I went back to the tuner today, and explained my concern, and he said that the most pressure you can program with HP Tuners on these transmissions is 96 psi?

He showed me the tables, and yeah, they only went to 96 psi.

This guy is a well respected tuner in my area, and he claims that he has other customers with much more extreme builds running similar pressures with no problems.

Guys, I'm confused. Is he correct? And if not, how do you raise line pressure on HP Tuners? Should I pose this question on the HP Tuners board?

 

In later models I am not sure as I tune my own OB1 car and you can put in numbers higher that that even over 100 but I did find that the line for whatever reason actually decreases over 99 .
But want more you can have it, Add the little spring from my tips tricks to the boost valve. This will raise the line (As Marronmonster pointed out by simulating increasing AFL pressure) The advantage to this method is its easy, requires no tuning and does so without actually raising AFL which can cause issues of its own such as solenoid flooding at WOT , I am sure you have seen the post on occasion of people posting they have maxed out the shift pressure and still hit rev limiter on the 2-3 and wont shift till they let off a little. I have actually advised them to lower the AFL in tuning and ths solved the issue. The problem never was that the clutches could not hold but rather the solenoid was being overwhelmed and keeping the 2-3 shift valve stroked. (My little added spring to the 2-3 shift valve also mitigates this and makes for a quicker 2-3 shift from command to actual shift. This proven in the data logs.
The spring basically Mimics increase AFL without actually increasing AFL and its on a curve so has least effect at low and part throttle and most effect at WOT due to spring compression.
I actually add that spring to every build.

 

I've decided I'm going to do Frank's boost valve spring mod a try, but before I take the pan off again, I've got a question about some strange pressure pulses I've observed when cold.


Sometimes, when cold and idling IN GEAR, or at light throttle, the line pressure pulses between 100 and 200 psi. I can't ever remember seeing this before.
Should this be considered normal, or is something afoot?

https://i.imgur.com/ufPfBkS.mp4

 

Looks like slide bouncing a bit, add 1/2 quart

 

UPDATE: I added half a quart, no luck. I took some more videos, and this is definitely looking like a mechanical/ hydraulic problem.
I hooked up a scanner, and put the live data on the PC solenoid (amps, duty cycle, etc.) and the readings aren't moving around with the pressure. This leads me to believe it IS NOT a problem with the tune or EPC solenoid.

I have to appologize in advance for the quality of the videos; it was very difficult for me to film, hold the gauge, and keep the truck straight. This thing bounces all over the road, and the steering needs constant correction.

As a reminder, here are my pump specs: Sonnax .490 boost valve, Sonnax oversized PR valve (22.5" vacuum), .0015" rotor clearance, 10-vane rotor, slide spring shimmed with the @MaroonMonsterLS1 approve method of a 5/16" bolt in the spring.

https://i.imgur.com/Bnw2AAL.mp4


https://i.imgur.com/u3lNxWC.mp4


Fun fact: If you've ever wondered what I look like, you can see my reflection on the screen.

 

ok well i can only think of two possibilities. Missing pump vane or badly leaking pump surface leak. . What does it look like harness unplugged at about 1800 rpm ?

 

Here you go, Frank:

https://i.imgur.com/Dba6b7p.mp4

I'm not going to swear on a stack of Bibles that I DIDN'T leave out a vane, but I'm pretty sure I didn't.

IF I didn't, what would the course of action be? Get the two halves of the pump machined?

 

Well that does look like what it is , We shall see I guess , Other possibilities would be badly worn rotor in center where the converter drives. But that usually is more erratic, The max line video makes it look very timed and consistent. The pump leaking could but again not usually consistent.

 

Okay, now what?




All vanes are in place, none are cracked, all are the same size. Pump slide spring does not appear to be broken.

3-4 clutches were what got burned. I'm pretty certain this happened when I forgot that plug. The worst burning is closest to the apply plate.




Overrun and forward clutches are like new.



I'm really at a loss. Would an internal pump leak really do this.

 

Guys, is there any chance that the shimmed slide spring could be causing this?
A gentleman from Sonnax seemed kind of dubious about the mod, and said that too stiff of a spring could cause problems.

This will be the fourth build I've done this on, and I didn't have this problem then.

 

Agree on missing plug for the 3-4.
The slide is part of the regulation circuit. I know if it stick with spring compressed it can cause low line always or if sticks the other way very high line . I have never shimmed the spring. I did at one time limit travel. Till I started machining the pumps then found the line even just limiting travel was usually high and erratic.
I have only experienced the clock like tick look on the dyno when a vane was missing. But I have seen the needle be very erratic with a leaky pump usually accompanied with a groaning sound at high line, But not something you would likely hear in a running vehicle .
My guess now is leaky pump sides . off center converter (how does bushing and inside of pump rotor look?) Of course a badly leaky AFL valve can cause strange reading too.
But As I said I never shim the slide spring. Of course I also do not do the block /plug of the 3-2 valve either(though doubt any relation to pump bounce)
Usually the way I look for pump leak signs are dull areas on the face or back , But close look at your pick looks like they have been hit with a flat stone at some point so can't tell zooming in.
Chucking the back in a lathe is a quick way to see just how flat it is . The front however is a bit more difficult to do and set up. You could do some pressure test through the various feeds. See how much air comes out around sides of the pump. Of course I have found if the face or back have been changed the pump most certainly leaks badly (miss matched) . I have found if you swap front or back then you need a machined flat , You can't just replace one side.
Me depending on time, I would either machine both sides and of course pocket (pockets a bit of a lain on the lathe) or I would replace with remain pump or lowest cost alternative (with risk ) replace pump with a known good virgin one.
The bouncy reading at a steady RPM is either pump or AFL related.

 

Yes, I sanded the front of the pump.

Here's a video of the back in a brake lathe. I know it's not the most scientific way of doing things, but it's what I have available.
It doesn't look that warped; how much warpage would be considered allowable?

Also, I think it's worth mentioning that I did not observe this behavior (pressure pulsation) prior to the rebuild. What had my attention was low line pressure under load.

https://i.imgur.com/RhgIuJY.mp4

 

Looks a bit out but really only by cutting it can you really tell, Of the ones I have cut not only were they warped but the surface in general very uneven.
Just remember if you cut the back ya gotta cut the front and if you cut the front you gotta cut the pocket the exact same amount. Contrary to belief the pocket can be done on a lathe . You will have to modify the bit a bit and you will cut into the bottom of the slide stops. But its ok they are not for sealing just a stop. Does however sound like hell when doing it.

 

Well, I dropped it off at a machine shop today, I had to go to four different shop until I could find one who could do it (this guy machines a lot of GM pumps, so I have a good feeling), and it's gonna be kind of expensive ($160).

 

YES on a lathe kinda a pain to set up and usually takes several passes per side tracking slow. Just make sure when done you have enough slide clearance. Not super scientific but without the o ring in slide should be able to level pass a razer blade from the front body to the slide without hitting it and with no discernable gap either. If that is good put your oring in and go with it, I don't however suggest the spring spacer as the slide is a part of the regulator system . And with a fresh flat pump. Trust me you need that part of the regulator set up.
Also note you are cutting pump thickness so recheck your converter to flexplate gap .

 

UPDATE: I got the pump machined. It wasn't 100% to my liking: I had .0025" rotor clearance instead of the .0015" I originally had, but whatever.



Next, I removed the 5/16" bolt spacer, and reinstalled the factory slide spring assembly.




And here's a picture of the pump assembled with all the vanes, just so no one can say "you musta left out a pump vane!":




Last of all, here is @FranksCustomTrans boost valve spring modification:






Verdict: The problem (line-pressure pulsation) is gone. Was it the pump halves?

The machinist said that they didn't look too bad when he was cutting them, he didn't have to take off much material, and he has a lot of experience with these pumps ( he had about ten ready to go, for exchange, but not an early non-PWM pump).

Was it the shimmed slide spring?

Maybe, but I don't think so. I've done that for three different builds (excluding this one), and had no issues. I will do it again.

Did Frank's boost valve mod fix it?

I don't know, but it did exactly what he said: it bumped line pressure about 20-30 psi.

What I can tell all of you after this fiasco, is that I'm still having low commanded line pressure issues like I mentioned here. Almost identical.

Full throttle pressure will jump to 200 psi, then a second or two later drop to 150.

Obviously a tune issue.

 

Hmm well good and not, But here is a quick test , Unplug the harness does it stay at 200 psi . If so then a tune issue i agree . Could be MAF MAP TPS . But I did see a defective PCS do that once on the dyno. But only once. Once thing I probably should have mentioned checking to is the pressure relief in pump . But not likely