A4LD Failure

[Nuggethead 420]

What would cause a total falure in an A4LD.
The old tranny I had had a falure that was instant.
I was driving out of the mall and got into traffic about 20 feet later nothing.
There was no reverse no forward nothing at all.
What wopuld go that would cause this condition.
Just curious????

 

[Jason94sport]

Most anything. The A4LD is not a reliable tranny. Sounds like something failed that caused total line preasure loss.

 

[Nuggethead 420]

I was hoping for more than the obvious answer.

 

[Brian_B]

Something in mine just snapped at a red light (loud noise). Its actually fairly common for them to just quit. Its not a specific problem in any of the ones I have seen. Glacier might be able to help you, but without symptoms, I doubt it.

 

[Nuggethead 420]

No symtoms I was driving and then Iwas not but the engine was still running.

 

[Glacier991]

Jason actually hit the obvious nail on the head. I bet your line pressure is gone. Now WHY that might occur catastrophically is the next question, and the one you really want the answer to.

The failure can occur in that the pump ceased to be driven (splines twisted off, broken input shaft, etc... low probability) it can occur due to some total pump failure (also low probability) It can occur because a seal failed in a critical part when the resultant leak was so massive it practically means total loss of line pressure (decent probability) A check ball could have gotten stuck in the open position.... (medium) your filter could be plugged (possible) and I am sure there are probably 4 or 5 more possibilities too. I'd recommend you put a pressure gauge on it and see what your line pressure is.

 

[Nuggethead 420]

It is already out. Had the valve body out and the check balls look good.
A small burr in the 3-4 shift spool bore but nothing to stop it from shifting position. Pump seal have not gotten that far yet. The tranny was very strong hauler up till that moment. It was not like it was getting slow or slipping prior to this event.
I will keep looking and following the rebuild diary like it was the bible.
Lots of good tips, by far one of the best posts I have come across, for me at least.
Any thing other than pressure loss??

 

[Glacier991]

There are check balls in the clutches too.

It is either lack of fluid, loss of line pressure, or mechanical failure. Those are the options. Alone or in some combination. Too many permutations and combinations to reliably predict or call.