4200/GP/QP Transmission and Ancillaries

[lozcb]

Thanks for the update... which reinforces the need to service by the book!!!

Agreed Peter , but this is an age old problem , you get charged for it but unless your there physically present, there is a tendency for gearbox and diff oil are frequently left undone

 

[mjheathcote]

So an update lads.

I went down to Barbagallo who have the Gransport for sale and it is now ready to drive. The car has been maintained by them since it arrived in Australia, and it really shows maintenance over mileage! The car has 112 000km (though I think it is actually in miles) compared to my 126 000km, clutch is similar age with both ~50% remaining, they're both 2007 LEs running the same TCU software and they're both black.

I needed to convince the sales guy to let me drive it for 5 minutes as he wasn't too keen as I had already told him I wasn't planning on buying it, but he gave in after some gentle persuasion. So what did I learn?

1- The engine definitely surges during gear changes. This is super counter-intuitive, and is half the reason the clutches get eaten out so quickly for sure, but this is 100% confirmed behaviour now.
2- In auto mode the car was super smooth whereas mine was not.
3- Wringing it out the car behaved almost identically. I believe this is because the SV is proportional, and when the demand is greater the leakage is relatively smaller.
4- Taking off and moving around in parking lots is significantly better in their car.
5- My AC is next level.

So my car hadn't had the hydraulic fluid and gear oil changed in ~7 years. This one had been done regularly.

As luck would have it, my spare used ancillaries arrived today. Without access to a hoist, I was only able to change one solenoid rather than the whole power unit - coincidentally, the clutch solenoid. I don't usually say this about wrecker parts, but I genuinely believe this came off a very low mileage car!

View attachment 68054

Squeezing my hands through this tiny cap in the heat shielding I was able to change the clutch solenoid in situ. You can see my shiny new solenoid in place.

View attachment 68055

So what was the result?

1- Pump activation has dropped to once every 3m13s while the engine is running from once every 15s!
2- There no shudder on take off, I had previously put this down to a hot-spotted flywheel.
3- Because the shudder had stopped I was able to significantly soften the clutch massively improving the drivability of the car in the real world.
4- Gear changes are no longer accompanied by a lurch
5- Leakage rates have changed from 140cc/m to 30cc/m (and still dropping) and 6cc/m to 27cc/m (stable)

Gear changes are still loud and clunky, so once I get access to a hoist I will pull the whole power unit and swap the whole assembly. As I've learned more about what was going on, I don't think any one part has failed, but everything has been worn out and an accumulation of small errors has given the impression of a big issue.

When I bought the original plan was just to swap in a completed gearbox with ancillaries attached, but with a few logistical issues I decided to do it piece meal to try and learn what was going on even though I had already purchased all the parts.

I now believe that the original gearbox had a sloppy diff from excessive wear. This was the binding at low speeds that was making the car somewhat unpredictable to turn. This was caused by 70 000km of no oil change which resulted in fine metal debris throughout the oil, further increasing the wear. When we changed this we bled the system which improved the ability for the system to change gear when revving out, but the excessive leakage was preventing the system for engaging the clutch smoothly at lower speeds making auto mode completely useless. Changing the clutch solenoid seems to have allowed the system to control the clutch timing greatly improving how smoothly the power goes into the gearbox.

If anyone has a theory or explanation for why the leakage rate increased for the clutch SV not actuated, I'm all ears. but my current guess is it is probably just a measurement error covered by the severe leakage of the clutch SV. This would seem to indicate to me that the clunking of the actuator is probably related to the gear selection solenoids as they are also proportional flow type, and I see the same behaviour in that the harder I drive the less of an issue it becomes. I'm optimistic that changing the whole unit will finally resolve the transmission behaviour.

I can say now with absolute certainty - if you are one of the people who also has a transmission that is perfect when you drive it like a manual (lift off with gear changes) that is an indication that the transmission is in poor health. If you're shopping for a car, take note of the behaviour I describe in this post! The transmission is absolutely meant to engage smoothly when in auto and driven easy. You should not need to lift off the throttle to drive the car normally.

I've always said this, Maserati state you shouldn't lift, but there are many who do and think this is normal for a smooth shift, it's not!

 

[lambertius]

I've always said this, Maserati state you shouldn't lift, but there are many who do and think this is normal for a smooth shift, it's not!

When I went down to the dealership and they described my car as 'better than average' and I wasn't convinced still. The car is uncommon, and it has a reputation for being a harsh shift so most people just go 'oh well, yeah, it is harsh I guess'. I mean look how far I've had to dig to just get some technical information to confirm one way or another. How many people would do that?

 

[lambertius]

Has anyone tried to rebuild the solenoids before? I had to get a special tool made, but the solenoid is extremely simple internally.

Only the exterior has o-rings


The pintle (left) has channels cut into it and is hollow. The channels would be to allow for lubrication at contact surface.



There is an extremely fine wear pattern on the centre ring. I suspect this is what causes the leakage.



It took me a while to realise it but it is caused by the hole above the centre ring.



I suspect the leakage is caused by the internal metal-on-metal wear and not an o-ring failure. I'm thinking of getting another pintle made to swap it in and to recyle the solenoid for a like $15-$50 instead of the ~$450 odd that it costs per solenoid. The tolerances are extremely fine, I'll need to get it measured in a special lab if I try it out.

As for my car, the transmission has had my spare actuators and power unit swapped on. I haven't had a chance to read the leakage rates and won't for another three weeks, but it is what it is. All things considered, I'm expecting an improvement.

 

[Zep]

Yes, there are a few threads on it.

 

[lambertius]

I can't find any here, or the other forum or through google, do you know if anyone was successful?

 

[Zep]

Search for actuator rebuild. There are a lot of posts.

 

[lambertius]

I can find a fair bit on the actuator - though no one ever posts up the results... Nothing on the solenoids or power unit though!