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RRPhil

Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 969

ZF 6HP26 teardown

First, a bit of background .....

Click image to enlarge

Pierre Lepelletier is one of my heroes. He was born in 1928 and spent the whole of his career working for Ferodo (now Valeo) in France. At the age of 59 he took early retirement and then, two years later, filed a patent application for a new geartrain arrangement for automatic transmissions that could produce six well-spaced ratios using only 5 clutches, a Ravigneaux epicyclic and a simple epicyclic.

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This was in December 1989. A few years later he had signed licenses with Aisin-AW (the world’s largest automatic transmission manufacturer), ZF, Ford, Jatco & GM allowing them all to manufacture transmissions using his geartrain system.

Why was his invention so important? Well, in ZF’s case - compared with the 5-speed 5HP24 unit that it replaced - the 6HP26 had 29% fewer parts (down from 666 to 470), was 44mm shorter (reduced from 697mm to 653mm) and weighed 12% less, despite its higher torque capacity and increased ratio spread. Most of the world’s OEMs switched to 6-speed transmissions as a result.

A colleague of mine was lucky enough to meet and have a chat with Monsieur Lepelletier at a conference a few years ago and told me that he’s a perfect gentleman. Now in his mid-eighties, I hope he enjoys a long and healthy retirement – and hopefully he’s made a few quid from the 20 million or so 6-speed transmissions that have so far been produced using his patented design!

The ZF 6HP26 transmission first appeared in 2001 in the 7 Series BMW, the year before the L322 Range Rover was launched, but since Ford had taken Land Rover off BMW’s hands in 2000, the L322 driveline development was frozen resulting in the Range Rover being launched with the already out-of-date 5-speed ZF unit in 2002. It wasn’t until 2006MY, when the Jaguar petrol engines were introduced, that the Range Rover finally caught up and the 6-speed unit became available. The diesel version had to wait yet another year for the TDV8 to be introduced before the infamous GM 5L40-E was finally abandoned in favour of the 6HP26.

Strictly, the Range Rover is fitted with the ZF 6HP26X transmission (the ‘X’ stands for external 4WD i.e. fitted with a separate transfer box) with part numbers starting 1068 020 XXX, the rear-wheel drive variant being the ZF 6HP26 (part numbers starting 1068 010 XXX) and the ‘internal 4WD’ version for Audi & Bentley being designated the ZF 6HP26A61 with part numbers starting 1068 030 XXX.

Anyway, on with the teardown ….

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I saw this particular transmission on eBay, actually from a supercharged 4.2l V8 Range Rover Sport, with a starting price of £50 – and I turned out to be the only bidder.

After sliding the torque converter off its splines, and placing it safely to one side, I drained out the transmission fluid. The drain plug is at the back of the plastic sump pan.

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Incidentally, the filler/level plug is on the right side of the casing, in a location similar to the 5-speed units

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Sump pan removal next – there are 21 screws in all and it’s good to see that the head size has been increased to Torx T40, from T27 used on the 5HP24, to make the heads less likely to strip

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These screws are tightened to 8Nm. ZF warn against removing the sump pan at fluid temperatures above 40 deg. C due to the risk of the plastic distorting at higher temperatures!

The sump pan then just pulls off

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The filter is an integral part of the sump pan and the photo shows where the oil enters the filter at the very bottom of the sump and also the suction tube which engages in a hole in the oil pump housing

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This particular sump pan/filter had never been changed, as revealed by the 2005 date stamp

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The OEM is Filtran (as for the 5HP24)

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and two sump magnets sit either side of the drain plug at the rear of the sump pan

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The electrical connector sleeve is removed next, by first pulling out its retaining clip

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and the connector sleeve will then come out of the casing

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It’s easy to see, from the casing corrosion which has coated the two O-ring seals, why this is a very common source of oil leaks in the 6HP26 transmission.

The electrical pins on the Mechatronic module can be seen through the hole in the casing where the sleeve was extracted

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There are ten screws in all (Torx T40) which bolt the Mechatronic module to the casing - seven long and three short - and these are easy to distinguish from the screws which hold the two valve block halves together which are only T27 and have a smaller head size

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The rooster comb pin engages in a slot in the manual valve which also drives the slider on the (brown) potentiometer so that the controller knows which gear position has been selected by the driver

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The Mechatronic module can then be lifted out

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The Mechatronic module is a combined hydraulic valve block and transmission ECU. It also houses both the turbine and output speed sensors and also the fluid temperature sensor. There’s a risk that electro-static discharge could damage the ECU so ZF recommend that a ground strap is worn when handling it

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This is how the underside of the casing looks with the Mechatronic module removed

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Next, the bridge seal to the pump housing just lifts off

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and then each of the four rubber jump tubes has to be extracted

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In terms of length, there are two small, one medium and one large tube

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The park lock engagement mechanism can be seen in the photo above and this is removed next, together with the selector shaft

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So that’s it for the underside, next our attention turns to the front of the transmission.

The oil pump and stator support assembly is retained by 13 Torx T27 screws

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and each of the (identical) screws is fitted with a washer with a rubber insert to prevent leaks

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The assembly can then be drawn out from the casing

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Next out is the A & E clutch assembly, which includes the front epicyclic

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Followed by the B clutch assembly

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To remove the static C clutch (& D clutch) housing, the large snap ring has to be extracted first

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and it can then be drawn out

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The two rectangular blocks in slots on the outside of the drum prevent the assembly rotating in the casing

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Now the Ravigneaux epicyclic, together with the D clutch pack, follow

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Which just leaves the output shaft

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The intricate basket weaving around the annulus gear is actually the target wheel for the output speed sensor

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Turning to the back of the transmission, the rear output seal is removed

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to reveal a snap ring that retains the insert which locates the rear axial bearing

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A couple of threaded holes allow extraction bolts to be screwed in to assist with its removal

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So that’s just about it. The casing is now empty

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A very simple process requiring no special tools.

Next step is to disassemble each of the subassemblies in turn. I’ll follow up with reports on progress with those.

Phil

Admin note: this post has had its images recovered from a money grabbing photo hosting site and reinstated

19th Nov 2012 11:43pm

KurtVerbose

Member Since: 08 Aug 2010
Location: Les Arses
Posts: 5848

2007 Range Rover Vogue TDV8 Stornoway Grey

Thanks Phill, good read.

I always did think they should've used torx 40's instead of 27's.

Question for you. All these ZF 6 speeders, are they basically the same regardless of whether they're fitted to a BMW 116 or a Bentley W12?

20th Nov 2012 3:28am

SteveMFr
Site Sponsor

Member Since: 22 Nov 2009
Location: Strasbourg, France
Posts: 1641

Very interesting as always, Phil. Learned a lot on this post - thanks.
And it is really good to see that there are still engineers who get their hands dirty!

Did this particular trans not have any probs? Seems that the six and up speeds are much more reliable than both the ZF and GM 5 speeds. Prices are considerably less for many late model transmissions. Maybe we need to rethink what it would take to actually do a swap. A CAN translation module would not be much trouble.
RRC 2Dr, RRC 4Dr,
P38, and 2 L322s
(wife thinks I'm nuts - prob right, too)

20th Nov 2012 6:52am

simon1233

Member Since: 13 Jun 2011
Location: Leyland, sometimes Darmstadt
Posts: 650

Really interesting post Phil, I must say that I am fascinated/terrified in equal measure by the sheer complexity of these transmissions.

Looking forwards to the next updates

20th Nov 2012 7:19am

ebajema

Member Since: 24 Mar 2011
Location: New Plymouth
Posts: 4782

2010 Range Rover Autobiography 5.0 SC V8 Galway Green

Excellent post Phil, wish we still had people like you doing the workshop manuals of cars in this way !!!
MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

20th Nov 2012 7:58am

Gazellio @ Prestige Cars

Member Since: 22 Jan 2010
Location: Chilterns, UK
Posts: 11309

Wow great write up Phil

20th Nov 2012 8:17am

47p2

Member Since: 05 Oct 2010
Location: Gone Beyond, Subaru
Posts: 8048

Awesome write up as usual Phil, I just wish I understood it all

20th Nov 2012 8:53am

mrd1990

Member Since: 01 Jun 2011
Location: N. Wales
Posts: 267

More detail can be found in this video:

20th Nov 2012 11:19am

kingpleb

Member Since: 07 Jun 2011
Location: Maybe here. Maybe there, I get everywhere!
Posts: 8455

FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

20th Nov 2012 11:24am

simon1233

Member Since: 13 Jun 2011
Location: Leyland, sometimes Darmstadt
Posts: 650

The Rockwell video is fantastically illuminating, really cleared things up for me...

20th Nov 2012 11:39am

madcima

Member Since: 25 Oct 2011
Location: Italia
Posts: 137

Congratulations, nice service!!

20th Nov 2012 12:13pm

mzplcg

Member Since: 26 May 2010
Location: Warwickshire. England. The Commonwealth.
Posts: 4029

2014 Range Rover Vogue SE SDV8 Corris Grey

Wow, just Wow !!

As for the sub-assemblies, are there any special tools needed for overhauling these?

I've rebuilt many a manual gearbox but never an auto. This makes me understand that they are not quite as scary as I thought.

Cheers. Dom.

20th Nov 2012 1:24pm

RRPhil

Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 969

Thanks for your kind comments.

@KurtVerbose

ZF have a range of three 6-speed transmissions to cover different torque capacities. These started out as the 6HP19, 6HP26 & 6HP32 but were later upgraded to ‘2nd generation’ versions with higher torque capacities and renamed 6HP21, 6HP28 and 6HP34 respectively. The 6HP28 was introduced by Range Rover when the 5.0l V8 was launched for 2010MY. I’m afraid I don’t know what proportion of components are common to all of them.

Click image to enlarge

@ SteveMFr

The history of the particular transmission that I’ve stripped is somewhat uncertain. It was listed as ‘working fine when removed’ but it’s sourced from an individual rather than a dismantlers so why anyone would wake up in the morning thinking “Hmmm, my gearbox seems to be working fine at the moment. I think I’ll take it out of my car and stick it on eBay for £50” I’m not sure. The fluid looks a bit contaminated to me so I’m thinking that I might find some issues once I start getting the subassemblies apart – we’ll see.
I agree that, with 11 years of use under its belt now, the 6-speed unit appears to be much more reliable than the 5-speeds (especially the 5L40-E!) it replaced. Certainly the ‘second-hand’ prices are a lot less. 5HP24s are generally priced around £1200 and the 6HP26s around £700 – probably a reflection of the fact that they’re much more plentiful, having also been used in the Disco 3, Disco 4 and RR Sport.
Interesting thought about retrofitting the 6-speed into the ’02-‘05/’06 models…

Unfortunately I don’t have speakers on my PC at work so I’m not learning much from the Rockwell video I’m afraid – but I’m looking forward to viewing it in all its glory this evening where I hope to receive full technology transfer.

Phil

Admin note: this post has had its images recovered from a money grabbing photo hosting site and reinstated

20th Nov 2012 3:39pm

KurtVerbose

Member Since: 08 Aug 2010
Location: Les Arses
Posts: 5848

Thanks Phill.

20th Nov 2012 4:05pm

KurtVerbose

Member Since: 08 Aug 2010
Location: Les Arses
Posts: 5848

simon1233 wrote:
The Rockwell video is fantastically illuminating, really cleared things up for me...

Yes, it certainly covers one or two things that Phill has missed out.

Is it just me, or does anyone else hear 'doodie' when Americans say 'duty' - as in 'heavy doodie'?

20th Nov 2012 4:10pm

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