Technical Low velocity shake
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Technical Low velocity shake
From your early work you did some vibration/spectral analysis. I assume you have access to accellerometers and a FFT analyser or similar. The 3x wheel frequency you saw certainly seemed to be related to the tripod joint. Can you do some more analysis with this kit? I'm not sure that problems would show up as visible wear in the tulip. On non-auto models re-greasing the tulip often helped and there were long discussions about using the exact amount and type of grease. I think there is some kind of geometric lock-up going on in the Tulip. Gearbox / engine mounts could affect this by changing shaft positions etc.
There are 3 engine / gearbox mounts and they ll seem to be simple rubber types. The rear gearbox mount would likely have most effect. They cost around €50 http://www.ebay.co.uk/itm/Febi-Bils...Mount-23673-/161891767307?hash=item25b180540b
It would be worth having look it or possibly just changing it.
Robert G8RPI.
There are 3 engine / gearbox mounts and they ll seem to be simple rubber types. The rear gearbox mount would likely have most effect. They cost around €50 http://www.ebay.co.uk/itm/Febi-Bils...Mount-23673-/161891767307?hash=item25b180540b
It would be worth having look it or possibly just changing it.
Robert G8RPI.
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Great the way things trigger memories.
A good shout to look at engine mountings.
When British Leyland introduced the Princess model, in 1975, there were problems with driveshaft vibration on manual models. The auto was OK.
The fault was eventually found to be the engine position, and the mountings were changed to alter the engine height in relation to the driveshafts.
Weak mountings will allow the engine to drop a little, and the Vectra/Croma may be quite susceptible to this.
Have a very good look at the engine mountings. Do they look even slightly sagged?
A good shout to look at engine mountings.
When British Leyland introduced the Princess model, in 1975, there were problems with driveshaft vibration on manual models. The auto was OK.
The fault was eventually found to be the engine position, and the mountings were changed to alter the engine height in relation to the driveshafts.
Weak mountings will allow the engine to drop a little, and the Vectra/Croma may be quite susceptible to this.
Have a very good look at the engine mountings. Do they look even slightly sagged?
One thing just occurred to me, we keep talking about automatics, but these Cromas have the 5 cylinder engine which is longer and heavier. This will put more strain on the mounts.
Robert G8RPI.
tarquin1867
Member
When you looked at the pics were there any grease apparent?
The Fiat manual I have states the grade and amount of grease for the tulip joint as Tutela MRM Zero 140gms. When I changed the outer shaft for a new one it only reduced the wobble by 50% but when the correct amount of the right grease was packed into the joint it almost disappeared even with a "worn " tulip .
That's a good point.
The correct grease for the inner joints is difficult to get hold of. It is different from the outer CV joint grease, but most joint and boot suppliers supply the same stuff which is wrong. The inner joint should have a quite liquid grease, that almost flows, like an oozing glacier. The outer joint should use the black stuff containing molybdenum disulphide. (Sad that I didn't have to look that up!) This is the stuff that is readily available and supplied for the inners too.
Finding the correct stuff for the inner joints is difficult as it is scarce. When Rover still existed they did it in nice little sachets. I think Vauxhall do supply it in reasonable sizes.
Edit:
The Vauxhall stuff I was thinking of is for the brake caliper slider pins, another specialist grease, but usually replaced with ordinary stuff, or worse, copper grease, which is not a lubricant!
Only grease I can find for inner joints is this: https://www.merlinmotorsport.co.uk/p/gkn-tripode-joint-grease-300-grams-gkn-ms9u025
Expensive for just two joints, but significant that GKN market two different greases for inner and outer joints. Their products!
The correct grease for the inner joints is difficult to get hold of. It is different from the outer CV joint grease, but most joint and boot suppliers supply the same stuff which is wrong. The inner joint should have a quite liquid grease, that almost flows, like an oozing glacier. The outer joint should use the black stuff containing molybdenum disulphide. (Sad that I didn't have to look that up!) This is the stuff that is readily available and supplied for the inners too.
Finding the correct stuff for the inner joints is difficult as it is scarce. When Rover still existed they did it in nice little sachets. I think Vauxhall do supply it in reasonable sizes.
Edit:
The Vauxhall stuff I was thinking of is for the brake caliper slider pins, another specialist grease, but usually replaced with ordinary stuff, or worse, copper grease, which is not a lubricant!
Only grease I can find for inner joints is this: https://www.merlinmotorsport.co.uk/p/gkn-tripode-joint-grease-300-grams-gkn-ms9u025
Expensive for just two joints, but significant that GKN market two different greases for inner and outer joints. Their products!
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I'm sure the GKN grease is fine, maybe even a newer improved product but it states no solid lubricants i.e. no MD, but the Fiat specified lubricant, Tutela MRM Zero does have MD. http://tbl.onion.it/commonfile/eng/pdf/1867_scat_ENG.pdf
The lubricant in my (1.9 16V M32 6 speed) Croma's old tulips was semi liquid with MD (distinctive colour). It only take a small amount of MD as it is actually a surface modifier.
Robert G8RPI.
Did anyone find the reason for this shake at 15-20mph under load and then again at 40-60mph under load? My auto has had a complete new inner & outer near side drive shaft and after fitting the shake is exactly the same. I now suspect an engine mounting (but these have been checked by the garage and I have been told they are all OK) or the gearbox diff. I consider there is too much up and down movement on the inner drive shaft where it exists the gearbox. An autobox specialist does'nt agree and they say its not the auto-box but they dont know what is causing the shake.
anybody with this fault changed/had changed the gearbox top mount that under the battery ? After spending 3.5 hours under and in the engine bay mine seems weak and I think this might be the answer, BUT normally a car unless its a subaru with a boxer engine where the pistons are moving sideways rather than up and down should not, in my opinion induce side ways movement.
Did any of you 3 with this problem ever find the reason ? Its cost me a lot of money to have 2 new complete inner & outer drive shafts fitted (they arrived from Italy as full units for each side, so inner and outer were already connected). Even now the car is still shaking badly when accelerating at 35-45 mph, especially uphill. I am really sick of the problem now, I even had the engine mounting under the battery removed, inspected & re-fitted, that's not the problem. I suspect the gearbox is the problem, but the autobox specialists say it cant be as otherwise the gearbox would be leaking oil as it would have blown the seals. Any help very appreciated. Remember car hit a huge pothole prior to the car starting to shake (but did not shake immediately, only after 1000 miles or so)
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Mine was cured with a drive shaft (used Vectra C item) replacement. I think you have some kind of wheel or suspension damage from the pothole. It's no good just changing things.
The best tool for finding out what is going on is to measure the vibration. Pico Technologies Automotive NVH (Noise Vibration Harshness) is great for this.
https://www.picoauto.com/library/ca...engine-mountings-with-the-nvh-diagnostics-kit
You should try and find a auto electrician or diagnostic expert near to you
who has this kit. A message on their forum https://www.picoauto.com/support/ might help locate someone.
I have the Pico oscilloscope and accelerometers but not their specific NVH kit, but If you are near Cambridge I'd be happy to give it a go. Someone with experience of the kit would be better though.
Robert G8RPI.
