[DRIVING] VW Touran powered by Nissan Leaf [FINISHED]

[arber333]

I was thinking on some failure modes for transmission diff section....

Contaminated gearbox oil (or lack of oil).
Grinding due to insufficient lubrication.
Vibration from increased friction and heat.
Drain and inspect oil for metal shavings or burnt smell.

Worn differential bearings
Grinding noise because of bearing wear.
Vibration especially noticeable at low RPM when load is minimal!
You need to look for metallic parts in gearbox oil and inspect bearings for play.

Damaged pinion or side gears, i would think probability of this would be lower...
Grindingnoise here means worn gear teeth.
Vibration because of uneven torque transfer between wheels.
Look at gear teeth for pitting or breakage.

Damage to output shafts, this is why i asked if you can actually apply torque on the way up hill.
If splines are worn on CV joints... Inspect stub shafts for damage.
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All in all you need to drain the sump and inspect the oil for metal shavings. Maybe use a small magnet and move into the drain opening to see if you can pickup additional shavings.

Than take off the stub shafts and inspect them for wear.

After that you should find a specialist with propper tools if you want to dissassemble transmission further...

[johu]

Today we got cracking on the gearbox swap. I got an overhauled one for roughly 900€ delivered. It is in and very shiny

When turning manually even without oil it sounds much smoother than the crusty one

As arber suggested a lot of metal was in the oil. Did we use the wrong oil? Did we not fill up all the way? Or is the gear box just old? Who knows. This time I know I need to get 2.5l in there and the oil came with the gear box.

While at it I also inspected the shaft coupler and splines and everything looks great and has no play.

Should be back on the road tomorrow, perhaps with a quieter and more efficient car.

[arber333]

....
As arber suggested a lot of metal was in the oil. Did we use the wrong oil? Did we not fill up all the way? Or is the gear box just old? Who knows. This time I know I need to get 2.5l in there and the oil came with the gear box.

While at it I also inspected the shaft coupler and splines and everything looks great and has no play.
....

Hm... do you shift using clutch or simple upshift or downshift on unloaded motor?
Could be that your old TX was already bad when you got it...

With the new one i recommend you drain and replace the oil. Which year Touran do you drive? Up to 2010?
As far as i see your Touran should use 2.5l synthetic 75W-90 gear oil that meets VW specification G 052 171 A2 or G 052 726 A2.

Release oil from the bottom plug, refill oil through the side plug. This will show you are full when oil overflows.

[jrbe]

Synchros are very likely bronze, / brass, so a bronze / gold color. Some glitter is normal on a high mileage transmission.
Bearing bits are chrome / shiny / dark. Gears are too.

What rpm are you spinning the motor to normally? It's still my guess that the input rpms were run too high and one or both of the input shaft bearings failed from high rpm then got into other sensitive areas and cascaded.
Is there slop in the input shaft?

Gear oil and engine oil end up almost the same viscosity when you look at them on a chart. VAG gearboxes usually need friction modifiers for the synchros to work well, but otherwise as long as there's oil in them up to the fill point they're usually fine.

Do you have any close ups of the metal bits? May be able to identify some pieces.

[johu]

Hm... do you shift using clutch or simple upshift or downshift on unloaded motor?

No clutch, see above. But I hardly ever shift but keep it in 3rd

Touran should use 2.5l synthetic 75W-90 gear

Nailed it that was included with the tranny

What rpm are you spinning the motor to normally?

Most of the time it sits around 4000 rpm, max speed is 7500 rpm but I rarely ever go there

Is there slop in the input shaft?

No, it's solid. Also if I change to neutral, hold on to the input shaft and spin the output the noises are still there.

There weren't solid pieces in the oil (or they haven't come out), more of a glitter, bronze and chrome.

Too bad I can't take the transmission apart because it is sent back in exchange for the new one. I could ask them to send me pictures or a report or something, maybe they've got the time...

[Bratitude]

surprised you didnt op to put the leaf gearbox in, but i guess this is now just mechanic work, rather than a "project"

[arber333]

surprised you didnt op to put the leaf gearbox in, but i guess this is now just mechanic work, rather than a "project"

On Mazda i replaced tramsmission with Mitsu gearbox and put it to fabricated mounts. In the end i needed to reweld the 3rd mount as the mounting plate was cracked because of motor torque. I had to reweld and strengthen some corners and now hopefully i will have peace .

It goes to show that OEM mounting points are not neccessariliy optimal for electric drivetrain...
I think J correctly decided on lesser evil by just swapping a part vs drivetrain redesign. However time will tell if TX was faulty or the E motor can cause wear and tear on 3rd gear which is used a lot in ICE as well.

[johu]

yes that is the primary reason why I didn't, the second one is that I don't want to dive too deep into field weakening and the 3rd is I want to be able to reach high top speed

[Proton]

Most of the time it sits around 4000 rpm, max speed is 7500 rpm but I rarely ever go there

In know that is not recommended to keep the transmission at high RPM because it gets hot. Now I do not know if 4000RPM is good or bad for your transmission. Are you monitoring the temperature of the transmission?

[johu]

The original petrol motor went to 6500 but of course that's not an operating point you'd use. I think at highway speeds (130 kph) the input shaft spins at roughly 4000 rpm in 6th gear. I usually drive 120 kph max in 4th which is like 5000 rpm.
I don't measure transmission temperature but could stick a probe in there after the next longer highway drive.

[jrbe]

I'd expect 5krpm would be ok.

How much regen do you run?

[johu]

How much regen do you run?

That's the thing, quite a lot. Not so much off-throttle but brake blending regen up to 40% of acceleration torque.

[jrbe]

That's the thing, quite a lot. Not so much off-throttle but brake blending regen up to 40% of acceleration torque.

This is my second best guess as to what may have caused this. Any idea how much 40% regen deceleration is vs the ice engine braking? Seems like it would be maybe 2x or more.

Is 25-30% regen or a value to get it similar to the ice engine braking workable for you? A stronger transmission swap may be a fairly drop in solution if this isn't ideal if it happens again. VWs are like Legos.
What transmission group is in your car?

Sometimes different gears can have different weaknesses.
Did the shifter feel wonky at all or jump when you got on / off throttle? What about in 3rd instead of 4th? If not it's sounding like it's the diff bearing that went.

There are also rivets in ring gears in a lot of vag transmissions that can weaken and shatter from a lot of heavy forward and reverse torque cycles on the ring gear. There are ring gear bolt kits but it means splitting the transmission to install.

[arber333]

That's the thing, quite a lot. Not so much off-throttle but brake blending regen up to 40% of acceleration torque.

Hm... this is why i prefer to have only off throttle regen. Maybe 10kW at 50km/h and 40kW at 120km/h. Brake system i prefer to keep mechanical since there is still ABS and other safety sistems to consider... Beter to not lock your wheels on the crossroads...
I also have a button that i can press and all regen torque is removed, just in case for winter...