Disco 3/4 Automatic Transmission FAQ - 6 Speed
Since my D3 has been getting the shudders I thought I'd post some of my research on a new thread rather than generating heaps of posts on the FAQ. Happy to be corrected on any points that other people know of, maybe we'll all learn something. So to kick it off....
Transmission is a ZF 6HP26 unit. Is currently fitted to BMWs, Ford Falcons and Territories, Audis and Jaguars to name a few
The transmission has been around in one form or another since 2001 when it was introduced on a 7 series
ZF have designated the transmission as "sealed for life" but a more accurate description of this strategy would be "sealed until the warranty period is over"
The Land Rover variant uses a plastic sump which has an inbuilt filter which is a throwaway with the sump at service time. The filter also means that the engine has to be lifted from one mount to fit the new sump. ZF make a steel sump part number 1068 103 820 01 Kit Sump. an alloy sump may also be available ex Ford. These variants do not have the filter inbuilt and can be fitted / removed without lifting the engine.
Fluid for these transmissions is ZF LifguardFluid6 part number S671 090 253 for a 20 litre drum. Dealers charge $78 a litre, other repairers less but it's still expensive.
Other alternatives may be Motospecs Part # 749626, Ford RI-28, Shell ATF M 1375.4, Mercon SP XT-6-QSP Ford have a RRP of $48 a litre for their oil.
The design of the 6hp26 is different in that it does not have bands but rather clutch packs and the transmission is completely electronically controlled. The torque converter clutch is modulated in that it can be engaging and releasing at a rapid rate to allow a transition between fully locked up and disengaged. The torque converter clutch can lock up in all gears
Due to these transmissions having no service schedule they develop a "shudder" that is similar to driving over a ripple strip embedded in the white line at the edge of a road. This is caused by the degredation of the oil and causes wear to the torque converter clutch and potentially damages the rest of the transmission through contamination and overheating.
It would seem that 50,000KM would be a good time to change the transmission fluid to delay the fault above happening.
Sport mode reduces the shudder substantially, possibly because the transmission is more likely to kick down a gear in response to increased load rather than modulating the torque converter to allow some slip.
There are reports from the UK of coolant contamination from the transmission cooler in the radiator becoming porous. It may be worthwhile to consider testing old fluid for glycol as a transmission flush will not help for long.
It's NOT a "Land Rover Problem".... Googling the transmission model number brings up lots of tales of woe from owners of these transmissions that have failed due to lack of oil changes.
When off road in steep country it is preferable to lock the vehicle in a suitable gear to reduce heat load on the transmission rather than leaving it in drive.
A new transmission will cost you in the vicinity of $7000 so regular oil changes make sense.
Thats all I can think of for now, any other thoughts welcome.
RMP, maybe when we have a complete list we could revise and put in the FAQ?
Regards,
Tote
Last edited by Bytemrk; 29th December 2016 at 07:37 AM.
Reason: Title change after splitting out 8 speed
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