P0740

[Izzy]

Loren,

Just got the code P0740 (no CEL) in my 99 996 Tip. Would description be the same as the Boxter, torque converter clutch issue?

The car seems to run perfect, and the transmission is smooth as silk. I am a bit perplexed and heading. Thank you

Izzy

[Loren]

http://www.renntech.org/forums/index.php?s...ost&p=49446

[Izzy]

Ouch. Thanks, I was affraid of that. Will check fluid and if that is not it, head for the dealer.

[Izzy]

Results,

Had to wait 4 hours for oil to cool down to 35C. Added with the pump about a quart of ATF before it began to spill, I was surprised. The older ATF looks pretty dirty, so will do a full drain and refill this weekend. Hope that is it and not a major mechanical issue. Will keep checking the codes and let you know. Thank you

Izzy

[Loren]

If you are going to change the fluid I would drop the pan and change the filter and gasket too.

Didn't you do this last year? How many miles?

[Ubermensch]

I don't own, and therefore am not as familiar with, the Tip transmission, but in my past ownership experience of automatic cars, a simple drain and fill was not every effective at replacing the fluid. In particular this does not change the fluid residing in the torque converter itself. I believe a drain and fill generally changes about 20% of the actual fluid in the system. Many people prefer a full flush which actually drains and fills the system while it's running and pumping to do a full change. Alternatively you can repeat the drain and fill procedure without it running multiple times to bring the old fluid to a dilution level you're comfortable with.

Shawn

[Izzy]

Loren,

13K miles ago I did the filter, gasket and fluid. So I probably won't change filter again. Hopefully it was just low on fluid, but will track the code for the next few hundred miles. After adding more fluid last night, it doesn't "feel" to shift any different, still smooth as silk. Thanks

Izzy

[Izzy]

This morning drained and fillled (almost 6 quarts out of the 9 needed for full capacity) of ATF. Follwed shop manual instructions of drain and filled. The old one, with only 13K miles, was pretty black. I am wondering if 10 track days (200-250 miles each) since last change puts more strain on the Tip. Codes are cleared, so will check daily to see if it recurs.

The shifting was very smooth still, no issues on power, all else was perfect with the Tip even on a 100F day on track.

Fluid was at 38C when changed, and a quick drive afterwards showed no difference in shifting, as measured by the "butt meter"

[Izzy]

Here is the fix for code 0740 on Tiptronic. After refilling fluid (by the dealer the last time), the code would come back after 100 miles or so. The potential fix from Porsche was a new tansmission, around $7K. Before I spend that kind of money, did some research that lead me to the following for P0740 code:

Since the fluid was changed, went to step 3. Here is the location of the pressure regulator and how to remove it. You have to drain the fluid and remove the ATF pan to get to this part, then it will be obvious. There are ATF filter change instuctions in the DIY that will help with additional detail.

Part number is 986 352 603 00

I know, it is a Boxter part, but that is the part listed for the 996 too. $220 or so in my hands, easy install. The only difference I did notice post install was how much quicker the transmission will shift upwards. For example, 5th gear could come at 38mph, before the fix it was 48-50mph. Short of that, same smooth shifting. And a heck of a lot cheaper than a new tranny.

Hope this saves others some $$ :drive:

Izzy

[texanz71]

Thanks for the awesome info, I would have been lost without your post.

If anyone else is trying to look for the Pressure Regulator I found it under part # 986 325 603 00

The best I could find was for $320, where did you see it for $220?

[Turboflyer]

I ran across this post. What timing. Hope some one is still on it. Been dealing with the 0740 torque converter lock up code.  Since I am in Ca. It will not pass smog. Car runs great. It’s an O1 986 S. Have had it almost 20 years. I too love this car. I think I found the part number  for the solenoid but not sure.  986 325 601 00. Getting up there  in years so the getting at is getting tougher, but doable. Would appreciate any help given. I see from this post the part number I have was incorrect,  but which one is it? ABCDEF or G?

[Silver_TT]

This is a 10+ year old post so part numbers listed may very likely have been superseded.  I would call Sunset, give them your VIN, and order the latest part from them.

 

This is a fantastic thread.....the information given by Izzy is very helpful.

Edited January 17, 2021 by Silver_TT

[ricardo zwaig]

I just had my ATF changed as well as new filter after 0740 code showed up. My 2000 911 Carrera shifts quite smoothly, but after about 100 miles the code showed up again. Is it safe to drive? What should I do next?

[ronegarnett]

My car: 2001 996 C4 Cabriolet, Approximately 110K miles.

 

It had the 0740 error along with a bunch of others.  The car would go into Limp Mode and it felt as if it were slipping in 3rd gear only.

• P0733 Gear sel. monitor 3rd gear
• P0734 Gear sel. monitor 4th gear
• P0740 Solenoid Valve - torque converter clutch
• P1585 Fault lateral acceleration / speed from PSM
• P1574 Porsche code 364 - Stop light switch signal implausible

 

Short Story and Current State:  

• I ordered a ZF solenoid / regulator kit, carefully replaced all 7 parts and had one new one left over. I'm curious as to why there was one left - Is it supposed to go somewhere else?   
• Now, I'm only getting the 0740 and a different, more basic stop light switch signal that comes on occasionally and kills ABS when it does.  That may be a red herring.   Will try another switch.
• On the fluid: I filled with Pentosin, started the car and ran through the gears.  Then I stopped, checked/refilled, and ran through the gears again.  Then, I checked/refilled it and drove it a bit to make sure the fluid got everywhere it was supposed to get before a final check at the proper temperature. 
• The only symptoms I'm getting in the transmission are somewhat abrupt shifting, mainly into 3rd but sometimes maybe into 2nd.  I've tried the quick 3 pumps of the accelerator trick and that does alter the shifting.  I'm not sure it fixes it, though.  Sometimes it seems less abrupt, but I haven't nailed down that scenario yet. 
• I haven't had the shift points recalibrated, so that's a potential action.  Any other ideas, insights, etc.?

Long Version (TL;DR):  

A stack of symptoms led to a set of maintenance tasks which I performed starting in November of 22.  Symptoms going in:

1. Strange clunk under the rear seat when hitting or coming off the gas
2. Clicking noise from the front end when turning right
3. Routine brakes and oil change needed
4. Somewhat rough idle
5. ABS light coming on sporadically
6. The shifting was somewhat heavy

---

1. Solved: It was a torn transmission mount. I didn't see it on initial inspection and pursued #5 until I figured it out, then replaced that and the motor mounts.  Clunk gone.  I made my own tool for pressing in the new trans. mount.  It worked but was painful.
2. Solved:  I discovered a very shot front, passenger-side CV axle while changing the differentials' fluids, and replaced it.  Also a couple of linkages were worn so I replaced them.
3. Solved, Obvious.
4. Improved:  Put in new plugs and coil packs. 
5. Ongoing:  Replaced the stop light switch, but still getting the same error
6. Ongoing : 

• I dropped the pan, put in a new filter, and filled with a Febi product that is supposed to be proper.  I also changed the fluid in both differentials.  
• The initial fluid that came out was dark grey as I recall.  In the bottom of the pan was a bit of sludge but I didn't see any metal shavings when I cleaned all the magnets.  Once back together, I started noticing the 3rd gear revving up unusually at times so didn't drive it much while I researched.

• I made the mistake of putting a gasket varnish/sealant on the new pan gasket, the kind you paint on. Apparently it didn't seal too well. After noticing significant leakage, I once again dropped the pan to replace the gasket, and filled it back up. I didn't see any seal or sealant fragments in the pan. That time, I used Pentosin.
• It seemed to get worse after that, though.  Still slipping in 3rd and then limp mode started popping up.  
• At this point, I took it to a Porsche tech I trust.  He said I needed a new valve body for only $5400 + installation.  Ouch.
• I pondered sending the valve body off to be rebuilt, but decided to try the ZF solenoid and regulator kit instead after talking to both that shop and another.  That takes us back to the short story at the top.  Very drivable, but need to figure out the P0740 before declaring it road-ready.