Big problems a340 automatic

[absolutjimmy_85]

I have a really wierd broblem with my -91 mk3 automatic.
I cant find an answer anywhere.

The problem is that i have no rewerse (it fells when i put R in, but it just slips) and it cant behave when driving forward ither.its dificult to explain but i'l try.
When driving like 100 km\h i can hold that speed at 2500rpm but it slips. it holds the same speed at 3500rpm but at ca 4000rpm it behaves as it should.(goes faster=no slip) At wot there is no slip at all at any gear or speed.

There are no codes in the ecu or ect ecu.
I have replaced the automatic (not speedsensor at the back left side of the gearbox) still same problem.
I have replaced the ecu for the gearbox.
Ihave measured all ports on the ect ecu.
I have measured throttle pos sensor.

Now what can i do? I cant be the only one in this world with this problem.

Jimmy/ Sweden (hope i dont spell to poorly

 

[modmonster2008]

have you checked the tranny fluid?

 

[absolutjimmy_85]

Well, yes. Brand new dextron3. I also changed to an other converter when i replaced the gearbox.

 

[Nick M]

There is no "T" in Dexron. That sounds like low fluid.

 

[absolutjimmy_85]

trust me it's not low fluid. The day this hapened it was my first tought so i filled it up, no differens, i even tried to overfill a bit , still same result. Now with an other identical gearbox , it is filled to the correct line no more no less.
still exactly the same symptom

Well if its not the oillevel , could it be oilpressure? I tried to "de connect" the oilcoolers (one in the radiator and one small infront of the radiator) incase the oil could'nt run thrue them , but no differens.

 

[Nick M]

Unplug the range selector switch. That is the harness on the side that has a position arm. Do not touch the arm, just unplug the harness. Then drive it and come back with how it drives.

 

[IJ.]

Clogged screen in the pan

Coolers won't affect pressures even if the cooler is blocked solid as the circuit is only a bypass.

 

[absolutjimmy_85]

Now i have unplugged the two round conectors that goes to the right side of the gearbox to the thing that feels which gear it is.
The car wont start. I suppose it has to know if it is park or neutral .

I also opened the first gearbox to look inside. i removed the valvehous and i all i could find in the screen,valvehous,and the rest of the gearbox that i can see is pure red oil.

 

[TurboStreetCar]

Completely unplug the ECT ECU. Its located in the passenger side kick panel (at least it is on my 89) and take the car for a drive.

You will have to manually shift the transmission, the pattern will be as follows.

L = 1st
2 = 3rd
D = OD

You should have no lockup also. If the problem goes away its electronic. This seems doubtful to me as the electronic part of the transmission is only gear selection and is very basic.

Did you check the adjustment of the Line pressure cable to the throttle body?

 

[absolutjimmy_85]

I have tried to remove the ectecu . still no rew. i havent taken it for a drive so i dont know how it behaves in forward gears.

I find it hard to belive the problem lies in the gearbox becous it's almost not possible to find an other gearbox with the same wierd problem. And it worked fine in the car it came from.

The only thing on the gearbox i havent replaced is the speedsensor on the rear left side on the gearbox, If i understand the tsrm correct, the gearbox operates by speedsensor and throttleposition sensor.
(governorpressure throttlepressure) if it is'nt controlled by ecu.

What exactly does this speedsensor at the rear left do?

 

[3p141592654]

Did you check the screen like IJ suggested? It sounds like low internal pressure to me, and a clogged screen is a very big possibility. Pull the pan and clean/replace the screen.

The electronics cannot make it slip as far as I know.

 

[Nick M]

Did you check the screen like IJ suggested? It sounds like low internal pressure to me, and a clogged screen is a very big possibility. Pull the pan and clean/replace the screen.

The electronics cannot make it slip as far as I know.

They prevent shift, not slippage. That is why I wanted him to drive it with the range selector unplugged. It just rules the out the possibility.

 

[Pokey2301]

sounds like your tranny is done, reverse is always the first to go, and the your overdrive and drive and starts going lower, tranny needs to be rebuilt or you could swap to a 5sp, thats what i did and ill never go back to automatic!