Ping transmission dudes...

Did a day's off-roading in the Disco (300Tdi with EDC, ZF auto) on Saturday
and got the front end submerged in wet mud several times. On the way back
to the campsite it started to play up. Medium to full throttle, no problem.
Idling or over-run, no problem. But on a smidgin of throttle (going through
villages etc) the revs were dying back to zero and then coming back
intermittently, and the "check engine" light was flashing at the same time.
Back at the site, I found nothing wrong/missing/loose under the bonnet, but
the transmission oil cooler was clogged with mud throughout its length. I
tried to clear it out with a hose, but not very successfully. Next day,
towing a caravan, it did about 5 hilly miles and then as we were climbing a
long hill it started making horrendous squeaking noises (as if from a stone
caught between brake disc and mudshield) and the transmission overheat light
came on. When we stopped, there was a very hot smell coming from
underneath. Transmission oil level was OK (bearing in mind that the rig was
hot and it should be measured cold) - at least there was oil on the stick.
We rested it for a while and then carried on very gently, and got home
without further problems. Holding it down in lower gears seemed to help.

I pressure-washed the transmission oil cooler and got it completely clear,
and I have had no problems in the 2 days since, although I haven't tried
towing yet.

Questions:

1. Could the two problems (engine and gearbox) be related? If so, why?
Intercooler/engine oil cooler/radiator were not affected, and the engine
temp was normal throughout.

2. Assuming no further occurrences, could I have caused long-term damage to
the autobox?

Anything else I should do?

Thanks for any info.


--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)

"Richard Brookman" <[email protected]> wrote in message
news:[email protected]...
> Did a day's off-roading in the Disco (300Tdi with EDC, ZF auto) on
> Saturday and got the front end submerged in wet mud several times. On the
> way back to the campsite it started to play up. Medium to full throttle,
> no problem. Idling or over-run, no problem. But on a smidgin of throttle
> (going through villages etc) the revs were dying back to zero and then
> coming back intermittently, and the "check engine" light was flashing at
> the same time.
> Back at the site, I found nothing wrong/missing/loose under the bonnet,
> but the transmission oil cooler was clogged with mud throughout its
> length. I tried to clear it out with a hose, but not very successfully.
> Next day, towing a caravan, it did about 5 hilly miles and then as we were
> climbing a long hill it started making horrendous squeaking noises (as if
> from a stone caught between brake disc and mudshield) and the transmission
> overheat light came on. When we stopped, there was a very hot smell
> coming from underneath. Transmission oil level was OK (bearing in mind
> that the rig was hot and it should be measured cold) - at least there was
> oil on the stick. We rested it for a while and then carried on very
> gently, and got home without further problems. Holding it down in lower
> gears seemed to help.
>
> I pressure-washed the transmission oil cooler and got it completely clear,
> and I have had no problems in the 2 days since, although I haven't tried
> towing yet.
>
> Questions:
>
> 1. Could the two problems (engine and gearbox) be related? If so, why?
> Intercooler/engine oil cooler/radiator were not affected, and the engine
> temp was normal throughout.

More likely to be a coincidence, I'd have thought.

> 2. Assuming no further occurrences, could I have caused long-term damage
> to the autobox?

Yes. By overheating the fluid it breaks down chemically, giving a massive
reduction in the lubricating properties. Replace the fluid immediately, and
again in a week or so (due to a fair quantity of the old oil remaining in
the torque convertor) and it ought to be ok unless you have burnt the
clutches.

> Anything else I should do?

Pray?

Badger.

so Badger was, like...
> Questions:
>>
>> 1. Could the two problems (engine and gearbox) be related? If so,
>> why? Intercooler/engine oil cooler/radiator were not affected, and
>> the engine temp was normal throughout.
>
> More likely to be a coincidence, I'd have thought.

'Swat I thought, but to happen on consecutive days, less than 20 miles
apart, after a mucky bit of off-roading made me think they might be linked.
Perhaps the early signs of an overheating box confused the EDC or something.

>> 2. Assuming no further occurrences, could I have caused long-term
>> damage to the autobox?
>
> Yes. By overheating the fluid it breaks down chemically, giving a
> massive reduction in the lubricating properties. Replace the fluid
> immediately, and again in a week or so (due to a fair quantity of the
> old oil remaining in the torque convertor) and it ought to be ok
> unless you have burnt the clutches.

Hope I caught it in time. Seems normal at present. I'll change the fluid
though.

>> Anything else I should do?
>
> Pray?

Thank you, Mr Cheerful I will, if I can remember his email address.

--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)

"Richard Brookman" <[email protected]> wrote in message
news:[email protected]...
>
>>> Anything else I should do?
>>
>> Pray?
>
> Thank you, Mr Cheerful I will, if I can remember his email address.

ha ha. Seriously though, my own zf4HP22 autobox (in a 4.0v8 110 recovery
vehicle) has started to show initial signs of wear, not surprising
considering the sheer abuse it tolerates! The fluid is still clean and
translucent but when idling in "P" the engine is stable at 850rpm, if I
select "N" the revs drop and fluctuate by around 25-50rpm, dropping by the
normal 100 or so on selection of "D" or "R". As far as I can remember,
there's no difference hydraulically between P and N, I think I need to dig
out the flow charts and check.....
Might look into replacing it with a 4HP24 fitted with a manual (non-ecu
controlled) valve block as I'm considering a 4.8 stroker kit......

Badger.