Vibrations...

[Jens Munk]

Thanks a lot Allan,

Unfortunately Denmark is not Rover-land, so I am still wondering about the surprise.....

So at least I am not the only one with this obnoxious problem. I will work through your nicely prioritized list and see if any clues appear as well as keeping you updated. Tomorrow is a holiday here, so I have a three day weekend ahead.

Apr 30, 2015 8:59:21 GMT Welsh Warlock said:

Oh dear. Here we go again.

I asked the questions at the start of the thread relating to engine/drive train to try and narrow down the issues.

Chuck, with all due respect, what you are referring to are drive train issues. Jens has confirmed his vibration is engine speed related as the vibration is present at specific revs with the car in neutral (and also presumably park) and stationary.

It seems that when it comes to vibrations people confuse engine speed and road speed vibration issues. Of course the two can be linked and both can be present. I'm only dealing with engine vibration issues in this post.

I have spoken to many people about this subject, some have even sought me out having spoken to other well known and well respected members of the club who have pointed them in my direction as a result of my (non conclusive) experience of this issue.

I have been through a whole world of pain trying to track down the vibration. The engine has been apart twice and all moving parts balanced by one of the most experienced of Rover V8 engine balancers that does work for all of the Midlands based V8 builders. Everyone is out of ideas. But I haven't given up just yet. However I have had to put things on hold due to life getting in the way.

Of course Jens, your vibration could be caused by different factors than mine. For reference purposes mine is around the 1700 to 2200 revs. A number of the people I have spoken to with the same issue seem to have the problem around the same revs.

Now that you have established it’s the engine not the drivetrain, here's my suggestions to narrow the field.

Take the two drive belts off (Power steering and fan belts) or at least slacken them so they are loose enough that the auxilliary pulleys don't turn and run the engine briefly and through the rev range. Is the vibration still there? This will also eliminate the fan being out of balance.


Next, assuming vibration is still present, inspect the engine mounts and the damper. Place a little strain on them using a jack to check for any splits or wear (I changed mine as I had a new set knocking about) and take the load off them, loosen the bolts, lower the engine and re-seat it in case it wasn't fully resting in its mounts. Then retighten the nuts and test. Cured?

If not look at the gearbox mount. Is it split or damaged. is it secure? If so remedy/replace/tighten.

Front pulley is an awkward one. I tried an alternative pulley and also had mine checked for balance (it was fine). Its awkward because its difficult to remove without taking the radiator off, the bolt is tight and locking the engine up is difficult if its not still connected to the drivetrain (ask me how I know), and it needs a good puller to persuade it off the crakshaft nose (don't lose the woodruff key).

Torque converter: Remove the half moon plate and rotate the flexplate so you can undo and remove the four bolts and move the TC back from the flexplate. Then run the engine again BRIEFLY and test for the vibration.

Still there? Remove the gearbox and run the engine without it connected and test for vibration?

Still there? Remove engine, strip and have all moving parts balanced.

Still there? Find another solution and let me know...

This thread has set me thinking again. If Jens had no vibration and all he did was rebuild the carbs could this be to do with how the vacuum builds up and affects the lift of the pistons in the dash pots.
Although the vibration in mine feels like a mechanical issue of something out of balance I suppose a partial misfire could cause the same feeling.
I also know Jens had to change one of the subframe/engine isolators (I sent him an old one of mine as he couldn't get one in Denmark - You still owe me a surprise Jens ;-)). However, I changed the whole subframe and put in all new isolators and the vibration existed before that so I know it’s not related.

N.B. As in previous threads on this topic I am trying to assist by giving the benefit of the time amd money I have spent in trying to resolve this issue to save others time and money and am happy to discuss it. If anyone wants an argument or to make personal remarks please take it elsewhere.

[johnwp5bcoupe]

Apr 30, 2015 11:12:31 GMT Jens Munk said:

Apr 30, 2015 7:20:53 GMT johnwp5bcoupe said:

Jens was this problem there before you rebuilt the top end? have you split the engine and gearbox?

Yes it was there before, and I have never personally split the engine/gearbox. I can see from the pile of receipts that came with the car that it has been done in the past.

And it's a standard 3.5L Jens?

[Jens Munk]

Apr 30, 2015 13:01:22 GMT johnwp5bcoupe said:

And it's a standard 3.5L Jens?

Yes.

Sent from my GT-I9305 using proboards

[Jens Munk]

Just a short update on this topic.

It appeared that both carburettors needed quite a bit and different amounts of damper oil added. In addition the ignition was a little more than a degree of. Seemed to help somewhat, but then the alternator died and I am waiting for a new one. In addition I am on a business trip, so the project is on a halt.

To be continued......


Jens.

[JohnC]

I had something very similar last year. My P5B started to vibrate at about 2000 rpm stationary. I did all the checks and eventually dropped the gear box and examine the torque converter. I found that the status bearing had failed. Fitted a replacement converter now running fine. A little more than a rubber mount but that's what owning a P5 is all about.

[Welsh Warlock]

John, can you give me more info on the "status bearing" or is that a typo?

[enigmas]

The stator is the component in the torque convertor between the impellor and the turbine that multiplies torque at lower speeds when under load or taking off.

[Jens Munk]

How did you determine that the converter stator bearing was bad? Any checks to verify this before taking the car apart?

Jun 1, 2015 15:09:48 GMT JohnC said:

I had something very similar last year. My P5B started to vibrate at about 2000 rpm stationary. I did all the checks and eventually dropped the gear box and examine the torque converter. I found that the status bearing had failed. Fitted a replacement converter now running fine. A little more than a rubber mount but that's what owning a P5 is all about.

[harvey]

If you want to eliminate the converter as the problem remove the 4 bolts that secure it to the flexplate and run the engine for a short test. If the vibration disappears it's most likely the converter.

I've just cut a converter in half (which is the only way you'll know what's going on inside) and if I get the chance I'll have a look at what the stator runs on.

[JohnC]

I cut open my converter and found that the status had lost two of its vanes. Unfortunately in my haste I did not take any pictures. I obtained a good second hand converter from a friendly auto box repairer, who also took the old unit. My vibration took a while to track down. Good advise about removing the converter bolts to eliminate from list. However I am told that the position of the bolts must be marked and replaced in the original position as they "may" assist in the engine balance. Nothing worse than a vibration with a smooth V8, good luck.

[harvey]

Jun 2, 2015 16:20:58 GMT JohnC said:

I cut open my converter and found that the status had lost two of its vanes.

I would think that if two vanes broke off the stator in use then the converter would be really noisy, and if by some chance the two broken vanes were able to find somewhere to "hide" then the mere fact that they were missing would be enough to cause a vibration.

[enigmas]

Most of this has already been covered regarding the mysterious source of the vibration including isolating the torque convertor from the engine as Harvey suggests. Years ago I had a similar problem causing the ignition keys to jingle at exactly 60 kph! The source was the torque convertor but the cause very discrete and not obvious. The convertor was a rebuilt unit (with a warranty from a 'reputable' company.) When the torque convertor was split for the rebuild the cases were marked. Components were rebuilt or replaced and then the unit was rewelded according to the alignment marks. This caused the issue as the unit with its rebuilt components wasn't checked for rebalance. I only learned of this rebuild practice when I approached another company that specialised in manufacturing race convertors and spoke to their technical expert. When I replaced the original unit with one from the second company the vibration was gone.

(Note: If the stator partially broke up inside the torque convertor, I'd be concerned about debris going through the transmission!)

[Jens Munk]

Can you reveal the names of these two companies? I.e. the one to buy from and the one to not buy from?

Jun 2, 2015 23:26:36 GMT enigmas said:

Most of this has already been covered regarding the mysterious source of the vibration including isolating the torque convertor from the engine as Harvey suggests. Years ago I had a similar problem causing the ignition keys to jingle at exactly 60 kph! The source was the torque convertor but the cause very discrete and not obvious. The convertor was a rebuilt unit (with a warranty from a 'reputable' company.) When the torque convertor was split for the rebuild the cases were marked. Components were rebuilt or replaced and then the unit was rewelded according to the alignment marks. This caused the issue as the unit with its rebuilt components wasn't checked for rebalance. I only learned of this rebuild practice when I approached another company that specialised in manufacturing race convertors and spoke to their technical expert. When I replaced the original unit with one from the second company the vibration was gone.

(Note: If the stator partially broke up inside the torque convertor, I'd be concerned about debris going through the transmission!)

[JohnC]

I too was worried about the possibility of debris contaminating the gear box. I flushed the unit twice (and with fingers crossed) with no further problem.

[enigmas]

Jens Munk I reside in Victoria Australia, so listing the 2 torque convertor manufacturers would be of little benefit to you! Your best bet is to look for a manufacturer that builds race convertors as well as the more prosaic bread and butter change over units. Most 'average', daily driver convertors just have the vanes on the impellor and turbine locked in place with tabs that are bent over to lock them with large thrust washers used between the elements. Specialized race or towing convertors have all the vanes furnace brazed and run torrington bearings rather than plain thrust washers. They can also have the vane angle tweaked to raise or lower the stall speed of the convertor for improved performance, depending on how the car is used. Yes, you'll pay more, but get a specialized convertor which will work more efficiently and better match your engine's torque. Just ensure you ask the company to guarantee the torque convertor is precision balanced and not just welded back together using the alignment marks on the case halves when it was split for a rebuild.

Consider the current torque convertor on your P5B. The car runs a BW35 auto trans. There are 3 front pump variants and 3 torque convertor options. Your P5B runs the intermediate sizes of both. (eg. Baby bear, Middle size bear and Big bear) Usually the smaller torque convertor produces the highest stall speed. The input shafts are also incrementally increased for each size up of torque convertor. The P5 MK3 BW35 runs the smallest convertor and as a consequence can/does strip the splines on the stator support.

Also consider that the torque convertor fitted to your car, unless original could be fitted to any make of car running an intermediate size front pump and convertor.
I have no idea whether Rover tweaked the convertors that went on P5Bs to better match the V8 engine? I do know that P76 convertors had a different stall speed (higher) than the change over convertors purchased from most after market manufacturers which produced a one size fits all version.
Perhaps the club has an (old/failed) original Rover factory convertor which could be split open and the vane angles examined and recorded. Then a batch could be manufactured?

[enigmas]

Here's a nice little video of a torque convertor loading the engine thrust bearing under acceleration.

[Warwick]

Vince, is it possible to build a manually lockable converter for any gearbox?

[Jens Munk]

I have thought of that too. If possible, this would be at least as interesting as the overdrive currently featured in club magazine.

Jun 4, 2015 10:00:49 GMT Warwick said:

Vince, is it possible to build a manually lockable converter for any gearbox?

[barryr]

Also there was an interesting video on the innards of a torque converter on same page.

[enigmas]

Warwick said,

Vince, is it possible to build a manually lockable converter for any gearbox?

I don't believe so Warwick, the valve body hydraulics/circuitry simply don't allow for it. The pressure feed is through the turbine shaft and there is no provision for this. It would probably be easier to design a clutched version of this gearbox and add John's overdrive modification to it.

[Warwick]

I thought perhaps the hotrod people might have developed a cunning method.

[enigmas]

The 'serious' hotrod people Warwick only need a 2 speeds and that comes in the shape of the Power glide...a venerable old trans capable of handling up to 2800 HP.

For those interested:
www.superchevy.com/how-to/transmission/ghtp-1108-powerglide-transmission-build/