4L60E transmission slipping during lockup

[dtgoodwin]

I have a 2002 TrailBlazer 4x4 with 174K miles on it. It has the original trans with a secondary stacked plate cooler added. It has been flushed (draining by opening the cooler line while running until it just runs out and them immediately stopping the engine, filling 4 quarts, and repeating 3 times), and the filter replaced at 50K intervals with non-synthetic oil. About 10K miles ago, I started noticing that at lower speeds when the torque converter should be fully locked (50-60MPH), that it will lockup like expected, but then there will be a couple seconds of slippage, allowing the engine RPM to increase 200-400 RPM, and then back to full lock. I've heard that there is an issue with the TCC valve bore wearing and causing a pressure loss. I also know that this is a PWM lockup, however this particular condition is new and definitely different than it used to behave. There has been no trouble code recorded yet for slippage, and even though I can see it on my tach and hear it in the drone of the engine (lovely straight 6 exhaust note), my AutoTap ODBII which has the "enhanced GM diags", never shows a slip value above 1 or 2 RPM. The problem goes away at around 65 MPH and above.

I'm not sure what to think. Has anyone experienced this? I know you can buy a new "liner" for the TCC bore after it has been reamed out. I really don't want to pay a transmission shop to tear it all down to do this, as I'm sure they would recommend a full rebuild. I know there are other problems that I could encounter, but I don't expect to own this vehicle much past 200K miles, and don't want to sink a lot of $$$ into it.

My biggest concern is that we're headed for a 3K trip from Utah to Dallas and back and I don't want to cause any additional problems, or especially suffer a catastrophic failure along the way. I'm thinking that the worse likely problem is that I wear out the clutches for lockup and end up having to replace the torque converter.

Thoughts?

Thread closed due to necro-posting spammer.

Zenmervolt - AnandTech Moderator

 

[Gillbot]

Only read the title but, likely a bad TCC lockup circuit or a bad TCC clutch.

 

[ShawnD1]

it will lockup like expected, but then there will be a couple seconds of slippage, allowing the engine RPM to increase 200-400 RPM, and then back to full lock

Dun dun dun!
That's what my Corolla was doing. I took it in under warranty and they ended up replacing the entire transmission. I really hope there's a cheaper way out.

 

[joutlaw]

I have the exact same issue between 50-60MPH in my 2004 Z71 5.3L/4L60E 3.73 with a 265 tire.

I had my truck tuned by Justin at Blackbear Performance. I asked about this issue and this is his response:

The partial lockup is a bit normal, as GM doesn't ever fully lock the converter, it is pulse width modulated. We can alter the minimum lockup percentage to take care of that.

I have also read it has something to TCC valve bore. I have also read that a new valve body will correct this issue.

This is sometimes referred to as torque converter shudder. There are some shudder fix additives on the market. I didn't notice much of a difference after using it in my case.

I have learned to avoid that MPH range. You could also drive in 3 and manually move to OD after 60MPH... although MPGs may suffer.

 

[joutlaw]

Found this on another forum.

If I'm interpreting the post correctly...

Yep, there is a TSB for code P1870. It's due to wear in the valve body bore around the TCC PWM valve. In stock form, the steel spool valve rides in the Aluminum bore in the valve body. After a few years of cycling, the bore wears (obviously, being the softer of the two metals). This contributes to less than full apply pressure being commanded of the actual TCC valve, and subsequent tq. convert clutch shudder, falling out of lockup, etc. and the accompanying tripping of the MIL for P1870. Been there done that. A quick fix for this is to lock the PWM valve into full pressure position (via inserting a spring in the bore), and getting on/off TCC engagement as in the pre-electronic 4L60E (the 700R4s used an on/off strategy until 93 when they became the 4L60E). Sonnax recommends against this practice, stating that the TC clutch assy. is not designed to take full non-PWM TCC apply pressure at all times under all conditions. Admittedly, this elimination of the PWM valve stroke is a common mod in shift kits so as to get a firmer apply and less TCC heat. I myself have this in my truck, but I have begun to wonder if Sonnax's warning about this is not somehow relevant to my repeatedly cracking flex plates. So, I'm personally questioning the advisability of locking out the PWM valve to full apply pressure on a daily driver. But I digress....

GM's reman transmissions address the PWM valve bore wear by reaming the bore and installing a larger valve. Sonnax has a much better solution. They have you ream the bore and install a steel sleeve along with a new hard-anodized valve. I have the Sonnax setup in mine since my problems with P1870 popped up years ago.

....

I would give some thought as to whether or not to lock the PWM in full apply position or whether to leave it functioning. With the Sonnaz hardened valve and hardened sleeve in there it will be a very, very long time before that valve is cycled enough to wear the bore again. If you want the TC clutch to grab a little better, put in a bottle of BLACK LubeGard (yes, BLACK... not red) and leave the PWM functioning, IMO.

Just my thoughts.

 

[joutlaw]

Apparently this is the part that can fix this problem:
http://www.transmissionpartsusa.com/77754_04K_4L60E_transmission_TCC_valve_p/400-07775404k.htm

Instructions on the install:
http://www.sonnax.com/system/instructions/77754-04K-IN.pdf

Do you have a reputable transmission shop in your area? I would highly advise having a pro do this type of install. Valve body reaming is not for first timers IMHO.

 

[ShawnD1]

I have learned to avoid that MPH range. You could also drive in 3 and manually move to OD after 60MPH... although MPGs may suffer.

That's what I started doing in my car. Surprisingly the change in gas mileage was extremely small.

The instruction manual will also say something to the effect that you should lock the gear if it seems to jump around lots. Constantly switching gears or locking and unlocking is not good.

 

[kornphlake]

I've noticed the same slippage in my Astro with a 4L60E at 50-55mph, it doesn't really bother me much though, typically I'm only driving 50-55mph on my way to 60-65mph.

I might look into the Sonnax fix, I'm not really anxious to have my transmission torn apart though.

 

[SparkyJJO]

My old car did that. Here's the fix I found and it worked perfectly!

Transgo makes a kit called the SK-4L60E and it is designed specifically for fixing this issue (and a few other things). It is pretty cheap too, only like $50 or so. However, it makes sense when delving into the trans to get a new separator plate and seals as I can assure you that the seals will tear when you take it apart.

ctpowertrain on ebay has a kit that includes the SK-4L60E, a new separator plate, seals, and the Sonnax pinless accumulators for around $100. WELL worth it. My car went from basically having no more TCC lockup on the highway at all to locking the torque converter up as if nothing ever happened. Beautiful. I put the same kit in my 02 Trailblazer's transmission, just in case.

Do that kit install, and I'll bet your problems will go away Just be sure to get the kit for 96+ since the separator plate did change a couple times in the older ones.

Dun dun dun!
That's what my Corolla was doing. I took it in under warranty and they ended up replacing the entire transmission. I really hope there's a cheaper way out.

Your experience with your corolla was an ENTIRELY different issue. Totally different transmissions. The only relation is they are both automatics, but that's it.

 

[LTC8K6]

My old car did that. Here's the fix I found and it worked perfectly!

Transgo makes a kit called the SK-4L60E and it is designed specifically for fixing this issue (and a few other things). It is pretty cheap too, only like $50 or so. However, it makes sense when delving into the trans to get a new separator plate and seals as I can assure you that the seals will tear when you take it apart.

ctpowertrain on ebay has a kit that includes the SK-4L60E, a new separator plate, seals, and the Sonnax pinless accumulators for around $100. WELL worth it. My car went from basically having no more TCC lockup on the highway at all to locking the torque converter up as if nothing ever happened. Beautiful. I put the same kit in my 02 Trailblazer's transmission, just in case.

Do that kit install, and I'll bet your problems will go away Just be sure to get the kit for 96+ since the separator plate did change a couple times in the older ones.



Your experience with your corolla was an ENTIRELY different issue. Totally different transmissions. The only relation is they are both automatics, but that's it.

He also argued with us about it, and now he is saying what we told him as if it's his own opinion...

 

[dtgoodwin]

Thanks for all the advice! I had heard about the Sonnax kit. The part is cheap, but the reamer, and the skills necessary aren't. Has anyone here had it done? I feel comfortable taking out the valve body to a shop, but I'm not sure if they would want to do that or not.

And I put a bottle of the RED lubegard anti-shudder in. Was debating about it or the black. Since I leave in two days, maybe I'll try a quick flush and filter change and put the black in and see if it works. Am I correct in thinking that if it's related to bore wear and low pressure that further damage I am likely to cause would be extra wear in the converter? I could live with that as they aren't 2-3K like having the transmission fully rebuilt.

My route from SLC to Dallas involves a lot of 45-55 MPH stretches. If I notice it being bad, I'll either try and increase my speed, or pull it into third if it's too bad.

Thanks again for your advice!

 

[SparkyJJO]

That's why I went with the Transgo kit. No special skills or tools required. You just have to be somewhat mechanically inclined and not scared to take stuff apart put it back together correctly.

Here is what I got:
http://www.ebay.com/itm/4L60E-4L65E...Parts_Accessories&vxp=mtr&hash=item51954b678c

And I also got the Corvette servo for good measure:
http://www.ebay.com/itm/700-700R4-4...Parts_Accessories&vxp=mtr&hash=item439ce1e231

Been flawless since install on both transmissions I put them in. One of which is my 2002 Trailblazer, so similar vehicle I put it in at 120k, I now have almost 150k on the truck.

 

[kornphlake]

That's why I went with the Transgo kit. No special skills or tools required. You just have to be somewhat mechanically inclined and not scared to take stuff apart put it back together correctly.

Here is what I got:
http://www.ebay.com/itm/4L60E-4L65E...Parts_Accessories&vxp=mtr&hash=item51954b678c

And I also got the Corvette servo for good measure:
http://www.ebay.com/itm/700-700R4-4...Parts_Accessories&vxp=mtr&hash=item439ce1e231

Been flawless since install on both transmissions I put them in. One of which is my 2002 Trailblazer, so similar vehicle I put it in at 120k, I now have almost 150k on the truck.

After reading a bit more it sounds like I need to do this repair, I haven't had error codes yet but the TCC does slip at a certain speed range and I have had an occasional hard 1-2 shift. My parents had to pay for a rebuilt 4l60e in a s-10 Blazer they had and it sounds like it had the same symptoms, but they didn't do anything about it until the torque converter was worn out, a $200 repair turned into a $2000 rebuild. I've checked with the experts at astrosafari.com and the sticky in the transmission section suggests the same parts upgrade, minus the corvette servo, although other sites do recommend the corvette servo, for $15 it's probably not a bad idea since I'm going to have the transmission apart anyway. I am due for a transmission fluid/filter change that I was putting off for spring, so really the oil pan was going to come off the transmission regardless, I might as well pull a few more bolts and replace a few more parts while I've got it apart.

As much as I'm glad I read this thread, I hate threads like this, 2 days ago I thought my van was in pretty good shape, now that I know what I should or should not notice I'm noticing all the signs that I need to do some work on the transmission. I'd rather be aware of the problem and take care of a repair when its convenient than be unaware and destroy the transmission. I guess I know what I'll be doing over Thanksgiving weekend.

 

[SparkyJJO]

Be aware that once you install that stuff, it does stiffen some of the shifts a bit. I don't mind that at all, I prefer to know when the trans shifts personally (and it also means a bit less wear since it doesn't slip the clutch packs as much to make a smooth shift).

 

[kornphlake]

When you say it stiffens the shifts a bit, is it so stiff that someone who had never ridden in my van before would notice shifts are rough like if I'd installed a shift kit? I'd prefer something more like a factory shift, but a little firmer wouldn't be bad.

 

[ShawnD1]

He also argued with us about it, and now he is saying what we told him as if it's his own opinion...

http://forums.anandtech.com/showthread.php?t=2139997&highlight=automatic+transmission

Generally happens when there's a little bit of traffic. Shifting to overdrive will drop the engine rpm below 1500 and it's only a 4 cylinder engine. It has no torque at all when running at that speed, so lightly touching the gas makes it shift down.
There's nothing wrong with the car. It's just a little bit aggressive when it comes to shifting into overdrive. I plan to drive this car into the ground, so knowing whether or not this constant shifting shortens the life of the transmission is something I'd like to know.

I know the owners manual says to keep it in 3 if pulling a trailer or if the car is carrying a lot of stuff.

I started a thread asking if regular driving was hard on the transmission because it gear hunts all the time.
I mentioned the instruction manual before anyone else did.
Eli was the first to say that gear hunting was bad.
ichy was the first to declare that automatics don't have clutches :awe:
I was also the first to mention that driving hard was very hard on an automatic compared to a standard because it involves very large rpm differences and it's doing that while the engine is still throwing out full power.

 

[SparkyJJO]

When you say it stiffens the shifts a bit, is it so stiff that someone who had never ridden in my van before would notice shifts are rough like if I'd installed a shift kit? I'd prefer something more like a factory shift, but a little firmer wouldn't be bad.

No, not at all. It doesn't feel like a performance shift kit. Just you may notice it coming from how it was originally, but most people won't notice. It isn't rough.

*snip*

Please stop cluttering this thread. That has nothing to do with the topic of this thread at all.

 

[IcePickFreak]

Shift kits generally include fixes to problems that occur over time - valve bores wear out, stick, etc - ie. issues that arise after a particular transmission has had lots of real world "testing." With a stock converter it's not likes it's suddenly going to be slamming gears like a drag car or something, but yeah it'll firm up the shifts a bit.

An just an "IMO" I know $2,000 isn't nothing to sneeze at, but if you shop around you should be able to find a better deal than that. At 175k, that's the equivalent of about 7 trips around the Earth (at the equator, anyway)... shit is gonna wear out.

 

[joutlaw]

I was quoted for a upgraded build at $1300 in my area. There are millions of 4L60Es on the road. They are very similar to the 700R4 so there are many shops familiar with them too.