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Old 05-06-2012, 08:11 AM   #1
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Default constant high line pressure 4l60e

I have a strange problem with my rebuilt 4l60e 1995, I have a constant line pressure of about 180psi in all gears including park and neutral. The pressure does not change when I rev the engine. All gears work fine, overdrive and lockup too.

No codes from the ecu, tried another ecu as well but same pressure. I assume something is wrong inside the transmission but dont know where to start, would rather not remove the transmission from the engine. It has been the same since rebuilt, dont know how it acted before.

Any suggestions?

Thanks in advance.
/Hakan
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Old 05-06-2012, 09:52 AM   #2
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Forgot to mention that the transmission shifts late and sometimes the engine overrevs before the transmission shifts in to next gear, this occurs in wot.

Have also checked the tps since I had a code "low tps signal". Now set to 0.678 Volts.

The transmission is rebuilt with tci pro super rebuild kit.

/Hakan
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Old 05-06-2012, 01:41 PM   #3
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My best educated guess is that something is preventing the relief valve from bleeding off line pressure. Too stiff a spring, something broken. Having said that, if it were my problem, I'd ask dynamic396 he does transmission everyday and knows chapter and verse.
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Old 05-06-2012, 02:55 PM   #4
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Thanks for your reply. Do you mean the pressure control solenoid?

I tried to disconnect the high and low signal from the pressure control solenoid, one at a time and the pressure jumped up to about 200psi both times. Would like to try all none evasive investigatios before I have to open the transmission.

/Hakan
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Old 05-06-2012, 04:07 PM   #5
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I was referring to the pressure valve thats in the pump itself, but you have a valid point also. The pressure control solenoid, or its wiring to the pcm could be bad also. Still say ask dynamic396, he knows much more than I about the inner workings of the 4l60e.
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Old 05-07-2012, 03:27 AM   #6
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As I understand the force motor (EPC) is adjustable? Some sort of screw in front. I was thinking that maybe this is causing my problem?

Can anyone confirm?

/Hakan
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Old 05-08-2012, 08:37 AM   #7
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Please post if you have any ideas what can be causing my transmission to behave this way?

Thanks
Hakan
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Old 05-09-2012, 03:51 PM   #8
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Thoght I would post a update on how work is progressing. I still have not figured out what is causing my transmission problem. I have talked to several transmission rebuilders and they have all contributed in some way, for wich I am thankful.

I am a bit puzzeled to whether this is a limp home, mechanical or electrical problem.A lot of things point in the direction of limp home mode but as I understand all gears should not work and certainly not lockup? All this is ok in my trans.

Since the force motor controls line pressure I have payed this a lot of attention. As I said before the pressure climbs to 220psi when I disconnect it from the ecu. I even tried to feed it with a separate power source of 5v to see what pressure readings i got, and the gauge showed 180-190psi just like it did whith epc was connected to ecu.
I ordered a new force motor (epc) and hopefully I can put it in this weekend.

The motor and trans sits in sort of a hot rod (1978 Volvo) and has the engine and harness from a 1997 camaro while the trans and ecu is from a 1995 camaro. The harness and ecu has been professionally rebuilt to function in older cars.

No matter what I try I cannot get the pressure below 180psi in any circumstance. So I am assuming there must be something wrong inside the trans, do you agree?

Any thoughts on this?

/Hakan
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Old 05-16-2012, 04:29 PM   #9
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Ok so this thread did not get many answers, anyway the problem is solved. Thougt I should post the solution and maybe help others with the same problem. It was the force motor or pressure control solenoid that was broken, replaced it with a new borg warner model and now the transmission shifts and feels like it should.

/Hakan
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Old 09-13-2012, 05:27 AM   #10
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The 4L60E is broken again. This time it will not go in to overdrive (fourth gear). It shifts thorugh 1-2-3 without any problems but will not shift into od. It feels like the trans is trying to shift into od but nothing happens, I think the clutches are gone. If I drive downhill and give some throttle at the end of the hill, the trans slips for a second or so and then shifts back into third.

The transmission oil is black. It shifts strong without any slip in R-1-2-3.

I have the Sonnax super hold servo for fourth gear. Could this have caused it?
I will of course replace the worn clutches but would like to get an idea of what was causing the problem in the first place.

Any input will be much appreciated.

Thanks
Hakan
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Old 09-13-2012, 04:40 PM   #11
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Before you run out and start buying parts, you need to hook car to a scanner that does real time sensor data. Check the trans solenoids and switch unit for proper operation. Each switch and solenoid must work correctly to go into all gears.
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Old 09-14-2012, 07:36 AM   #12
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Thanks for the input, I forgot to mention that I have checked for codes and also all solenoids appear to be working as they should.

Maybe this is a result of the previous high pressure. I was thinking that a cracked piston could result in a burnt 4th clutch assembly? The band should be ok because I have a strong second gear with absolutley no slip.

/Hakan
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Old 09-18-2012, 09:03 AM   #13
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My apologies for missing this thread. It has been crazy busy here!

I'm glad you solved your line pressure problem. In short, yes, your EPC solenoid was stuck in the open position.

What you need to do with your current "no 4th gear" problem is to see if the PCM is indeed commanding a 3-4 shift. If it IS commanding a shift, yet no shift is occurring, that will be one set of things to check. If the PCM is never commanding the shift, well, that's a different diagnostic strategy altogether.

If your 2nd gear is solid then, most likely, your band is fine. The 4th gear portion of the band servo is a VERY simple mechanism and it is unlikely that anything is wrong with that. But, the possibility DOES exist. My suspicion is that the PCM is not commanding the shift for whatever reason...
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