10 replies to this topic

[naughtyboydan]

Hello me and my dad built a mini from the growned and the car has done about 400 miles. Last sunday while i was driving i was sat at about 25mph and i lost all power. It reved but no motion. I then looked under the car at the diff because i could hear grinding and noticed the driveshaft had poped out of the C.V joint. It destroyed the splines off the shaft. So i replased the shaft i put the C.V joint first then the pot joint it all weny back to gether well. Today it drove for about 6 miles and its done the same again. Could some one pleas help me. Thanks danny

[cal844]

I believe the only way this can happen is if the shaft or pot joint is worn, strip and inspect???

[surfblue]

Had a similar issue many years ago (28th October 1996 to be precise!)

Worn / rusted drive shaft splines at pot joint end leading to no drive on a dual carriageway on a dark winter's night. Recovery by AA.

Replaced both pot joint and shaft and all good again.

[naughtyboydan]

They are boath brand new.

[tiger99]

Is it definitely the shaft splines that are rotating in the inner member of the pot, and not the pot having lost its balls or broken its cage? Could the locking clip be missing, broken or weak, so that the shaft has pulled partly out of the pot inner member? Can you post a picture of the shaft, and the remains of the pot?

 

Obviously surfblue has had this happen, but ordinarily there is a huge reserve of strength in the drive shaft splines, and in the pot joints themselves, and as long as parts from different pots are never mixed, sudden failure used to be almost unknown. Has your engine been tuned to an abnormally high power?

 

The splines must be greased, along with the innards of the pot of course, and as the original pot joint grease is no longer available, it is normal practice to use CV joint grease (NEVER anything else, such as LM, and definitely never graphite, although it looks almost the same, it must be Molybentone). It is possible that if the splines were dry, fretting corrosion caused the failure. You can go to your nearest main dealer for any modern FWD car (which more or less excludes BMW and Merc), and get a tube of CV joint grease for a medium to large car. Last time I got one for a Ford Focus, and although it was not cheap, there was enough for 2, maybe even 3, Mini pots or CVs. But make sure you get CV grease, modern cars often have "tripode" inner joints (and yes, I did spell it correctly), which use yet another type of grease, best not risked in a Mini. I have seen CVs and pots supplied with yellow grease, probably LM, and that is ideal in the nipples and many other places, but will rapidly ruin the CVs and pots, as it lacks both the molybdenum disulphide lubricant and the sticky bentonite.

 

I suggest that when you get whatever new parts (again) that seem to be necessary, you do a trial fit of the pot to the shaft, off the car, and feel for free play in the splines, in and out as well as from side to side, and report back with what you find, so maybe someone can come up with more constructive suggestions. I am suspecting that you possibly are yet another victim of bogus Chinese parts, so perhaps you may want to be very careful about where you obtain the next ones. I wish I could tell you which parts are known to be good, but it is not as easy as that. Bogus parts are a menace in every industry.

[Dan]

You say you bought new shafts, new shafts come without circlips. Did you buy and fit new clips too? Did you try to rescue the clips from the ruined shaft?

[naughtyboydan]

Dan it was a brand new shaft that was on to start with and a spair the went on after. The C.V joint is brand new that it keeps coming out of. They boath have standard clips on them. And its only a 1275. No mods on the engine just a 1275. I used cv grease in the shaft splines. The clips on the shafts were in good condition so no need to change. It has happened to 2 sepret shafts now cant go wasting money. Will put a picture up later.

[Dan]

Yes please, pictures always help.

[GraemeC]

Where were the joints bought from? I'm sure I've heard of some that hadn't been cut properly and didn't have a groove for the clip to locate into

[naughtyboydan]

These C.V's have no grove in them. Cant quite remember where they are from. But we dod only pay about £27 for them.

[tiger99]

I think I have confused the issue, and myself, because surfblue was talking about the POT and you were referring to the CV. I should read things more carefully.

 

The locking clip arrangement is very similar in both cases, but at the CV end of the shaft there is a heavy square section clip in the inner groove, and if that is missing, the shaft will push too far in, and move back and forth due to suspension movement, until the locking clip disengages. Also, the inner member of the CV may be fitted wrong way round, which prevents the locking clip from engaging properly.

 

Please also check that the shaft is the right way round, the rounded groove(s) used by the Rover tool for extracting the shaft from the pot joint should be at the outer end.

 

Also, has the suspension been set up with a lot of negative camber?

 

Can you confirm that the splines have failed, or has the shaft just disengaged?

 

Eit: There is no groove as such in the CV, just a chamfer on one side and a recess on the other. You can take the CV apart and fit the inner member on its own to the shaft to see that all is well.

Edited by tiger99, 16 March 2014 - 07:12 PM.