NVH - noise, vibration and harshness in Elans

[europatek]

My Elan has always had some driveline harshness. Was there when purchased and was there after I took the whole
car apart and put it back together. It's similar to this post I found:

elan-f14/worrying-vibration-t18319.html

This is how it is; It's only really noticeable on transient throttle at 3500rpm in 3rd gear. If you increase the rpm's
to 3500 in 3rd and then hold on very very light/transient throttle it feels like some part of the drivetrain is touching
the frame. You can also create the same condition on rapid deceleration. If you hit the gas at 3500 it disappears instantly. Under 3500 - nothing. I'm sure it's there at other engine speeds but not as noticeable. For sure it's drivetrain. The car cruises at all road speeds smoothly.
Any ideas?

I've looked around the car and all looks good. The car is in great shape. I can't find anything touching the frame or body.
Everything is tight and I used new nylocs or conelocks everywhere. I've got new CV's, new UJ's etc......
Rebuilt the gearbox (see my restoration post for all the work I have done)

Any thoughts would be appreciated.

PS - I've had several Cortinas and never experienced this kind of harshness. Perhaps it's the Elan's diff vs frame??

[DaveAlmey]

Hi,

I had a similar condition on my RS Escort, after lots of searching it ended up that the propshaft was out of balance, there was a little square of corrosion on the shaft (10 x 10mm) where a little spot welded balance weight tag had departed.

I saw a similar weight on my S4 prop shaft when it was out on the rebuild and checked its security.

Just a maybe thought

Dave

[elanfan1]

Sounds like propshaft to me too - my first Sprint had the same issue. It might be that I didn't note its orientation before I took it out and when putting it back I put it in 180 degrees from where it had been. Anyway out it came (which was one hell of a job) had it balanced and the problem ceased. I think this is the most likely problem.

Otherwise to get these symptoms surely it must be something moving/vibrating in the drivetrain so I guess that would start at gearbox - is the mounting secure and engine mounts too, aforementioned propshaft, diff mounts top and bottom, donuts in good condition and bolts all tight right through to A frames all tight calipers bolts etc. Could you have a loose drive peg in a wheel or maybe rounded holes and the wheel is moving on the hub a tiny bit. These just my thoughts - far from being an expert!

[nebogipfel]

The other thing I can think of is to make sure that the diff casing is set up so that there is clearance between it and the chassis at the bottom. You probably have checked but it's an easy thing to overlook and can be worsened if the chassis has been bent slightly by jacking under the rear centre.

[oldelanman]

The only two things that come to mind and they are both unlikely in view of your meticulous rebuild.......do you have the correct spacers fitted to the gearbox rear mount if not the driveline angle may be incorrect. Also when you refurbished the diff did you check/reset the pinion bearing pre-load? Excessive end float on the pinion may result in too much backlash between crownwheel and pinion which would show up when the driveline is not under load.

Slightly off topic...having just read through your restoration post I like the look of your seat belt retractor mountings. I am considering fitting retractors and was wondering how best to mount them. What thickness material did you use ?

Regards,

[jimj]

I had JUST the same thing, vibration when neither accelerating nor decellerating and checked/replaced all the above. I spent hours and money faffing with a stethoscope etc. It just had to be the newly rebuilt diff. from Leslie who kindly offered to take it back and investigate. I thought I`d undo those awkward little bolts that secure the diff. flange to the propshaft first. You`ve guessed, they were working loose. New high tension bolts, loctite, nylocs, spring washers, belts and braces, and now all is smooth and tranquil though I still have the bruises from kicking myself.
Jim

[europatek]

Was in the car again the other day. Do you think I could replicate the harshness! Tried several time to no avail.
Oh well. It's one of these mystery type events that happens occasionally then. Car felt good though.

I've been wandering whether some of the harshness is coming from the exhaust. I have the muffler mounted
as per an S4 in the book. Two rubber isolators at the front and the strap at the back. They make for a pretty stiff mounting of the muffler. I recently suffered two heavy groundings on the exhaust with one nearly tearing the muffler off.
Thankfully the only damage was bent brackets. The groundings seemed to change something within the NVH of the car
and I've had the exhaust off and apart a few times now to see if anything changes. I've also "waisted" the isolators around the middle for some more compliance. Last time out it felt a little better.

OLDELANMAN - the seat belt brackets are 1.6mm MS. The large return was to stiffen them as much as possible.

[oldelanman]

OLDELANMAN - the seat belt brackets are 1.6mm MS. The large return was to stiffen them as much as possible.

Thanks.

[69S4]

I've been wandering whether some of the harshness is coming from the exhaust. I have the muffler mounted
as per an S4 in the book. Two rubber isolators at the front and the strap at the back. They make for a pretty stiff mounting of the muffler. I recently suffered two heavy groundings on the exhaust with one nearly tearing the muffler off.
Thankfully the only damage was bent brackets.

Is this the twin pipe S4 "muffler" or have you got a different one, as my twin pipe setup has only one mounting point at the back where it bolts through the boot floor. Before that the only fixing point is the plate by the gearbox mount. Over the years I've had the system ground so many times that's its worn through the pipe just before it enters the muffler and it's had to have patches welded on. Now I keep an extra exhaust clamp bolted onto that bit of pipe. It's not connected to anything, it's just there as a sacrificial offering to wear away first.

[europatek]

Re the exhaust - to clarify; at the leading face the muffler has the two rubber isolators mounted to the boot floor
and at the trailing face a rubber strap , again through the floor. Brain Bucklands book has an image showing the design.
The exhaust system is like a Sprint with the single box at the back. I have no other hangers for the exhaust except the engine it hangs off. The mount on the gearbox is long gone. So maybe the muffler is mounted to rigidly but it is as per the factory design.

I should preface all my posts by saying that I am a bit of a perfectionist and like things just so... therefore usually spend quite a bit of time making improvements and refinements where I can.

Maybe with the NVH this is just how Elans are?!?!

[rgh0]

My 1973 plus 2 has this style arrangement with a single strap at the rear and 2 rubber bushes at the fromt of muffler and no gear box mount

My 68 Elan has always just had a mount at the rear of the twin mufflers and the gear box mount but nothing at the front of the mufflers.

I am sure Lotus probably had lots of different details in these arrangements over the years depending on what they could buy at the cheapest price and most probably never documented the variation fully in manuals.

A good Elan is a very smooth car with minimal NVH apart from the intended exhaust noise so if you have an annoying vibration from the exhaust I would explore the mounting arrangements. The clearances around where the tail pipe and muffler run are tight and if you have grounded the exhaust you may be hitting the chassis or body somewhere.

cheers
Rohan

[Famous Frank]

Europatek,

I too just looked at your restoration. Absolutely wonderful!

One question if I may. There is one picture showing something mounted at the inside top of the rear window with a wire going to it. What is that? 3rd brake light? Or ???

Thank you, Famous Frank

[europatek]

Famous Frank - yes it's a high mount stop lamp. It's actually one of those LED lamps the "too fast too furious" guys
like to mount under and in their motors. I bought a red one, adapted the wiring and mounted it direct to the rubber
with small self tappers.
Well I've spent some time today making another, front of muffler, hanger bracket. It's just a couple of hooks and a
rubber ring. It has helped but their is still some vibrations coming from somewhere. Hard to pick it. Everything looks as it should be and the exhaust in now well isolated. Maybe it's just the way it's always been and I'm being picky.
I decided the gearbox mount is not necessary at all and if anything a hinderence to thermal expansion of the system.
Cortina's never had this mount and it's never been a problem. Working at GM a few years back I remember working with the exhaust guys developing bumper cutouts and they mentioned the exhaust grew in length by 25mm. I'm not suggesting this happens in the Elan but the thermal expansion should be considered. IE - no gearbox mount for me.