L322 Gearbox judder. Live data shows 11.2volts

Ok so still not got to the bottom of the strange judder I'm getting at 53-60mph. Don't feel it through the steering wheel but through the seat.
Wheels have been swapped and balanced to eliminate them.
It happens with minimal throttle only and not when accelerating at say half throttle. It's very noticeable when in moving traffic. .
Seems to be when the torque converter locks in 5th gear.
Had it on a snap on diagnostic today.
I'll post a photo of the data taken as it was juddering. 2 things struck the tech as odd although a he's not specifically a Land Rover technician.
Firstly the torque converter was constantly switching from locked to passive and back to locked. He thought this behaviour was strange. Also the gearbox voltage was showing only 11.2volts whereas the car was showing 13.9volts everywhere else.
Any thoughts would be appreciated thankyou

I assume we’re talking about a TD6?

Something slightly strange about the figures. The turbine speed is measured as 2016rpm and the output speed 2656rpm so that gives a 5th gear ratio of 0.76, which is about right. The axle ratio is 41/10 and assuming 255/60 R18 tyres with a rolling radius of 378mm the output speed is equivalent to a fraction over 57mph. So at 57mph in 5th gear with 23% throttle how can the turbine speed be higher than the engine speed? Surely it can’t be in overrun at 23% throttle and with the LUC 91% engaged?

Might be worth pointing out that, unlike the 5-speed ZF transmission used for the petrol models, the GM 5L40-E torque converter lock-up clutch friction plate does have a spring damper to help isolate driveline torsional vibration. You would expect this damper to be doing the most work immediately after the LUC had gone from its controlled-slip mode to fully locked i.e. with the engine speed at its lowest. Perhaps you have an issue with this damper?





Phil

You sound far more technically minded than I am Phil, thanks for the info, I have heard your the man when it comes to these gearboxes. Hope you don't mind me picking your intellect further?
Do you think the voltage is correct at 11.2volts? Seems very low to me and also the tech that looked at it. Also should the t/c not go to completely locked once it settles at a constant speed rather than jump back and forth between passive and locked?Can I ask where you think my next step in diagnosing the fault should be?
And yes sorry should of said its a TD6.
It's done 223000 miles, this is its third gearbox, second hand unit fitted 20,000 miles ago, t/c not replaced at this time.
I did an oil and filter change on the gearbox, oil was in good condition, no swarf in the sump or particles on the magnet.

I love the car but don't want to get into swapping parts unnecessarily in the hopes it solves the issue as I know it's not worth a huge amount with these miles on it, having said that it was a 1 owner car when I got it and was very well serviced

Did you solve this issue? I have the same issue, vibrations between around 50-70mph when in 5th, I don't get the problem if stay in Sport mode which didn't shift higher than 4th.

Mine had a new TC last year so can't believe this has failed already.

Wifheld99 said:

Did you solve this issue? I have the same issue, vibrations between around 50-70mph when in 5th, I don't get the problem if stay in Sport mode which didn't shift higher than 4th.

Mine had a new TC last year so can't believe this has failed already.

Click to expand...

The last post was in 2016, so we were never told ....

which is a shame for guys like you ....

Wifheld99 said:

Did you solve this issue? I have the same issue, vibrations between around 50-70mph when in 5th, I don't get the problem if stay in Sport mode which didn't shift higher than 4th.

Mine had a new TC last year so can't believe this has failed already.

Click to expand...

It's usually the valvebody that goes up the creek and causing a hydraulic pressure inefficiency that causes the clutches to slip..
A fix is the sonnax Valvebody..

This was resolved but I believe on a different thread.
It turned out to be a faulty injector and nothing to do with gearbox etc.
I was very lucky that another member contacted me and passed on his experience that was identical to mine.
Only injector issue I knew of was smoking for a very short time on initial start up in the cold.
Decided to go down the injector route as much cheaper to fix than gearbox.
Bought 6 injectors that were tested and local, the guy even tested my old injectors for me after I’d fitted the replacements and had solved my issue of juddering.
I injector faulty so sold the other 5.
Total fix was less than £100.
Was a huge relief.

Wow, we're they able to diagnose the faulty injector with a leak off test or only once they had them all out? Thanks for coming back by the way

Leak off test showed very slight difference but not enough to suggest an issue.
From memory the injector showed poor pattern under load but can’t remember exactly. Again it wasn’t a huge problem on the surface but left me with this misfire that made the car feel like it was juddering at 53-55moh