General Transmission Support Bracket Failure?

[umanemo]

I began this conversation on an older thread but there have been some discoveries to date. What I have written below is the last update. I have identified the R/L side upper brackets issue. (motor-mounts) But there is a third mount at the rear bottom of the transmission that I had thought I had addressed but now I have found out that there are two rubber bearings to the rear mount. (#4 in the ePer diagram attached)

Does anyone have experience with this end of the lower rear mount failing? Does it cause the issues that I have been chasing?

Any heads up is appreciated! Thanks!


[Last Post from Previous thread]

Back to the beginning again.

Some kilometers back I posted the dilemma of having this persistent vibration and thought it could be the gearbox. I found a stellar gearbox rebuilder in NL that invited me to let him have a look at my issues. He is a large worldwide distributor of gearboxes and had thousands of rebuilt gearboxes on the shelves and ongoing refurbishing in the shop by what looked like very skilled technicians. Schoones Transmissies BV.

The owner gave my Motorhome a run around the industrial estate and then out onto the motorway and really put it through a thorough test. His judgment was that these transmissions with the stamp 20KM57 are the most heavy-duty and reliable FIAT has ever produced. He also said there were no tranny issues - even after 335,000km! and that I shouldn't expect any for the life of the vehicle. He also refused to take any money from me, there was nothing wrong with my trans.

So back to square one with the vibration issue. Having just replaced just about everything from the CV shafts to the clutch, all 3 engine mounts I am still stumped. Given that everything under there appears tight, I have just kept my acceleration very conservative and keep the torque just below when the vibration begins to appear. Take off at first gear, and second gear if I step into it. Third gear can show the vibration but only if climbing a hill.

This all vaguely seems to have started with the replacement of the left side motor mount (bearing) so I am going to replace it again. But I do wonder if the LH and RH mounts are exactly the same part? The FIAT part number is 1307907080, but the extensions are RH 1827.19 and LH 1827.17 those numbers differ. IF THEY ARE DIFFERENT COULD THE PROBLEM BE THAT I HAVE A RH WHERE THERE SHOULD BE A LH? Inquiring minds want to know before I order another part.

If anyone has any suggestion of the origin of these symptoms or the answer to if these are truly different parts in configuration or manufacture please let me know.

As always thanks for your invaluable advice and input!

4/3/2000 FIAT Ducato 18Q - 2.8 i.d.TD
8140.43 (Direct Injection)
122 PS (90kW;120 hp) @ 3,600 rpm
5 Speed

VIN: ZFA23000005887229
Engine: 3050633
Chassis: 05887229
MVS (SINCOM): 232.330.1.0

 

[portland_bill]

For the mounts, the long number is the part number. The extensions you refer to are I think codes for change points, where there was a change of specification of that part. It could be rubber elasticity, or a change to its shape to give more or less movement. Often such changes can be fitted to earlier vehicles, but the change may come at different points, hence the different numbers.

Aftermarket mounts may not be the same spec of rubber, and may just copy the original, and whilst they may then cross-refer to later part numbers, their spec may be early. Sometimes aftermarket do keep up, and may be latest specification, mimicking the OE. A lot of aftermarket parts will come from the OE manufacturer, so would be latest spec anyway. Difficult to know, unless supplier source is known, which is often well protected. Bigger brands, at of course, higher prices, tend towards better sources.

When replacing any engine mount, pay attention to any tightening sequence, if set out in any manual, as some require to be tightened up in a set order. Also ensure that the motor is in its correct place, supported there, while the mount is fitted. Using the mount to pull the engine into place can stress it, leading to short life, and if the rubber is always stressed, can allow vibrations.

The lower mount is there to restrice the rotation of the motor, resisting the forces when the engine is pulling. On the smaller cars, these are usually a bar with a rubber moount at each end, often described as a 'dogbone'. Yours seems to be a bracket with two separate mounts, but pay particular attention to these, as when they get soft, the motor moves more than it should, and can destroy exhaust systems.

A compression check of the engine might be a good idea too. If there's a misfire, or one cylinder is doing less work than the others, this can create a vibration, which new mounts won't fix. Also ensure the vibration is motor related. There are driveshafts, and suspension mounts which can also allow such issues.

 

[umanemo]

Thanks, Bill,

It is yet to be investigated that the forward bushing of the lower rear mount is indeed the source of the vibration. I will have a look this week. As I have replaced the rear bushing of that motor mount combo this is my last resort.

If it passes, then I still have a long road to vibration freedom. I will use your suggestions if that is the case.

 

[umanemo]

Okay, it's okay. At least from what I can feel when using a tyre iron to push/pull the transmission from a nearby frame member. I don't know how much torque it would take to show an issue but I put some force on it and it seemed solid and no play. The isolator bushing assembly at this end seems hefty and well able to withstand a lifetime.

Back to square one.

So while under there I wiggled violently the exhaust piping assembly. I didn't really have the goods to emulate engine vibration but at least I did not hear anything suspiciously hitting the frame, etc. But I did notice that at the forward end at the springy connection to the Turbo downpipe the pipe flange did have a pretty good bit of movement. How much play is normal? Should I be able to see the play? or should it appear like a solid connection even though it is buffered by the springs?

Does this springy exhaust flange connection fail often? Enough to need replacement periodically? Could this bit of play be causing my vibration issues all the way down the exhaust system and that harmonic is exaggerated by engine vibration when accelerating?

I am really grabbing at straws now. Soooooo FRUSTRATED with this issue!!!

 

[umanemo]

Okay, this end of the mount bracket seems okay. At least from what I can feel when using a tyre iron to push/pull the transmission from a nearby frame member. I don't know how much torque it would take to show an issue but I put some force on it and it seemed solid and no play. The isolator bushing assembly at this end seems hefty and well able to withstand a lifetime.

Back to square one.

So while under there I wiggled violently the exhaust piping assembly. I didn't really have the goods to emulate engine vibration but at least I did not hear anything suspiciously hitting the frame, etc. But I did notice that at the forward end at the springy connection to the Turbo downpipe the pipe flange did have a pretty good bit of movement. How much play is normal? Should I be able to see the play? or should it appear like a solid connection even though it is buffered by the springs?

Does this springy exhaust flange connection fail often? Enough to need replacement periodically? Could this bit of play be causing my vibration issues all the way down the exhaust system and that harmonic is exaggerated by engine vibration when accelerating?

I am really grabbing at straws now. Soooooo FRUSTRATED with this issue!!!

 

[Anthony489]

Hi umanemo

I'm not that familiar with the exhaust setup for a year 2000 van, but the exhaust flange you describe is very commonplace for transverse engines. The manifold and downpipe both have flared ends, between which sits a chunky metal sealing ring. A further flange holds the assembly together, using two bolts with stiff coil springs (which should be tight but not coil bound). The idea is to allow enough angular movement to take the strain off the exhaust pipe and prevent it cracking. The exhaust pipe should thus play no part in restraining the engine.


It's difficult to describe how tight this thing should be, I would guess that you should be able to just change its angle by hand. There should be no in-out or side to side movement. Some of these joints leak very slightly until the system has warmed up and expanded a bit. If the joint was loose, I can imagine it making buzzing noises at the engine vibration frequencies but this is a higher frequency range than the vibration you have been describing.

I have lost track a bit, but have you checked/changed the front wishbone bushes ?

 

[Communicator]

30 years ago, my first MH was a Pilote, on a Talbot Express (Peugeot J5) chassis.

I had two, or perhaps three exhaust front pipes fail in the first year. Having purchased a hard copy of the workshop manual, I investigated and found the clamping nuts grossly overtightend to the extent that the nuts were being spread, by having been forced partly onto the unthreaded section of the studs. I could not fit a 13mm spanner onto the nuts.


The tightening instructions in the manual were "Tighten the nuts until the springs are coil bound, and then back off by one full turn, and then tighten locknuts.", or similar wording with the same meaning.


After replacing the damaged nuts, and tightening as above I had no further problems in that area.