Torque Converter Ripoff??

[skaa]

With my torque converter in my hands, how can I tell if it has failed? My parts guy at the local shop says I have to bring it, and $150, and he'll replace it. He says it may or may not have failed, but at any rate, he has to cut it open (destroy it) to tell if it failed!! So, I have to buy a replacement torque converter no matter what! Does that sound right?
The story: my 722.303 rebuilt tranny (less than 10k miles, 18 months) suddenly failed last week as I came over a small hill. Abruptly, just no power to the rear wheels. Nothing. Engine was fine, just nothing to the rear wheels. No abnormal noises, no gradual failure over the preceeding days or weeks or months, just a sudden nothing! The gear selector would go to N-D-2-1, but not into R until after several tries, and into P only after several tries and a chattering sound. Had it towed.
Figured trouble was most likely in the valve body, so I dropped the pan, and it was clean as a whistle. Dropped the main valve body, opened it up, but no broken springs or valves, or clogged channels. Put it back in, refilled it, but same as before with no power to rear wheels, and same troubles/noises with shifter in R and P.
Called the local shop I used for the rebuild parts 18 months ago, and they said it sounded like a complete torque converter failure. So I removed it, and the tranny, checked the front and rear tranny shafts for wear, but nothing I could see. Drive shaft, flex discs, on back, were fine. Of course, the warranty was 12 months on the rebuilt torque converter, and it's been 18 months
Any help on DIY torque converter tests/diagnoses would be sincerely appreciated, (and a valuable addition to the Forum Stickies for future searches...) Thank you in advance

Skaa

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1982 300SD 400+ k miles

[rscurtis]

If you had trouble getting it into park, I would suspect a failure further back in the transmission which is still allowing part of the output shaft to turn- hence the noise when you engage park. I can't see a TC completely failing from one moment to the next without some form of warning such as noise or a gradual loss of power transmission.

Torque converters are routinely cut open, repaired, and welded back together as part of an overhaul process.

[shadetree77]

find a shop that specialized in MB transmission, there is a tool that can be used to bench-test torque converters without opening them up, but they are make specific (i think they use 2 or 3 different tools; i know one is used to keep the stator from turning)

[rs899]

I am with rscurtis. I can't really see it as TC failure. If you have it out, and you have already rebuilt it once, why don't you pull it completely apart? If you don't find anything you can see, then that would have to leave the TC as the culprit.

[skaa]

rscurtis: I was just wondering if there was anything I could do or see as I looked at the torque converter that would indicate it actually needed repair... Any more thought on what I might be looking for if I do open the tranny up? It is on the bench right now.

shadetree77; Per your post, I just called the biggest shop in town, talked to the rebuild guy, and asked if they had the specific testing equipment. He said he did, and he'd rebuild it for $275. OUCH ! MB owner = $$$, I guess.

rs899: I'm beginning to see a consensus forming. Anything I might specifically look for? It has been an excellent 18 months, no leaks or problems, and I was S-O-O-O proud of myself for even attempting a transmission rebuild, my first, let alone a Mercedes!

Thanks for your prompt responses

Skaa

[Zulfiqar]

A very oldschool basic check is to shake it - you should hear a solid thud of movement, if you hear jingles like loose marbles its duff.

btw a TC fails quite catastrophically, it would make all sorts of clanging and grinding sounds before it actually gave up, however some failures (unheard of in MB) are the splines to the input shaft breaking clean, Japanese domestic mistu Galants do that so do the stupid Honda CVTs. - They just emit one clunk, two or three grinds and its done - no drive.

[skaa]

Zulfiqar: I heard nothing when the tranny failed. I'll have to have a big bowl of Wheaties before I can grab that steel donut and shake it around. And maybe a Snickers bar, too. I am old school, though. Graduate of "What's Sa Matta U ?", Class of 1978 !!

Skaa

[Diesel911]

One way to find if it is the Torque Converter or the Transmission is to install a used Torque Converter from a Car that the owner knew it worked on.

If it works just leave it in there.

If it does not work you have the Answer.

If it was warranted for 1 Year the warranty is over and they don't have to warrent it if they don't want to.

[Stretch]

Originally Posted by skaa

...

The story: my 722.303 rebuilt tranny (less than 10k miles, 18 months) suddenly failed last week as I came over a small hill. Abruptly, just no power to the rear wheels. Nothing. Engine was fine, just nothing to the rear wheels. No abnormal noises, no gradual failure over the preceeding days or weeks or months, just a sudden nothing! The gear selector would go to N-D-2-1, but not into R until after several tries, and into P only after several tries and a chattering sound. Had it towed.
...

Perhaps there's more to the story?

But if you'd started the thread by saying just the bit that I've underlined in the quote I think the advice given would be different. I don't think many would have said torque converter...

...perhaps someone would have said front pump. Who can tell? The cat is now out of the bag.

To test if the torque converter was working or not I'd have done the following BEFORE taking everything to bits =>

Either

1) Remove a transmission oil cooler line to see if the oil from the front pump squirts or dribbles (this is the messy option)

2) Measure the working pressure and compare that with the data in the (German) FSM / ATSG

The front pump won't work if the torque converter for some reason or other isn't doing its job.

These tests don't say for sure that the torque converter is at fault or not - but it does indicate if the front pump and the torque converter as a pair are working properly or not.



Anyway looking at the problem as described by the underlined bit in the quote above

I'd be looking at the control rod (command?) mechanism in the valve body for a start.

[layback40]

Originally Posted by Army

Perhaps there's more to the story?

But if you'd started the thread by saying just the bit that I've underlined in the quote I think the advice given would be different. I don't think many would have said torque converter...

...perhaps someone would have said front pump. Who can tell? The cat is now out of the bag.

To test if the torque converter was working or not I'd have done the following BEFORE taking everything to bits =>

Either

1) Remove a transmission oil cooler line to see if the oil from the front pump squirts or dribbles (this is the messy option)

2) Measure the working pressure and compare that with the data in the (German) FSM / ATSG

The front pump won't work if the torque converter for some reason or other isn't doing its job.

These tests don't say for sure that the torque converter is at fault or not - but it does indicate if the front pump and the torque converter as a pair are working properly or not.



Anyway looking at the problem as described by the underlined bit in the quote above

I'd be looking at the control rod (command?) mechanism in the valve body for a start.

If the 2 pump drive pieces are broken off the TC then the pump wont run. This can occur with no warning & sudden.
This does sound more like an internal failure in the trans though. Probably a broken shaft.
You can place a piece of flat steel down the hole & into the splines. If there is no resistance to turning when the TC has fluid in it then the TC is toast.
This test is a little rough but it works for an initial indication.

[Stretch]

Originally Posted by layback40

If the 2 pump drive pieces are broken off the TC then the pump wont run. This can occur with no warning & sudden.
This does sound more like an internal failure in the trans though. Probably a broken shaft.
You can place a piece of flat steel down the hole & into the splines. If there is no resistance to turning when the TC has fluid in it then the TC is toast.
This test is a little rough but it works for an initial indication.

Hi layback,

Like you told me a few years ago this sudden failure is more likely on the 722.1 transmissions - but good point. I guess as the torque converter has been removed it would be noticeable if the tabs were snapped off.

Can you confirm this skaa?

As for the broken shaft - yes I have the same idea. Statistically speaking I have no reason to think this but I am reminded of the governor drive shaft problem ps2cho had a few months back

http://www.peachparts.com/shopforum/tech-help/308281-help-stuck-road-722-3-no-3rd-4th-gear.html

I think that if the command rod is OK then the most likely trouble will be governor related.

It seems as though the 722.1s have trouble at the front whereas 722.3s have trouble at the back.

[Stretch]

I keep forgetiing to add this =>

I suspect the governor because the OP said it was difficult to select reverse.

These transmissions have a hydraulic lock out that stop reverse from being selected past a speed of about 10 kph. If the governor "thinks" that the car is going too fast then it won't allow the selector lever to go into reverse.

(This would only happen if the torque converter and front pump were working however)

Anyway the first thing to do before blaming the governor is to check for smooth operation of the command rod going into the valve body.

Looking at the outcome of ps2cho's thread, the link to which I posted previously, I am reluctant to recommend a DIY removal and refit of the governor.

I get the impression that a transmission rebuild sometimes means new friction material and seals - there isn't much mention of governors. This is silly as the governor controls it all.



Anyway I think this thread needs a bit of feedback from the OP before I convince myself that it was due to cosmic radiation or martians...

...I'll wait until then!

[Zulfiqar]

The break off I wrote about is very stupid and annoying - the transmission pump will work and will show pressure, but the input shaft wont turn because the splines that connect the internals of the convertor break off cleanly. I had a freind with a mitsi galant and it did that - when it was took out - we got hold of a spare input shaft and tried to spin it - the shaft did not engage anything inside. The dogs on the converter pump drive were good. Talk about stupid failure.

But this is unheard of in MB. and honestly this problem more looks like a failure at the back or in the valve body like Army said. It can also be a disconnected D/shaft output yoke by the holding nut coming loose. - someone on this forum experienced it too.

[skaa]

Army: I'll be looking at the valve body operation a little closer when I open the tranny up on Saturday. Tabs are fine. Any other thoughts about the governor?

layback40: That's a good, practical test for anyone to try. Thanks!

Zulfiqar: Good point. The driveshaft output/yoke "failure" was what promoted the rebuild 18 months ago. Replaced with all new output shaft, yoke, nut, center support bearing, and flex discs. Output shaft/yoke looks good, though.

All-in-all, I'm thinking it's internal. I'll be looking for broken shafts, bad pump, and worn valves. I also re-tapped the K2 drum with the 3 new screws as per the rebuild instructions, and I'm thinking maybe they could've worked loose and leaked. So, in 48 hrs, I'll be taking everything out to get to the drum, anyway...

Skaa

[Zulfiqar]

Originally Posted by skaa

Zulfiqar: I heard nothing when the tranny failed. I'll have to have a big bowl of Wheaties before I can grab that steel donut and shake it around. And maybe a Snickers bar, too. I am old school, though. Graduate of "What's Sa Matta U ?", Class of 1978 !!

Skaa

Jam the convertor in a small tire and let the tire shake it - you just need to kick it like its a criminal and you are in the medieval times