1870 Transmission Component Slipping

I have a 1997 Blazer 4/4 and every so often my tranny will shift hard, and then go away... if I restart my engine. Note: the SES light will remain on and no codes can be recovered. However, if I don't shut off the engine then the 1870 code is detected. So what's causing this?

The tranny seems to be working properly 99% of the time, and the Tranny shops (I talked with two) want me to drive it some more so that a "hard failure" can help them pin point the problem. Personally, that does not sound like a good idea to me.

However, now that I have read a few other threads... (this is a great site) I think my problem sounds like my TCC solenoid may be the culprit. Can someone tell me how to change out this part next week when I get my Tranny flushed properly!

NOTE 1: THIS PROBLEM STARTED WHEN I LET MY MECHANIC CHANGE TRANNY FLUID. He later told me he did not have the equipment to change the torque converter fluid. Then he sold me some JB Tranny stuff to see if that helps my shifting problem . It didn't work.

NOTE 2: I get the feeling the SES goes off more often when I drive long distances, so I also think this has something to do with the "lock out" feature I read in other Threads; however, I'm not sure how all this is related.

It would be great if someone can clarify for me what I can do cheaply to possibly fix my hard shifting problem which is intermittent at best.

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Here's a good comment, which I took from another thread, that seems to describe my problem:

a) A low input TPS code (P0122) will set off an intermittent SES light. This will inhibit TCC lock-up on the transmission, which will give you the P1870 code, excessive component slipping - the TCC. The computer will then, by default, set maximum line pressure for the transmission, which will most likely give you the hard 1-2 shift. The P1870 will also inhibit fourth gear from applying.

Yup, check connections, at computer and at the TPS. If you know how to check the TPS with a voltmeter, that would be a good idea, but it most likely needs to be replaced. Clear codes, take it for a spin and see what happens. Tranny flush is a good idea, fluid and filter.


Question 1 : Where is the TCC Solenoid? Is something a fluids shop like Jiffy Lube can do. They seem to have the right tranny flush equipment in my area.

Question 2: Do I need to get that JB Transmission additive out of my Tranny ASAP or is it a good additive? (Personally, I have use Lucas oil additives and I find them to be a good product. BTW, Lucas makes a Tranny additive... Any comments on using it?)

...One more comment: I did change my Ignition Switch (Cable).

I think it is possible to somewhat accurately check the function of your TCC solenoid by driving at a steady speed of about 50 mph on a flat surface with the engine at normal operating temp and then slightly depressing the brake pedal (just enough to make the brake lights come on) while keeping your foot steady on the gas. The TCC solenoid is supposed to unlock your torque converter clutch and your engine speed should jump up a few hundred RPM. When you let off the brake, the RPM should jump back down as the TCC locks up again. If this is not happening, then it follows to troubleshoot the things that might prevent proper TCC operation. For myself, though, if I only started having problems after someone else changed my trans oil, I'd start by checking to make sure the level was right (correct it and road test if not), and if it was then I'd go ahead and drop the pan to see if anything obvious was wrong, like maybe the filter isn't installed correctly or the seal that the filter slides into is damaged or some wiring was damaged or something. Hope this helps a little.

Did the mechanic change the filter when he changed the fluid?

Yes... The filter (Fram) was changed when they dropped the pan.

Question 1: Where is the TCC solenoid? Is it in accessable in the pan or does a Tranny Shop need to pull the tranny to address this problem?

Question 2: My fluid is about 1/2 quart high. (Probably from the additives I put in.

Question 3: Should I change the fluid again just to get the additives out?

Did you top the fluid up and check the ride again?

It is possible that when the mechanic dropped the pan, he had to pry it off. I spoke with my mechanic after my failed attempt to drop the pan. He asked if I had trouble with shifts or torque converter lock up afterwards. His reasoning is the solenoids that literally switch fluid through valves are located in the rear of the pan area. Overenthusiastic removal of the pan, or having to pry it down can put pressure on these solenoid bodies by accident and damage them. Luckily, it is not a terribly expensive repair as the solenoid "pack" can be gotten for $40 and it's a drop-out, slip in and re-torque into place repair. I would ask around for a second opinion, and diagnosis before bringing it right back to the same shop you had the pan dropped and serviced - sounds to me like they *may* have damaged this body. A reputable transmission place is a good place to ask, like an AAMCO or a shop specifically outfited to work on electronic transmissions.

Did you top the fluid up and check the ride again?

My fluid is currently above the top line by 1/2 qt. (Probably due to the additives I put in it based on my mechanic's advice.) Do yo think this could be causing the 1870 code? (I was told "no" by the mechanic.)

... My other thought is that is that the Tranny Shop is in the business of overhauling transmissions. And I get the impression they want me to continue driving the Blazer, instead of swapping out the TCC solenoid, to create a "hard failure" vs what I have now which is a "soft code."

Therefore, I would like to know how easy is it to swap out the solenoid and how costly is it? I don't mind going on this fishing trip, given what I have read in this Forum, and given the alternatives the tranny shop is proposing: $400 to pull the tranny and inspect it. $1300 to $2000 to repair it. ......When they don't know what they are looking for or what they will find. ..... Vs.... I might be able to fix the problem by inspecting the wiring to the solenoid and/or replacing it. What do you think I should do?

The TCC solenoid is computer controlled based on driving conditions.

Check to make sure all computer connections are clean and dry and properly connected.

Sounds like Wolfox has replaced TCC solenoids before and that it is pretty easy once you've got the pan off. I've only ever done PCSs (since those are what we make where I work), and I've never even bothered to look too hard at the other solenoids while I was in there. Since the whole pack is only $40 and Wolfox says the replacement is easy, I'd certainly attempt a DIY diagnosis and repair. Did you already do the road test to check for TCC solenoid function?

You quoted me...aww thanks. For the TPS to be bad or unstable like a bad or irregular reading, the PCM will most likely recognize that and throw P0122 (TPS code). It could be a few things, but I would start with the most obvious first. You don't want to wait for a hard failure. Driving it this way with the P1870 and high line pressure, they know you'll be back if you don't get it fixed soon - cause it will eventually fail. Since you stated that it started after the fluid and filter flush...I have a sneaky feeling that the mechanic who did the fluid and filter change did not put the filter in properly, or reused the old O ring from the old filter. Anyone who has done this job knows how hard it is to get that O ring out. Some people try to skip a step and reuse the old one. If you do that or if the new one isn't put in properly, the filter will start sliding out, allowing oil to leak and escape giving low oil line pressure to the tranny. The PWM will recognize the low line pressure and ramp up the EPC motor. It will eventually give you a the P1870 code and inhibit TCC lock-up (not a solonoid problem), and throw maximum line pressure to the tranny. If you have the SES light on, the system is designed not to go into lock-up or inhibit it. This is suppose to save the torque convertor from burning up because of low oil line pressure. Another issue that you mentioned is the deal of getting the code only when the SES light is on before you shut it off. After it goes on once, it should always be there, maybe light not on, but it should be stored there even after you shut the truck off. I would start with the first suggestion and see what happens.

Too true, the filter gasket is a royal *pain* to get to. Any failure to get the old one out, OR - worse yet, scoring the bore it goes into will cause it to suck air, instead of fluid. The tranny may be boosting up pressure to overcome the slight air leak caused by a bad/damaged seal and bore causing TTC lockup failure. I borrowed a cotter pin removal tool that is blunt to poke through the bore of the seal and gently pulled it out without scoring the bore the seal sits in. Then using a wooden dowel just the right size, gently tapped the new seal that came with the filter up into place. It only goes so far and a gentle tap-a-tap is all that is needed to get them back into place. If this step was overlooked, the bore/seal damaged or was neglected and not replaced, Blazes9395 would be right on the money in my opinion. Whenever *anything* goes wrong after servicing it, you have to examine the work done, proceedures, etc. Hopefully you will not even need to touch the solenoids at all and the bore seal for the filter is caput.

As for working on GM trannies before - the only one I ever had to tear into was an older 200-4R on an Olds Delta 88 wagon. Any little thing would make it misbehave. On other vehicles I have owned, never had any problems swapping filters and fluids. The 4L60E is just a liiiiiiitle picky, but thankfully it has enough electronic controls to decypher what's wrong.

After talking with another tranmission shop, I was given the following information, and unless someone says otherwise I will plan on taking my Blazer to this person tomorrow to:

1) Replace the Acumulator Valve with a redesigned kit. Apparently, I am told, this tranny and others like it, are known for having a check ball get stuck....and the kit is designed to fix the problems I am having: hard shifting and a lock-out issue (which could ruin my tranny if I keep driving it).

2) Replace the metal clad seal (I think this is what is meant by an o-ring previously described, but I'm not sure.)

3) Check the Throttle Possition Sensor (TPS) and clean contacts as needed.

What do you guys think about this approach?

Many thanks for sending me your comments. I'm trying to avoid the irony...that if this all started with good intentions to change my tranny fluid, it would be a shame for that to end up as a tranny overhaul.

[QUOTE=imnprsd]After talking with another tranmission shop, I was given the following information, and unless someone says otherwise I will plan on taking my Blazer to this person tomorrow to: 1) Replace the Acumulator Valve with a redesigned kit.

==== Correction ====

==>> I need to make a corection to the above paragraph: It should read, "Remove the TCC Solenoid... Inspect the valve body, and use a TCC Solenoid bore-out kit to repair warn area." Note: this does not mean your TCC solenoid is defective. It means there is both spring wear and wear in the channel which is getting suck and that can be repaired with the pay off. You don't need to pull the tranny.

Here's the bottom line on this thread -- and this is based on expert Transmission advice (not from me).

*** The 1870 code can mean a lot of things. However, if your condition is like mine: meaning your SES light comes on ocassionally, and most often when you are driving on the hwy, and that is followed by hard shifting.... Only to find that the code is rest when you turn off the key...

...It's because your PCM detected clutch slippage at least 3x in a specific period. That triggered the 1870, code and the PCM is telling the TCC solenoid to engage a lock-up condition (which is what happens on this type of transmission when you are trying to get maximum gas mileage by locking the drive shaft... Anyway, a lock-up is created then the TCC solenoid is flipped to create high pressure... And that results in hard shifting.

*** Solution: Drop the pan, inspect for any damage to the TCC solenoid first; then inspect the channel and use a bore-out kit if necessary.

NOTE: I really had to check around to find a shop (1 in 5) who would only do the work I mentiond above. It cost me $200, and that included a regular service. All the other shops wanted me to let them pull the tranny for a complete inspection... and we all know would only lead to a premature overhaul of $1800+!!! I'm telling you these tranny shops managers all seem to go to the same tranning camp: Hook'em, clean'm, scalp'm, and charge'm up the ying-yang. If you don't believe me... just notice all the used cars for sales outside some of these shops!

Now I'm not trying to smear all the good tranny shops out there... I'm just saying that it took me all day to find the right shop.... But thanks to comments from this forum's memebers, I was able to talk with the tranny shop to do only that which is required... And that saved me a ton of money!!!

...Many thanks to all of you!

Did they actually have to use the TCC bore out kit or was it just a solenoid replacement or something else that fixed your problem... I'm very curious.

Thanks.

Last time I had my pan off I seem to remember several solenoid looking items. Does anyone have a pic or a diagram of the trans with the pan removed and can pinpoint the TCC?

This will give you some information on solonoids, and basiclly what the valve body looks like. Note the lock-up solonoid, thats the TCC solonoid, its at the front of the transmission, when its installed.

Heres the website.

www.pdqparts.com/content/pdf/CUA0102-1.pdf#search='4l60e20valve%20body'

The total solution cost, including labor was $318. The installed a TCC solenoid kit $45 (bore-out kit for the valve body wear), they replaced the TCC solenoid ($26), and the wiring harness which apparently was required for the kit ($63), they replaced the fluids, changed out the o-ring, and everything seems to be working fine. Just remember, this fix is only recommend if your tranny is working perfectly well with the exception of the lock-up problem occuring at high speeds. ...Just be prepared to look for a while to find a good tranny shop who will do the work. 4 out of 5 shops I talked to only wanted to do the full overhaul... But to be fair, you probably will not get the tanny shop to guarantee this will fix the problem. Why? I'm not sure. The problem of having a lock-up at high speed, coupled with hard shifting after the code is tripped, coupled with everything is fine again after you turn off the motor -- seems to suggest this is an appropriate fix. Good luck to all of you who expereience this problem. For me personally, I feel like I avoided a pre-mature overhaul and saved myself $1500.

Glad to hear you got off as cheap as you did. Thanks much for the update... bet this will end up helping a few people.