94 Car with 95(?) Transmission

[Gojira94]

I already posted this at LS1Tech's LT1-LT4 forum, but thought I might have better luck here (apologies). Kind of long but I think I have all the details I know.

I've got a 94 A4 that's been tuned like a 95. The trans is aftermarket, was in the car when I got it, had about 1000 miles on it when the engine fried and it came to me a couple months later. After the engine swap (stock replacement 94 Trans Am engine with 41k on it) I discovered that the trans is at least a 95, since it has PWM stamped on the pump housing.

So- when I got it running again, I didn't know the trans was PWM, got a hidden code 84 (3-2 downshift solenoid operation error). Limp mode, no OD, no TC lockup. I talked to my tuner and had the PCM flashed as a 95, ran a wire from PCM D6 to case connector pin U. That should have done the trick. I haven't tried to pull codes to see if the 84 is still there, but the behavior hasn't changed. No 4th gear, limpy starts.

Today I got a chance to check some things on it. I checked the resistance of the solenoids to see if one was out of spec. First I completely disconnected the battery and got values that were all above the spec. Then I connected both battery cables and got nothing at all. Then I disconnected the battery negative only and got these, which I think are legit values:

1-2 solenoid: 22.3 ohms; spec for 95 is 20-40 ohms
2-3 solenoid: 22.4 ohms; spec for 95 is 20-40 ohms
3-2 solenoid: 11.8 ohms; spec for 95 is 9-14 ohms
TCC solenoid: 29.3 ohms; spec for 95 is 20-40 ohms
PWM solenoid: 12.0 ohms; spec for 95 is 9-14 ohms

I just put the meter in the PCM connector pin holes with the - side and the + side of the meter to the batt + block in the pass. side fender behind the batt.

When I first ran the wire for the PWM solenoid, the battery would drain to dead in about 2-3 days. It's been a while since I had a chance to do anything with the car. Thought I had misplaced the pin at one end or the other, that's why I did a sanity check to see if I saw correct resistance in the solenoids at the trans end, or possibly a ground fault. That tells me the wiring is right at the case end, and the only thing I touched at the PCM end was add the wire on D6. I'm stumped for the moment.

Anything else I can cover with a multimeter before I assume there may be mechanical damage to the trans? This is a K-case trans that would be worth rebuilding but $7-900.00 is more than I can swing right now. May look for a used 95 from a known F-body in the interim.

I saw from Frank Cahall's sticky that "'94 computer won't recognise new TCC strategy, and will burn lock-up clutch and 3-4 clutches up." I wonder if this has already occurred over the 1000 miles or so it was run in the car with the original '94 factory tune.

Thanks

[popo8]

Cahall

[CPT]

When you're referring to "Limp Mode", you mean 3rd gear starts and high line pressure? If it's in limp, it won't have 1st gear.

Frank

[Gojira94]

Correct- max line pressure and 3rd gear start mode, etc per GM ("soft landing mode"). I really need to check again to see if the code 84 is gone with everything connected. Thinking back on it, I may have caused an unrelated issue with a drain to ground that's coincidental. I was trying to get the driver's door master switch working consistently to cycle the locks. I'll unhook the master window switch and see if the batt drain stops, and scan for the code 84. May be just coincidence on the batt drain, and the logical fault is actually gone by running the wire and updating to 95 tune, but I don't observe a change in how it's working due to mechanical damage. Thanks for the help- I'll get back with an update as soon as I can with more info.

[CPT]

If it's in limp mode then it has to have a code. Have you checked for 12 volts at pin "E" in the harness?

[Gojira94]

In the past I've had difficulty getting the case connector off without first supporting the tailshaft housing with a jack and unbolting the trans mount and letting it drop a little. But no big deal to do that if need be to get at pin E in the case connector. Just a pain with the cooler lines in the way and the tunnel so close on top. Is there a trade secret to getting the case connector on/off without partially dropping the trans? :) It seems that Pin E provides power for all the solenoids in there. If none of them were getting power due to a fault with pin E, what would the behavior be? Same or (?)

Sorry for all the questions. Just trying to get my head re-wrapped around the problem and maybe come up with a solution this time.

[CPT]

No power to pin E will put it in "limp mode". I usually don't have that much trouble getting the case connector off. It's pretty tight though.

[popo8]

Just wanna say thanku to Frank. He never lets us (this community down)...

[Gojira94]

Just wanna say thanku to Frank. He never lets us (this community down)...

Absolutely. Very much appreciated. Be back with pertinent info ASAP.

[Gojira94]

I haven't been able to spend any time with the car to get firm answers to helpful questions, sorry about that. Car's in an outbuilding at our old house, presently rented out (we reserved the outbuilding). Hit the busy (silly) season and it's been cold as crap since. I know, NC folks don't know anything about real cold compared to folks in the Northeast right now. In the past I've built cribbing under the car to hold it securely with no chance of moving/ falling while I do work underneath. The pre-work setup will take up some time the next time I get over there. Just weird wrenching at somebody else's house who you only know because they rent from you.

Here's what I do have to add until I can get some real data to share:

1) If the ignition feed circuit (circuit 239, fuse 11; provides power to all solenoids) is open, multiple DTCs will be set (per GM service manual). Since I only have one DTC- code 84, my gut tells me there will be power at pin E. In my notes from April 2011 when I first discovered the issue putting the car back together, I had continuity at pin E from PCM pin B29 (5 volt reference).

2) I re-read Frank's details on the 95 trans in the 4L60e sticky here and one over at ImpalaSSForum, posted there by member V8killer. There was mention of the 3-2 downshift changing around mid-year from 9-14 ohms to the 20-31 ohms solenoid. I don't know if that refers to solenoid change and corresponding PCM programming in just the B-body cars, or all car lines. I'm not sure where to even look in my F-body PCM programming to find what value range the PCM is looking to see. It'd be hilarious if changing the 3-2 solenoid to the 96 style fixed it. I hate to throw parts at anything, but I might pick one up as something to try while I'm at it.

[Gojira94]

Back from the dead thread.

With the help of some folks who do lots of GM EFI tuning on another forum , it was determined that the tune was bad. The 94 PCM mask was still used and the tables that are normally empty for PWM control were filled with 95 PCM data. This would never work because when the PCM reads its mask info it treats the normally empty areas of the EPROM as empty, no matter what.

So I got hold of a factory 95 tune and did it myself, basically not much more than doing the O2 sensor relocation since it has headers and duals. The guys at the other forum verified for me that everything was good and it was 95 code and the PCM was reading the tables for PWM.

It still throws a silent code 84. My last idea is to pull the internal solenoid harness, thinking it may be a custom harness of some sort or is just faulty. First pull it and clean it and check the pinouts vs what it should be in the wiring diagrams.

I'm just out of ideas...

[CPT]

You most likely have a '96-up 4L60E. Simply swapping the solenoid will get rid of the code, but it doesn't address the real issue. the actual valve body casting and 3-2 valve line up are different. Just changing the solenoid without addressing the other mismatch will cause forced downshift (kickdown) issues.

Frank

[Gojira94]

Thanks, Frank

I'd almost give my left nut for a copy of the build sheet on this transmission, lol. Can you elaborate on the 3-2 valve lineup and what those forced downshift issues look like? Would replacing the 3-2 valve be part of addressing the real issue? I'm going to go back and read the year swap thread if I can find it to understand the differences and how to make different years work back and forth. I may try the solenoid swap and see if that takes away the code and gives me the issues with downshifts like you said. Or If I knew what to look for on the valve body casting I can drop the pan one more time and look for visual evidence that it's a 96+ transmission.

[CPT]

Thanks, Frank

I'd almost give my left nut for a copy of the build sheet on this transmission, lol. Can you elaborate on the 3-2 valve lineup and what those forced downshift issues look like? Would replacing the 3-2 valve be part of addressing the real issue? I'm going to go back and read the year swap thread if I can find it to understand the differences and how to make different years work back and forth. I may try the solenoid swap and see if that takes away the code and gives me the issues with downshifts like you said. Or If I knew what to look for on the valve body casting I can drop the pan one more time and look for visual evidence that it's a 96+ transmission.

You can't just swap the valve. The actual valve body casting is different. The up to '96 valve body used a 2 piece 3-2 valve with 2 holes in the separator plate over the valves. In '96, the valve changed to a 1 piece design with only 1 hole in the plate. The problem now is that you can't simply swap the valve body and plate now because the pump has to match the valve body. The ONLY way to make what you have work correctly in your car is to pull the trans back out and have the front pump, valve body, separator plate, and internal wiring swapped. You can Ohm the 3-2 solenoid to see if you have the wrong one. Yours should have a tan connector with steel stem that goes into the valve body or a gray connector with plastic stem. Tan connector with plastic stem is the wrong one for a '93-'95 vehicle.
Depending on the mismatch, it either won't have kickdown or will exhibit a 3-neutral-2 downshift.

Frank

[CPT]

1996: The 3-2 downshift strategy was changed to an on /off arrangement. The 3-2 downshift solenoid was changed to a 20-31 OHM solenoid, from the previous 10-15 OHM solenoid. The 3-2 control valve was changed to the second design valve. The easiest way to identify the valve is, the second design valve will fall out as soon as the solenoid is removed. The first design has a plug and retaining clip. TCC solenoid remains 10-15 OHMs, which is the same as the '95 arrangement. Has PWM stamped cast in pump. pump is the same as '95. Will not interchange with '95 unless changing 3-2 solenoid, valvebody casting, and seperator plate. Has holes in plate marked in diagram. '94 or '95 computer will not accept the 20-31 OHM 3-2 solenoid and will throw an SES light and throw the transmission into limp mode. Some less knowledgeable builders will swap the solenoid so the computer will see the correct resistance, but the valve itself then causes downshift issues. If only the solenoid is changed, it will result in a 3-2 downshift cut loose. In other words...3-neutral-2 downshift. Speedo moved to passenger side of tail housing, but easily changed.

[Gojira94]

I get 11.8 ohms, right in the middle of the spec for 94-95's 3-2 spec of 9-14 ohms. The VSS is on the driver's side but that could have been moved when it was built. If it's a 96+ transmission after all I think I'd rather find a 94 trans and call it a day. I'm tired of fighting this thing. I did change the 3-2 solenoid when the problem first appeared in 2011, not knowing any better. I don't recall whether or not the valve tried to come out behind it but I don't think so.

[Gojira94]

Finally have some pictures of the valve body/ solenoid arrangement. I do see on one of them the valve body has 95 cast into it, and a number sequence that looks like 3678593 or 3678595 but my eyes aren't great and neither is the picture, so 3s look like 8s look like 5s and 6s to me, lol.

I guess next I need to dig into the internal harness. Pull it and compare to a known good one for 95 maybe, if I can't at least account for the presence of the right number of wires coming from the case connector.

[Gojira94]

I fished the case connector and VSS pigtail up to the engine bay where I can work with it easily. I have a 1 1/4" socket to pop the case connector out of the case. I'm trying to get the pressure control solenoid out of the way for that but it's hitting the accumulator housing.

Before I pull the accumulator housing I wanted to ask before I run into any surprises trying to reassemble. I know there's a pair of pistons and a pin that moves on the housing side, the other pin is part of the housing. Spring in the middle. Bolts are torqued to 110 in. lb. on reassembly, careful with the acc. housing gasket of course. I think I'm going to go ahead and just be careful getting it down so I don't have the spring scattering stuff around as it comes off. Then keep going with the internal harness and removal of the solenoids.

Goal here is to be able to bench test the whole arrangement outside of the trans using 12V available at the battery.

[Gojira94]

well, damned if I can get the case connector out of the case. I'd read that a 1 1/4" 12 pt socket is the way to go but I can't force it down onto the tabs to compress them. Trans is in the car, limited room but I can get a prybar on the back side of the socket and apply pretty heavy force to it but it's not going over the tabs. Maybe should have picked up a 1 5/16" lol.

Interesting what I saw when I removed the accumulator housing. From the acc housing going upward toward the case, I have 3 large washers on the fixed pin in the housing, a spring perch on top of the washers, a spring, just one piston, and another spring on top of that. It appears the separator plate blocks the recess that would be in the case. Maybe I'm thinking 700R4 and this is normal and the 1-2 and 3-4 are on opposite sides, with one of them in the valve body.


Getting the case connector out- I guess my next step is to try to get at it better from the top. For what I've got that means unbolting the cross brace and letting it hang a little lower and maybe get on top of it better and figure something out. Kind of pissed I'm this close and stuck.

[Gojira94]

Lowering the trans a bit helped me get the socket wiggle I needed to drop the case connector through the case.I pulled all the solenoids and checked them again for resistance. Values in ohms are:

1-2 shift 21.2
2-3 shift 21.9
Press. Control 4.6
3-2 control 11.4
TCC 23.8
TCC control 11.2

Here's the bench- notice the PCM removed so I can apply voltage down the wire to pin E and ground through the PCM connector pins for each solenoid (except the pressure control solenoid). PCS can be tested with a 9V battery briefly. Testing from PCM down to solenoids gives me more confidence things are working. Honestly, I'm hoping to find something wrong with the harness and just replace it and be done. I'm done for tonight, testing tomorrow and hopefully the final answer.

[Gojira94]

I tested all the solenoids except the PCS, will have to dig up a 9V battery for that one, but I did check the resistance between the PCM pins that go to it (no direct 12V from pin E, only gets signal from PCM).

The 3-2 is the newest solenoid since I replaced it back in 2011 when I first encountered the issues. The PWM solenoid click doesn't sound nearly as stout as the 3-2. They are 2 different manufacturers, the PWM has been in there since before I got the car.

Here's the kicker- the TCC solenoid (built into the harness) does NOT click for me. I can't find a definitive answer as to whether it SHOULD make an audible click, but I'd at least think so. I tested 1-2, 2-3, 3-2, TCC, PWM with IGN239 circuit hot with PCM disconnected and used a small wire to ground the PCM connector pins at each solenoid's PCM location. To eliminate the engine harness I went through the case connector on pins E and T straight off the battery. Again, the TCC solenoid does NOT click. Its resistance is still at 24 ohms after this testing through PCM connectors and direct to battery.

Frank must be on vacation, had hoped to hear from him. :D

[Gojira94]

I picked up a new harness with TCC solenoid. BWD S9844. Has Delphi printed on it in a couple places. Same manufacturer overseas makes a bunch of Delphi stuff these days, all the same. I tested the new harness the same way as the old one and this time I got a nice loud click from the TCC solenoid. Got the car all back together, just have to fill up the fluid and let it rip and scan for codes. It's too loud to fire up after 9PM in my neighborhood. Answers tomorrow. If it's fixed I'll learn to dance a jig, lol.

[Gojira94]

Tentatively going to say it's resolved. But not how it thought it would be.

Yes, the harness needed to be replaced due to the hidden issue with the TCC solenoid built into the harness. But that wasn't the cause of the code 84 3-2 downshift circuit problem that kept it in limp mode. I replaced the harness, buttoned it up, filled it up and crossed my fingers. I used GaryDoug's Scan9495 utility to monitor for trouble codes and the code 84 almost immediately popped back up. I'd clear it and it'd come right back in 2-3 seconds. Looking at the electrical faults tab in the program, it made me think from another direction when it said 'open circuit' on the 3-2 downshift solenoid circuit. I have a spare PCM...

The spare was from a 94 Z28 with 3.23s. So I threw it in and fired it up and scanned again. No codes, no circuit faults. The current PCM threw the code 84 under both 94 and 95 calibrations. I ran it for almost 20 minutes on the spare- no codes, no faults. Ok, so I can't use a 94 tune on a 95 trans. My 16210041 calibration ID on the PCM I've been using all along has the 95 code and some small mods for O2 relocation, etc., and has good data. Could the PCM internal circuit traces for the 3-2 circuit be damaged?

I set up my flash bench and uploaded the tune to the spare PCM with EEHACK. Threw it back in, crossed my fingers and... no codes. took it for a run around the block. Amazing to feel first gear in D at normal line pressure. I'll take it for a longer drive later and see how it goes. But it's never run for more than a few seconds before throwing the code 84 and now I've had 2 run cycles of nearly 25 minutes with no DTCs. I never considered the PCM might be at fault.

The mail order tune I got in 2010 was useless garbage and the reflash was good money after bad but it put me on the track of finding the hidden TCC solenoid problem and I learned more about the 4L60E. Way more than I wanted to actually, but it was good to learn.

[superspirit]

Good to hear that you made so much progress, persistence pays off.

[Gojira94]

Good to hear that you made so much progress, persistence pays off.

Thanks! I drove it for about 1/2 hour at sunset around the rural roads where I live and it really rips now, despite the 2.73:1 rear. I would have liked to put the 3.42 from my M6 in it with a ring spacer to see how that would feel with the corresponding shift points. 3.23 A4s are pretty quick, thought 3.42s with an A4 would be interesting. Sorry to say I'm selling it and dividing the proceeds between my 94 M6 upkeep and a 92 C1500 400HP TBI project. Neither of my step daughters are interested in it. They're more in love with the phone integration gadgetry of my wife's 2017 Subaru Forester. ~sigh~