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Post by Jens Munk on Apr 28, 2015 12:41:40 GMT
There are some vibrations in my P5B, and I wonder if you know the source of them. It idles and drives fine with no particular vibrations, but when it takes off from stand still, it vibrates quite a bit with the engine revs until it gains a little speed. If I release the accelerator pedal shortly it goes away and I can accelerate normally (or seriously) with no vibrations.
Valves, lifters and cam+gear+chain are overhauled or replaced recently but made no notable difference on this. The carburettors have also been overhauled and their pistons are moving freely (damped, of course).
Could this be the torque converter?
Thanks,
Jens.
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Post by johnwp5bcoupe on Apr 28, 2015 12:56:27 GMT
There are some vibrations in my P5B, and I wonder if you know the source of them. It idles and drives fine with no particular vibrations, but when it takes off from stand still, it vibrates quite a bit with the engine revs until it gains a little speed. If I release the accelerator pedal shortly it goes away and I can accelerate normally (or seriously) with no vibrations. Valves, lifters and cam+gear+chain are overhauled or replaced recently but made no notable difference on this. The carburettors have also been overhauled and their pistons are moving freely (damped, of course). Could this be the torque converter? Thanks, Jens. A difficult one to diagnose Jens I would look at the engine mounts, gearbox mount first then the normal suspect things like prop shaft centre support rubbers, centre bearing and universal joints. It doesn't sound like the TC to me! Good Luck
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Post by Welsh Warlock on Apr 28, 2015 15:28:34 GMT
Jens,
The first thing to determine is whether it is road speed or engine speed related.
Does it vibrate when the car is stationary and in neutral as you gently increase the revs?
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Post by johnwp5bcoupe on Apr 28, 2015 17:31:28 GMT
I think reading Jens post Alan he has vibration when under acceleration then when he takes his foot off it is fine! even if he continues putting his foot down.
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Post by Phil Nottingham on Apr 28, 2015 17:36:35 GMT
It might just be the exhaust or engine mounts or prop shaft or even a missfire through a tracking HT lead
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Post by Jens Munk on Apr 28, 2015 19:19:30 GMT
A difficult one to diagnose Jens I would look at the engine mounts, gearbox mount first then the normal suspect things like prop shaft centre support rubbers, centre bearing and universal joints. It doesn't sound like the TC to me! Good Luck Thanks. Sounds like I should order some "rubber". Jens.
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Post by Jens Munk on Apr 28, 2015 19:22:29 GMT
I think reading Jens post Alan he has vibration when under acceleration then when he takes his foot off it is fine! even if he continues putting his foot down. Exactly! That's why I thought of the TC. More specifically if the stator free wheel is flaky. However, the consensus seems to be misc. rubber mounts. Jens
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Post by Phil Nottingham on Apr 28, 2015 21:19:49 GMT
Do or at least check the easy bits first then pull everything apart
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Post by enigmas on Apr 29, 2015 1:50:34 GMT
The explanation of the vibration doesn't really clarify much! If when taking off under acceleration and especially against an incline (slight hill or gradient) there is a slight but annoying vibration felt through the seat, that seemingly 'disappears' with increasing speed, it's a driveline /diff pinion flange angle issue. (Settled rear springs and/or in combination with the tail shaft centre mount alignment.) If you can get the car on a hoist and check all of these angles with a 2 metre straight length of timber and an angle finder gauge for the flange angles. (Primarily at the centre support and diff pinion.) You can adjust the diff pinion angle with wedges. Don't presume 'new/replacement' rear springs will fix it. Getting the angles corrected with whatever springs are fitted will do it.
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Post by Warwick on Apr 29, 2015 3:08:35 GMT
Can you get Contrasonic engine and gearbox mounts, ... or tyres?
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Post by johnwp5bcoupe on Apr 29, 2015 6:04:51 GMT
The explanation of the vibration doesn't really clarify much! If when taking off under acceleration and especially against an incline (slight hill or gradient) there is a slight but annoying vibration felt through the seat, that seemingly 'disappears' with increasing speed, it's a driveline /diff pinion flange angle issue. (Settled rear springs and/or in combination with the tail shaft centre mount alignment.) If you can get the car on a hoist and check all of these angles with a 2 metre straight length of timber and an angle finder gauge for the flange angles. (Primarily at the centre support and diff pinion.) You can adjust the diff pinion angle with wedges. Don't presume 'new/replacement' rear springs will fix it. Getting the angles corrected with whatever springs are fitted will do it. It sounds like an axle orientated problem Vince I agree that would be the next check for me after making sure all is bolted down prior to the axle. If he has wind up it could be a collapsed spring/springs, front spring bushes, Y mounts/bushes etc etc
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Post by enigmas on Apr 29, 2015 10:19:09 GMT
The more I think about it, the more I wonder about the centre bearing support John. How often if ever does it get examined. The 2 centre bushes eventually develop a deep groove and the support ends up functioning/simulating a big lump of jelly with the support oscillating under load.
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Post by johnwp5bcoupe on Apr 29, 2015 10:51:49 GMT
It could be Vince if they have been soaked in oil over the years? it's a case of checking everything and eliminating
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Post by Jens Munk on Apr 29, 2015 11:55:54 GMT
Thanks for all your answers. I appreciate it.
Based on your input I have just done a little test drive. It seems to be related to engine revs only and not whether the car is moving. Leaving it in P it will vibrate somewhat above idle going away at higher revs. Putting it in D, holding the brake and rev it to the same rpm will generate the same vibrations, which at least eliminates any concern of the drive shaft since it is not rotating in any of these cases.
I think that my driving experience is that I apparently always depress the accelerator to the same rev when taking off from stand still, and this happens to be where it vibrates.
Looking at the engine reveals that it is vibrating at this rev (1500 rpm, I would guess, but I will check). There doesn't appear to be any misfires and it is otherwise running smoothly. Could it be carburettor sync? Mixture diffs? Different behavior of the of the dampers? The carburettors have been overhauled by myself with lots of new parts including needles, springs, jets, damper pistons etc. and it is did this before.
I have not replaced the engine and gearbox mounts but they look OK, which is of course not the same as they are OK.
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Post by johnwp5bcoupe on Apr 29, 2015 13:27:37 GMT
That's a totally different scenario Jens you will have a few answers to that one Alan over to you for starters Why did you change the dampers Jens? they are matched to the chambers!
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Post by Jens Munk on Apr 29, 2015 17:28:28 GMT
Why did you change the dampers Jens? they are matched to the chambers! I overhauled the carburettor and just bought essentially all the new parts I could get. It was my intention to buy new carburettors, but they don't make the correct housing anymore. Sent from my GT-I9305 using proboards
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Post by Phil Nottingham on Apr 29, 2015 18:17:41 GMT
Unbalanced carbs cause vibrations like a missfire
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Post by enigmas on Apr 29, 2015 23:02:17 GMT
Your re-evaluation of the vibration changes everything Jens. Years ago when I fitted a new torque convertor from a reputable company my car developed a vibration period at exactly 30 mph which occured at that particular engine rpm range, stationary or moving. Apparently when some companies rebuild torque convertors they mark the cases and then split them, refurbish the parts but do not rebalance the assembly. (The complete engine assembly had been fully balanced previously so finding the issue was a matter of deduction.) I was told this by an alternate convertor rebuilder that built race units. When I replaced the first rebuilt convertor with the second unit the vibration period was gone.
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Post by johnwp5bcoupe on Apr 30, 2015 7:20:53 GMT
Jens was this problem there before you rebuilt the top end? have you split the engine and gearbox?
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Post by Chuck Berry on Apr 30, 2015 8:12:54 GMT
I had vibrations!!!!
Seriously; How are the rear springs? Look at the angle of the drive train; the axle Diff UJ has to be "looking" downward, very slightly. I had vibrations and went through the (DG) gearbox - oil changes, filter changes, even adjusting the linkage and kick-downs. Thankfully I didn't go the gearbox out-and-refurbish route.
After Changing the last UJ at the axle it did improve a little, then the axle was shimmed to give it a more downward angle - BINGO! In the end the rear springs were changed and it now runs as it should. When the power is put on the drive train, there is a tendency for the axle to be pushed up and back, so it should be horizontal/in-line when under power. If the axle is already near horizontal or has a slight upward incline then the angle of the axle under load will increase causing the problem.
Only problem now is the back end is rather high and the (JRW) HD springs are a hard ride. I am now thinking of removing a leaf out of the spring nest - just a thought at this time.
Hope this helps
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Post by Welsh Warlock on Apr 30, 2015 8:59:21 GMT
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.
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Post by enigmas on Apr 30, 2015 9:10:59 GMT
Chuck, this point has already been discussed and eliminated as the vibration period occurs when the car is stationary. As an aside... the diff pinion tends to climb the crown wheel under engine torque and visa versa when backing off the throttle under engine braking. The P5 split drive shaft tends to confuse matters. With a one piece driveshaft from gearbox flange to diff flange it's straight forward. The link below... spicerparts.com/anglemaster/measuring-angles...illustrates 2 diagrams, the second is relevant to the P5 tailshaft. (Skip the explanation about the gauge being advertised) Note an imaginery centre line through each assembly, engine (crankshaft) gearbox (mainshaft) and differential (pinion). Match all these angles and the flange angles on each component will also match. That's where you 'd attach the angle finder on the flange of the gearbox and also on the differential pinion flange. With rear leaf springs cart springs) and no top link to constrain differential movement up or down (at the pinion flange) there's bound to be out of phase periods under hard acceleration and off throttle conditions coasting down steep gradients. Arbitrarily moving the nose of the diff up or down without checking these angles (whether using old springs/new springs or something in between) will only lead to aggravation and guess work in correcting drive line vibration periods. Drive line phasing link. jniolon.clubfte.com/drivelinephasing/drivelinephasing.html
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Post by Jens Munk on Apr 30, 2015 11:12:31 GMT
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.
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Post by Jens Munk on Apr 30, 2015 11:18:18 GMT
I had vibrations!!!!
Seriously; How are the rear springs? Look at the angle of the drive train; the axle Diff UJ has to be "looking" downward, very slightly. I had vibrations and went through the (DG) gearbox - oil changes, filter changes, even adjusting the linkage and kick-downs. Thankfully I didn't go the gearbox out-and-refurbish route.
After Changing the last UJ at the axle it did improve a little, then the axle was shimmed to give it a more downward angle - BINGO! In the end the rear springs were changed and it now runs as it should. When the power is put on the drive train, there is a tendency for the axle to be pushed up and back, so it should be horizontal/in-line when under power. If the axle is already near horizontal or has a slight upward incline then the angle of the axle under load will increase causing the problem.
Only problem now is the back end is rather high and the (JRW) HD springs are a hard ride. I am now thinking of removing a leaf out of the spring nest - just a thought at this time.
Hope this helps
Thanks Chuck, The rear springs are brand new (high and hard JRW) - I replaced them a few months ago. No change in vibrations and vibrations are present at stand still, but thanks for this advice and I will check during the scheduled oil change this weekend.
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Post by Jens Munk on Apr 30, 2015 11:21:53 GMT
Thanks for the extra info and links. Although it is probably not the problem here, it is certainly worth checking out. Jens. Chuck, this point has already been discussed and eliminated as the vibration period occurs when the car is stationary. As an aside... the diff pinion tends to climb the crown wheel under engine torque and visa versa when backing off the throttle under engine braking. The P5 split drive shaft tends to confuse matters. With a one piece driveshaft from gearbox flange to diff flange it's straight forward. The link below... spicerparts.com/anglemaster/measuring-angles...illustrates 2 diagrams, the second is relevant to the P5 tailshaft. (Skip the explanation about the gauge being advertised) Note an imaginery centre line through each assembly, engine (crankshaft) gearbox (mainshaft) and differential (pinion). Match all these angles and the flange angles on each component will also match. That's where you 'd attach the angle finder on the flange of the gearbox and also on the differential pinion flange. With rear leaf springs cart springs) and no top link to constrain differential movement up or down (at the pinion flange) there's bound to be out of phase periods under hard acceleration and off throttle conditions coasting down steep gradients. Arbitrarily moving the nose of the diff up or down without checking these angles (whether using old springs/new springs or something in between) will only lead to aggravation and guess work in correcting drive line vibration periods. Drive line phasing link. jniolon.clubfte.com/drivelinephasing/drivelinephasing.html
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