Automatic gearbox/clutch problems

Hi forumites

A few times recently my van has juddered while coming to a stop.  It's just like the noise/feeling of when you stop in a manual car and forget to press the clutch pedal because you forgot you were not driving an automatic.  The engine never quite stalls but picks up again.  Nevertheless it's a bit alarming.  Any ideas where to start investigating?  So far I have just checked the gearbox oil level (which is fine).  It's an LH117 automatic with the old 3L engine (Model U-LH119V-RRPES)

Hi. What was the state of the fluid in the transmission? Was is clear reddish brown or dark and smelling burnt?

Hi there g00se, the gearbox was serviced a few months back. The oil is a clear reddish brown.

Did you have the transmission flushed or just the fluid changed? I've read that flushing old transmissions can hasten issues that already exist.

As I'm from the UK, I had very little experience of auto transmissions before my Hiace - but I've had to look into them a fair bit because of the issue I had (which was ECU related in the end). if it is similar to a manual not letting the clutch out, then it could be something internal. They have lots of clutch-type mechanisms in there but they seem to be controlled by bizarre looking vales that seem to bear a very close resemblance to a marble-race toy!

On thing i thought of is it could be related to the torque converter - a sort of fluid clutch that is the main component that 'slips' the transmission automatically between gear changes and acceleration changes. When you get to a high enough gear and revs, it will physically lock the transmission to the engine and feel like a manual, so you then feel engine braking etc and not that surging. When the lock engages, it feels like a mini-overdrive kicking in - only dropping a hundred revs or so. Normally, as you slow, at some point it is supposed to release - at that point the revs drop considerably. I was wondering if the lock is not releasing and causing the stall-like circumstance? if that's the case, you may only notice it when slowing to a stop from a reasonably high speed.

Out of interest, what transmission do you have? It should be on the chassis plate. Probably one of:

A44DE, A45DL, A45DF, A45DE

My van cut out when it dropped to low revs and that was air in the system, you might have a small bubble moving about. Mine was more than a bubble and it would cut out completely when I slowed down but it went through the "judder not putting your clutch in" phase first.

You could try sticking your van in neutral before you actually stop and see if it still does it, if it doesn't then that would point to the transmission and if it does then it could be air.

Reddish brown = you need to change the fluid.
I wrote at length on this somewhere, as g00se notes, changing it is a process

If the oil is always changed regularly: no problem, as it's always clean.
If not, some people leave it - but this will wear everything faster: not good, and will eventually fail going up some hill in the middle of nowhere, when it's raining.

The first fluid change is a very severe 'hit' for the gearbox as it cleans like a machine polisher on speed.
I did this with mine - after 10 miles I changed it, as it was evil !!
You then need to change it every so often, I would say for a badly neglected box

1st change new DXIII Synthetic (check level while idling)
Drive 10 miles
Change it again, measure how much comes out (3L ish), replace that amount.
Drive 50 miles
Change it again
Drive 100 miles
change it again

Repeat as required:
Drive 200 miles
Change it again

Each time you empty it, look and smell, once it comes out as cherryade (as it goes in!!), smelling the same as it went in, it's clean, and you have restored your gearbox, as best you can, without a clever man taking it to bits

You may not need to do all the steps, base it on how the old oil looks when you take it all out

Whether to drop the sump and change the gauze filter?
I've never seen a filter clogged, even a little bit, as they are gauze, and big bits are not in the oil, so personally I don't consider this is required.
.. unless you find big bits in the oil when you empty it!