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Is there a test I can do to vary the pressure? Seems like I've seen where folks do that with a scan tool. If you know of a reasonably priced tool I could use to do that, I'd be down to buy one. I'll do the unplug check first of course. This question might be OBE after that check.
I ran the test with the main tranny plug out and I got a pressure reading of 240psi in park, and now I feel really stupid. I guess I wasn't giving it enough throttle when I monitored the pressure while coasting through the neighborhood yesterday. I had to be careful because the hose to my gauge wasn't long enough to go through window. So, I had to hold the door and gauge while driving. I put a longer hose on today, and was able to give it 75% throttle or so. At 75% throttle, I'm getting around 200psi which I assume is good. Still getting a weird hesitation between 2-3. Not super noticeable, but it's definitely there. Like I mentioned before, not seeing a noticeable change in rpm during the hesitation. Almost like a long drawn out shift (from a newbie).
Last edited by Weathers5; Dec 7, 2020 at 03:15 PM.
I ran the test with the main tranny plug out and I got a pressure reading of 240psi in park, and now I feel really stupid. I guess I wasn't giving it enough throttle when I monitored the pressure while coasting through the neighborhood yesterday. I had to be careful because the hose to my gauge wasn't long enough to go through window. So, I had to hold the door and gauge while driving. I put a longer hose on today, and was able to give it 75% throttle or so. At 75% throttle, I'm getting around 200psi which I assume is good. Still getting a weird hesitation between 2-3. Not super noticeable, but it's definitely there. Like I mentioned before, not seeing a noticeable change in rpm during the hesitation. Almost like a long drawn out shift (from a newbie).
I expected as much...
If the EPC was exhausting line-pressure down to 75 PSI all the time... things would be much worse than just a 2-3 shift timing issue.
The transmission would be slipping all the time!
Sounds like a plan! I'll drop the pan and pull the valve body off ASAP. What parts/materials do I need to make the upgrades? I'll go ahead and get that stuff.
Sounds like a plan! I'll drop the pan and pull the valve body off ASAP. What parts/materials do I need to make the upgrades? I'll go ahead and get that stuff.
It is going to vary...
We like to have the valve-bodies vacuum tested after being removed (to test for worn-out valves).
So before you take the valve-body apart, post some detailed photos... double checking what is stock and what is not.
After the vacuum testing, the valve-body can be disassembled and you can order any needed parts.
200 PSI is fine unless you are making over 500 HP...
Lets get that valve-body looked at and improved!
What do you propose that he do inside the valve body to improve line pressure? Much over 200psi and you'll blow the 3-4 snap ring out of the input drum.
I ran the test with the main tranny plug out and I got a pressure reading of 240psi in park, and now I feel really stupid. I guess I wasn't giving it enough throttle when I monitored the pressure while coasting through the neighborhood yesterday. I had to be careful because the hose to my gauge wasn't long enough to go through window. So, I had to hold the door and gauge while driving. I put a longer hose on today, and was able to give it 75% throttle or so. At 75% throttle, I'm getting around 200psi which I assume is good. Still getting a weird hesitation between 2-3. Not super noticeable, but it's definitely there. Like I mentioned before, not seeing a noticeable change in rpm during the hesitation. Almost like a long drawn out shift (from a newbie).
OK. Yeah, that makes a big difference. Back to the 2-3 shift timing then. Do you know what the line pressure is doing during these flare shifts?
I tried to watch it while driving, and I didn’t really notice a change in pressure. It’s kind of hard to monitor but I would’ve noticed any big change.
What do you propose that he do inside the valve body to improve line pressure? Much over 200psi and you'll blow the 3-4 snap ring out of the input drum.
What do I recommend he do to increase his line pressure? ...nothing at all... 200 PSI is fine for a near stock build.
I would prefer to see the max line pressure at about 235 PSI in units up to 450 - 500 HP... but that would require a change in the pump, via the pressure regulator boost-valve/ sleeve assembly.
200+ PSI is not going to blow the 3-4 clutch snap-ring out of the input-drum, when the transmission is properly assembled...
I have had the line pressure up to 320 - 350 PSI on the Transmission Dyno/ Run-Stand...
All that happens is the Pressure-relief ball in the pump opens to drop the line pressure (I build high power THM700-R4s at 300+ PSI all the time, I have to shim the spring for the ball).
It makes a cool sound and you can hear it quite well!!!
The valve-body modifications will be to help correct the 2-3 shift timing, additional 3-4 clutch circuit leaks, and other valve-body issues.
What do I recommend he do to increase his line pressure? ...nothing at all... 200 PSI is fine for a near stock build.
I would prefer to see the max line pressure at about 235 PSI in units up to 450 - 500 HP... but that would require a change in the pump, via the pressure regulator boost-valve/ sleeve assembly.
200+ PSI is not going to blow the 3-4 clutch snap-ring out of the input-drum, when the transmission is properly assembled...
I have had the line pressure up to 320 - 350 PSI on the Transmission Dyno/ Run-Stand...
All that happens is the Pressure-relief ball in the pump opens to drop the line pressure (I build high power THM700-R4s at 300+ PSI all the time, I have to shim the spring for the ball).
It makes a cool sound and you can hear it quite well!!!
The valve-body modifications will be to help correct the 2-3 shift timing, additional 3-4 clutch circuit leaks, and other valve-body issues.
Then we agree. I thought you were saying to upgrade the valve body for more line pressure, but I reread your post. I had misread what you were saying. Yes, more line pressure would be a pump mod. And yes, 200 psi is great for up to a moderate build, as long as you have a good 3-4 stack in there.
I've seen a few drums blow out at little over 200, and I've seen many of them survive at 230-240 like you were saying. It used to seem like a crap shoot sometimes. I only build a few of those things anymore, so I don't have nearly the "database" to draw from like I used to. I have more fun building the diesel stuff these days, but I do miss the old 60's sometimes.
A little bit of additional information...I put a higher fidelity pressure gauge on the transmission today and let it idle for about 30min. Stayed at 70psi the entire time. I’m not sure if that’s good info or not, but I saw someone on YouTube perform that test to see if the base pressure went down over time.
Also, I ordered the parts for the vacuum test stand and I hope to have it built by the end of the weekend. Hopefully, you experts can guide me from there.
I took the valve body off today and took a few pictures. I noticed a little bit of metal down in the pan which kind of scared me, and I did find one sizable metal shaving (pic attached). I think this shaving may have somehow gotten leftover from when I reamed out the hole for the sonnax tcc regulator valve. Please take a look at the pics, and let me know what y'all recommend I do next. Like I mentioned, I have the parts coming for the vacuum test stand and I should have that together by the end of this weekend. I found a diagram of circuits to vacuum test on the sonnax website. I suppose I can start there.
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