2 Months Into Ownership, Some Issues - '99 C4 Tip

Previous thread for reference: https://rennlist.com/forums/996-foru...99-c4-tip.html TL;DR - just see post #2 Roughly 2mo. in on ownership and am starting to be pretty concerned about the tiptronic transmission and haven't quite for an exact answer... So far it's been great overall and I've done the following things: - oil change & analysis - brake pads, sensors - RSS motor mounts - Function-First Trans Inserts (tiptronic, soft) - front / rear hatch struts - plugs - front diff fluid - K&N "CAI" I have a new fuel filter since apparently the 996.1 is supposed to be replaced - cheap and easy, just haven't gotten to it yet, as well as a new belt. Upon putting it on the lift while doing some of the initial maintenance, it does look like some recent work has been done. No maintenance history was/is available. Rear control arms seem to be new, and have 997 p/n stamped on them. Motor mounts were completely shot. Lots of oil on the driver-side engine and there's been a very, very slight leak I've noticed while parked in the garage near the rear passenger side. I've determined that the AOS probably needs done. No confirmation on if the IMS has been done in this still, and that is still in the budget and can be done. Is looking real nice though...people definitely aren't used to seeing a 911 w/ a bike on top, ha. Now with regards to the transmission (Note: I've heard since purchase what I thought was a ground loop noise, but turns out has probably been gearbox/torque converter whine the entire time) - it seemed OK on the initial drive back, which was just highway cruising and seemed to progressively get worse as the weeks went on. I'm sure I've driven it much harder than it's been used to as well. There was a noticeable noise when shifting into D/R from P on cold start so I took it the trans mount was going out. Since it's the 996.1 the stock mount, from what I've gathered, is a pain the push out while in the car, or the trans has to be removed completely. Additionally, I couldn't find a p/n to match the stock mount that was in stock. After some research, Lemforder seems to make one that matches; P/N LEM-3470501 (for a '99 boxster at least) - which is currently sitting on the parts shelf just in case. I will note those that this mount looks different, though it does look like it'll work - the cutouts in the rubber do not match the factory ones at all, i.e. the trans inserts wouldn't fit anymore... I purchased the RSS mounts and the trans inserts at the same time, but the RSS mounts were backordered ~3.5 weeks, so the trans inserts went in a few weeks before the RSS mounts. Immediately after installing the inserts w/ stock mounts still, shifting was great, fast and crisp. Rode with this setup for a couple weeks and it seemed fine, installed the RSS mounts and it started to get worse overall, hopefully the mounts are just coincidence. Transmission noise was still there and shifts were getting way worse. In auto mode, was getting lots of surges going into 2-3 sometimes 4th. Very sporadic clunks downshifting, but not often. Occasional clunks upshifting - I can best describe this as what a bad center support bearing would feel like/sound like. Mostly though was getting the really bad surges and what feels like slipping on upshifts. In manual mode, the noise is still very much there but I have lot more control over the shifts and it's not as bad. Thing is, in manual mode as well, if I'm holding say 2nd, it still feels like it's slipping or surging, shifting into 3rd, even before I select 3rd. Pulled code and got the P0740... This thread: https://rennlist.com/forums/996-foru...tiptronic.html seems to point in the right direction. I've ordered TransGo 5HP-19-PR - Link: https://transgo.com/product-details/...ulator-repair/ First dumb mistake: prior to reading the above thread and digging deeper, I figured a trans flush would be the easiest, best way to start, so that was done - while it shifts much better, the surging/lunging/slipping is still there and it's overall still terrible to drive in auto mode. I did not take note of the valve body style while I was in there...so I will have to pull the pan again to see if the transgo part will even work. Copy of oil analysis:

What I can't seem to find is whether or not: Are all 5HP19 trans are the same - i.e. will any replacement solenoids be compatible? I've found a few out there or I have access to internal BMW dealer stuff and can just source the parts direct from BMW much cheaper. Would just the transgo fix "solve" this issue, assuming no damage is done to the torque converter? Should the torque converter need to be replaced, should the replacement torque converter and seals/gaskets/etc for that job, plus the transgo fix "solve" the issue? Since the 996.2 trans are based on the merc 722.6 and use the updated TCU, with my current trans, could a swap w/ the updated TCU + reprogram be essentially plug and play? While researching replacement trans if it were to come to that, is there a difference between the '99 C2/C4 trans? Could an '02+ (722.6) trans, with TCU replacement, and a simple reprogramming be done - or is there more ECU trickery involved with this? Durametric does not seem to read actual values for the 99MY Tip, how would I go about this? Am I missing something else here? Does anyone have experience with the Revmax torque converter? Link: https://revmaxconverters.com/product...que-converter/ Note: the battery was left connected before/after the trans fluid job, issues were still there. I did last night leave the battery disconnected for ~30min and noticed a very, very minor improvement, but has only been through 1 drive cycle - albeit a spirited one. Does anyone know the amount of drive cycles it takes for the "relearn" - if there even is one for this TCU.

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I doubt that a 722.6 trans will work without an inordinate amount of other work. 722.6 trans ECU won't work on the 5HP trans. Difference between a C2 and C4 is the output shaft for the front wheel drive. C4 has it, C2 doesn't.

If you can find a good used transmission just buy it and replace it. Trying to keep alive a failing automatic transmission with unknown service history can get expensive really fast. Sounds to me that yours is dyeing.

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It still seems easier working with what you know - like assuming there's no damage to the valve body or serious internals, why buy one that you truly don't know the condition of... If replacing the torque converter, seals, and possibly the solenoids for the valve body fix the trans, that seems like an easier job. Especially considering I would just do the IMS/RMS job at the same time. I'm not afraid to tackle any of the jobs I've mentioned so far and I've redone valve bodies and seals/solenoids on a GA6HP19Z before and it's a piece of cake. Fluid was clean and 0 metal shavings when the trans job was done, too, fwiw. It still shifts great when running hard and in manual mode, crisp and clean.

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I figured a swap to the 722.6 wouldn't necessarily be worth it... This SB made me think about what all would really need to be done to swap out w/ the newer TCU.

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Does it look like anyone else was in the transmission before you started working on it? You know, they did a fluid flush and cleaned the pan. Were you able to scan the transmission for codes? Since you can do all the work, maybe it's worth trying to fix it.

Sounds to me like valve body issues, things are sticking and not moving smoothly. The flare could also be caused by wear as fluid may be squirting around the pistons. ZF uses standardized color-coded solenoids that aren't very expensive, you can find OE replacements on Ebay in the $50 range, there are also aftermarket replacement kits. The PN is marked on the solenoid connector if you don't trust the color coding. I think a Transgo rebuild kit may also be worthwhile for internal wear. I'm getting ready to try one on my Saab 9-3 which is having similar symptoms, though it's a PITA to access the VB unlike the Tip. Worse case it doesn't fix it and you're out a few hundred dollars in part costs but no harm done. Not super familiar with your Tip but presumably it has a calibration procedure that will need to be run after the part changes. Can the adaptation values be cleared and relearned? This is pretty easy to do on a PDK but not sure about the Tip.