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About a week ago I rebuilt my 700r4 with the street strip kit from probuilt. Since the rebuild, it has a couple quirks that I'd like to get sorted out. I've been working with Dana from probuilt but figured I'd post here to get some more ideas as well. Since it's probably important information, the torque converter is a new Edge 2600 stall 9~ish inch unit.
Quirk 1: After sitting overnight, particularly on cold nights, the car seems like it's laboring, then after some driving it will suddenly feel like it frees up (usually when I'm in the 30+ mph range). Most of the time but not all the time there is a little pop/clunk when it frees up. Dana suggested it could be a sticking governor causing me to take off in a higher gear. I cleaned and made sure the valve moves freely in the governor and it still seems to happen. I'm wondering if maybe the 2-4 band is somehow not releasing fully?
Quirk 1 "solved": Turns out that it is the SA changing when the threshold of 113* is reached. At the higher stall with the new converter, it has quite a drastic change. At 2400 RPM it goes from 14* to 33* which was the free-up sensation I was feeling.
Quirk 2: During anywhere from about 1/3 to 1/2 throttle acceleration (maybe more), there's some sort of weird lock-up issue. It feels like it goes into lockup for about 1 second, comes out of lockup for about a second, then goes back into lockup and stays there. This happens consistently. Under light throttle it just stays in lockup after it gets there.
Quirk 2 solved: Issue was the trans has a N/O 4th gear switch, but the AUJP chip was expecting a N/C. So it thought it was in 4th in gears 1-3 and out of 4th in 4, so the tables it was using were mixed up.
Quirk 3: During WOT acceleration, in first gear (I think) it feels like there's a grinding or vibration. After it shifts out of first it smooths out. Maybe it could be a clutch grabbing and slipping rapidly that shouldn't be engaging? It's a bit difficult to describe.
Any ideas on what could be happening or things to test to narrow down these quirks would be appreciated!
Last edited by someone972; 02-18-2016 at 04:01 PM.
I seem to remember a similar feeling on my first rebuild on a 4L60E in a Tahoe. It would feel like something was dragging when first starting up cold and backing up, and I think in first gear as well. Then it would free up all at once, like something was dragging and then suddenly released. I never figured it out, because it went away after a while on it's own. But if I was to guess, I may have had the band too tight.
I did install the Corvette servo as part of the rebuild kit. Maybe I do have the band too tight still (I left out the gold washer even), or the piston could be binding up in the bore perhaps?
A quick update about issue #2: I checked my datalogs I took and the TCC Status does in fact go LOCKED->UNLOCKED->LOCKED corresponding with the issue. What would cause this to happen? Could it be the pressure switch is bad, or maybe there's actually some sort of hydraulic issue that causes it to sense pressure, then pressure drops, then returns? I can post a picture of the graphs of the issue, and maybe the datalog if it would be helpful. I'm stumped so I'm happy to hear any ideas.
In your data log check the TPS%, MPH, and 4th gear (high gear) switch status. If the 4th gear switch is intermittent that can cause the ECM to switch between the 2nd & 3rd lockup table and the 4th gear lockup table.
These tables are based on TPS% and vehicle speed. Either the MPH or the TPS% drops out the ECM will unlock the convertor.
Ok, I found the 4th gear indicator and checked it and the other values. The TPS% and MPH are both fine, no drop-outs or weirdness. The 4th gear bit shows that it's in 4th for the lower 3 gears, then when it goes into 4th it switches to saying not in 4th and that's when the lockup drops out. I should note that I'm using the S_AUJP v5 NbO2 adx. The memcal is not the original for the car, when I swapped from a 305 to a 350 I got an AUJP for Automatic, so I'm not 100% sure the flags are set up properly.
Forgot to mention: the transmission apparently came from a U-Pull-And-Pay, so although it is a V8 700R4 I can't verify if it has been set up properly for my application, or whether the pressure switch is N/O or N/C. Would having the wrong pressure switch cause this issue? Maybe I could get some new switches and try swapping it out for the other style?
It looks like I'm going to have to go the chip-burn way, which isn't necessarily a bad thing since I've been meaning to get set up for that anyway. I verified that there is in fact a NO switch in my transmission, and that the AUJP chip I installed is expecting a NC. Since I can't for the life of me find a NC switch I'll just have to do the burn. To test it without having a NC switch, we rigged up an inverter using a relay. I happened to have the four prong male and female connectors, so it just plugs in to the trans and into the existing wiring harness and flips the state of the sense wire. Since doing that it shows up in 4th gear like it should and the issue with the lockup is gone, so issue #2 is now solved (although I need a more permanent solution than our hacky relay). Thanks for the help.
Still would like any opinions on quirk #1 or #3, although I'm suspecting a sticking valve or bad band clearance. I've ordered a couple new band apply pins just in case. I believe it feels like it frees up when in 3rd, so I'm thinking the band is holding it in 4th and then releases.
So here's a bit of a brain teaser for you. Today I definitely felt a free up in 4th gear, at around 37 mph. The sensation is that I have a constant throttle, then all of a sudden I can feel the car accelerate a little and the tone of the engine changes, and I thereafter have to use less throttle to go the same speed. Note that the TPS is functioning perfectly well which I verified through the logs. I'm still not ruling out the band, but it may not be the only issue. There's only so many clutches, so I guess we can rule out the following:
3-4 clutch - Applied in 3rd+4th, so would not explain the "free up" in 3rd/4th.
Forward clutches - Obviously (unless it was slipping for some reason?)
Overrun clutches - Obviously
So that leaves the band and the reverse clutches if I'm remembering correctly. However, seeing as it seems to labor in reverse as well, I'm still suspecting something up with the band.
Resurrecting this thread from the dead. I've since tried cleaning out the valve body again, making sure that all valves move freely. I've also increased band clearance with a shorter pin, and it made no difference. The servo's seals all look fine, and it moves in the bore OK (doesn't seem to have any servo-related shifting issues). I'm starting to suspect torque converter, since I can't think of anything else that would cause the symptoms I'm seeing. My best guess right now is that the one-way clutch on the stator is slipping when cold, and suddenly grabs when it gets warm enough. I'm going to put the old torque converter back on and see if it changes anything. I'm not too concerned about putting the old one back on since there was hardly any debris in the pan before the rebuild, so should be fine.
I've figured out why it feels like it is freeing up, and it is actually a tuning issue. I took it out and kept in in second gear so the rpm would be up closer to where it is with the higher-stall converter, and I found out that right before it indicates closed loop there is a 20 degree jump in spark advance which directly correlates to the "freeing up" feeling. You can see in the following graph that after the spark advance the RPM raises 100 rpm without me doing anything with the throttle (as expected). So I'll be moving the discussion to the DIY prom section, and will post the link here when I make the thread. EDIT: Here it is: https://www.thirdgen.org/forums/diy-...-tune-not.html
Last edited by someone972; 02-18-2016 at 03:06 PM.
Glad you fixed it, now re-install the longer pin. The minimum band clearance is for the 3-4 clutch pack apply, it helps get more oil to the clutches, instead of moving the band off. Remember the 2-4 band is on in 2nd and 4th gear (overdrive).
I'll replace the old pin when I pull the transmission again to remove the old torque converter. By the way, are you selling the Vigilante torque converters again? I'm pretty happy with the Edge, but after putting the old torque converter in I think I'd prefer something more around 2200-2300 like you originally suggested. Also, is there any way to raise the 3rd gear shift point under very light throttle by a few mph? If not I won't worry about it, it works just fine but would feel a little better coming in just that little bit later imo.
The Edge torque converter can have the stall brought down some. The Vigilante cannot be brought down any lower than the Edge, and probably not as low as the Edge torque converter. With the 9.5" lockup an apx. 2,400 stall is about the lowest it will go with a mild cam. If the camshaft is more a mid range to big end camshaft, then the stall will be lower as the torque decreases with more camshaft duration. With the stock diameter (12"), the stall can be brought down to an extremely low stall (1,400 - 1,600 rpm).
There are "two" springs in the governor. Remove the weaker of the two springs and this will make the part throttle shifts later. Otherwise use the Sonnax shift extender here to get the later part throttle shifts.
01-12-2016, 12:10 PM
