350SDL Transmission Woes - Page 6 - PeachParts Mercedes-Benz Forum

MongooseGA · #76 11-22-2016, 06:22 PM

Thanks for the feedback today everyone! I'll try to answer everything:

I did find some SAE 10 oil at a tractor supply store about 30 miles from my house. I bought a 2 gallon jug and replaced the fluids from the other day with it. (Including the torque converter. I swear, I can do the filter/fluid change completely blindfolded by now. No joke)

I did turn the T-bar 3 additional full turns today. I did this before leaving the house to pick up the oil, and it did seem to improve the drive-ability. However, it is somewhat difficult to fully judge because the car's symptoms are not 100% consistent. Never the less, it was better on that drive.

Replaced the fluid with the oil, and so far it has been behaving. 1-2 shift is exactly as it was prior (whenever it does happen), but now my 2-3 and 3-4 shifts are actuallysofter despite the increased line pressure from the modulator. I'm guessing this will be a sign of the thicker fluid in there. I'm intending to drive the car exactly as it right now, and can adjust the modulator on the fly if I need to. I'll leave the diapers off so access is easy.

I have researched the pistons/springs. I don't remember which ones (k1/b1/k2/b2/abcd123,etc) but I am curious if it's worth trying. FWIW, each time the fluid has been drained, it's coming out bright red. Granted, it's never more than a few thousand miles old, if that, but clean anyways. Also, you won't find a stray spec of dust in any of my vehicles, let alone twinkie wrappers under the go pedal :-D Actually, I'd disconnected the KD switch when this all started happening just to rule it out, and it's still unplugged.

Now, a question I came up with about increasing the pressure: It was mentioned earlier on that it's not a problem setting the pressure, it's just unable to maintain it. I imagine a vacuum leak is totally possible, but if that's the case, could I not theoretically just keep turning that T bar each time the pressure drops, to keep it within the same spec?

Big hand to everyone who has been following this thread and providing input. It's greatly appreciated!

spock505 · #77 11-22-2016, 06:34 PM

Quote:

Originally Posted by MongooseGA

Thanks for the feedback today everyone! I'll try to answer everything:

I did find some SAE 10 oil at a tractor supply store about 30 miles from my house. I bought a 2 gallon jug and replaced the fluids from the other day with it. (Including the torque converter. I swear, I can do the filter/fluid change completely blindfolded by now. No joke)

I did turn the T-bar 3 additional full turns today. I did this before leaving the house to pick up the oil, and it did seem to improve the drive-ability. However, it is somewhat difficult to fully judge because the car's symptoms are not 100% consistent. Never the less, it was better on that drive.

Replaced the fluid with the oil, and so far it has been behaving. 1-2 shift is exactly as it was prior (whenever it does happen), but now my 2-3 and 3-4 shifts are actuallysofter despite the increased line pressure from the modulator. I'm guessing this will be a sign of the thicker fluid in there. I'm intending to drive the car exactly as it right now, and can adjust the modulator on the fly if I need to. I'll leave the diapers off so access is easy.

I have researched the pistons/springs. I don't remember which ones (k1/b1/k2/b2/abcd123,etc) but I am curious if it's worth trying. FWIW, each time the fluid has been drained, it's coming out bright red. Granted, it's never more than a few thousand miles old, if that, but clean anyways. Also, you won't find a stray spec of dust in any of my vehicles, let alone twinkie wrappers under the go pedal :-D Actually, I'd disconnected the KD switch when this all started happening just to rule it out, and it's still unplugged.

Now, a question I came up with about increasing the pressure: It was mentioned earlier on that it's not a problem setting the pressure, it's just unable to maintain it. I imagine a vacuum leak is totally possible, but if that's the case, could I not theoretically just keep turning that T bar each time the pressure drops, to keep it within the same spec?

Big hand to everyone who has been following this thread and providing input. It's greatly appreciated!

It could be similar to my own where the modulator maybe at fault. I can adjust mine back and forth for 3-4, then the otherway for 1-2 but not 100% on all four if that makes sense.

On the 722.x transmission the pistons are readily accessible (look familiar

, what model is your box?

Frank Reiner · #78 11-22-2016, 07:41 PM

Quote:

Originally Posted by spock505

On the 722.x transmission the pistons are readily accessible (look familiar

, what model is your box?

1) The designator "722" refers to MB autoboxes in general; they are all 722s, followed by a xxx suffix. One design group is composed of 722.0xx, .1xx, .2xx. Another is 722.3xx, .4xx, .5xx, then 722.6xx, and so on.

2) In speaking of pistons in an autobox, it is usually understood that the term "piston" refers to that device that provides the apply force to a friction element, either a clutch or a band. Hence, a "K" piston provides the force to clamp a clutch, and similarly, a "B" piston provides the force to clamp a brake band.
In the picture above, under the plates at the marked locations, are "accumulators" or "valves".

MongooseGA · #79 11-22-2016, 07:43 PM

I've seen exactly that picture, and I know exactly that image! They do look easily accessible. It wouldn't be hard to change them out, but I do hope I don't have to drain and refill this thing too soon, again.

I forgot to mention in the last post that I used about 12 oz of the Lucas and about the same of the Trans-X.

Also, would anyone have a diagram of what exactly is happening when I'm turning this Tbar? I'm curious to see it and better understand the thing.

spock505 · #80 11-23-2016, 05:47 AM

Frank, I did wonder that after reading your reply, but MB do refer on occasion to both pistons and valves, see packaging in K1, K2 link below.

MongooseGA, I thought you may recognise that image, been down the same road as you bud, pan off maybe 8 -10 times but things have improved.

You may want to consider using an oil extractor such as this one: http://www.pelapumps.co.uk/default.aspx?A10PAGE=PL650 - it has two nylon tube, the smaller of which fits into the dipstick hole reaching the pan floor, great for engine oil changes too.

The drawback is you can't really re-use the oil if clean as after the first use it may get contaminated.

With regard to the B1, K1 and K2 accumulators, my recommendation here would be to side step MB and order the complete kit from Bob at Superior Transmission Parts - the reason behind this relates to how difficult it is to match up parts with EPC.

See details here with additional info:

http://www.peachparts.com/shopforum/diesel-discussion/379453-k1-k2-b1-722-4-valve-replace.html

This is the route for me next year once the weather improves.

On the topic of modulators, it seems they regulate vacuum shift pressure.

You mention yours is on the passenger side which would indicate the left hand side standing at the front looking back, mine the opposite on 722.435.

Again this is another job for next year, change out the modulator. On earlier models MB redesigned the modulator completely - good overview by MBS

https://www.youtube.com/watch?v=gM4KZvwsCW0

Feel free to add your findings onto the K1, K2 thread if helpful, it might come in handy for other facing the same sort of issues.

Frank Reiner · #81 11-23-2016, 10:34 AM

Quote:

Originally Posted by MongooseGA

. Also, would anyone have a diagram of what exactly is happening when I'm turning this Tbar? I'm curious to see it and better understand the thing.

Quote:

Originally Posted by spock505

On the topic of modulators, it seems they regulate vacuum shift pressure.

The T-pin (T-bar) of the modulator turns a screw inside the modulator. That screw presses on a spring, which in turn presses on a diaphragm. The outboard (spring) side of the diaphragm is connected to a less-than-atmospheric-pressure air source (a "vacuum" source), and the inboard side of the diaphragm is exposed to atmospheric pressure inside the transmission housing. The inboard side of the diaphragm pushes against a pin that controls a hydraulic pressure relief valve, and thereby controls the working pressure of the transmission oil.
When the engine is operating at low power settings (light throttle) the air pressure on the outboard side of the diaphragm is quite a bit lower than the atmospheric pressure on the inboard side, the spring force is reduced, the relief valve is opened further, and the working pressure is reduced.
As the throttle is progressively opened, the air pressure on the outboard side of the diaphragm rises, the spring force increases, the relief valve is closed, and the working pressure is increased.

Quote:

You mention yours is on the passenger side which would indicate the left hand side standing at the front looking back, mine the opposite on 722.435.

The modulator on the 722.3xx transmissions, as with their little brother, the 722.4xx, is located on the left side of the trans case.
As Gertrude Stein (slightly paraphrased) pointed out, "The left, is the left, is the left, is the left."
The left side of the car remains the left side, irrespective of the location of the driver's controls, irrespective of where one is standing, or which way one is looking, and remains the left side even if one is plagued with that rather common condition known as spinal inversion.

spock505 · #82 11-23-2016, 10:58 AM

Quote:

Originally Posted by Frank Reiner

The modulator on the 722.3xx transmissions, as with their little brother, the 722.4xx, is located on the left side of the trans case.
As Gertrude Stein (slightly paraphrased) pointed out, "The left, is the left, is the left, is the left."

The left side of the car remains the left side, irrespective of the location of the driver's controls, irrespective of where one is standing, or which way one is looking, and remains the left side even if one is plagued with that rather common condition known as spinal inversion.

Jay bob mentioned early on, to which OP replied thanks, I took this to mean opposite of mine - just trying to avoid confusion without knowing which box it is.

"The vacuum actuator is down on the passenger side of the transmission.

ROLLGUY · #83 11-23-2016, 11:12 AM

I believe the four bolt pan transmissions (722.1XX) have the modulator on the right side, and the six bolt pan units (722,3XX, 4XX) have it on the left.

spock505 · #84 11-23-2016, 11:48 AM

Quote:

Originally Posted by ROLLGUY

I believe the four bolt pan transmissions (722.1XX) have the modulator on the right side, and the six bolt pan units (722,3XX, 4XX) have it on the left.

Cool, that could be good news for the OP if he has one of the early modulators prone to loose caps leading to vacuum loss, especially if it's been on and off a few times.

Frank Reiner · #85 11-23-2016, 12:06 PM

We should not forget the thread title:
350SDL Transmission Woes

350SDL>1990-91, hence, 722.3xx, hence, modulator on the left side.

spock505 · #86 11-23-2016, 03:04 PM

Quote:

Originally Posted by Frank Reiner

We should not forget the thread title:
350SDL Transmission Woes

350SDL>1990-91, hence, 722.3xx, hence, modulator on the left side.

We should not forget some members reside in countries where this model was never manufactured, at least not in diesel variant!

Hence the aforementioned member who was just trying to help, asking what box had been fitted.

400Eric · #87 11-24-2016, 01:58 PM

Quote:

Originally Posted by spock505

Eric, have you gone down the road (excuse the pun) of checking vacuum pressure to the box?

In order to smooth things out after changing pistons (as above) i also opted for a softer modulator setting, this works well but I suspect the real fault is with the modulator itself.

As I said before, I was just trying to crutch a weak trans, just as Mongoose is trying to do. Turning in the T-bar was a quick, simple, easy, dirt cheap, solution that worked in the first trans, so I didn't pursue any other solutions cause I didn't need to. Four years and 20,000 miles ago, I'd have bet good money that that trans didn't have 5,000 miles left in it. (Just listen to that awful flaring in that first video I linked earlier in this thread!) [Edit: It's also worth noting that I've NEVER even changed the trans fluid/filter in that car!]

I also said that this is not something that I would do to a tight trans. I've touched the T-bar in only three of my cars.

I still don't have 4th in the second trans but I've left it's T-bar in anyways because doing so has solved almost all of it's other issues. It even gives me second gear chirps now too! (I just love those!) That's why I refuse to give-up on that trans. How can a trans that gives second gear chirps be "bad"?

I strongly suspect that the no 4th issue in my second trans is because of a K2 issue because of the other one remaining issue of there being no engine braking in either first while in the "2" position on the selector or while in reverse.

I've seen posts about K2 pistons and K2 springs. Did you replace the spring, the piston, or both?

Lot's more good posts here, but I have to go for now. I'll be back later. Happy Thanksgiving guys!

400Eric · #88 11-24-2016, 04:08 PM

Quote:

Originally Posted by MongooseGA

I did turn the T-bar 3 additional full turns today. I did this before leaving the house to pick up the oil, and it did seem to improve the drive-ability. However, it is somewhat difficult to fully judge because the car's symptoms are not 100% consistent. Never the less, it was better on that drive

Please read the above post again as I've added to it.

Three full turns are not enough. Three turns hardly did anything for my first trans. As I said before, You never know where you are starting from. My first tranny's T-bar was out about 10 turns, while my second tranny's was out only 5 1/2 turns. Either way, you've got to turn it in all the way! I don't know how to be more clear about this. We are trying to crutch a tranny here that is clearly sick. We need all of the line pressure we can get!

400Eric · #89 11-24-2016, 04:44 PM

Quote:

Originally Posted by MongooseGA

I forgot to mention in the last post that I used about 12 oz of the Lucas and about the same of the Trans-X.

Seeing as how you are now using a non-detergnt "fluid", I would have gone with a full quart of Trans-X and a full container of Lucas Mucus. (I can't remember, is that a full quart too?)

Quote:

Originally Posted by MongooseGA

Also, would anyone have a diagram of what exactly is happening when I'm turning this Tbar? I'm curious to see it and better understand the thing.

You don't need to understand it to know that it works and to do it!

spock505 · #90 11-24-2016, 05:02 PM

Quote:

Originally Posted by 400Eric

As I said before, I was just trying to crutch a weak trans, just as Mongoose is trying to do. Turning in the T-bar was a quick, simple, easy, dirt cheap, solution that worked in the first trans, so I didn't pursue any other solutions cause I didn't need to. Four years and 20,000 miles ago, I'd have bet good money that that trans didn't have 5,000 miles left in it. (Just listen to that awful flaring in that first video I linked earlier in this thread!) [Edit: It's also worth noting that I've NEVER even changed the trans fluid/filter in that car!]

I also said that this is not something that I would do to a tight trans. I've touched the T-bar in only three of my cars.

I still don't have 4th in the second trans but I've left it's T-bar in anyways because doing so has solved almost all of it's other issues. It even gives me second gear chirps now too! (I just love those!) That's why I refuse to give-up on that trans. How can a trans that gives second gear chirps be "bad"?

I strongly suspect that the no 4th issue in my second trans is because of a K2 issue because of the other one remaining issue of there being no engine braking in either first while in the "2" position on the selector or while in reverse.

I've seen posts about K2 pistons and K2 springs. Did you replace the spring, the piston, or both?

Lot's more good posts here, but I have to go for now. I'll be back later. Happy Thanksgiving guys!

You have me at a disadvantage there Eric, not sure what a 'chirp' is, but it sounds like I need one..lol

yep, changed out the K1 and K2 pistons with springs (see thread link). This eradicated the very hard shifts on 2-3-4, although 1 -2 is still there but with the modulator turned to soft it's acceptable.

Changed ATF along with box/TC flush at the same time, this could have helped too. I also found by turning the T bar to max then back one turn will give a super smooth shift ..but will slip or double shift when floored, it could be the modulator is just stuck or sticky.

The first or second ATF change produced a thick silt after only a handful of miles, some of that's bound to have worked it's way around the box, valves.