Thread: Discovery TD5 Automatic transmission lockup

Do they have issues in the UK with breaking the flex plate? There is a belief that this may be do due torque convertor heat, when pulling large caravans, typically Australian vans are much heavier then European designs. This because of the nature of where we take them. Fitting a cooler seems to reduce flex plate failure.

Originally Posted by Blknight.aus

its not slipping , its torque multiplying, thats why its called a torque converter and not a fluid coupling or fluid flywheel. providing your TC is in good order its nothing to worry about you're not loosing power (well other than the pumping losses and the heat buildup in the fluid) your changing it from low torque higher RPMS to higher torque at lower RPMS.

Lets just say that your TC is setup with a stall speed of 2000 Rpm if you're driving along and the gear your in mean the input side of the box needs to see 1000RPM to do that speed in theory the engine can be doing up to 3000RPM for every rev the input side does over the output side the more pronouced the effect is.

the reason that its unlocked earlier rather than later is simply to do with the smoothness of operation and the life of the clutch in the TC

That's right, and I'd argue you want a higher stall on a TD5, this allows the engine to come up, and stay on boost, it will make it launch quicker and reduce the feel of turbo lag, no different to fitting a highstall in a muscle car with a big cam, not uncommon to run a stall of 3000 + when running a big cam + single plain manifold on an old v8. The idea is the same when you hit the throttle the TC allows the engine to come into its torque band so it will launch hard, and remain in the torque band while driving. It makes a big differance, in acceleration.

It's good to see someone has resurrected my old post.
My TD5 Auto is still the same and it still annoys me. This setup would be fine with the petrol engine where peak torque is 3000 - 4000 RPM ????, but it doesn't make much sense with this engine where peak torque is at 1900 RPM.
I often pull it down to 3rd gear when in the hills and speed is rarely above 80 kph.
I also question the term "its not slipping , its torque multiplying". I think this is wrong with the TD5 when peak torque is at 1900, when the converter unlocks the power just falls off. With a petrol engine when the converter unlocks the engine speeds up to the RPM where peak torque is developed, then its "torque multiplying"
Changing the converter to a larger unit would be nice but is expensive if there is no other reason to pull the unit down. I was rather hoping a module may be release for the Nanocom allowing the unit to be reprogrammed to something more sensible.
The other option is to get the 3.0 litre Disco 4, we can all dream.

The high stall is great for a drag car but not good in a Landy. When I bought my 130 it would spool up to 3000rpm and take off like a missle. Nothing could beat me off from the lights. While fun it was a pain trying to be gentle. I now have it dialed down to around 2000 as they couldn't get it lower.

Originally Posted by shaunp

That's right, and I'd argue you want a higher stall on a TD5, this allows the engine to come up, and stay on boost, it will make it launch quicker and reduce the feel of turbo lag, no different to fitting a highstall in a muscle car with a big cam, not uncommon to run a stall of 3000 + when running a big cam + single plain manifold on an old v8. The idea is the same when you hit the throttle the TC allows the engine to come into its torque band so it will launch hard, and remain in the torque band while driving. It makes a big differance, in acceleration.

Except peak torque in the TD5 really is around 2000 rpm... So you want to hit it and stay there....

But yes, my "streeters" ran much higher stall, around 4000rpm+ but thats where those big cams made their power.

The TD5 when towing is running 2200-2700 rpm so on the verge of stall when unlocked all the time...

The new, larger torque converter I fitted runs 2200 and is just brilliant.

Hi Blknight, you are right it's not slipping, thats why I put it in quotation marks,

although you are very knowledgable on autos I have to disagree, a tuned TD5 is way too revvy with the stock converter, fit a higher stall speed converter if you want to drag race your disco but if not then as Tombie has found the bigger one drives much better

at the moment we modify the V8 converter to fit the stock TD5 flexplate and boss, when I have a minute I will draw up a modified boss and flexplate so you can fit the stock V8 converter, this will be a much cheaper alternative.

Dave

Have you checked the performance of the airflow meter??? This has a big bearing on shift point and performance of the Td5 trans/ engine package.

JC

Originally Posted by justinc

Have you checked the performance of the airflow meter??? This has a big bearing on shift point and performance of the Td5 trans/ engine package.

JC

Whats the best method of testing the performance of the airflow meter?