Lotus Elan

loss of drive

PostPost by: garyeanderson » Tue Jan 04, 2011 1:47 am

Hi Ian

Does the speedometer read like you are moving when you have it in 2nd. 3rd or 4th gears and the clutch is out?

Gary
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PostPost by: rocket » Tue Jan 04, 2011 5:46 pm

Just had rear wheels in air both same time spun one and other wheel turned in opp direction as expected but only for maybe 15 or so revs then tho i continued to spin wheel the opposite side ceased to turn.Turned same whhel in reverse direction and opp wheel turned for a few revs then stopped.As i was doing this prop remind stationary.

With wheels still in air i started car popped into first gear and wheels both turned!!!...obviosly prop spinning too...

Dropped car back to floor..popped in first gear car moves about 2 foot then stops..


Getting really confused...assume diff is missing some teeth..but what is odd is that once car stops moving if you let clutch out prop trys to turn but wont,jammed in diff? car willl still push along in gear no prop movement..and surely if clutch right out and prop not turning engine would stall so clutch prob? gearbox?


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PostPost by: billwill » Tue Jan 04, 2011 7:24 pm

JJDraper wrote:Jacking up one wheel at a time will show if, and which drive shaft has failed. If both wheels are turning, as in just pushing the car along, the wheel with no broken shaft will turn the propshaft. If you jack up both wheels, with good drive shafts and try to spin one wheel, the other will go in the opposite direction. This is how a diff works, but is difficult to explain without pictures!

Jeremy
PS this may not work with a limited slip diff..


I'm not sure that turning the wheel with the intact shaft will turn the prop shaft, because the broken one will spin instead, inside the diff.
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PostPost by: miked » Tue Jan 04, 2011 7:35 pm

Hi Ian, I have not read all the thread but I helped my friends in summer with a Sprint with a problem that sounds the same (when we were travelling). We had to change the Diff' in France. When the Diff' was opened I believe the crown wheel bolts had all come out. They had also gouged into the Alloy case. Bit unbelievable, but true. We could not move the car very far as it would jam when pushed forward or back.

Car had travelled from about 500 miles and this happened at about 10MPH when pulling out of a garage after refueling. No prior warning.

May not be this but thought I would share it as we were scratching our heads at the road side. My first thought was a sheared output shaft but I was wrong.

Mike
Last edited by miked on Tue Jan 04, 2011 10:51 pm, edited 1 time in total.
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PostPost by: rocket » Tue Jan 04, 2011 7:38 pm

Hi Mike,

Can you recall what happened when in gear letting clutch out? Did it stall or????

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PostPost by: alexblack13 » Tue Jan 04, 2011 7:44 pm

I think you are right. It does look like some teeth are off the diff' either crownwheel or pinion. Or one of the output shafts have sheared.

Get someone to hold a rear wheel whilst you turn the other. The prop' should turn. If it doesn't. A) Teeth off diff. B) Diff output shaft broken? This could be difficult to spot if inboard of the bearing as in pic' previously posted.

All being well with the back end should produce a rotating prop' when one wheel is held and the other is turned. If the prop' doesn't rotate then the problem is there.

What foxes me is you said the prop shaft did not turn when engine running and car in gear. How do you know this? Did you look at the prop shaft? Are you sure it was not rotating?

Its highly unlikely you have had two instantaneous failures at same time.

Check out that diff'.. Looks like culprit to me...

Keep us posted.. And you will find it.


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PostPost by: miked » Tue Jan 04, 2011 7:51 pm

Hi Ian,

It would have stalled, had we let the clutch fully out. The engine was lurching on it mountings and the car was sitting down at the back as the engine tried to work against the locked diff'.
Just like trying to drive against a handbrake (not an Elan one). The odd part was that the car would push (in neutral) for 5 or 6 feet and then lock up, forward or back.

Mike
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PostPost by: rocket » Tue Jan 04, 2011 7:58 pm

Its a puzzler i shall be pulling diff out as this must be faulty.Am concerned that there is damage in gearbox/clutch as i cant see why prop turns when the rear wheels are raised but not when they are grouned..time will tell and at least i dont really use car untill spring so no rush.

Thanks for help chaps will let you know when diff is out..

Cheers,

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PostPost by: alaric » Tue Jan 04, 2011 9:29 pm

Hi. I've just had a read through the thread. Are you sure the clutch is working properly? It just seems to me that the pedal may feel ok, but if something in the mechanism in the bell housing or hydraulics has failed then maybe it won't return properly - so when you lift your foot off the clutch pedal the clutch is only making slight contact and will slip easily, and not heat up much etc. That would give all the symptoms that have been described and actually be easier to fix than pulling out the diff. As a suggestion though, if you can jack up both rear wheels again, and rotate both together in the same direction, then the resistance you feel should be the grip of the clutch through the gearbox ratio, so if you put it into 1st gear it'll be harder to turn the wheels than if you put it into 4th gear. Check the pushrod that comes out of the clutch slave cylinder - is it jammed out near the end of its travel?

Hope you find the fault soon.

Regards.

Sean.
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PostPost by: alexblack13 » Tue Jan 04, 2011 9:36 pm

Do the hold one wheel and turn the other check 1st... Before ripping out the diff'.

If the prop' does not turn, the issue is in the rear axle. Diff' or driveshaft..

Alex. 8)
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PostPost by: StoatWithToast » Wed Jan 05, 2011 5:20 pm

Hi Ian,

From what you said about getting the car in the air I agree the problem is somewhere from the prop connection back to the wheels, either the prop linkage into the diff, the diff itself, the output shafts, the drive shafts or the drive shaft to wheel connection.

If it is NOT the back section as I just suggested then in your test the prop should have started turning when the opposite wheel stopped turning.

On a working diff (not limited slip):
If the car is out of gear, jack the back up, hold one wheel stationary and turn the other then the prop should turn.
Put the car in 1st gear (without engine running) and you should not be able to turn the wheel unless either the other wheel slips to compensate, or something forward of the prop is broken --- this last one should turn the prop again as the diff is working.
Still in gear let go of the stationary wheel and now that wheel should turn opposite the turned wheel --- if the prop turns then the resistance through the diff to the opposite wheel is more than through the prop so something from the prop forward is broken and/or the opposite wheel has seized bearings, stuck brake, etc.

Good luck!
Dave
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PostPost by: alaric » Wed Jan 05, 2011 9:39 pm

Hi again. It's quite easy to get the diff input flange bolts out, and once removed you should be able to break the connection to the diff. With that connection broken you may get a better feel for what's going on. I wouldn't spin the disconnected prop under engine power. Previous post sounds spot on re the testing etc. Are there any oil leaks from the diff?

Good luck.

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PostPost by: bob_rich » Thu Jan 06, 2011 1:57 pm

Hi Folks
been following this one --it does seem very strange. there seems to be conflicting info regarding just what is going round and under what conditions. I am surprised that broken up gears in a diff do not make a most dreadful noise. the one wheel off the ground test should be fairly clear cut as to what is going on. both wheels of the ground can be confusing because of the relative friction of each wheel brakes bearings etc. I found this when trying to check the ratio of my diff and gear box before I removed them.

The only other thought I had which would explain transmission "Appearing to" lock up is could the servo fail such a way that it can apply the brakes without brake pedal operation? Dont know if that is even possible --- but just a thought.

whatever I do hope it is not 2 serious and U get it sorted

best of luck

Bob
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PostPost by: ken ob » Thu Jan 06, 2011 3:16 pm

Bob, I had exactly that happen with a servo some years ago.

I dont know if it is the reason for this problem but in my case the brakes would gradually come on until locked. A quick hard stab on the brake pedal released them for a few miles. Cured by full servo overhaul.

Ken.
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PostPost by: rocket » Thu Jan 06, 2011 5:46 pm

Ok after finding wheels turn when in air in forward and reverse i came to conclusion that the clutch may be slipping , preventing enough drive to propel car.I have sat pushing clutch in and out for a few mins and now pedal has gone very firm,also can now change through the box so clutch must be jammed in disingaged position.Thinking this may have changed things ai diff end i jacked one side of rear and turned wheel,prop moved about half a turn then stopped again...


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