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Maybe I missed it, did you discuss part throttle accumulation plans? Are the accumulators modified? Or does the computer manipulate accumulation? I have an idea of how it works on the 700R4 but never the 4l60e
Looking good. I'm sure assembly seemed easier the 2nd (or n'th) time.
Did you check/estimate the end play on the input shaft?
The spec is .015 to .035.
Yes, I checked it and I would say it's samewhere in that range. I might take out the feeler gauge this morning and double check. Assembling it the second time definitely went much faster. The slowest part was putting the valve body back together because I was following along with the transmissionbench videos to make sure I got the check ball locations and bolt lengths correct. Also I prepped the dowel pins for the pump install and valve body the night before...they really help make those two parts of the rebuild a breeze.
Maybe I missed it, did you discuss part throttle accumulation plans? Are the accumulators modified? Or does the computer manipulate accumulation? I have an idea of how it works on the 700R4 but never the 4l60e
The computer controls/changes line pressure during the shifts. Tuning tables set the pressure mostly according to torque, but can be modified according to trans temperature (to soften shifts when cold). Separate values for the 1->2, 2->3 and 3->4 shifts.
Changing the tuning values is very noticeable and gives fine control. I have fiddled with them to give me quick but non-jerky shifts for light throttle city driving. I have the Transgo HD2 shift kit installed with my own mods.
Cory: Do you have a higher stall converter? A stall converter softens the shifts.
Trans is back in the car and I did a test fire with pressure. Trans at idle in park is 75, in reverse, its 150ish, in drive it starts around 75, but if I put a load on the engine, I see it move with load(something I didn't see before I tore it down). I also saw line pressure as high as 225 in neutral right when the car almost stalled(running with open headers and no o2s for the test start). I know based on the info in this thread that reverse should be closer to 200, is that any concern? Overall I'm really happy that I see line pressure moving with load. I will try to test drive the car sometime this week, I need to finish getting my new exhaust installed and there is still some snow melting onto the roads around here. Thank you to everyone that has contributed to this thread, I have learned a bunch!
The computer controls/changes line pressure during the shifts. Tuning tables set the pressure mostly according to torque, but can be modified according to trans temperature (to soften shifts when cold). Separate values for the 1->2, 2->3 and 3->4 shifts.
Changing the tuning values is very noticeable and gives fine control. I have fiddled with them to give me quick but non-jerky shifts for light throttle city driving. I have the Transgo HD2 shift kit installed with my own mods.
Cory: Do you have a higher stall converter? A stall converter softens the shifts.
I kept my Circle D at the stock stall. My truck will never see a track, so I went with stock for gas mileage and less heat. I really only notice it in stop and go traffic repeatedly shifting 1-2 and 2-1. It's not harsh, but when you're stuck in traffic for an hour the bumps get a little annoying. It's like a reminder that I'm stuck in traffic.
Trans is back in the car and I did a test fire with pressure. Trans at idle in park is 75, in reverse, its 150ish, in drive it starts around 75, but if I put a load on the engine, I see it move with load(something I didn't see before I tore it down). I also saw line pressure as high as 225 in neutral right when the car almost stalled(running with open headers and no o2s for the test start). I know based on the info in this thread that reverse should be closer to 200, is that any concern? Overall I'm really happy that I see line pressure moving with load. I will try to test drive the car sometime this week, I need to finish getting my new exhaust installed and there is still some snow melting onto the roads around here. Thank you to everyone that has contributed to this thread, I have learned a bunch!
150 PSI with no throttle input in Reverse is PERFECT!......EPC will boost it higher with throttle input.
150 PSI with no throttle input in Reverse is PERFECT!......EPC will boost it higher with throttle input.
EPC boost up to 225 PSI is also very good.
This is with the Sonnax boost valve?
Correct, the sonnax was installed this time around. So the question is, was the boost valve the issue or the EPC? I'm leaning towards the EPC since I did not see pressure move with load before I tore down the transmission.
Checked pressure again today and it was the same results as yesterday. Finished installing the new exhaust on the car and took it for a 5 mile test drive that was a success. I want to put the car back on jacks and do a few cosmetics to it but I will be out accumulating miles this week through weekend as long as the weather is nice.
Correct, the sonnax was installed this time around. So the question is, was the boost valve the issue or the EPC? I'm leaning towards the EPC since I did not see pressure move with load before I tore down the transmission.
When you change both at the same time....Tough to know. You could always reinstall the old EPC & retest.....In Park/Neutral! If you didn't have a TG boost valve in there before I wouldn't even consider the Boost Valve & Sleeve.
We have to consider that when you removed the Current from the EPC....Pressure was good, Meaning the EPC was working In it's extremes (0 amps & 1.0 amps).
The EPC is a pretty bulletproof part....Especially the "Black" Holley ones, But I always suggest installing new electronics & harness in all transmission builds because "**** Happens".
Agreed that the black Holley EPC's are pretty robust (unlike the later Delphi's), but they do fail from time to time. I've got one on my bench right now that died from failed EPC solenoid.
We have to consider that when you removed the Current from the EPC....Pressure was good, Meaning the EPC was working In it's extremes (0 amps & 1.0 amps).
Yea, I thought it was weird that the EPC was working in its extremes as well, but I'm not an electrical engineer lol.
Anyway, I have about 30 miles on the rebuild now and will be hooking up the pressure gauge in the morning to make sure everything is still working as it's supposed to. I also updated the tune to incorporate torque management back into the trans.
Trans has about 300 miles on it now. I took it to opening day at the local track yesterday and got 5 passes in on it.
I'm pretty sure i lost 2nd gear in the car/ maybe never had it. The car is clearly doing a 1->3 shift at WOT. Under part load driving 2nd gear never felt right(in both rebuilds). I wasn't sure if it was just characteristic of this big of a stall, but after doing some more research this morning I'm convinced something isn't right with the 24 circuit. After my first rebuild failed, the band still looked new, but the 34 clutch pack was toast(assuming this was due to low line pressure with the faulty force motor). Now that I know line pressure is working correctly, what could be causing the 24 circuit to not be fully energized? It has a brand new band and servo pin. The accumulator pistons are sonnax metal replacements. I checked the encased checkball for leaks during the first rebuild. Also, all electronics are new in this build.
I plan on dropping the pan to see how the fluid looks today.
EDIT:
Dropped the pan, fluid was a little dirty, but I'm pretty sure I caught the issue in time to save the frictions this time. I'm thinking something in the valve body may be wrong. I checked servo end play and removed both shift solenoids. So far everything was done correctly. I definitely need one of the experts to chime in with their ideas.
Similar issue was just outlined in a recent thread:
Do you still have 2nd gear start with your transmission?
I lost 2nd gear start when I had problems with my 2/4 servos. Also, if my gear selector was in 3rd or 4th, I would always skip/flair over 2nd and go from 1st right into 3rd. I know you said you checked the servos, but I would check them again.
Are the screens clean in your shift solenoids? And that other thread you posted has a very good point that needs to be confirmed. I'm not a 4L60E guru, but I hope this makes sense and may give you some ideas.
^Servo play seems fine. Both solenoid screens are nice and clean. I checked the shift solenoid valves as much as I could.(could not get the 23 HD valve out). I would say with the selector in D2 the car is most likely doing 3rd gear starts. The trans is commanding 2nd but I'm in 3rd gear. Corvette servo is brand new this rebuild and I checked the picture of i took of it right before I put it in, it's assembled correctly.
Looking at that manual, it looks like a stuck 12 accumulator piston or valve could be the culprit. Since I have 4th gear and the servo/servo pin/ 24 band are all 300 miles old and servo travel checks out, further confirm my theory. I disassembled the 12 accumulator both times and am confident the piston is not stuck. I'd like to inspect the accumulator valve, but am unsure how to get it out because I think it is held in with a pin. I'm waiting for someone more knowledgeable to chime in as I'd like to keep the valve body matted to the case unless I really need to drop it to get the accumulator valve out.
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.....In Park/Neutral! If you didn't have a TG boost valve in there before I wouldn't even consider the Boost Valve & Sleeve.
