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  #1  
Old 04-06-2013, 07:34 AM
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722.3 Transmission spinning not engaging

Well the 603a turbo motor running perfect when all of sudden yesterday the transmission failed to engage. The engine would rev but no forward movement. I checked my fluid and discovered it was too high. I drained it to the proper level but still nothing. The fluid was the nice red color not brown and did not smell burned.
I checked my vacuum and linkage connections. All were as they should be.

I can put it in gear and without touching the gas pedal it will move forward and in reverse on its own. If I apply the gas the engine spins and it does not engage.

Luckily I was able to get it into my garage before it refused to go any further.

Any help is appreciated.
Mark

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  #2  
Old 04-06-2013, 09:00 AM
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Take a look at the trans output flange, there have been a few reports of the nut working loose and flange splines stripping out. Elevate the rear wheels, parking brake off, put trans in park then try to rotate the drive shaft. You might have to use a bar to gain leverage.

Swapping the flange is easy.

To check the rear diff flange, leave trans in neutral, block the rear wheels or apply parking brake then rotate the drive shaft.

The next things to check would be trans line pressure, if the pressure regulator spring failed, line pressure would drop and not burn the fluid.

Past that, the input splines in the trans gear train may have stripped out.
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  #3  
Old 04-06-2013, 09:23 AM
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Since this is an old g-wagen the tranny has a short drive shaft that goes to the transfer case. All looks good there. Through a little research this morning I am leaning toward the pressure modulator valve on the side of the transmission. Since it is slipping in all gears it makes sense that it would be the problem.
Thoughts?
M
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  #4  
Old 04-06-2013, 12:17 PM
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Why was the fluid too high?

Does your G wagon share a radiator with a transmission oil cooler?

Are you sure the fluid is now correct?

Have you checked the Bowden cable / accelerator linkage?

Have you checked the gear selector rod and bushings? (Probably not this if the car moves but I like to go down the whole list!)

Have you checked the working pressure? (you need a gauge for this)

(All simple stuff - I reckon you are better off looking for the simple if you haven't done so already before you start thinking about more complicated stuff)
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  #5  
Old 04-06-2013, 02:12 PM
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Quote:
Originally Posted by Stretch View Post
Why was the fluid too high?
During the engine swap the torque converter lost alot of fluid. I refilled to bring it to the mark but the ground may not have been level enough and gave a false reading.

Does your G wagon share a radiator with a transmission oil cooler?
Yes it does

Are you sure the fluid is now correct?
Yes

Have you checked the Bowden cable / accelerator linkage?
Yes those are all in place

Have you checked the gear selector rod and bushings? (Probably not this if the car moves but I like to go down the whole list!)
Good there

Have you checked the working pressure? (you need a gauge for this)
I have not will do that tomorrow

(All simple stuff - I reckon you are better off looking for the simple if you haven't done so already before you start thinking about more complicated stuff)
I agree 100%
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  #6  
Old 04-06-2013, 02:26 PM
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Perhaps I should start with a drain and renew of the tranny fluid. Draining the torque converter as well.

M
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  #7  
Old 04-06-2013, 03:17 PM
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If the fluid looks red a fluid change won't help but, if the filter collapsed changing the filter will help.

Don't move the car by driving, if the trans isn't damaged, moving it will cause problems.

Here is a tech file for the 722.3 / 722.4 showing test points and other info. The test points are 10 mm x 1.0 pitch ( some brake lines use this thread for a quick EDIT > thread pitch < EDIT test )

You can use a banjo bolt or weld a hydraulic or pipe fitting to a bolt to make an adapter.
Attached Files
File Type: pdf Mercedes_722.3_722.4.pdf (436.0 KB, 205 views)

Last edited by 97 SL320; 04-06-2013 at 09:39 PM.
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  #8  
Old 04-06-2013, 05:58 PM
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You could have a pump failure. The fluid could have drained back to the oil pan
thats way the level was too high.
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  #9  
Old 04-06-2013, 06:02 PM
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pump

Quote:
Originally Posted by spit64 View Post
You could have a pump failure. The fluid could have drained back to the oil pan
thats way the level was too high.
Did not realize that that was one of the characteristics of a pump failure.

Mark
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Old 04-07-2013, 01:56 AM
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Quote:
Originally Posted by inkblotz View Post
Did not realize that that was one of the characteristics of a pump failure.

Mark
It is just one thing there are other possibility's too.
Incorrect modulating pressure. Modulating pressure control
valve or pressure relief valve is dirty or sticking. Vacuum line to
transmission vacuum capsule clogged or leaking. Working pressure
control valve dirty or sticking. Low working pressure. Defective
primary pump. Pump failure I guess sometime you will hear a whining noise before total failure. Pump failure must be rare also.
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  #11  
Old 04-07-2013, 02:20 AM
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Pump gear failure assuming no gears at all. Remove cooler line from radiator, start engine...if nothing comes out you know its the pump gear. Have a helper start the car while you hold a bucket under it. It will fill extremely quick so be ready to shut it down immediately.

Modulator would not cause no gear, only a lack of shifting, same with governor.
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  #12  
Old 04-07-2013, 03:13 AM
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Here's a link for the front pump reseal

722.315 Pump Re-seal pictures

But measure that working pressure first!
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #13  
Old 04-07-2013, 06:11 AM
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Great thanks thanks for the advise. To start, I will run with ps2cho's test today and go from there.

Mark
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  #14  
Old 04-07-2013, 06:19 AM
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Also I see that there is a secondary pump. What is this additional pumps function and could it be suspect as well?

M
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  #15  
Old 04-07-2013, 06:29 AM
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Secondary pump is required only for towing and tow-starting
vehicle. It is designed as an external gear pump and is positioned in
rear section of the transmission.
If needed, secondary pump is driven
by centrifugal governor shaft. Secondary pump operates only if engine
is not running and vehicle is rolling (tow-starting procedure), while
brake band B-2 slowly engages. Pump stops operating when vehicle comes
to a stop or if transmission has shifted into 4th or 5th gear (engine
running).

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