New Owner! Tranmission cutting out on freeway :/

[OslosisJones]

Astro, yes there are plenty of unknowns here and I have no idea what the cause of the problem is. Sounds like you have some experience with these transmission and could help me out here.

I am looking for help in diagnosing the problem in a methodical way. If all else fails, then yes, I may be looking at a full rebuild or replacement. But we're not there yet.

I certainly have not been 'slamming' into gear since buying the car; I didn't even notice a significant issue until the fluid change! And I know to let off the throttle when the problem occurs to avoid most of the 'clunk' when the gear re-engages; it mostly feels like a firm positive shift and is likely comparable to typical wear. If it actually is slipping, then that may not be the case...

Oddly enough, the disengaging doesn't seem to occur on my commute home, even if I try to hang out it the revs where the problem typically occurs. Commute home is more uphill, commute to work is more downhill, only thing I can think of that might have something to do with it.

I did reset the fluid counter and adaptation in VIDA tonight. Also found the 'Activation Gear Indication' which uses the warning (triangle) light to signal lockup status. Went on a short drive and noticed nothing unusual; no light for 1-3 gears, brief flashing (slipping lockup) when shifting into 4/5 then constant (locked lockup) signal after shift was complete. Will activate for the commute in the morning to see if issue coincides with lock-up slipping.

Also noticed the 'TEST Mode' that can be activated to lower the threshold needed to detect and store a code, which might come in handy.

Checked my fluid level again, looked good (maybe a touch high) for 105 C (I think... should I be looking at 'TCM-Oil Temperature' or 'TCM-Engine Coolant Temperature'?), pic of dipstick included along with color of the drained fluid.

Here's my methodology thus far:

1. Verify ATF level is correct
2. Reset Fluid counter and Adaptation
3. Activate lock-up detection mode to determine if lock-up is slipping
4. Add Seafoam Trans Tune to fluid, drive for a couple hundred miles, Drain & Fill/Flush ATF, reset fluid counter/adaptation, perform new adaptation.
5. ?? Determine if problem could be solved with solenoid/valve body repair.
6. Profit (or fork over a few grand for rebuilt transmission)

Here are the codes VIDA pulled, though I've no idea how recent they are:
ECM-120D Air Mass- signal too low
ECM-121B Mass air flow (MAF) sensor- Flow too low
ECM-212D Long-term fuel trim - signal too low
ECM-216D Long-term fuel trim - signal too low
ECM-21ED Long-term fuel trim - signal too low
ECM-280C Fuel pressure sensor - signal too high
ECM-2900 Fuel pressure- Faulty signal

These seemed to go away after updating, will see if they show up again. Doubtful that these are at all related to transmission issues. Possible that MAF codes weren't cleared when new sensor was installed.

I appreciate the input from you guys, keep it up! Looks like I'll be reading up on Sonnax material for the foreseeable future...

[Xfingers]

I didn't reread the whole thread but your tranny problem is that it slips on high-speed acceleration at 65-70 mph? Otherwise the trans shifts fine? I know freeway driving can get dicey at times and the ability to punch it can be critical to avoid a potential hazard, but for the sake of your tranny maybe try to ratchet it down a few notches when on the freeway. Maybe try to anticipate more so you can avoid jumping on the gas so much. Otherwise, rebuilt trans can go for $5,000+. I understand freeway driving in heavy traffic can be very hectic...

From my exp., replacing worn ATF fluid with new will def affect shifting behavior. In my case, a 2-3 shift flare reared its ugly head AFTER the swap although as a whole I felt the trans ran smoother. I didn't have DICE to do reset/adaptations, but after @2500 mi. of careful, easy driving I guess the trans adjusted and no more shift flare. Even if I had dice, I'm not sure my 2-3 flare would have allowed me to do the adapts correctly. I may still have some line pressure issues because sometimes if I'm moving very slowly in low gear up a slight incline, trans will hesitate to shift and RPMs rev way up but this I can deal with!

I don't have yrs. of experience with these cars but maybe you have an adaptation issue? The adaptation procedure only requires vehicle to reach speeds I think of 50 mph so maybe tranny will not have the opportunity to relearn high-speed shifts at 65-70 mph? Being an optimist, I'd try to do gradual accelerations at 65-70 and see what happens. If ok, maybe over time trans will adapt and you'll get to the point where it can handle punching it at high speeds. Now let me just say, I'm not in the car when it happens but the transmission going out of gear on a freeway at high speeds sounds like a scary, dangerous proposition so my "take it easy and see if it works itself out" approach may not be sound advice.

[OslosisJones]

Yes, it is more than a little unnerving to suddenly lose power at highway speeds. I was aware going in that I might seeing the shifting behavior change, but this seems much more than that.

It is not happening when I 'punch it' so much as when I just try to maintain speed or accelerate slightly in 5th gear. Just hard to pin it down because it happens so inconsistently. I'll try the gradual acceleration approach, and maybe punching it to see if it still downshifts okay. Lock-up indicator was consistently lit (locked lock-up) in 5th, even when it drops out of gear. I'll try TEST mode to see if I can pull any relevant codes.

Also have been noticing a consistent shudder at higher speeds. Again, hard to say if this is transmission related, could be excessive road noise from worn engine/tranny mounts, suspension, or steering components.

The way I see it, I could have one or more of the following problems:
1. Dirty fluid fouling valve or passage -> Seafoam Trans Tune, Drain&Fill/Flush
2. Pressure losses due to bad/leaking seals -> Valve Body rebuilt (Sonnax Zip Kit)
3. Sticking/leaking linear solenoids -> Replace with new/reman solenoids
4. Worn transmission internals (belts/clutches/etc) -> rebuild/replace transmission

Anybody know what is involved in a full transmission rebuild? Most of the material I've read addresses the valve body. Is it possible to just replace the relevant wear components for this specific case (likely 5th gear belts, clutch)?

[Astro14]

Rebuilding a transmission involves replacing the parts you mention. Generally, you replace all the "soft" parts, seals, gaskets, clutches. If they look bad, then "hard" parts are replaced as well, steels, sprag, etc. it's similar to rebuilding an engine - special tools, understanding, evaluation of components, and care are all required.

I've done a TH-400. Stone simple by comparison. Easy to do.

You might consider buying this to understand what you're getting into: https://www.amazon.com/ATSG-AW55-50-...rds=ATSG+AW-55

The valve body rebuild takes a test bench to ensure correct performance and calibration.

To be honest, I've done engines, and transmissions, but I would farm this rebuild out. You can get a quality, durable, rebuild that includes the valve body work from a variety of sources, including your Volvo dealer. But I was considering these guys if my valve body fix hadn't worked.

http://www.level10transmission.com/services.html

[OslosisJones]

Nice reference, looks like a fun read. Might look into it if it comes down to the transmission internals.

I'd be inclined to try the valve body job myself first. I'll have access to a workshop when I'm back in school in the fall; we build and maintain ocean research devices. We have some pressure testing equipment typically used for pitot tube calibration, in addition to an absurd amount of tools that I could borrow. Anything specific I would need as part of a test bench?

Transmission itself sounds like a bear, just getting the damn thing out probably goes beyond the scope of what I'm capable of. For now I'm considering this the worst case scenario.

Still curious if this could be an engine power loss or ECM confusion issue causing the transmission to momentarily drop out of gear (coast in nuetral or downshift). Sources could be:
-Slight misfires: no codes atm, but will be replacing spark plugs this weekend hopefully, along with fuel filter
-Plugged or leaking vacuum lines, PCV clogged
-Some combo of bad throttle, fuel pressure, MAF, oxygen sensors. (VIDA showed codes for MAF, fuel pressure sensor, and fuel trims. Problem might have been fixed and codes were never cleared, idk)

[Astro14]

Wrong link in my reply below.

These are the guys: http://www.levelten.com/Level_10_PTS...1800-3000s.htm

"Bulletproof", they call it.

I haven't done a valve body, so I don't know what's required for test/calibration.

Howard has some great links on his site, but Google Sonnax and AW-55 and you'll find a ton of discussion about this transmission.

[youropeen]

I'd replace your fuel pressure sensor before doing anything else with the transmission. Your symptoms are similar to a faulty fuel pressure sensor. I had the same symptoms though not as intense as you describe along with sensor related codes. It's a relatively cheap and easy replacement that looks like it needs to be done anyway.

[OslosisJones]

I'd replace your fuel pressure sensor before doing anything else with the transmission. Your symptoms are similar to a faulty fuel pressure sensor. I had the same symptoms though not as intense as you describe along with sensor related codes. It's a relatively cheap and easy replacement that looks like it needs to be done anyway.

Engine check light finally came on this morning on the drive in, definitely noticing some major hesitation and shuddering. Will have to wait until I get home to check what codes it's throwing. I do hope it's as simple as a fuel pressure sensor, and I have an IPD warehouse about 20 minutes from where I live.

When it falls out of 5th and struggles to re-engage, I can still gun it into 4th with no problems.

Otherwise, its likely a combo of valve body issues and 4th/5th clutch burnout and wear on the the steels.

[JRL]

I doubt it's a VB issue or any combination thereof

[OslosisJones]

I doubt it's a VB issue or any combination thereof

Are you saying its more likely to be the internals or something else entirely?