that is about as far as I go. An auto tranny is very complex, and packed full of ways to FUBAR it.
 
I think what you posted is very good, and well done.