27 replies to this topic

[Goacher65]

Firstly I would appreciate if people read the symptoms here before randomly spewing possibilities for loss of drive. Right here goes:

 

I have recently finished building my 'Rally' Mini from a bare rolling shell which I bought nearly 4 years ago. I have fitted a rebuild 1380 metro engine coupled to a rebuilt (by myself) straight cut gearbox, including a Guessworks X-pin diff. I have had a previous clutch issue which having taken the clutch blackout and rebuilding, is solved. This turned out to be incorrect spacing of the backplate to the lightened flywheel causing dis-engagement troubles. Having read a very good article by Minispares, this was a relatively easy fix, apart from needing to remove the bell housing and flywheel with the engine in situ. With this now sorted I got the remaining bits of trim, glass, wiring sorted and booked the MOT, excellent no?

 

Well it passed the MOT, with one slight glitch.... loss of drive meaning the tester wasn't able to drive out of the brake rollers as the last stage in the test! Anyway, being a friend of mine, he was happy to pass the MOT as there was nothing else of any concern to be found (to my relief!). I readjusted the clutch throwout stops and checked the hydraulics were giving the correct amount of travel, and most importantly that the clutch arm return stop wasn't preventing the clutch fully engaging. All was well, and when tried again, the drive had returned... although still with no explanation. I put some tax on it, and decided I'd attempt the journey home. About 500yards off the yard of the garage, I lost drive at traffic lights and wasn't able to get going again so pushed round into a side road. I checked everything was in place and that the arm was returning fully and all seemed well... At this point I tried driving up and down a side road and couldn't get the problem to re-occur. I carried on my journey home and the drive dropped out a handful of times when cruising gently in 4th at 1750-2000rpm but dip the clutch or change down to 3rd and it'd re-engage. I probably drove about 20 miles yesterday afternoon and it only dropped out another twice, again at low torque cruising in 4th. 

 

I got home and stayed in for the afternoon for a few hours, time for the car to cool down, and when I came to go out in the evening got another 300yards up the road and then lost drive again. It then came back for long enough for me to park it on the drive and then I gave up and left it until this afternoon as it was dark and I was starting to get peeved...

 

I went out this afternoon and started her up, selected a gear and tried to pull away and nothing. I did however notice that the speedo flicked around a small amount. I then tried selecting 4th, and the speedo flicked around hovering over 40mph. Now this now tells me that the clutch is not the problem but that the gearbox is engaging and the output shaft is turning as the speed 'displayed' is slower in 1st than it is in 4th, suggesting what i'd expect at the RPM in that gear. I didn't want to spend too long running it incase drive returned unexpectantly and I found myself "wearing" a garage door!

 

So the question is, what could be the break in drive, that is intermittent, and the only correlation I can come to is that its improved when it's all up to temperature and already covered some miles. Also, possibly slightly more confusingly, why it's intermittent. Has anyone ever had this before or can suggest what to try for a solution. Have I left something loose in the gearbox? Have I forgotten a spacer or similar? Any help would be much appreciated, I've explained as best I can and sorry for the essay!

 

Thanks in advance! H

[Gadgets]

Hi

Could be that you have chewed off the splines in the actual drive flange/s and its only picking up drive with little power going through the drive shaft's?

 

Or the splines on the CV joint have worn?

 

That would be my first point if you are sure your clutch is engaging the gears ok and you have drive output.

 

easy to check, jack it up at the front, with engine turned off, put in second gear  and with a mate turn the front wheels, do you both have resistance or can both of you turn the wheels very easily??

[Goacher65]

I haven't yet tried jacking up a corner and turning to feel the movement in the diff. Though this is the next step when it's light again...

 

In terms of splines on things, its the complete opposite, its when the drive is slack that it drops out. When I buried my foot it pulls hard right up through but I slowed off because I'm still running the engine in and don't want to give it a lot of thrashing. 

 

Even when I'm jacking up, it's the fact the the drive is either there or not there, at the moment I don't think it is so I don't expect and resistance but if the drive was there I'm sure it would be. How can the problem be intermittent?!? It's driving me crazy!

[Spider]

Hi

Could be that you have chewed off the splines in the actual drive flange/s and its only picking up drive with little power going through the drive shaft's?

 

Or the splines on the CV joint have worn?

 

That would be my first point if you are sure your clutch is engaging the gears ok and you have drive output.

 

easy to check, jack it up at the front, with engine turned off, put in second gear  and with a mate turn the front wheels, do you both have resistance or can both of you turn the wheels very easily??

 

 

I tend to think Gadgets is probably on the money here. That you say you have indictaion on the Speedo shows that there is drive at least as far as the Mainshaft in the Gearbox. Loss of drive 'drown stream' from that normall induces a pretty savage noise and usually permenant loss of drive (but not always), as it would be a stripped / split Pinion. lost teeth on the Crown Wheel, Broken Output Shaft (from the Diff) or Broken Drive Shaft (usually at the CV). About all that does spring to mind that will give intermittent drive and no noted noise would be stripped splines, especially if say on 'Drive' where the CV Nut may tighten, but then loss of drive on the over-run where it may loosen.

[Goacher65]

Surely the drive is then at least to the output shaft so rules out gearbox problem. Must be either the pinion on the output shaft or anything downstream from that which is either diff or output shafts. 

 

The diff is a brand new Guessworks x-pin, the pot joints are new, the driveshafts are the "uprated" Minispares Monte driveshafts, and then CV's are also brand new, into metro hubs that has splines in good condition.

 

There was an amount of engine braking too as I drop down through the gears when coming to a stop, which never lost drive at that point. The hub nuts were also done up to the specific torque.... worryingly tight for single split pin hole...

Edited by Goacher65, 16 December 2014 - 08:51 PM.

[Goacher65]

Today I shall carry out further investigations...

[Spider]

Can I also just say it's always wise to keep on open mind when fault finding and assume nothing, trying looking at it all with 'fresh eyes' (like you'd never seen any of it before) and just because new parts are there, doesn't mean they aren't playing up in some way.

[Goacher65]

I shall indeed. I'm thinking jack one side up and feel whether there is any resistance through the diff with it in gear. And then also try with the front on axle stands putting it in gear with the engine running and check if anything visible is turning outside the casing to rule out splines or cvs.

[Spider]

Yeah, but first, with a decent marker, mark the CV shaft and the Drive flange so you can see if there's been any movement / change.

[black olive]

our lack of drive problem was caused by a "mechanic" who changed the clutch to sort out a judder problem ( which turned out to be a rear subframe mount debonded) somehow managing to reassemble a pot joint with a missing ball in the "mace" . found this out by standing at the side of the car whilst the clutch was let out in first, the pot joint was jerkily rotating on the shaft. ( and after Id split the engine and box and had the box in for investigation as he reckoned it was a diff problem ) not saying it is this, but dont assume because something is new, its ok. 

[Gadgets]

Easy enough fix then, good result but use a different "mechanic" from jow on lol. Glady you got it sorted though. (but very disappointed that the splines were not the fault lol)

[Goacher65]

Well to update. First side I jacked up, near side, the pot joint isn't turning when I turn the wheel. Driveshaft is spinning in the joint. Either a ball has dropped out into the gaitor when fitting or a brand new pot joint has dismantled itself.

Still wonder how this has been intemittent, will dismantle and ensure that splines on the diff are still ok before reassembling.

[Cooperman]

Well, now you have identified the problem and thankfully it's easy to fix and the engine doesn't have to come out (again).

Check thoroughly inside the pot to ensure that no damage has been caused. You can leave the 'pot' engaged in the diff output and just pull the end of the shaft out. That way the gaiter will be off with the shaft and the fault will be immediately obvious.

It's still strange that the drive was intermittent, but that's Minis  .

[Goacher65]

Yes Cooperman, I'm glad, as you can imagine, that the engine isn't coming out. Worth a call to Minispares I think as they come sealed up with the gaitors on and I haven't tampered with it. Shame to lose the oil after 20 odd miles but not necessarily a bad thing to have a flush out after a fresh engine/gearbox build, just not quite as soon as I was anticipating!

 

Thanks again for the comments and thoughts! Now where is my ball joint splitter? (*scratches head*)

Edited by Goacher65, 17 December 2014 - 12:26 PM.

[Cooperman]

With Mini-Spares excellent customer service and care I'm guessing they will just send out a replacement rather than have you fiddle about trying to sort the one you have. Speak with Simon there who is always so helpful.