A4LD ask for advice, no reverse

[Momohenri]

after having rebuilt my gearbox it was necessary to find out why I did not have first and reverse gear, I apparently found for the first gear, now it is fine, but not for the reverse gear no movement even when putting gas, could you tell me where to search to solve this problem

 

[franklin2]

Who rebuilt the transmission?

 

[Momohenri]

Myself, I did it calmly by following a video

 

[franklin2]

I am not a transmission guy. And I have done what you did before, taken something apart that I knew nothing about, and put it back together solely on instruction, and had it turn out ok. But if anything went wrong, I would have been in trouble. Sounds like that is were you are, and unless you want to take it back apart and try to go through the whole thing again, it sounds like you might have to take it to get it professionally done. That is one of the reasons I have never messed with a auto trans very much, they are too much of a pain to pull in and out to experiment with and learn on.

 

[RonD]

Reverse requires a higher pressure to engage, this is why automatics often have slow to engage or no Reverse when they get older

The pump sends pressure to Valve Body, the valve body then routes this pressure to the clutches and bands to change "ratios"(gears)
Forward(D) and reverse(R) are selected by the Shifter directly but pressure still needs to be high enough to engage the clutches and bands, especially for reverse

There is a reverse "servo" that has a cover plate that needs to be tight, sealed, or you will lose pressure an no reverse

 

[Momohenri]

2 ideas that come to me:
1 - when I put the rear servo back (without spring) it did not want to go in, even pushing hard, turning it and playing a little with suddenly it went in, I removed it and I didn't see anything that could prevent it from entering, could it relock?

2 -
by doing the code test with the innova car reader tester I got the code 89 which corresponds to: AXOD Lock-Up Solenoid (LUS) circuit
failure or Clutch Converter Override (CCO)
circuit failure could this come from
sorry for my english, i'm french speaking

 

[RonD]

If its a "circuit" code that means its a wiring or Solenoid issue

But I have
Code 89 A4LD - Converter Clutch Override solenoid - Transmissions
or
AXOD Torque Converter Control solenoid circuit - Transmissions
or
Exhaust Heat Control (heat riser) solenoid circuit - Solenoids
Same codes were used for multiple vehicles and mean different things


In a 1988 A4LD there are 2 solenoids, TCC(converter clutch) and 3-4 shift(overdrive)
There is a 3 wire connector on drivers side of trans
Center wire will have 12volts with key on, it powers both solenoids
Each outside wire runs back to computer, the computer GROUNDS that wire to activate that solenoid

Since a solenoid is just a coil of wire, when key is on the computer should see 12volts on each of those "ground wires"
If computer does NOT see the 12volts it will set a code for that
You can use an OHM meter between center pin on trans to either outside pin to test if solenoid has a full circuit, you should see 26 to 40 OHMs, if not then solenoid or wire inside trans is bad

The TCC locks the torque converter to engine RPMs, the computer uses engine RPMs and Speed to test if the torque converter is locked
RPMs and speed should change at the same time when torque converter is locked, no delay when accelerating or decelerating, no "slipping"

There are pressure test ports on the outside of the transmission, these can be used to narrow down what might be wrong

The image has lots of info: https://www.explorerforum.com/forums/media/a4ld-specification-chart-from-transgo.39537/full

But I think the 1988 was first year of the 2 solenoids, not 1989, but yours may only have the 1 solenoid, wouldn't matter for Reverse or troubleshooting

 

[Momohenri]

Thanks Rond, can you tell me if the tcc solenoid controls reverse gear?

 

[RonD]

No, just locks torque converter, when speed is high enough

 

[Momohenri]

another idea that could explain that reverse gear does not work ?
I found that but it's in French it says that the od is activated for reverse gear

 

[RonD]

The OD one-way clutch(sprag) is "holding" when in Reverse, but it does that in ALL gears except OD
So I would expect forward gear issues if that was the problem

 

[Momohenri]

ok thank you i keep looking tomorrow

 

[Transman304]

Very easy to miss the tab on reverse band when installing servo. Band will rotate and move forward out of location when building transmission. Can be moved back into location while transmission is installed. Need to see the tab of the band where servo pin installs.
Brad

 

[Momohenri]

Thanks Transman, I have already withdrawn the piston three times and tried with a Phillips screwdriver, the band comes out, despite this that it could be put on badly?
is it true that it does not slide well, when I push it in, it does not come back easily, normal?
what are the main cause of the reverse gear problem, the body valve, the servo, what else?

 

[Momohenri]

last news I removed the valve body to check all the springs and valve, everything looked correct but the seal of the separator plate was damaged, I took the old plate or the seal was in very good condition now I have no more power neither in forward nor reverse, by searching a lot, I found that these plates were not all the same (see photos).

Could this cause a power problem?
I tried to test the solenoids, not sure that they work well especially the converter