Brief Encounter II - The Sequel

[ACTIVE8]

The flex plate can also have as shown here, depending on the design a flywheel ring gear on it, as shown in the picture below, which is on a 5.3 litre Chevy V8. 8)


Below is a picture with the torque converter in place.

[CitroJim]

That's a good and intersting link ACTIVA, thanks for posting that up.

The V6 has three bolts and mine were very tight indeed and not easy to get good purchase on, having thin heads.

On the V6, they're dead simple to check, even with the exhaust headers in place. You can just slip the "half moon" cover off the bottom of the bellhousing (3 x 10mm bolts) and then as you rotate the engine over, they will come into view. You can also see the flex-plate reasonably and check most of it for any potential cracks. You cannot check the torque of the bolts with he headers in place as there is only just room to get a thin 13mm spanner in. However, with a normal 13mm spanner, they should be as tight as you can possibly get them.

Other sources of noise in this are can be the torque convertor lock-up clutch and the torque convertor stator sprag clutch although if either of these were in trouble, there would be other symptoms. Trouble is, at the moment, never actually having driven a V6, I don't know how it feels if the lock-up fails or what happens if the sprag fails. If there are stator problems though, the torque convertor will operate very inefficiently and fuel consumption, for one thing, will go through the roof.

Noises generally in a 4HP20 can come from two sources. A whine related to engine speed only will most likely be the oil pump suffering starvation and any noises related to road speed is likely to be down to something in the diff, reduction gear or epicyclic output gear. The 'box only has three gears in it and all of them are massive and most unlikely to wear. Each gear is supported on equally massive taper roller bearings.

As the noise is most apparant for you going between P, N and R, Black Clio, I agree it is most likely torque convertor related.

I assume the car drives perfectly otherwise and there are no other symptoms apparant from the gearbox.

Sadly, to get at the torque convertor it is necessary to lift the engine and transmission complete out of the car. The gearbox cannot be removed on its own. Luckily in a 406 it is a slightly easier job than in the Xantia.

Please do keep us informed of the outcome.

[addo]

Something else I'm curious about, Jim.

Would a failing converter (ie; one where the clutch was breaking up) show a significant imbalance? I have no idea of what sort of masses are involved in the loose materials.

Regards, Adam.

[CitroJim]

This is the V6 flex-plate...

Not a very substantial thing at all...

[CitroJim]

Would a failing converter (ie; one where the clutch was breaking up) show a significant imbalance? I have no idea of what sort of masses are involved in the loose materials.

Good question Adam,

If the lockup clutch was shedding its friction material then I'd think not as the mass of the stuff is tiny compared to the weight of the convertor and the weight of oil in it.

If the sprag or stator were into trouble than yes, maybe, depening on the failure mode. If the sprag were to partially collapse say, the stator vanes could well come into contact with the pump or turbine vanes and noise with accompanied vibration are more than likely. In extreme cases, you'd also potentially have rollers from the sprag rattling around inside and that would quickly result in carnage I would have thought.

These aspects of torque convertor health are difficult to check as a drained torque convertor rattles anyway as the sprag has lost its rigid support (a splined extension from the oil pump cover) and this allows the stator to flop around somewhat. It is also impossible to see very much inside the convertor by peerring down the drive hole. Certainly no parts of the lock-up clutch can be seen. maybe with an endoscope something could be seen.

[Deanxm]

That plate is called the flex plate, and problems can happen with them here's some information on them.

Very interesting info there, i have never heard of one breaking up so badly though although with the one in the picture having 6 TC mounting points i should imagine it was from quite a substantial power plant

These aspects of torque convertor health are difficult to check as a drained torque convertor rattles anyway as the sprag has lost its rigid support (a splined extension from the oil pump cover) and this allows the stator to flop around somewhat. It is also impossible to see very much inside the convertor by peerring down the drive hole. Certainly no parts of the lock-up clutch can be seen. maybe with an endoscope something could be seen.
_________________
Jim

I would really like to cut a TC open just to see it in the flesh so to speak but i dont have one at the moment that i would be willing to kill.

D

[bl4ck clio]

The flex plate can also have as shown here, depending on the design a flywheel ring gear on it, as shown in the picture below, which is on a 5.3 litre Chevy V8. 8)

a good posting here
thank you very much!

[bl4ck clio]

That's a good and intersting link ACTIVA, thanks for posting that up.

The V6 has three bolts and mine were very tight indeed and not easy to get good purchase on, having thin heads.

On the V6, they're dead simple to check, even with the exhaust headers in place. You can just slip the "half moon" cover off the bottom of the bellhousing (3 x 10mm bolts) and then as you rotate the engine over, they will come into view. You can also see the flex-plate reasonably and check most of it for any potential cracks. You cannot check the torque of the bolts with he headers in place as there is only just room to get a thin 13mm spanner in. However, with a normal 13mm spanner, they should be as tight as you can possibly get them.

Other sources of noise in this are can be the torque convertor lock-up clutch and the torque convertor stator sprag clutch although if either of these were in trouble, there would be other symptoms. Trouble is, at the moment, never actually having driven a V6, I don't know how it feels if the lock-up fails or what happens if the sprag fails. If there are stator problems though, the torque convertor will operate very inefficiently and fuel consumption, for one thing, will go through the roof.

Noises generally in a 4HP20 can come from two sources. A whine related to engine speed only will most likely be the oil pump suffering starvation and any noises related to road speed is likely to be down to something in the diff, reduction gear or epicyclic output gear. The 'box only has three gears in it and all of them are massive and most unlikely to wear. Each gear is supported on equally massive taper roller bearings.

As the noise is most apparant for you going between P, N and R, Black Clio, I agree it is most likely torque convertor related.
I assume the car drives perfectly otherwise and there are no other symptoms apparant from the gearbox.

Sadly, to get at the torque convertor it is necessary to lift the engine and transmission complete out of the car. The gearbox cannot be removed on its own. Luckily in a 406 it is a slightly easier job than in the Xantia.

Please do keep us informed of the outcome.

Nice posting too Jim!

I mean the noise become lower if going from P to R (from release to in), in cold condition.

but if failure from TC, that's realy a bad news.
In my country, the price is about 1200 pounds, it means 1/3 of my car. just only for the TC!

one thing is important, it's only have a noise when cold!
is TC failure has this sign??

[CitroJim]

I mean the noise become lower if going from P to R (from release to in), in cold condition.

That has me thinking now

I'm beginning to think it may not be the TC and it could be something else. It is signigficant the noise changes when going from P to R. In P only Clutch B is engaged and the epicyclic gearseat is freewheeling and there is no load on the TC or gearset. As soon as R is engaged, the freewheeling stops and the gearset stops revolving until the brakes are released; the TC and gearset are effectively working against a load and anything that might rattle under freewheel conditions will now find it harder to do so.

Can you describe the noise better? Does it sound like a rattle or more like a whining (humming) sound? We'll be better able to think about the possible causes then.

I've spent some more time today and have began cleaning ready for reassembly. Brake D (reverse) caused me a small problem in that to dismantle the brake it was necessary to compress its diaphragm spring to release a wire clip that holds the whole assembly together. The offficial tool is a metal mandrel that fits over the spring "ears" to allow them to compress when the assembly is squashed down in a press.

I fabricated a substitute by cutting a round hole in a piece of MDF. The following photos shows the improvised tool in action:

This is the D Brake assembly on the bed of the hydraulic press. The spring "ears" are visible around the periphery of the spring.



This is the special tool in place:



And this is the assembly under pressure and the retaining clip being popped out.



Worked a treat!

This is the D Brake all in bits. It is in fine condition but quate an elaborate device just to allow the car to go backwards



Another task was to remove the D Brake operating piston from the very bottom of the gearbox casting. There is only one way to do this as it effectively sits in a blind cavity and there is no purchase on it whatsoever.

The method is to use compressed air on the hole where pressurised oil normally flows to engage it.

Like this...



The piston itself is the amber coloured ring. A quick puff of air at around 80psi pops it out a perfect treat

Then it was down to inspecting and cleaning before reassembling the D Brake assembly ready for refitting. What was scary was how much muck had collected under the D Brake piston. It had accumulated in the crevices like silt. In fact, I have noticed that both this 'box and my other, much lower mileage spares 'box both have all their internal surfaces covered in this fine silt-like deposit. I cleaned up an oil baffle that looked dark matt grey and after a wipe it was bright silver.

In light of this, it is no wonder the filter clogs after a time and it shows how valuable regular partial oil changes can be at extending the working life of the 'box.

[xantia_v6]

On the flex-plate aside... My dad once had a cracked flex plate on a Toyota Corolla, and it sounded like an irregular bottom end knock, bit only at certain RPM when it hit resonance. The crack ran most of the way around the centre boss, and was only visible from the back of the boss.
The crack was caused by a Nissan 350Z driving into the side of the Corolla at some speed (Police estimate the 350Z was doing 90MPH in a 30 MPH zone before the accident). The Corolla was pushed sideways 60 yards. The insurance companies bizarrely decided to write off the 3 month old 350Z, but repair the 5 year old Corolla. The repairs to the Corolla ended up costing many times its value, due partly to the many mechanical items damaged (including bent drive shaft, bent differential output shaft, cracked bellhousing, cracked flexi plate) that were only apparent after the bodyshell was straightened and the car back on the road.

[bl4ck clio]

report :
my car is on workshop from today.
the suspect is flex plate TC temporarily.

[CitroJim]

report :
my car is on workshop from today.
the suspect is flex plate TC temporarily.

Keep us updated please

Been a good day today insofar as I've actually got a bit done on the gearbox.

I wanted to fully strip the clutch/brake operating piston assemblies and that meant compressing their diaphragm springs to release the spring retainers.

For that special tools are necessary and I had to make my own substitutes.

This is my version in use for Brake F:



It's a ring of MDF with radial screws that touch the ends of the spring "ears" and with the bar press down on the spring "ears" to release the retainers.

Here's one of the retainers being teased out:



This is another view of the tool:



And this is the piston being gently released from its housing with compressed air:



And here it is removed:



It was all beautifully clean in under there (unlike Brake D) but worth it to be sure.

Next I moved on to Clutches B and E and again some improvisation was necessary to compress their diaphragm springs to pop their retainers.

This is for Brake B



I used a tool here (again made from MDF) that I originally made for pressing a bearing off a BE3 gearbox input shaft.

This is the spring:



Followed by the piston:



On to Clutch E. Some real ingenuity was needed here involving copper water pipes!!!



Once again the tool I made for the BE3 'box has been called into service!

Out comes the piston..



Followed by the B piston coaxially under it..



And finally, all in bits..



The B clutch drum is definitely beyond repair. I dismanted this part especially to see if I could find any underlying reason for the failure cof Clutch B but none (above that already found) were evident except that it had been running jolly hot..

A good afternoon's work

[Deanxm]

very interesting as always but um, does swmbo know your taking that gearbox apart on her rug

D

[jgra1]

Jim, you've had a good day there, I am glad I didn't ring you 16 times to pester you about firewashers and incorrect injection pump timing

great stuff

[CitroJim]

Jim, you've had a good day there, I am glad I didn't ring you 16 times to pester you about firewashers and incorrect injection pump timing

No worries at all John Thoroughly enjoyed our chats throughout the afternoon!

One time you did call half way through the drilling of all those holes for the screws in the Brake F tool but apart from that your timing each time was spot-on

does swmbo know your taking that gearbox apart on her rug

It's not so much that she's worried about Dean, it's the colour clash between the rug and the hydraulic press that really bothers her...