Vibration/Shuddering

[Ashaman]

Hey, I haven't posted any requests here for a while; but I had something come up I thought I would check with the group on today.

At the end of the year last year, I had experienced some vibration/shuddering on the Elan. Over winter I replaced a wheel that was slightly bent and had a new set of tires mounted.

Hooked up the battery today for the first time and went for a test drive; and I can't tell exactly WHAT, but something just isn't right still. Basically, if I am at low RPM and try to accelerate, I get really nasty shuddering, almost like it is shaking side to side. Other times, at lighter loads, things are pretty smooth.

My first guess was a wheel being not quite tightened down properly, but I did a double check and they are all fine - but that is what it "feels" like.

Right/Left turns really don't seem to have any effect, no extra noise, etc; it is mainly when I get on the throttle (especially in 4th gear it seems).

I took a quick look at the engine mounts (well the, two that are somewhat visible anyway), but I didn't see anything major wrong. I replaced the "nightmare" one already a couple years ago, so I can't imagine that would be it again...

Anyone have any ideas? Since I can't tell what is causing the problem, I am not even sure what type of place to take it for to check it out!

[Candles]

So you are saying the shuddering is like the engine is pulling jerkily? If this is the case, I'd go straight to Elanscan and have a look at the engine parameters.

Just one quick thought; have you put fresh petrol (gas!) in it?

Candles.

[M100 TWO]

ashman take a look and see if the engine dampers are in good working order

[pjohn151]

One possibility might be the new tyres? Have they worn in yet, or are they a different brand/tread pattern to before? How long was the vehicle standing over winter, did the tyres form a flat spot from standing - usually goes after a bit of use...

Phil

[Guest]

OK, still quite cool here so I am not missing any driving time; but this weekend I decided to do a little troubleshooting.

I removed the hood (the one over the engine ) so I could see the engine while this was happening. Basically, the whole engine on the passenger's side is shaking! Almost a circular motion really; it is strange.

So thanks for the suggestions, but it definitely isn't tire or engine (running-wise) related. It is very speed related, you can barely feel it most of the time, but it really kicks in at ~60 mph in 4th or 5th gear when you get on it.

My first guess would be the engine mount on that side, but from what I can see it looks like it is in good shape. Tomorrow I will jack it up, support the engine & take it off though just to be positive.

One other thing is that the steering wheel shakes as well when this happens. I am not putting a connection between the two right now, why would the engine shaking around cause the steering wheel to pulse?

[Doug]

agree perhaps right engine mount so check that out

I might be so bold myself to put the front of the car on jackstands and then start and drive the front whels and see if it happens like that?

certainly a weird situation ? ? ?

[TheBard]

Please ignore, as I'd missed the last update with the engine jumping imagery...

Okay, I'm sure this has been ruled out, but... at the start you said you'd replaced a bent wheel. Is there any chance that the suspension/alignment could be knocked out of line in such a way that at low speeds the weight of the vehicle and the forces involved would mask any issues, but once you reach a specific speed (60mph plus according to your notes) the problem exceeds what can be corrected by tyre flex etc, and you get problems.

In my "I do software, not hardware" mind this seems to make sense, because surely an engine mount issue would occur at high revs in any gear, or in fact in neautral for that matter.

Just my numpty thought, cos nobody else seemed to have mentioned the bent wheel

Hope you get it sorted soon, good luck,
Ian

[Mike Y]

Is the shuddering coming from the gearbox side or engine side?

If its the gearbox it could be the damper on the gearbox mounting which is there to prevent this sort of harmonic movement of the drive train.

Regards Mike

[Ashaman]

Hey guys, thanks for the suggestions!

OK, I jacked up the engine and removed the motor mount in question. It was sagged, but definitely not broken. So I put it all back together.

Next I took your advice Doug and with a volunteer tried to recreate the problem with the wheel off the ground. With the wheel of the ground the problem was even worse. In fact, I thought maybe I was dealing with a defective tire or bent wheel again (though I had them checked out). So I traded it with the back wheel, but the problem continued.

Then I looked under the car, and I see that the whole driveshaft assembly (again this is on the passenger's side) is moving up and down. So I shut everything down, crawl underneath and take a closer look. It appears at this point it is the inner CV joint (the one right by the support bearing) that is causing the problem. With the wheel off the ground, moving it slightly forward or backward by hand will cause the driveshaft to move in an up/down motion.

So I am pretty sure at this point I have found the problem. In fact, I was just consulting the shop manual and found the following:

"A 'clunk' produced by engine torque reversals, or a shudder or vibration when accelerating, can indicate a worn inboard joint."

So it seems this is confirmed. My first thought against CV joints was due to the fact that it didn't change at all while cornering. Of course, the inner joints would not be affected by cornering at all; so now it all makes sense.

Or so I hope

Now off to "common parts" searching, and the archives to see if I can find out information about a replacement!

Thanks for all the input, I appreciate it!

[Mike Y]

I bet your a relieved man now that its just a CV joint

Did Lotus have one side of the M100 drive shafts on their sales list last year?

Regards Mike

[Ashaman]

Yes, nice to have found the problem and for it to be something relatively simple.

I am not sure, do you know where to find a copy?

As it is, I am trying to get the end of it out of the carrier bearing....grr.

Everything else went very smoothly, but I am supposed to "apply shock" to it. Problem is, there is no room to do so! Anyone have a trick for getting the outer half of the driveshaft out of there?

I was really hoping to be able to replace just this failed joint; as I imagine the Lotus part (which I think is available only as an axle/assembly) is quite pricey?

At any rate, I suppose I could just unbolt the carrier bearing and yank the whole thing out draining transmission fluid yet again and making a mess...but I am trying to avoid it if at all possible.

[johnbenk]

Hi

There is an article on replacing both and also short cuts to removing them
without disturbing the set of "shims" on the suspension it is listed under gearbox driveshaft and is dated 18th October 2005 page 4 problems

RH DRIVESHAFT/JACKSHAFT REPLACEMENT.

Hope this helps.

[Ashaman]

Hey, thanks for that, the picture was useful also.

OK, it is out. Turns out there is a tool just for this purpose, if only I would have checked that out earlier I might have saved myself an hour of hammering/prying/muttering

Autozone had the "Drive Axle remover" attachment for a slidehammer that made it ridiculously easy. Tapped it in place, 3 pops with the slidehammer and it was all over. Live & learn!

At any rate, I now have it out. I see that the entire axle for an Isuzu is $70; that sounds a bit more reasonable than the $600 it looks like a Lotus part is! Has anyone ever compared the two? Or from any of the Geo models? This has to be a common part, I can't imagine Lotus engineering these things up just for the Elan...

I will hit some places tomorrow to try to drum up more info.

If anyone has any more on hand however, I would apprecaite it!

[Doug]

FWIW, the inner CV joint sounds like very feasible answer. Glad you found it. How much would you have paid to get someone to diagnose that for you ??!!

[Ashaman]

All nice & smooth now!

Just as a follow-up...

It looked like a Lotus replacement was $500-$600. That is just nuts IMO, and I refused to pay it. I couldn't find any definite information on ac ommon part, so I did some checking.

I ended up ordering a replacement for a 1991 Isuzu Impulse RS, 2WD, Manual transmission. Upon arrival they said they thought it was the same. However, once I got it to the car it was clear that was not the case. While they might be the same overall length and look similar, the outer joint is longer with a shorter axle. This causes a problem with the "strut fork" it runs through (there isn't enough room). Further, I found that it has less splines and will not go into the Elan's hub.

The GOOD news was that from transmission up to inner CV, things appear to be the same. Which meant that I was able to buy a complete axle, remove the inner CV, and put it on my CV axle. So, not quite as good as a full axle, I did get one new joint and 2 new boots, all for $60! This price seemed constant with Autozone, Napa, and CarQuest.

So...I am happy. I did wonder though, I thought there had been some information regarding these on the site before? I couldn't find it when I was looking, might it be worth starting a section under common parts to report findings? Maybe others will come up with compatible parts as well?
From what I learned, it looks like the propshaft, carrier bearing, and inner CV will all interchange with the RS...it would be nice to know if there are other compatible parts...

I mean, maybe it is me...but paying 100X the price for a part just seems unacceptable.