4l60e slip and bump on take off
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Teching In
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4l60e slip and bump on take off Maybe some of you transmission experts can give me a hand. I have a fresh rebuilt 4l60e that has a brief slip and bump on take off. It's intermittent and completely random. Feels like the truck doesn't want to move for maybe a second then a soft bump and off it goes. Also having an occasional issue where the converter locks and unlocks randomly. Manually locking the converter in 1st with brakes on will stall the engine when cold but not hot it only lightly bogs and the TCC slips. Any ideas?
2006 Colorado 4x4
3000 re-stalled converter
Rebuilt pump
New raybestos clutches
New molded pistons
New bushings and seals
hd sunshell
HD2 Transgo kit
New solenoids
new forward sprag
Pinless accumulators
Vette servo
90 psi idle and cruise
230 psi under load
160° trans temp max
2006 Colorado 4x4
3000 re-stalled converter
Rebuilt pump
New raybestos clutches
New molded pistons
New bushings and seals
hd sunshell
HD2 Transgo kit
New solenoids
new forward sprag
Pinless accumulators
Vette servo
90 psi idle and cruise
230 psi under load
160° trans temp max
Sounds like you are possible leaking AFL oil not enough pressure to push the valve to the 1st gear position at idle and or low line pressure , when you give a little throttle pressure rises and the valve strokes so it jumps down into first. Could be a leaking or faulty shift solenoid or Oring the lockup issue when hot could be related, I would first do a pressure test at idle
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It appears as I suspected to be a pressure issue, The second video of driving is odd to me , The pressure rise is not steady but step like sudden jumps which is ODD. could be a sticking AFL VALVE or perhaps broken spring, Also perhaps a sticky Pressure control solenoid, Or even a bad TPS I would of course start easiest first and either replace or observe the TPS function to see if its jumpy like the line pressure, Then the PCS and AFL valve.
But for whatever reason the bump I would say if low AFL not enough pressure to stroke the 1-2 shift valve causing momentary second gear starts.
But for whatever reason the bump I would say if low AFL not enough pressure to stroke the 1-2 shift valve causing momentary second gear starts.
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Thank you. That gives me a place to start. I have been logging some transmission pids against speed, rpm and throttle position and all is smooth and normal with the tps. As far as the AFL valve, I only pulled it out, cleaned it and installed the additional Transgo spring. Do you recommend reaming it out and installing the sonnax valve?
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Teching In
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Today I logged force motor/PCS current. The commanded current to the solenoid matches up with the pressure gauge reading. The PCM's signal sent to the PCS solenoid is not a smooth curve. It's very abrupt. I verified the force motor table is stock. This seems to indicate that the line pressure is doing exactly what the PCM is telling it to and it's not a sticky valve causing the erratic line pressure rise. The random low pressure at idle problem continues and the PCM is commanding the same PCS current at idle every time. I'll link a log video to show what I'm talking about.
https://vimeo.com/299327385
https://vimeo.com/299327385
Well if the force motor current is the same with either pressure condition , I would have to think a valve or solenoid issue, A leak while possible would IMO tend to be consistent . Not up one time and down the next but anything is possible .
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I have another good valve body. I'm going to swap it in and see what it does. If that doesn't work and I'm looking for a leak it's going to be something in the forward clutch circuit correct? Nothing else is applied in D1?
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From: Iowa
in d1 the following is applied:
-forward clutch
-low/rev clutch
-overrun clutch
The pressure usually does jump around like that and the force motor current does as well. You should also log maf/map/tps when logging the pcs current and you will see that there is a fairly decent method for the madness that you see in the graph. The pcm is only giving pressure (controlled by FM amperage) when you actually need it.
If the new valve body fixes your issue...it's more than likely a function of AFL bore wear or another significant internal leak to the valve body.
-forward clutch
-low/rev clutch
-overrun clutch
The pressure usually does jump around like that and the force motor current does as well. You should also log maf/map/tps when logging the pcs current and you will see that there is a fairly decent method for the madness that you see in the graph. The pcm is only giving pressure (controlled by FM amperage) when you actually need it.
If the new valve body fixes your issue...it's more than likely a function of AFL bore wear or another significant internal leak to the valve body.
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I've been avoiding swapping the valve body. I really want to figure this out so last night I installed a sonnax TCC apply valve with the seal on it. I had one laying around and the TCC has acted up a couple times so I figured why not. I also worked all the valves I could get to with a screwdriver and pulled and cleaned the solenoids that I could get to.
Drove around for an hour and the slip and bump/low pressure never happened again. More surprising, the part throttle 1-2 shift is a lot less harsh now. How those two are related I don't know. I'll test some more tonight.
Drove around for an hour and the slip and bump/low pressure never happened again. More surprising, the part throttle 1-2 shift is a lot less harsh now. How those two are related I don't know. I'll test some more tonight.
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I didn't want to leave this thread open ended. So the problem continued after my last reply.I ended up taking the valve body apart and I found a piece of aluminum stuck in orifice 22 of the separator plate. I assume this was some junk from the new cooler. I also found the forward abuse valve was sticking. It was really hard to remove. I replaced the forward abuse valve with the sonnax valve. Everything is good now I appreciate all the help!