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Think I have blown the diff - can you confirm?
aka Keith - 11/12/10 at 04:00 PM

Took the car out today and floored it in first, pulled second an woah, feels funny and I pull into the side of the road.


I started the car up and put it in first, car moves forward very slowly but does not get faster if the throttle is stepped on. Clutch I thought - got the car home on a flat bed.

I took the clutch basked out, checked the flat plates, and the friction plates, everything seems fine. Put the clutch basked back in the car and started her up again.

Car will move forward at walking pace but if you use the throttle revs rise but no speed increase. Took the bonnet off, put the car in first, handbrake on started the car, the car starts and rattle from the rear end. if you increase the revs, the drive shaft from the engine spins faster but the car does not move. I assume that I have buggered the diff?

Is that a logical assumption? How else can I check? Anything else left to check?

Cheers
Craig (BEC MK indy)

Moorron - 11/12/10 at 04:05 PM

is it a limited slip clutch? one of your driveshafts may have come loose or broke and when this happens it feels like a slipping clutch.

marcjagman - 11/12/10 at 04:05 PM

Deffinately a FUBAR diff. Time for a new one.

aka Keith - 11/12/10 at 04:10 PM

quote:
Originally posted by Moorron
is it a limited slip clutch? one of your driveshafts may have come loose or broke and when this happens it feels like a slipping clutch.


Moorron, it is an LSD, I lost the bolts holding on the half shafts two weeks ago and had just got it back on the road - 10 miles to precise.

Moorron - 11/12/10 at 04:50 PM

mine came out so i lock tighten them back in (very slight damage to the alloy diff flange). They didnt last long before they fell out again and i can only summerise that locktight doesnt work on grease covered threads! i removed each bolt, cleaned them completely and also did my best to clean the threads in the holes.

Been fine since.

i would test the diff out by jacking one wheel of the ground and with the engine off and in gear try to rotate that wheel. Then check the other side too. If any of the wheels spin get under the car and try and look if the driveshaft is turning too. Atleast this will confirm its the inner parts of the diff.

good luck

Chippy - 11/12/10 at 04:55 PM

Probably a stupid question, but have you checked that both half shafts are still connected to the diff. It's very unusual for a diff to strip all it's teeth in one go, and apart from anything else it would make a heck of a racket with the teeth grinding past, or even if the pinion shaft had broken. If I were you I would check everything else before condeming the diff. HTH Ray

adithorp - 11/12/10 at 07:28 PM

If there's no horrible noises then I'd say either a shaft has come undone, broken or stripped the splines in one of the CV joints.

zetec mike - 12/12/10 at 12:56 AM

Is it a live axle ? If so prob a halfshaft.

MikeRJ - 12/12/10 at 11:08 AM

quote:
Originally posted by zetec mike
Is it a live axle ? If so prob a halfshaft.


It's an MK Indy so probably a Sierra diff. Sounds very much like a broken/disconnected CV joint to me.

aka Keith - 12/12/10 at 05:04 PM

A quick note to thank everyone for their input.

Put the car up on stands, started her up and bingo - whoa that should not be doing that. One of the half shafts was spinning in an eliptical orbit - undid the six bolts holding the shaft to the diff casing and the bearing fell out - bits of metal and balls everywhere.

Does anyone know if you can replace the bearing or is it cheaper and easier to just replace shaft assembly?

If the answer is to replace the bearing, what the hell is it called - looked in the haynes and could not find it identified.

Cheers
Craig

rusty nuts - 12/12/10 at 05:45 PM

IIRC there was a link on here showing full step by step instructions on how to rebuild a Sierra diff, I had it bookmarked until I had problems with the PC

rusty nuts - 12/12/10 at 06:07 PM

http://www.mc2racing.com/tech/20081104a/index.html

Hope the link works

adithorp - 12/12/10 at 07:15 PM

Which bit is FUBAR? The the CV lo-bro joint (with 6 screws through it) or the flange and bearing IN the diff that it attaches to? From your description it sounds like the CV which is removable from the shaft by removing the circlip on the end of the shaft. If it's the flange and it's bearing then you're looking at a diff rebuild or replacement.

aka Keith - 12/12/10 at 09:28 PM

quote:
Originally posted by adithorp
Which bit is FUBAR? The the CV lo-bro joint (with 6 screws through it) or the flange and bearing IN the diff that it attaches to? From your description it sounds like the CV which is removable from the shaft by removing the circlip on the end of the shaft. If it's the flange and it's bearing then you're looking at a diff rebuild or replacement.


thanks Adithorp, from looking at the diagrams, it looks ik the the bearing in the flange - which means that is a new diff - bugger.

cheers
Craig

sebastiaan - 13/12/10 at 08:17 AM

Bearings are in the flange (nut) and in the diff housing and can be replaced. Rebuild kits for a 7" diff aren't that expensive on Ebay.

If you have a 6,5" diff, see the second to last post on this thread: http://locostbuilders.co.uk/forum/9/viewthread.php?tid=85080&page=2&pid=222578 for part numbers of the (standard SKF!) bearings and seals etc. The bearings and seals might be the same on a 7" though...

aka Keith - 13/12/10 at 09:13 AM

Many thanks Sebastian,

And again, maybe I am not seeing the wood for the trees. All of rebuild kits I have seen look like tapered roller bearings, whereas, what came out last night were actual ball bearings (about half inch in diameter) rather than tapered roller bearings.

Any help much appreciated.

Yours
Craig

phelix - 13/12/10 at 12:29 PM

1/2 inch ball bearing suggests the inboard CV joint.

aka Keith - 13/12/10 at 12:56 PM

Thanks Phelix,

I have just got of the phone to a company called "Road and Race Transmission" based in Kent, and they came to the same conclusion - he suggested that is was in the inner lobro joint. Fantastic help over the phone - but they do not store the parts (they do caterham stuff).

So far then, I have identified that I have a 3.62 LSD diff with 100mm flanges.

Is it an easy job to replace the CV joint? Any recommendations as to knowledgeable source them get the part from. Do not want to be stung by and idiot (me) and their money (ebay).

Or quicker and easier to simply replace the drive shaft complete?

Cheers
Craig

phelix - 13/12/10 at 01:54 PM

I can only guess that it's a standard Sierra joint - try your local motor factors. No idea about price though. Or ebay for 2nd hand but you'll probably get the entire shaft.

I would offer the joint was either very worn (in which case it should have been noisy or clunky) or the bolts were loose. The joints don't normally fail out of the blue; they last a long time so long as they're filled (but not overfilled) with grease and the boots are intact.

aka Keith - 13/12/10 at 03:14 PM

many thanks Phelix, I expect that this CV went bang due to the abuse it got a couple of weeks ago when teh other end of it came away from the wheel assembly at speed. Result that it was spinning around all over the place till the car was stopped.

Cheers
Craig