Any A4LD experts there??? No oil to cooler....

[Marvial]

Today I was going to check transmission level and flush out some ATF to check what it looks like. The transmission shifts OK, EXCEPT that it will not lock the TC properly at 50mph, the feeling is weak lock.

So, when I disconnected the (upper) line at the radiator, I put a hose both on the line, and on the radiator nipple. Both hoses to a container. I start the engine, but there is NO oil coming. If I blow in the hose connected to the line, I have free passage, and can hear the air exiting (probably IN the transmission). This must be the return line. If I blow in the hose connected to the radiator, I ALSO have flow, but can hear/sense some blurping noise, so my conclusion is that that line ends up in oil. But, I do not understand, HOW can the truck be driveable, if I do not have proper pump pressure? Is there a separate pump for circulation? Also, note that when I check ATF level with the dipstick, warm engine, gear in neutral, I have oil up to top of crosshatch, it almost indicates overfill.

Regards from an Auto tranmission nerd.

 

[BrooklynBay]

Did you check the pressure with a 0 - 300 PSI guage? There is only one pump behind the bellhousing for the entire transmission.

 

[IZwack]

Isn't that line bypassed (by a valve) until the transmission's temperature gets over a certain level? If so, maybe that valve is stick closed?

 

[BrooklynBay]

Isn't that line bypassed until the transmission's temperature gets over a certain level?

Only on the newer 4R & 5R transmissions. The A4LD doesn't have a thermostatic bypass.

 

[IZwack]

Ah, well there goes my one and only idea

 

[Marvial]

Both lines seem "open"....

Thank you for the replies so far, I expected the forward line to come from the pump, I believe I have identified the return line, since blowing in the hose is effortless, no pressure, an "sounds open".

The forward line *also* has low resistance when I blow in it, ( with engine off!!) . I would have thought that the pump would offer some resistance, specially since it must be full of oil. There is some "slight" resistance, and some "bubble noise".

However, starting the engine, there is NO flow, and dipstick says "full". I did these tests when the truck had been parked less than an hour ( in -4 C), so maybee if there is some thermal bypass, that could be it.

I would have expected a) blow resistance due to pump, or b) blockage due to closed cooling circuit. Now it seems like c) open due to thermal valve bypassing cooler back into pan.

I added " a quart" ( 1 Liter) of ATF, figuring low oil would be more dangerous than overfill,
took the truck for a spin, transmission works very nicely EXCEPT no lock, or maybee a "very weak" lock is more correct.

I saw something written a few months ago, relating cooling to TC lockup shuttle valve, but cannot find the post. Hints welcome.

Best Regards, from the local Swedish 94-4x4 gang (daughter and I have one each)

 

[BrooklynBay]

Take a look at these two A4LD valve body diagrams:

It's important to take pressure readings in P R N D to determine if it has a blown valve body gasket or internal damage.

 

[Marvial]

Take a look at these two A4LD valve body diagrams:

It's important to take pressure readings in P R N D to determine if it has a blown valve body gasket or internal damage.

Thank you BrooklynBay, I will try to find something for the pressure measurement, am I correct in that there is a plug on the box, passenger side, 1/3 d from the front, where the preassure gauge should go? My guesses so far is that the TC shuttle valve is stuck, or has limited movement, TC and 3/4 solenoids are abt 35 ohm, as measured from the connector on the inner fender driver side. I have not been able to check computer activation, but will try to hotwire a LED so I can see when the PCM tries to activate TC lock. And, thank you for the nice pictures, so I know where to focus.......

Servicing the valve body just WILL have to wait, weather here is winter/spring, and we do not have access for a "permanent" garage. I will drop the valve body as soon as I can get a suitable time. This is also tricky, since I have to order new filter + gaskets from the US, these parts ar scarce in Sweden, + **expensive*. This is no big problem, only time and planning is needed .

I have never worked on an auto transmission before, but, hey big deal. Right now I am trying to gather info, and I am worried by the fact that I do not understand the thinking behind the "cooling", and the conflicting observations.

Regards,

 

[Marvial]

A few questions

I have now found a "ATSG manual for the A4LD". There are a few confusing things:

On pg 15 it says: To separate transmission problems from cooling problems check flow at the converter out fitting. Is this a separate test point, or is the manual refering to the "control pressure take off" located beside the gear switch lever? Or does this refer to oil line to cooler? I cannot find a point named "control...".

On pg 18 and 19, there are pictures of the TCC solenoid and TCC shuttle valve. These diagrams show a line "to cooler", so, it looks like oil is only sent to cooler if the shuttle valve is in a certain position. This seems to have som bearing on my observations, bad TCC lock and no oil into cooler. Can someone explain where the oil to the cooler should come from, and WHY it is not always flowing?

What does "line" refer to? Is that the pressure AFTER pressure ragulator, or something else?

Best Regards,

Marvial

 

[BrooklynBay]

The manual on page 15 says to check for a stuck converter charge relief valve. I would also check the TCC sock style filter, and the case filter spring. You should rebuild the valve body once it's off.

 

[Marvial]

Thanks BrooklynBay, yes, I am slowly beginning to understand what needs to be done. This EX belongs to my daughter, there were many latent problems with it, and together we have swapped out radiator, put new bearings in the wheel hubs, done brake overhaul, and replaced head gaskets. She is becoming fairly good at repairing, I am bringing back my early 70' s experience of fixing rides. Best achievement so far is diagnosing, finding and fixing a corroded pin in the PCM plug, that caused al sorts of malfunction. We are all novices when auto transmissions come up, but, life is for learning, and if it could be designed it can be made to run!