Torque converter or valve body?

[Karpiel73]

Last year my transmission started acting up and it's gotten worse since. It wont stay locked in overdrive, resulting in 300-400 rpms higher than normal. O/D light has never flashed either.

I'm just wondering if I should replace the torque converter or valve body. Every thread I've read with similar symptoms leans toward converter replacement.

2001 Sport w/201k miles. 5r55e trans

 

[imp]

Last year my transmission started acting up and it's gotten worse since. It wont stay locked in overdrive, resulting in 300-400 rpms higher than normal. O/D light has never flashed either.

I'm just wondering if I should replace the torque converter or valve body. Every thread I've read with similar symptoms leans toward converter replacement.

2001 Sport w/201k miles. 5r55e trans

@Karpiel73
O/D may have nothing to do with it. As the transmission upshifts through the gears, the last "shift" felt, and seen, on the tachometer, once light throttle cruising speed is reached, ~ 50 mph, is not a shift of gears, but rather the Torque Converter Clutch engaging. That eliminates the T.C. from the picture, causing the drop in rpm seen.

Test it this way: Once cruise is reached, add throttle LIGHTLY, carefully; if the TCC has engaged, the rpm will not jump upwards, but increase very slowly. Depressing throttle too much will result in the TCC unlocking. If rpm jumps up with LIGHT throttle increase, the TCC is not engaging properly.

Whether TCC or O/D related, trouble code(s) should be generated, as shaft speeds are not what they should be expected to be. imp

 

[Karpiel73]

@Karpiel73
O/D may have nothing to do with it. As the transmission upshifts through the gears, the last "shift" felt, and seen, on the tachometer, once light throttle cruising speed is reached, ~ 50 mph, is not a shift of gears, but rather the Torque Converter Clutch engaging. That eliminates the T.C. from the picture, causing the drop in rpm seen.

Test it this way: Once cruise is reached, add throttle LIGHTLY, carefully; if the TCC has engaged, the rpm will not jump upwards, but increase very slowly. Depressing throttle too much will result in the TCC unlocking. If rpm jumps up with LIGHT throttle increase, the TCC is not engaging properly.

Whether TCC or O/D related, trouble code(s) should be generated, as shaft speeds are not what they should be expected to be. imp

Thanks for the reply IMP. When i first get on the highway the TCC engages, but anywhere from 2-5miles down the road the rpms jump up again, always under light throttle and i have to baby the heck out of it to get to engage again.

Since it looks like the torque converter, what is a good brand? Rock Auto sells Dacco. Are they any good?

 

[jd4242]

5r55 could be a list of things..from servos,solenoids, stuck valves,sensors, broken bands, to converters..

That trans is really hard to narrow it down and none of the parts are cheap.

 

[transman304]

A lot of information for transmission to operate comes from engine side too. Just a few that have to do with LU issues would be TPS, ECT, MAF,brake switch and more all have an effect on LU strategy.

 

[Karpiel73]

A lot of information for transmission to operate comes from engine side too. Just a few that have to do with LU issues would be TPS, ECT, MAF,brake switch and more all have an effect on LU strategy.

LU is Lock up?

 

[Karpiel73]

5r55 could be a list of things..from servos,solenoids, stuck valves,sensors, broken bands, to converters..

That trans is really hard to narrow it down and none of the parts are cheap.

I have to start somewhere though haha

 

[transman304]

LU = lock up
TPS= throttle position sensor
ECT=engine coolant temp sensor
MAF= mass air flow sensor
Sorry about that. I use this lingo daily and forget not everyone speaks my language. Lol. Good luck! Let us know what you find out.

 

[Karpiel73]

LU = lock up
TPS= throttle position sensor
ECT=engine coolant temp sensor
MAF= mass air flow sensor
Sorry about that. I use this lingo daily and forget not everyone speaks my language. Lol. Good luck! Let us know what you find out.

I knew the other ones haha I'll be tackling this when the weather decides to stay above 30* for good! Will update then.

 

[imp]

A lot of information for transmission to operate comes from engine side too. Just a few that have to do with LU issues would be TPS, ECT, MAF,brake switch and more all have an effect on LU strategy.

@transman304
Great information! Seems to me, and I'm often wrong, that as soon as that baby unlocks, for whatever reason, PCM will detect it as mismatched engine speed vs. input shaft speed, since it's calling for LU, and losing it, and throw a code. No? Even if the TCC itself is mechanically faulty, and begins to slip, PCM knows about that. With my limited amount of resources (as in $$), I think I would wire in a temporary switch, available to the driver (me), to allow me to engage TCC LU just around LU time, then see if it loses LU by watching the tach. If it does NOT, TCC is not the cause, don't mess with the TC yet. OTOH, if it DOES lose LU, even with engage (LU) commanded ON by the switch, you eliminate TPS, ECT, MAF, etc., and have only maybe two likely causes: TCC Solenoid, or TC itself. Or, maybe I'm just nuts! imp

 

[transman304]

Imp, that would work in some early transmissions that did not rely on a electronic pressure control. The EPC/variable force motor ramps pressure from data collected from several sensors from engine,trans,vehicle speed even from AC compressor. So if pressure was not at correct level for lock up you would have a slip. A lot of manufactures use what is called PWM (Pulse Width Modulated) and the on off lock up has become a variable apply lock up which really never 100% locks up. Heck they are even starting to apply lock up in 2nd gear.

 

[Karpiel73]

UPDATE: I purchased a valve body off ebay with all solenoids, gaskets etc. When the old one was removed the gasket was slightly blown near the reverse servo. Installed the new one and while it works flawlessly, it did not fix my lockup issue.

So i added dielectric grease to the VSS, MAFS (after i cleaned it) amd TPS. I also cleaned all the major grounds under the hood. After all this i made in 24 miles down the interstate @ 72mph as opposed to 3miles. So progress is happening.

FINALLY, i pulled the throttle body off and it was beyond disgusting. I spent 1-1.5 hrs cleaning it. After it was reinstalled i made it 45 miles down the interstate @72mph without a lockup issue.

So i hate to jinx myself, but hopefully the problem is fixed! I'll find out this month on my trip to Colorado/Moab.