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RRPhil



Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 912

United Kingdom 
Magna Steyr DD295 Transfer Box Teardown

I’ve just bought a poorly DD295 transfer box off eBay for £50 as I thought it might be fun to strip one down to see what’s what. The seller’s description was that it “did drive but was noisy” and I can tell just from spinning the input shaft by hand that there’s something very wrong inside – it feels extremely rough.


Background

The Magna Steyr DD295 transfer box replaced the earlier New Venture NV225 unit in the Range Rover when the L322’s powertrain was revised with new engines and the 6-speed ZF 6HP26 transmission. For petrol-engined versions the changeover was at 2006 model year and, in the case of the diesels, it was for 2007 model year.

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This transfer box has been used ever since, and the same unit is also fitted to the Land Rover Discovery 3, Discovery 4 and the Range Rover Sport.

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The original NV225 unit, used in conjunction with the 5-speed transmissions, employs a Torsen Type-B differential to apportion torques front-to-rear (the split being nominally 50:50). The Torsen design limits the torque biasing to 65%/35% in either direction and, as many of us found to our cost when our front propshaft spline failed and left us stranded, the Torsen unit does not allow the differential to be ‘locked’. The DD295 unit on the other hand uses a ‘normal’ bevel gear differential, which again nominally splits torque 50:50 front-to-rear, and a multi-plate clutch pack is employed to vary the front-to-rear torque distribution with the clutch also having the capability to lock the centre differential.

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As with the NV225, the DD295 has selectable low & high ranges, high range being direct (1:1) in each case but low range ratio is slightly different for the two boxes : 2.93:1 in the case of the DD295 compared with 2.69:1 for the earlier NV225 unit.

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On with the teardown

So the first job is to drain off the fluid. The casing has a combined filler/level plug and also a drain plug (head size 8mm hex.), each tightened to 22Nm

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The fluid is Shell TF 0753 (as usual, Land Rover state that this fluid has been especially developed for the unit, contains unique additives, and therefore no other fluid must be used) and the capacity is just 1.5 litres from dry. The fluid that drained out looked nice and clean, so no particular clue there as to what the problem might be.



The next component to be removed is the shift motor, which is held on with four, 55mm long, external Torx head screws (head size E10) which are torqued down to 25Nm

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The drive gear in the motor is plastic :

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It’s interesting to compare the cost of this shift motor (IGH500040) at around £200 with that of the NV225 shift motor (IGH500010) which is now priced at around £1600 ....and climbing



Next off is the high/low range position sensor which is retained by two, 30mm long, external Torx head screws tightened to 10Nm. My smallest Torx socket is E8 and the head size is smaller than this so I used a plain 5mm socket to remove the screws, which seemed to work okay.

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Unlike the low/high shift fork used to achieve range changes in the NV225 - which glides linearly along a ‘rail’ - the DD295 shift fork pivots on an axis and this angular position sensor is attached to one end of this axle and therefore measures the shift fork angle directly.

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From examination of the Patent for this transducer it is of the ‘non-contact’ type - which is good to know considering all the problems people have experienced with the NV225 sliding-contact rotary potentiometer.

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The Land Rover part number for this sensor is IAB500191 and it costs around £85 to replace


The final component to remove before the casing is opened up is this solenoid :


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The shift motor is ‘dual-function’ in that it controls both the clutch actuation and the range changes and it’s this solenoid’s job to switch the mechanism (which is driven by the motor) over to perform whichever of these two functions is required at that time.

The solenoid is attached to the casing by three, 12mm long, external Torx head screws, tightened to 6Nm. The socket size is the same as for the high/low range position sensor screws.

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It can be seen in the photos above & below that the solenoid has a plastic T-piece attached to its centre plunger which engages in a fork at the end of the transfer box selector lever

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It was a bit of a pain to detach from the casing because the solenoid is designed to be removed (& subsequently re-installed) in its ‘energised’ position and this is achieved by using the diagnostic tool to power it up, which obviously means leaving the electrical connector attached until it’s lifted clear of the casing. Not having the right kit I just fiddled around until it eventually disengaged itself from the fork. The Land Rover part number for the solenoid is IGF500011 and its cost is similar to the high/low position sensor i.e. approx. £80

So, finally, we get around to splitting the casing halves so that we can have a look inside the transfer box. The two casings are held together with nineteen, 45mm long, external Torx head screws (socket size E10) which are tightened to 35Nm

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and, following their removal, the casing can be split to reveal the innards....

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That’s as far as I’ve got at the moment.....standby for the next exciting installment (bet you won’t be able to sleep now Rolling with laughter ). I’ll follow up with what I find as soon as I’ve found it, hopefully within the next couple of days!

Phil

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

Post #129850 7th Jul 2012 9:40pm
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47p2



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

Scotland 

Great write up as usual Phil, I was going to have an early night but I'm now going to keep hitting the refresh button until you update the thread Whistle

Post #129854 7th Jul 2012 10:02pm
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Joe90



Member Since: 29 Apr 2010
Location: Hampshire
Posts: 6400

England 

Great stuff Phil Thumbs Up .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember Wink
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Post #129855 7th Jul 2012 10:07pm
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47p2



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

Scotland 

Still hitting the refresh button Thumbs Up

Post #129857 7th Jul 2012 10:14pm
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kingpleb



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

United Kingdom 2005 Range Rover Vogue Td6 Bonatti Grey

Phil on behalf of the forum members here,

Thank you Smile

Also is it possible to swap or upgrade the NV225 to the DD295 with the only day to day issue being the lower gearing for low range?? FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

Post #129871 7th Jul 2012 11:05pm
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47p2



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

Scotland 

Whistle Whistle

Post #129880 7th Jul 2012 11:41pm
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RRPhil



Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 912

United Kingdom 

Unfortunately it’s not an option to swap the two transfer boxes as they were never designed to mate up to the same transmission. I would imagine that their installation sizes are different too. Also, their control systems will be quite different as the passive Torsen centre diff. in the NV225 was replaced with active clutch control in the DD295.

To be fair, the NV225 appears to be (mechanically) very reliable, if it wasn’t for the stupid shift motor potentiometer letting the side down. The sooner we find a separate source for this potentiometer we can stop Land Rover from being able to hold us to ransom on the complete shift motor assembly (the price of which has practically doubled in the last two years as failure rates grow and demand increases).

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Just to keep 47p2 happy until the next instalment (hopefully tomorrow) here’s some pictures of a cutaway DD295 from Cutaway Creations (the photographs are theirs, not mine) : http://www.cutawaycreations.com/
...now go to bed or the transfer box fairy won’t come... Laughing

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Phil

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

Post #129881 8th Jul 2012 12:01am
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47p2



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

Scotland 

Thanks Phil, I'm off to bed right now Laughing Laughing

Post #129885 8th Jul 2012 12:44am
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RRPhil



Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 912

United Kingdom 

The two halves of the casing separate easily with almost all of the components staying with the rear casing

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The exception being the front output flange which can be removed from its bearing by compressing the snap ring

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There are two Bellville springs which react against a circlip on the input shaft which appear to set up a preload force against the inner race of the input bearing

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and when I spin this bearing by hand it feels extremely rough & noisy. On closer examination I can see that the balls and races are very badly damaged

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There’s a magnet in the bottom of the casing which is covered in metallic debris

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which, when cleaned up, looks like this

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Clearly therefore the failed bearing has been producing a lot of debris and it’s amazing that the fluid that was drained out was so clean.


The input shaft can then be removed from the rear casing, and it brings the oil pump with it

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Removal of a snap ring enables the oil pump to be separated from the shaft

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This leaves the rear casing looking like this

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Next off is the front driveshaft sprocket and the chain

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It’s interesting to see that this Borg Warner Hy-Vo chain is exactly the same width as the chain fitted in the NV225, but is slightly shorter

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The other sprocket can only be removed as part of a sub-assembly with the torque-biasing clutch. The two levers which move apart to engage the clutch can be seen

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The bearings on the ends of the two levers sit on this cam which is rotated by the shift motor. As the actuator turns, the bearings ride up the ramps on either side, forcing the levers apart

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A circlip holds together the assembly

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and the photo below shows the ball and ramp mechanism which translates the levers’ angular movement into an axial displacement to engage the clutch

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The torque-biasing clutch has a total of ten friction plates

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So here’s what now remains in the rear casing, ready for the next instalment...

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Phil

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

Post #129976 8th Jul 2012 11:50pm
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47p2



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

Scotland 

Really interesting Phil, I take it the bearing is the only problem you've found so far?

Post #130033 9th Jul 2012 12:56pm
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RRPhil



Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 912

United Kingdom 

Yes, just that input bearing – and I strongly suspect that’s all I’m going to find wrong with it. None of the box’s internal parts are available from Land Rover so I’ll get the bearing out, check its size and get a price from a local bearing factor (just out of interest).

If anyone has experienced a problem with their (DD295) transfer box I’d be interested to know - especially if it was (vehicle-speed) noise related. My understanding, though, is that this is a pretty reliable/durable unit.

Phil

Post #130130 9th Jul 2012 7:39pm
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T24RES



Member Since: 22 Nov 2010
Location: Henley-on-Thames
Posts: 936

United Kingdom 

Is it just a lack of fluid that has caused the bearing to fail?

Post #130176 9th Jul 2012 11:20pm
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47p2



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

Scotland 

Thanks Phil, top post Thumbs Up

Post #130178 9th Jul 2012 11:32pm
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RRPhil



Member Since: 22 Aug 2011
Location: Blackburn, Lancashire
Posts: 912

United Kingdom 

The failed input bearing turns out to be a plain, single row, deep groove ball bearing of size 50 x 90 x 20.

Click image to enlarge


Although I’d expected this 6210 C3 bearing to be manufactured by one of the ‘high end’ suppliers such as SKF, INA/FAG, NTN, etc. it’s actually manufactured by a company I’ve never heard of – ZKL of Slovakia.

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I’ve priced a genuine SKF replacement from a local bearing factor, available from stock, at just £10.95+VAT.

Last week I saw two more of these transfer boxes on eBay, both for £50, both ‘still working but noisy’. If this is the start of an epidemic, someone should jump on this bandwagon quickly because re-manufacturing these ‘failed’ DD295s is going to be a piece of cake and cost next to nothing.

Phil

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

Post #131709 18th Jul 2012 12:28am
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T24RES



Member Since: 22 Nov 2010
Location: Henley-on-Thames
Posts: 936

United Kingdom 

Any idea of the bearing failure Phil?
Mine weeps from the casing join. Would it be a straight forward DIY removal and re-seal?

Post #131807 18th Jul 2012 2:24pm
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