Lotus Elan

Transmission vibration on acceleration?

PostPost by: Tonyw » Sun May 05, 2013 12:06 pm

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
Second childhood? no just an extension of my first.
Tonyw
Third Gear
Third Gear
 
Posts: 404
Joined: 23 Sep 2006
Location: Perth Australia

PostPost by: AHM » Wed May 08, 2013 4:26 pm

Your brother in law is a mass damper.
AHM
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1493
Joined: 19 Apr 2004

PostPost by: Tonyw » Thu May 09, 2013 12:49 pm

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
Second childhood? no just an extension of my first.
Tonyw
Third Gear
Third Gear
 
Posts: 404
Joined: 23 Sep 2006
Location: Perth Australia

PostPost by: oldelanman » Thu May 09, 2013 3:18 pm

Tonyw wrote: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.
Roger
S4 DHC
oldelanman
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1676
Joined: 02 Jan 2008
Location: Dorset UK

PostPost by: types26/36 » Thu May 09, 2013 3:36 pm

oldelanman wrote:[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,.
Brian
64 S2 Roadster
72 Sprint FHC
User avatar
types26/36
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 3655
Joined: 11 Sep 2003
Location: U.K.

PostPost by: Tonyw » Sat Jul 20, 2013 12:39 pm

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
Second childhood? no just an extension of my first.
Tonyw
Third Gear
Third Gear
 
Posts: 404
Joined: 23 Sep 2006
Location: Perth Australia

PostPost by: AHM » Sat Jul 20, 2013 2:29 pm

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

Tonyw wrote: 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.
AHM
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1493
Joined: 19 Apr 2004

PostPost by: gjz30075 » Sat Jul 20, 2013 8:26 pm

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
Greg Z
45/0243K Sprint
36/5727 pre airflow coupe
User avatar
gjz30075
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2975
Joined: 12 Sep 2003
Location: Roswell, Georgia, USA

PostPost by: rgh0 » Sun Jul 21, 2013 1:09 am

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
User avatar
rgh0
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 7515
Joined: 22 Sep 2003
Location: Melbourne, Australia

PostPost by: Tonyw » Sun Jul 21, 2013 3:17 am

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
Second childhood? no just an extension of my first.
Tonyw
Third Gear
Third Gear
 
Posts: 404
Joined: 23 Sep 2006
Location: Perth Australia
Previous

Total Online:

Users browsing this forum: No registered users and 6 guests