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.
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.
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.
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.
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
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
The drive gear in the motor is plastic :
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.
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.
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.
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 :
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 headscrews, tightened to 6Nm. The socket size is the same as for the high/low range position sensor screws.
The two halves of the casing separate easily with almost all of the components staying with the rear casing
The exception being the front output flange which can be removed from its bearing by compressing the snap ring
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
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
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
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
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
A circlip holds together the assembly
and the photo below shows the ball and ramp mechanism which translates the levers’ angular movement into an axial displacement to engage the clutch
The torque-biasing clutch has a total of ten friction plates
Hello Phil, I find my self rebuilding the T-case on my 06 RR Sport, your detailed breakdown comes in as a blessing, a little difficulty locating the new chain for my unit, but after your comparison to the NV225, it was easier to find.
Any thoughts or ideas on removing the transfer case from the vehicle, those last two upper bolts to remove the unit are virtually impossible to get to, I started to remove the unit about 2 hours ago and I already have it on a jack with just those 4 bolts left, any help would be greatly appreciated
The failed input bearing turns out to be a plain, single row, deep groove ball bearing of size 50 x 90 x 20.
Although I’d expected this 6210 C3 bearing to be manufactured by one of the ‘high end’ suppliers such as SKF, INA, NTN, etc. it’s actually manufactured by a company I’ve never heard of – ZKL of Slovakia.
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.
The failed input bearing turns out to be a plain, single row, deep groove ball bearing of size 50 x 90 x 20.
Although I’d expected this 6210 C3 bearing to be manufactured by one of the ‘high end’ suppliers such as SKF, INA, NTN, etc. it’s actually manufactured by a company I’ve never heard of – ZKL of Slovakia.
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.
Hi Phil,
I know I'm resurrecting this post from a decade ago, hoping you still read this forum. Great write up BTW. I have the same failed bearing, actually looks worse than yours. My question is which way does the bearing come out? Do I have to open the case to get to it, the snap ring is on the front side. I'd rather not open the transfer case/box if I don't have to. Also, how does it go back in? Do I need a press
The six E12 Torx bolts can be removed (with some difficulty - the threads being micro-encapsulated with Loctite) to release the end plate from the differential assembly :
The rear output flange bevel drive gear then lifts out :
to reveal what can only be described as a triumph of packaging by the Magna engineers where they’ve managed to integrate the 50:50 front/rear bevel gear differential and the reduction epicyclic for low range into the same unit :
The annulus gear for the reduction gearing, which is either earthed to the casing by the shifting sleeve for low range or connected to the carrier to lock the whole assembly together for high range (1:1), slides off :
The triple-planet reduction epicyclic tooth numbers are 43T sun, 21T planet, 83T annulus giving a reduction ratio for low range of (83+43)/43 = 2.93023256
There are synchronisers clipped to both the carrier and the earthing point, into which the two ends of the shifting sleeve slide to accomplish the smooth engagement of each range :
The annulus gear for the reduction gearing, which is either earthed to the casing by the shifting sleeve for low range or connected to the carrier to lock the whole assembly together for high range (1:1), slides off :
The triple-planet reduction epicyclic tooth numbers are 43T sun, 21T planet, 83T annulus giving a reduction ratio for low range of (83+43)/43 = 2.93023256
There are synchronisers clipped to both the carrier and the earthing point, into which the two ends of the shifting sleeve slide to accomplish the smooth engagement of each range :
thank you so much for the best part of Land Rover porn ever released.
I had been looking for spares for my DD295 for some time, which, for now, is still holding quite well.
I had located teh bearings (now sold in a kit by LR with the output shafts, as marketing only the seals were not enough)
I could source the chain from cobra auto transmissions.
But the other weak part, which at least fails a lot on other vehicles, is the multiplate clutch (in BMWs is a plague). These disks look almost the same as the ones in the X3 and X5, and costing around 5 to 15 USD depending on the source, it would be just a shame having to ditch a transfer box for the sake of some sad ferodo disks
Would be nice to take some measurings, but here is a lonk to the ATC500 transfer box from the X5, the friction plate (ferodo) disk looks really similar
As far as the bearings go, one of them is the same as the X3 ATC transfer bos, and I guess some internal parts might be compatible, a matter of trial and error and investigating, maybe
Anyway, thank you so much for sharing, helping so much with the details and cheers from Spain
Robert
I am trying to close my transfer, Can anyone confim me if two bellville springs aré installed like pictures ( one top and one downto make pressure) or two in same position,
Thanks for the great write up.
Could you please advise if the bearing is pressed outwards (circlip side) or inwards. I have just found that my bearing is damaged and neds replacing. I have seperated the case but not sure about removing the bearing.
Thanks
Garry
Heres a whole TC with shift motor and wiring on Ebay for 331 including shipping. Says its from a low mileage LR3, he's a Rover parts yard in Kentucky. Probably cheaper and quicker to just slap a new one in, rebuild your old one at your leisure for a spare, or for resale later.
Hello everyone, I’m indy repair shop in Brazil.
I changed a chain from a DD295 transfer case on an LR4, using lots of info from this post by the way, thanks a lot.
Now when reinstalled in vehicle, low range mode is blinking on cluster and I cant manage to reprogram it via Launch scanner.
Any thoughts on that please
Thanks again
Hello everyone, I’m indy repair shop in Brazil.
I changed a chain from a DD295 transfer case on an LR4, using lots of info from this post by the way, thanks a lot.
Now when reinstalled in vehicle, low range mode is blinking on cluster and I cant manage to reprogram it via Launch scanner.
Any thoughts on that please
Thanks again
thanks for your dd295 transfer case teardown. very useful to me.
cristiano
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