Transmission vibration on acceleration?

[Tonyw]

Hi everyone,

A small update, took the car out today after checking gearbox mounts, engine mounts torque rods diff mountings, tail shaft bolts for tightness and axles.

Car still vibrates but the funny thing is with a 75kg passenger vibrations almost dissapear, I had the brother in law bring his Sat Nav to check my speedo (reads to low by the way) and with him in the car there is a very noticlble difference to the vibrations! much less anyone have any idea why that might be?

I would be interested to see what others think, I am now leaning towards the hald shafts and that really is all that would change with extra weight I think?

Regards,

Tonyw

[AHM]

Your brother in law is a mass damper.

[Tonyw]

AHM,

Not sure he would appreciated being called a mass damper................!!! but I was wondering myself if this is actually what is happening.

I have tried without success to remove the tail shaft as per the WSM it simply will not come out there is just not enough room betwen the tunnel and the gear box rear housing so I will have to pull the engine out.

Sometimes I want to wash this car with petrol and dry it with a match...................

Tonyw

[oldelanman]

I have tried without success to remove the tail shaft as per the WSM it simply will not come out there is just not enough room betwen the tunnel and the gear box rear housing so I will have to pull the engine out.

I've not tried it myself so can't confirm for sure but I believe it's possible to take the propshaft out from the rear. The LH driveshaft has to be removed and the outer end of the wishbone dropped to make enough clearance. Might be worth giving it a go before you resort to taking the engine out.

[types26/36]

[I've not tried it myself so can't confirm for sure but I believe it's possible to take the propshaft out from the rear. The LH driveshaft has to be removed and the outer end of the wishbone dropped to make enough clearance. Might be worth giving it a go before you resort to taking the engine out.

I can confirm it is possible to remove the propshaft with eng/gearbox in place, I dont recall removing either the driveshaft or dropping the wishbone, as I recall you disconnect the propshaft and push it back as far as it will go over or under the diff (memory fades here a little)....but think it goes above the diff, support the gearbox and compleatly remove the mounting.
Again mememory fades a little and I think you lift the gearbox as far as it will go (I dont think you lower it) then you can wrangle out the propshaft forward and down.....I've did a few years ago when I wanted to have it balanced,.

[Tonyw]

Hi Everyone,

Just to give you an update on my vibration issue. I remeoved the engine and gearbox as I have just rebuilt a CR box, while it was out I had the tail shaft balenced.

I put it all back together again and road tested it. while better it was still not fixed, the vibration was still there.

If you remember i have uni jount type half shafts, one side was odd, the flanges that bolt onto the output flange (diff) and the hub did not line up, while they were in line they were at 90 degrees that is the yokes if you get what I mean, I removed the odd shaft and re-installed it so the ears from the two flanges were in line and hey presto all vibrations dissapeared.

I do not understant why it caused all this vibrations but I as just so happy that I can put my right foot to good use. I would be interested to hear from any of you enginers as to why this caused so much of a problem.

Regards,

TonyW

[AHM]

Great to hear you have fixed it - Vibrations are the most irritating and spoil the enjoyment - Fixing them counts double!

I would be interested to hear from any of you enginers as to why this caused so much of a problem.

If you read from the beginning you should find the answer - If not I'm happy to elaborate.

[gjz30075]

An earlier post asked about the propshaft bushing in the tailshaft of the trans. Was this checked? Prop should have no play when inserted in the tailshaft.

Greg Z

[rgh0]

Universal joints don't give constant output rotational velocity with constant input rotational velocity when at an angle. You generally need to use universal joints in pairs and have the joints lined up so that the cyclic variation in output speed of the first joint is cancelled by a equal and opposite cyclic variation in the second by having the pair have the same angle deflection.

CV joints aka Constant Velocity Joints do have a constant output rotational velocity with changing angle which is why they are used on front wheel drive cars to accommodate the steering angle as they don't need to be used in pairs with each one of the pair having the same angle deflection.

Technically the use of CV's on the Elan rear suspension is much better the UJ's as the angle of the outer joint is a little different from the inner joint over the range of suspension movement. In practice most of the variation cancels out along as the joints are aligned

cheers
Rohan

[Tonyw]

Thanks for the replies folks.

Greg I did put in a new bush on the extension housing, I had knocked up a drift on my lathe and tried a couple of second hand ones to check that the drift would not damage the bush, I found that there was no discernable difference between the used ones and the new one but obviously havong bought a new one that was left in.

Rohan, I think I understand what you are saying, I would have prefered to have CV joints but these came with the car so I was hoping to use them.

All good now the car is a pleasure to drive.

Tonyw