Wage92

So I have an ls swap with a 2003 5.3 and a 2004 4l60e. Everything works well. Lately the trans has been acting a little strange. When its first started everything acts normal, but once the trans warms up and i am cruising at speeds above 30-40 in 4th gear, it will downshift to 3rd. Until i give it more throttle, once i do it will shift back into 4th and hold it until i go back to a light throttle position. This is very repeatable once warm. Its definitely not the tcc, when it downshifts it goes up by like 600+ rpms. On the highway at 65-70 it will be at 3500-4000 rpms. Then i stab the throttle and it shifts perfectly to 4th and rpms drop to 2500 or so. This is definitely not a slip condition its a clear downshift and then it will upshift perfectly when i give it some throttle.

I have logged some data and tried to diagnose the problem a little and am having no luck. With hp tuners plugged in i have a log where when it happens i watch the transmission gear and when it downshifts the computer still displays that its in 4th gear with tcc locked. It never changes. I can manually shift the car from D to 3rd when it is in the downshifted position and no shift occurs and the rpms do not change, so to me this proves its actually in 3rd gear. Then i click it back into D and it shifts perfectly into 4th.

I have also checked to see if there are misfires and the computer is not displaying any misfires. There are no current DTC's but there is a P0179 in the history.

The only thing i can think of is that its a failing solenoid or something with the valve body, because it seems like the computer is commanding it to do the correct thing but something is not able to hold 4th when it warms up. Im looking for suggestions or any ideas from someone who is better with 4l60s. I have heard a transgo kit sometimes can fix similiar problems but id rather no just throw parts at it. Thanks for the help and sorry for the long post.

mrvedit

Glad you were able to use HP Tuners to confirm that the PCM is commanding 4th gear and even TCC lockup. Without that info, I would have suggested a code or overheating issue or even an intermittent Manifold Pressure Switch.
I recall only a few similar threads where 1st through 3rd gears worked perfectly and 4th was either flaky or non-existent. IIRC, in one a cracked 4th servo piston was the culprit; in the other the OP finally replace the valve body without ever figuring out the exact problem. With 1st-3rd working it doesn't sound like a shift solenoid or 3-2 downshift solenoid problem.

Maybe one of the pros has more suggestions, but I don't have enough experience to give a definitive diagnosis.

Wage92

in the case of replacing the valve body it fixed the problem?

also, 4th works just fine, it just has to be in a mode of constant accelleration. I can drive it without it doing the downshift anomaly. If you accelerate and then left off the gas, then accelerate then let off the gas. It only has this issue when trying to maintain speed on level ground or downhill.

Are there any solenoids that use a mechanical spring and line pressure to shift a valve? This would explain why when i give it throttle and raise line pressure that it would be able to hold 4th, but when line pressure is lowered the mechanical spring is not enough to hold the valve...? Just a thought.

Wage92

anyone? I was looking over the tune again and i was in the trans section and here is a screenshot of the hot chart for tps position vs shift points. If i am understanding this right it will upshift to 4th in the upper 40s mph and then downshift to third at 41? This doesnt seem right to me....anyone have any idea?

mrvedit

Looks right to me - you have to speed up to e.g. 45mph before it shifts into 4th. Then if you slow down below 41, it shifts back to 3rd.

However this is the "hot" table used only when the trans is overheated.
What does the Normal table look like? (Sorry I'm on the wrong computer to open your tune.)

Wage92

ah makes sense. I was thinking about it differently. The normal table is the same way so that must not be the problem. The more i thought about it, when it does the downshift, hp tuners tells me the computer is still calling for 4th so to me that means it more mechanical, maybe something in the valve body.

Would having the wrong rear end gear ratio in the tune cause any of these problems?

wht/73

That seems a little weird.
I don't notice it my sub or my s10 downshifting to 3rd on light throttle unless I put my foot into it.
I could see it if it was maybe 30 mph but 41 seems kinda high.
My 80e doesn't do it either with the compushift controller.
Now I'll have to look for it when I go out for lunch.

clinebarger

I don't think that is 3rd, With your RPM & speed.....Sounds like 2nd. If the 3-4 clutches can't hold while in 4th gear......The trans will fall into 2nd.

Get it nice & hot, Make a WOT run through the gears from a stop in D3.....If the trans flares on the upshift to 3rd....The 3-4 clutches are done.

I can count on one hand how many time solenoids have fixed a 4L60E in the 25+ years I've been messing with them.

By the time a customer brings me a 60E......The 3-4's are completely burnt to the ground, I enjoy the stories on how they don't think it's a burnt clutch, Because it holds in certain situations!!

Wage92

Interesting. I never thought it could be second but you do have a good point. I will try that as soon as i can. The driveshaft is out at the moment. But that may be it. So if that was it then it is definitely mechanical amd it needs to be rebuilt eh?

Wage92

The more i think about this i dont think its second. The car has 28" tall tires and 4.11 gears. A gear calculator says second should be at 5700 rpm at 70 mph. It was only at like 4000 plus/minus a few hundred. I need to get a driveshaft and test everything again.

caddisflinger

Did you ever get to the bottom of the problem with your transmission? I have a 2003 4L60E with the exact problem and nobody can figure it out. One shop wanted 700 bucks to look at the valve body, but I'm not ready to throw money at it without an idea of what is going on.

Wage92

If i can remember right, i played around with it some more after my last post. It was definitely 3rd gear it was dropping to, not second. I ended up ordering a complete valve body from ebay for like $60, a shift kit and a new governor. I dropped the pan and checked everything out. Everything seemed fine, but i replaced the valve body, put the shift kit in with the "street" springs etc, and the governor. New fluid and filter and the problem went away. I still think it was something mechanical/valve body related because it was not telling me electrically that it was dropping gears. If you havent already i would definitely try to log some data while you are driving and the problems occur. It can help immensely.

Jays_SSZ28

iTrader: (2)

A governor? Not in a 2004 4L60E. Never heard of a shift kit with "street springs"

Wage92

You know how you get a transgo shift kit and there are multiple sping kits you can replace. There is usually a street, strip and full race setup. Like 3 levels. I just did all the mods for the mild or "street" level.

Sorry i used the wrong term, not governor. The solenoid on the rear right side i believe. Up above the pan.

I hate trying to dia

So when it's cold trans shifts and hold as it should , once warm crushing between 55-70 it will drop out of 4th or OD into 3rd the rpms jump from 2200 up to 3000 running 65 or 70 , and will not shift back up into 3th it steady stays in 3rd no matter what indo with the throttle I have tried letting it come to a coasting stop in shoulder to punching it up to 85 annit will not up shift back into 4th until i come to a stop and it cools down then get back up to 60 or 70 it will shift into 4th for a mile or two then drop back into 3rd like I'm punching it frying to pass someone an then it won't go back into 4th . I recently replaced the intake gaskets and removed the dist , it's not throwing any codes besides both down stream 02 sensors no voltage cause there gone with my cats , so my question is , I'd the timing is off by a tooth it would not be running smooth correct ? Because you cannot time this engine with a light you must use a scanner which I don't have so I times it by tdc on compression stroke and drilled a hole in my dist cap and twisted the cap so that the spark was the shortest an going straight to the pin with no advance or retard , but If I have the cap an rotor on correct but the dist a tooth either way I would think I would notice in the engine idle but it runs smith as can be so I don't know enough about how the pcm works or if it controls the shifting with the timing I'm just lost when it comes to the computer part of repairs . The only scanner I have is a harbor Z13 in think it is

bbond105

Most likely the band is worn. You can check this by prying on the 2-4 servo cover on the right side of the transmission and measure how far into the transmission you can move the cover. Should move only around 1/8 of an inch. Some people have removed the servo pistons and welded a glob on the end of the pin and ground it down to get the correct travel or replaced the pin with Sonnax Extra Long Servo Pin part # 77787-02K and have been able to extend the life of the transmission longer. Even with the Sonnax pin you will need to grind it to the proper length,

I have attached the instruction to the Sonnax pin.