KiwiTDI · Oct 27, 2024

Some advice please. 1996 300tdi auto with mechanical injector pump. 360,000 km. No record of previous auto box work in service history.

After a trouble free 4 week 4000 km trip around nz, during the last 200km I noticed that after reaching 76kmph (the usual lock up speed) the lock up clutch was “slipping” and the lock up engagement not as “definite” as usual. The lock up was happening but if I applied a bit of throttle to go uphill, or get to 100kmph the revs would rise too quickly indicating the lock up clutch was slipping. I obviously avoided allowing the clutch to slip and drove home as slowly as possible.

Since I have owned the car (12 years and 60,000 km) the lock up has been a slight issue, when cold the first lock up would occasionally not happen if 76kmph was passed too gradually, eg slowly accelerated through, and after that lock up would continue to not happen until the car was accelerated quickly past 76kmph with right foot planted. After that no problems for rest of the day.

The fluid in the dip stick does not look burnt or brown etc. I changed/flushed it some 60,000 km ago at the same time as replacing auto box oil cooler hoses, but I did not remove the gearbox sump and do a full filter and oil change.

I have ordered an auto box filter kit from paddocks which will arrive in a week or so, in the hope a fluid change will fix the issue, my question is whether there is anything else I should check whilst the sump is off eg solenoid or valve, to increase my chances of fixing the issue. I am pretty sure the zf4hp22 box fitted, is the 100% mechanical not electrical type.

lynall · Oct 27, 2024

KiwiTDI said:
Some advice please. 1996 300tdi auto with mechanical injector pump. 360,000 km. No record of previous auto box work in service history.

After a trouble free 4 week 4000 km trip around nz, during the last 200km I noticed that after reaching 76kmph (the usual lock up speed) the lock up clutch was “slipping” and the lock up engagement not as “definite” as usual. The lock up was happening but if I applied a bit of throttle to go uphill, or get to 100kmph the revs would rise too quickly indicating the lock up clutch was slipping. I obviously avoided allowing the clutch to slip and drove home as slowly as possible.

Since I have owned the car (12 years and 60,000 km) the lock up has been a slight issue, when cold the first lock up would occasionally not happen if 76kmph was passed too gradually, eg slowly accelerated through, and after that lock up would continue to not happen until the car was accelerated quickly past 76kmph with right foot planted. After that no problems for rest of the day.

The fluid in the dip stick does not look burnt or brown etc. I changed/flushed it some 60,000 km ago at the same time as replacing auto box oil cooler hoses, but I did not remove the gearbox sump and do a full filter and oil change.

I have ordered an auto box filter kit from paddocks which will arrive in a week or so, in the hope a fluid change will fix the issue, my question is whether there is anything else I should check whilst the sump is off eg solenoid or valve, to increase my chances of fixing the issue. I am pretty sure the zf4hp22 box fitted, is the 100% mechanical not electrical type.

As I understand it the lock up is hyd controlled via the torque convertor, so it could be low/crap oil or the tc clutch is worn?

KiwiTDI · Oct 27, 2024

lynall said:
As I understand it the lock up is hyd controlled via the torque convertor, so it could be low/crap oil or the tc clutch is worn?

Yep TC (lock up side) could be worn out and given the hassle of replacing that (particularly getting TC parts at a reasonable price in nz…..) I want to give every possible “easy” fix a go before removing the gearbox etc.

My knowledge of fixing auto boxes/ TC is minimal and I hope to keep it that way

.

Oil level is fine on the dipstick, if anything I over filled it before my 4000km trip. There has always been a slight drip out of the TC housing drain plug hole, which may have got worse not sure. Also not sure if its engine or gearbox oil.

If I have to get the box out I have a car lift, but my shed is only 3m high, so the disco can only go up less than a metre.

KiwiTDI · Nov 8, 2024

for the record all is well after a fluid and filter change. Getting the sump off on a tdi is a PITA due to the cross member preventing sump removal and LHS gearbox mount preventing access to the rear LHS sump bolt. By loosening the 4 gearbox mount bolts and jacking the box up it is possible to do the job without removing the cross member or oil cooler pipe. I used penrite dexron3 as advised by penrite web site.

My feeling is a valve or governor 2as sticking as lock up is much more definite/quick now, and there is no slipping

I took a grinder to the edges of the old filter and did not find signs of a blockage, see pic (it is made up of 4 pieces one of which is a fine mesh, you can see signs of very thin layer sludge where i wiped my finger over one piece.

Sieklo · Nov 9, 2024

Here is a good 4HP22 manual, as far as I understood you did static oil change, so if I were you I would do another oil change in 100-200km because with static oil change you don’t drain it form converter. On my 4HP I did 4 changes in 400km so 100km and oil change. Also good idea is to torque the the valve body bolts to 8Nm cause the can get loose over time and you will lose pressure there.

KiwiTDI · Nov 9, 2024

Sieklo said:
Here is a good 4HP22 manual, as far as I understood you did static oil change, so if I were you I would do another oil change in 100-200km because with static oil change you don’t drain it form converter. On my 4HP I did 4 changes in 400km so 100km and oil change. Also good idea is to torque the the valve body bolts to 8Nm cause the can get loose over time and you will lose pressure there.

Thanks, its all back together now so can’t do the bolts but yes i bought 12 litres of dex3 and have about 7 litres left, so I have plans to drain/refill the sump in a 100km.

I could not see the manual but I found a pdf online, but could not see an obvious reference to the valve that operates the lock up clutch.

From my experience it appears the lock up clutch requires pressure to “clamp” (or push) the TC clutch plate (s) together, and insufficient pressure results in slippage. Urban myth (eg forums) says that’s how the TC works…..

Sieklo · Nov 10, 2024

KiwiTDI said:
Thanks, its all back together now so can’t do the bolts but yes i bought 12 litres of dex3 and have about 7 litres left, so I have plans to drain/refill the sump in a 100km.

I could not see the manual but I found a pdf online, but could not see an obvious reference to the valve that operates the lock up clutch.

From my experience it appears the lock up clutch requires pressure to “clamp” (or push) the TC clutch plate (s) together, and insufficient pressure results in slippage. Urban myth (eg forums) says that’s how the TC works…..

If you click first word in my previous comment it’s a hyper link to 4HP22 service manual. Yeah I will use whole oil you have to flush it as much you can.
In D1 lockup i purely hydraulic and it works as you said, additional pressure goes to converter and locks clutches inside so fresh fluid will work better, aside of that it’s good to reference to ZF oil list and select oil that’s ZF 4HP compatible
4HP manual LINK
Oil list LINK page 7 and 8 - 11a 11b

KiwiTDI · Nov 10, 2024

Sieklo said:
If you click first word in my previous comment it’s a hyper link to 4HP22 service manual. Yeah I will use whole oil you have to flush it as much you can.
In D1 lockup i purely hydraulic and it works as you said, additional pressure goes to converter and locks clutches inside so fresh fluid will work better, aside of that it’s good to reference to ZF oil list and select oil that’s ZF 4HP compatible
4HP manual LINK
Oil list LINK page 7 and 8 - 11a 11b

Thanks again, for a moment I thought I had not bought the right oil but then realised the 4 speed can use GM dexron2 compatible, phew. Penrite advise to only use the non synth (pure mineral) dexron in their range, so that is what I used. It’s a bit counter intuitive to NOT use the semi or full synth D3 penrite sell, but their product selector was very definite only the mineral was recommended.

I feel I dodged a bullet fixing the slipping issue so easily, and with no signs of burnt clutch etc. I hope it lasts

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