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I just had my 4L60E rebuilt. Its pretty much stock other than beast sunshell and transgo shift kit with corvette servo. Converter was replaced twice, once during rebuild process then again after the fact because I was given a high stall converter, but needed low stall.
EDIT: so no one new has to read through every reply.
Pressures were tested and found to be low while connected or disconnected from PCM.
Transgo boost valve was installed. (Made pressure go up, but goes back down when warm)
Transgo OS drop in Pressure Regulator valve was installed.
Gently oversized AFL valve was installed.
New Solenoids were replaced 3 times.
Forward accumulator was upgraded to aluminum.
Pressure manifold switch was replaced.
Wiring harness was replaced.
Decided to take everything apart myself and get to the bottom of what Could be going bad.
Replaced apply pistons.
Replaced separator plate and gaskets due to severe wear from checkballs.
Replaced a lot of seals/O-rings while I was inside of it.
Issues I've seen since we put it back in:
1- Low pressure in all gears. park is 40, reverse is 35, drive is 40 (all at stop).
2- At take off, the engine rpm goes up, but the transmission doesn't go into gear until rpms reach around 1300 to 1500 rpm with a solid kick into gear.
3- around 45-55 mph, it seems like torque convert clutch goes in and out with a slight rpm jump of 200-300 rpm every 5-10 seconds. (this is normally after driving 20 minutes and getting warmed up)
4- harsh 1-2 shift after 20+ minutes of driving.
Things that I have done to try and figure out the problem:
1- I have replaced all solenoids in valve body to see if that was causing any type of issue.
2- checked all valves in the valve body, everything SEEMED fine, but I'm no expert and I don't know for sure.
3- adjusted the pressure control solenoid 1/4 of a turn to raise pressure up some to see if this helps with anything.
4- took main connecter off and checked pressure that way to see if it was electrical issue, pressures went down more.
Any help would be appreciated, I have no idea what else to look for and the person that rebuilt it is not doing any more work at this time for some personal reason. I don't want to spend much more money when I just had it rebuilt.
Last edited by atlsoldier27; Jul 24, 2022 at 11:40 AM.
The filter is good and tight with its seal.
I haven't taken the transmission back out since it was put back in, so I haven't seen the boost valve at all. I was told it was upgraded with the transgo shift kit.
I was hoping it wouldn't come down to taking it back out to check any of that.
as far as the pressures around that RPM, I haven't documented what they are yet, I will have to get back to you on that one.
After some research, I now know that. I will have to give that a look. I was wondering if maybe forward abuse valve might be giving me issues? I also know that the accumulator pistons are still the original. I dont know why they were not replaced, but I want to get pin less Sonnax ones to replace them. Is there anything else I need to look at while I have pan dropped?
You can check all three accumulator pistons for cracks. The forward and reverse abuse valve maybe worn but I don't think that they would bleed off that much pressure.
Last edited by bbond105; May 23, 2022 at 10:40 PM.
I know the forward accumulator doesn’t have a crack, but the shank in it is worn out. The pin is very loose in it. On Wednesday, I will check pressures at the RPM you stated. Do I need to have it in drive or in park? Actually driving or at a stop with foot on break?
Measuring such a low pressure in Reverse and noting it is lower than even Park is the "KEY" clue to likely problems. And that pressure stays low or even lower with the connector off is another clue.
The mentioned accumulators and forward abuse valve are irrelevant to the Reverse circuit. Granted the reverse abuse valve could leak pressure but not that much unless it was left out. (And then Forward pressure would be OK)
I would bet money that the problem lies with the boost valve - perhaps it is installed upside down or the wrong one was installed (if a Sonnax replacement) or if the TG shift kit, the aluminum spacer was left out of a pre-2005 trans or installed on a 2005+ trans.
The boost valve is activated by the reverse circuit to automatically increase line pressure in reverse. With the connector removed, I would expect to see 200+ psi in reverse.
This diagram from the 4L60E Technician's Guide shows all parts of the Reverse circuit.
I would suggest dropping the pan and with a pair of snap ring pliers removing the cover for the boost valve, carefully taking out all the parts in order and posting a picture of them. Also tell us what year your vehicle/trans is. A picture of the area where the boost valve was removed would be helpful too as that will tell us whether you have an old-style or new-style pump, which affects the type of boost valve which should be there.
Note that you do NOT need to remove the trans to do this, just drop the pan. Unless the builder really messed up rebuilding the pump, we should be able to resolve this without removing the trans.
Thank you for your input on this. I will be dropping pan tomorrow and I will also take as many pictures as I can. The year is a 97 if that can give you any information at all. I know the boost valve was upgraded to a "transgo .500". But I was not aware that I could look at that without taking the trans out.
Measuring such a low pressure in Reverse and noting it is lower than even Park is the "KEY" clue to likely problems. And that pressure stays low or even lower with the connector off is another clue.
The mentioned accumulators and forward abuse valve are irrelevant to the Reverse circuit. Granted the reverse abuse valve could leak pressure but not that much unless it was left out. (And then Forward pressure would be OK)
I would bet money that the problem lies with the boost valve - perhaps it is installed upside down or the wrong one was installed (if a Sonnax replacement) or if the TG shift kit, the aluminum spacer was left out of a pre-2005 trans or installed on a 2005+ trans.
The boost valve is activated by the reverse circuit to automatically increase line pressure in reverse. With the connector removed, I would expect to see 200+ psi in reverse.
This diagram from the 4L60E Technician's Guide shows all parts of the Reverse circuit.
I would suggest dropping the pan and with a pair of snap ring pliers removing the cover for the boost valve, carefully taking out all the parts in order and posting a picture of them. Also tell us what year your vehicle/trans is. A picture of the area where the boost valve was removed would be helpful too as that will tell us whether you have an old-style or new-style pump, which affects the type of boost valve which should be there.
Note that you do NOT need to remove the trans to do this, just drop the pan. Unless the builder really messed up rebuilding the pump, we should be able to resolve this without removing the trans.
I went ahead and ordered a Sonnax .500 boost valve to replace the one I have. Tomorrow at some point I will drop the pan and check what you asked. I hope that having a Sonnax boost valve doesn’t affect the fact I have a transgo kit installed. I will also be turning the EPC solenoid back down the 1/4 turn since that didn’t help me with anything. I really appreciate your reply. Very good information.
I have both the Transgo shift kit and the Sonnax boost valve installed. I like the Sonnax because it has o-rings for better sealing.
he mechanic at a local trans shop installs the Sonnax boost valve in all/most trans he rebuilds even for Grandma cars due its better sealing capabilities. (Maybe he turns the EPC down a bit to restore stock shift pressure.)
@mrvedit I have the boost valve out. Got the pictures ready of the boost valve exactly how it came out (EDIT: I see where there is no spacer for this). I also went ahead and took the VB back out to adjust the EPC back down that 1/4 turn since that didn't do anything for me. I know there is a valve beyond this point, but I couldnt get it out. Nothing much to see here, But i was able to get the snap ring out and get the boost valve out of place.
I ordered a sonnax .500 boost valve to replace this, but im wondering if I got the wrong one. I have a 97 4l60e. This one i got says late models, no years in information. Could you point me in the right direction for the right boost valve?
Last edited by atlsoldier27; May 25, 2022 at 03:17 PM.
Reason: Adding a question.
Assuming that is the Transgo boost valve, then yes the spacer is missing as I suspected. I have never tested what happens if you leave that spacer off, but a lack of line pressure seems likely.
Neither the stock nor Sonnax boost valve uses such a spacer, but a builder using the Transgo kit should know that the spacer is needed for pre-2005 transmissions.
Sonnax makes two different boost valves, a longer one for pre-2005 and a shorter one for 2005+. (IIRC 2005 can go either way.)
Assuming that is the Transgo boost valve, then yes the spacer is missing as I suspected. I have never tested what happens if you leave that spacer off, but a lack of line pressure seems likely.
Neither the stock nor Sonnax boost valve uses such a spacer, but a builder using the Transgo kit should know that the spacer is needed for pre-2005 transmissions.
Sonnax makes two different boost valves, a longer one for pre-2005 and a shorter one for 2005+. (IIRC 2005 can go either way.)
@mrvedit I bought the wrong valve then. I will get the right one. I appreciate your help man. I will post back when I get all of this done.
If you do have the newer pump style then the boost parts in your picture are correct. Perhaps someone else can pass judgement on your pump's picture.
@mrvedit the transmission was the original trans in it from factory according to data plate on it. (Got 264k miles out of it) I’m not sure the difference of pump styles. Is there any photos of the differences?
Edit: looking at photos that were sent during rebuild, the pump cast has 97 stamped on it just like the VB itself has. So I’m pretty sure it’s early style.
Last edited by atlsoldier27; May 26, 2022 at 05:49 AM.
Reason: Adding info
@mrvedit the transmission was the original trans in it from factory according to data plate on it. (Got 264k miles out of it) I’m not sure the difference of pump styles. Is there any photos of the differences?
Edit: looking at photos that were sent during rebuild, the pump cast has 97 stamped on it just like the VB itself has. So I’m pretty sure it’s early style.
@mrvedit i got a transgo .500 boost valve from a local builder. Got it out in a pressure is up, but not up to where I’ve seen people state. Reverse is low until I press on the gas and it shoots up past 90PSI for sure. The delayed engagement that I was feeling on take off is shorter. But I still have the fluctuation in RPM in 4th gear. Could this be the PR valve above the boost valve?
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Rebuilt 4L60E issues. Finally fixed! 
