Citrojim's Pixo, Saxo and Cycling Tales

CitroJim · Post by **CitroJim** » 01 Nov 2009, 18:37

I was lucky today to catch sight of the official ZF repair manual for the 4HP20.

Of great interest was the following statement:

The oil does not have to be changed until it has been in service for ten years.

So, not quite as "sealed for life" as they first claim..

Deanxm · Post by **Deanxm** » 01 Nov 2009, 18:38

That does look very similar Jim yes, yours seems to have a few more pump outlets/inlets though??
anyway, i will stop contaminating the blog now interesting stuff is starting to happen, its looking good 8)

D

CitroJim · Post by **CitroJim** » 01 Nov 2009, 18:59

Deanxm wrote:i will stop contaminating the blog now

No. Don't do that Dean! Keep all contributions coming..

Good luck with your upcoming house move, hope it has a nice, big garage and driveway!

Deanxm · Post by **Deanxm** » 01 Nov 2009, 19:24

Well the flat we rent now has a big drive and garage, the house we are buying has a grass lawn that will be a drive and i will have to settle for as bigger shed as i can get at the bottom of the garden

sadly could not afford a ready done drive and garage..............one day maybe once the bathroom and kitchen.......and heating are done

.

D

Post by **xantia_v6** » 01 Nov 2009, 19:57

CitroJim wrote:I was lucky today to catch sight of the official ZF repair manual for the 4HP20.

Of great interest was the following statement:

The oil does not have to be changed until it has been in service for ten years.
So, not quite as "sealed for life" as they first claim..

It seems a bit odd giving only a time-based lifetime for the oil.

CitroJim · Post by **CitroJim** » 02 Nov 2009, 21:03

After a relatively quiet day yesterday, it was down to business today. Whilst we were reasonably confident the torque converter had failed, it was vital to open up the gearbox and have a check. After a fight with a couple of corroded bolts, those nearest the front of the 'box in direct lime of salt sprays, the 'box came apart.

The good news is that the clutches are absolutely fine after 140,000 miles and on the original oil

Here's a B Clutch (the one that works hard) lining:

The F Brake, which can wear, is also fine. However, looking at the top of the oil filter, the picture is not quite so rosy. The grey stuff is fine metallic powder

The bottom of the 'box contains more of this deposit and a couple of lumps of unidentified metal.

next up for inspection was the oil pump and it was found to be rather worn.

Here's a few shots of it's components showing the scoring. The oil pump gears show signs of fretting and "picking up"

Note the scoring at the green arrowhead and also the condition of 140,000 mile old oil. Not bad at all!

Here's a shot of the pump gears:

Note the damage at the heads of the green arrows.

So what happened? The best we can think is the stator sprag or lockup clutch in the TC began to break up and shed some metal. This found its way into the TC tail bearing and then into the oil pump. The debris visible on the oil filter may be remnants of this or bits of the TC tail bearing. Whatever and wherever it came from, it has wrecked the oil pump and this must be replaced. What we do know is that none of it originated in the gearbox proper

I called for some quotes for spares prices and had a most interesting conversation with the parts man.

I asked for the cost of a new oil pump and torque converter and he said:

"Ahh, I bet you pulled the converter off and found a bearing welded to its neck.."

"Yes, precisely!"

"It's how they all go.."

He went on to say that nobody quite knows why. ZF reckon it's oil contamination and others say it's overheating. In truth the jury is out...

The cost of an oil pump, which is only supplied as a complete unit, is £288 whilst the torque converter is a more reasonable £99 + carriage for a remanufactured item. It is rebuilt by a firm in Glasgow. With consumables on top of that, (filter, seals, transmission cooler) the old wallet is going to take a battering

Thinking on, I wonder if these reports of the odd lock-up and lurch is the first sign of the TC tail bearing going and momentarily seizing?

My own V6 needs a little fettling this week. She's clearly jealous of another V6 in her place and has complained by springing a minor LHM leak from her rear electrovalve

To round off the day today, I briefly saw Gareth in his Activa. he was en-route for the Milton Keynes IKEA and popped in for a quick Lexia session

I really got a quick taste today of what it might be like if I started up my own small specialist business

Deanxm · Post by **Deanxm** » 02 Nov 2009, 21:37

Hi Jim

The cost of an oil pump, which is only supplied as a complete unit, is £288 whilst the torque converter is a more reasonable £99 + carriage for a remanufactured item. It is rebuilt by a firm in Glasgow. With consumables on top of that, (filter, seals, transmission cooler) the old wallet is going to take a battering Twisted Evil

I would like to know who the firm is in glasgow, thats £40 cheaper than i could find a re worked T/C and £40 is £40.
Oil pump price seems very reasonable considering the build of the thing, still a fair whack of money but its not omg volumes of cash.

The condition of the clutches dont surprise me though, have a look at this with a nats wisker under 90k under its belt

D

Post by **xantia_v6** » 02 Nov 2009, 21:55

CitroJim wrote: So what happened? The best we can think is the stator sprag or lockup clutch in the TC began to break up and shed some metal. This found its way into the TC tail bearing and then into the oil pump. The debris visible on the oil filter may be remnants of this or bits of the TC tail bearing. Whatever and wherever it came from, it has wrecked the oil pump and this must be replaced. What we do know is that none of it originated in the gearbox proper

My theory is that the "misfire" I felt driving on the motorway was something breaking up in the torque converter. debris from this would find its way into the bottom of the transmission (but couldn't get through the filter back to the pump) The car drove 45 miles like this. But when the car was stopped for a couple of hours, some oil, with debris, drained back from the torque converter and into the pump. When the engine was subequently started and rum for about 1/4 mile, a peice of debris has scored the pump and then seized the torque converter bearing.

CitroJim wrote: I really got a quick taste today of what it might be like if I started up my own small specialist business

But you did have unusually polite customers

Sid_the_Squid · Post by **Sid_the_Squid** » 03 Nov 2009, 13:10

Interesting how well the clutches have been preserved, and wow is that oil dirty!
Change at 10 years does seem a particularly arbitrary statement, but it lends weight to my suspicion that 'sealed for life' is a marketing ploy as opposed to genuine recommendation from the gearbox designers.

MikeT · Post by **MikeT** » 03 Nov 2009, 14:32

I would just like to say thanks for taking the time to take and display all these clear photos for the rest of us interested forum members that have never delved into the depths - I, for one, can certainly appreciate the extra work involved!

CitroJim · Post by **CitroJim** » 04 Nov 2009, 18:46

Thanks Mike

There follows some more pictures...

Grrr

not enough progress today and little tomorrow as I've been called back to work to attend to something urgent

Still, there has been progress.. Hopefully, I'll be free again on Friday and I've negotiated replacement days off next week..

First up [on vehicle work] was to attend to the LHM leak on my V6. It was not bad but just bad enough to cause a drip from the bottom of the rear hydractive sphere and occasionally drip a little onto the drive. You all know how I absolutely hate leaks

The source was the hydractive electrovalve. Replaced and all is now LHM-tight again

Onto the gearbox...

I started by having a look at the hidden swarf collection magnets behind the diff. This is what I found

I thought two startled cats had got in there...

That is a LOT of swarf. More than I could account for. I cleaned the magnets and went in search of the source. Before I reveal from where, here's some nice clean magnets...

I began by disassembling the F Brake and then, on removal of the piston, I found this:

The output gear bearing has broken up and shed a lot of swarf. The bearing is black and it's surrounding blued. It has damaged the phosphor bronze bush within the shaft which supports the input shaft. The bearing, as expected, is noisy and has huge play.

Here is a close-up of the bearing:

I now have a good idea of what happened. This bearing started to break up. The swarf collection magnets did a good job of catching a lot but not all. the bearing is in close proximity to the oil pump and a path exits for swarf to enter the pump via the torque converter tail. The bearing on the converter tail is splash lubricated from oil that would be swarf-laden. Bits of swarf got into that bearing and caused it to fail and weld up.

I hate to think of the cost of a new output shaft and bearings as it is part of the output gear assembly. Luckily, I have a good one in my scrap gearbox.

It would be easy to miss this failure as it is hidden behind the F Brake, which needs special tools to disassemble. Failing to notice this may be the reason why some gearboxes that have suffered an apparently similar failure have failed again soon after. It would be easy to miss...

One good thing is that the oil filter has done it's job very well and despite all the carnage found thus far, there is no swarf apparent anywhere in the sensitive parts of the gearbox.

Off now to start stripping my scrap 'box to retrieve the good output gear from it...

Post by **xantia_v6** » 04 Nov 2009, 19:24

I assume that the failed bearing is the cause of the occasional vibration at 90+MPH uphill (on European motorways). If so, it has done at least 2000 miles like that.

How is that bearing lubricated?

The burning of the bearing might explain why the oil is much dirtier than last time I checked it 6 months ago.

CitroJim · Post by **CitroJim** » 04 Nov 2009, 19:36

xantia_v6 wrote:I assume that the failed bearing is the cause of the occasional vibration at 90+MPH uphill.

Yes, it could well be the reason as we saw the intermediate driveshaft bearing is in perfect order.

The bearing is lubricated by splash/mist.

Deanxm · Post by **Deanxm** » 04 Nov 2009, 21:56

Hi Jim

Exellent work and writeup as usual, seems the cause of this failure was the same thing that can kill any transmission then.

Daveid Attenborough's 'LIFE' or Jim's 'V6 Gearbox Rebuild'?

The latter wins hands down for me

Indeed, ive come back from our new house to the flat where my internet is just to see this threads updates!! although David attenborough is a close second

D

CitroJim · Post by **CitroJim** » 05 Nov 2009, 22:59

Not a very exciting one this evening

Despite having to work today and Thursday being my evening with the girls, progress has been made.

I've recovered a serviceable Output gear from my spares 'box and am now ready to start reassembling following the arrival of all the spares. The torque converter would also have arrived today had I been home but TNT are redelivering in the morning. Considering it was picked up for it's trip to Glasgow on Tuesday and back on Thursday, that's not bad. The rebuild was done by Mackie but under the auspices of Automatic Choice who really have proved to be a top company to deal with.

No more damage has been found and no more swarf either

I did, last evening, have a brief foray into my scrap valve block. I tentatively undid a few screws to release a plate covering some valves and thankfully was ready for there being a very big spring underneath. My jury is still out as to whether or not to dismantle the valve block given that I can find no evidence of swarf contamination in the vicinity. One thing I was pleased to find was no contamination appears to have affected the cooler. Good job too as I priced up a new cooler and nearly fell over. It costs over £200

One small error. The output bearing (the failed one) is semi-pressure lubricated from a drilling along the input shaft that jets oil up into the middle of the two taper rollers that comprise the bearing set. I'm not sure of the exact source just yet but I suspect it is a drilling off the gallery that supplies the torque converter. I shall blow all the drillings and galleries with air to ensure they're 100% clear during reassembly.

Tomorrow is a clear day so I hope by the end of it to have the 'box back together.