RRPhil wrote:

If it were mine, I'd drain & refill every 20k miles (which will replace about half of the fluid) and replace the filter every 40k miles. I emphasize that this is just my personal opinion.

Phil

No - just for the GM 'box in the TD6. The ZF 5HP24 & 6HP26 transmissions don't have anything like the same problems.

Phil

What if any mileage would you recommend oil changes for the later box? eg-Mine 2008my TDV8

Thanks in advance

@ Johnte

I was wondering about whether your symptoms could be related to the common spring failure in the 2nd clutch accumulator (photos from a 5L40-E that I recently stripped):

Click image to enlarge

Click image to enlarge

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

@ T24RES

The first 6HP26s appeared in 2001 so there’s 10 years of evidence to confirm that it’s a pretty robust transmission. For that reason I’d normally be tempted to stick with the manufacturer’s recommendation i.e. 100k miles.

However, the high detergent levels in automatic transmission fluid mean that (in my view) you’d be taking a risk of dislodging wear particles from the clutch packs, etc. that had accumulated in all the nooks & crannies of the hydraulic system after such a period of time which could then have a catastrophic impact on the control system (pressure control solenoid valves, spool valves, etc.) if they were flushed through the mechatronic unit by the new fluid. For that reason I’d be tempted to drain & refill at 50k miles.

For the 5HP24 much depends on the condition of the cooling system. We all know about the issues with the bottom of the radiator becoming blocked with sediment and choking the cooling supply to the transmission fluid cooler. The resulting higher temperatures cause the fluid to oxidise much more quickly than ZF had planned for when they quoted ‘filled for life’ (i.e. 100k miles). It’s therefore essential to maintain the health of the cooling system and I’d also recommend changing the fluid at 50k miles. Certainly the fluid should be replaced if the transmission has ever operated in its ‘cooling strategy’ mode i.e. holding on to the lower gears with TRANS OVERHEAT displayed on the instrument panel – in which case the fluid temperature has reached 140 deg. C

A tribologist at Shell told me that at elevated temperatures a fluid’s life is halved for each 10 deg. C rise in its temperature. Pretty alarming

Phil

Thanks for all the info and guidance RRPhil.

I didn't know what one was either:

A tribologist:

"One who studies or is a specialist in the science of the mechanisms of friction, lubrication, and wear of interacting surfaces that are in relative motion."

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Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
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

@RRPhil
Thanks for all you info. I have no issues (touches big bit of wood) but enjoy reading all your gearbox info. You really ar the gearbox king! Would love to get my head round how an auto box works. Not sure if you have the time but if you could put together a basic discription with a few of you quality pics I'm sure it would go down well, as I for one would appreciate what goes on in the box of tricks under the gear leaver a lot more. [img]http://www.fuelly.com/driver/rob2529/range-rover[img/]
04, 4.4V8, Vogue Oslo Blue with LPG.
"You can sleep in your car, BUT you can't race your house!!!!"

If something can't be fixed with a hammer....... You have yourself an electrical fault!

I think if you do a quick search on the frenchcarforum or citroenxm forum, dont mean to step on any toes RRphil just thought i could save you a load of time

http://auto.howstuffworks.com/automatic-transmission.htm

Thanks RRPhil for the comprehensive reply, most informative