Thread: Disco 3/4 Automatic Transmission FAQ - 6 Speed

Dropped 5L out of mine today for its annual drain and refill to keep the box healthy. Used my alternative fluid choice of Motul ATF VI that I’ve been running now for three seasons. Did on a WA early morning - my only chance at getting the gearbox temp low enough to set the correct fluid level. Reset adaptations. The box is back to silky smooth again. Of recent I’d been finding the box was clunking when down-changing into first. Now it’s like new again. I think when I last did it I didn’t get the temp spot on and maybe the level wasn’t just right. Not sure, but this time it’s like new again. 243,000km rocking on.

Originally Posted by DiscoJeffster

Did on a WA early morning - my only chance at getting the gearbox temp low enough to set the correct fluid level.

The temp thing has me a bit confused. In the topix handbook on a basic replacement, fluid level check the temps are different.

At the start of the instructions it has a caution:
"CAUTION: The gearbox fluid level must only be checked when the temperature of the fluid is between 30 degrees and 50 degrees. The fluid level obtained will be incorrect if the reading is outside this temperature range."

Then in the instructions for getting ready for the fluid check it has this caution:
"CAUTION: Make sure the transmission fluid temperature is below 30 degrees before starting the fluid level check."

Then in the following fluid replacement section (when you move it through the gears) it has this caution:
"CAUTION: The gearbox fluid level must only be checked when the temperature of the fluid is between 30 degrees and 50 degrees. The fluid level obtained will be incorrect if the reading is outside this temperature range."

So this is all a bit confusing.

My take is that before you start the gearbox and oil must be below 30 degrees (I assume as you go through the process with engine running etc the fluid can get over 50 degrees). But when you do the actual fluid level check after changing the oil - it has to be above 30 and below 50.

Is my take on this correct and it is only before you start that the oil has to be below 30?

Cheers

Garry

Originally Posted by garrycol

The temp thing has me a bit confused. In the topix handbook on a basic replacement, fluid level check the temps are different.

At the start of the instructions it has a caution:
"CAUTION: The gearbox fluid level must only be checked when the temperature of the fluid is between 30 degrees and 50 degrees. The fluid level obtained will be incorrect if the reading is outside this temperature range."

Then in the instructions for getting ready for the fluid check it has this caution:
"CAUTION: Make sure the transmission fluid temperature is below 30 degrees before starting the fluid level check."

Then in the following fluid replacement section (when you move it through the gears) it has this caution:
"CAUTION: The gearbox fluid level must only be checked when the temperature of the fluid is between 30 degrees and 50 degrees. The fluid level obtained will be incorrect if the reading is outside this temperature range."

So this is all a bit confusing.

My take is that before you start the gearbox and oil must be below 30 degrees (I assume as you go through the process with engine running etc the fluid can get over 50 degrees). But when you do the actual fluid level check after changing the oil - it has to be above 30 and below 50.

Is my take on this correct and it is only before you start that the oil has to be below 30?

Cheers

Garry

Spot on. When you’re filling it you need to have the engine running which in itself bumps up the temp. If you start too high you’ll have little chance to get it within temp.
I actually remember it (I think in the ZF instructions) as being 34 degrees as the perfect temp to set the level. LR I think just say 30-50 in their instructions I guess to help the workshops get through the work rather than aiming for perfect.

So it is a must to have a IIDTOOL or similar, in order to do the fluid change?
To set the level and also reset the ECU?

Originally Posted by specwarop

So it is a must to have a IIDTOOL or similar, in order to do the fluid change?
To set the level and also reset the ECU?

You’ll need a tool that can read gearbox temp and reset the adaptations. You could ignore the adaptations reset and presume the box temp is within 30-50 degrees and do it without, but you’d be flying a bit blind and might not get the best result.

I am a poor Discovery owner, is there anything cheaper thatll do both, other than the IIDTOOL

Originally Posted by specwarop

I am a poor Discovery owner, is there anything cheaper thatll do both, other than the IIDTOOL

Join the club!!!! I believe the Nanacom can however it’s not much cheaper, if at all. I looked at it such that the IID was the cost of one service at a dealer. I’ve saved so much by having it and being able to DIY it’s paid for itself in no time.

I am very DIY, would prefer to do all the work myself where possible.
Fluid change aside, How many errors/things has it flagged for you?