Date: Thu, 17 Dec 1998 05:44:01 -0700
From: Dave Edge
Subject: [imps] Gearbox
If everyone remembers my problem with the vibrating noise coming from the flywheel, I reckon it could probably be best explained by a bent input shaft, in view of this, does anyone have a gearbox for sale.
Anything high geared or five speed would be nice.
Dave
From: Smith, Neil
Date: Thu, 17 Dec 1998 13:56:59 -0000
Subject: [imps] Re: Gearbox
I just had to replace the gearbox in mine, and I had a bit of a problem finding one. I ended up buying the box from the Imp in the scrapyard in Wolverhampton. Thanks to Nicola Burgess for that tip.
Good luck with the search.
Date: Fri, 18 Dec 1998 07:59:12 -0800
From: Kenneth Barlow
Subject: [imps] Re: Gearbox
I have about 7 lying around here in Nz, not that it is of any help to you over there.
Kenneth
Date: Thu, 17 Dec 1998 19:10:07 +0000
From: am018 Andy MacFadyen
Subject: [imps] Re: Gearbox
On all boxes Imp (JK and factory) The input shaft is mounted via a semi flexible muff coupling it is very unlikely to be bent --- in any case it is very easy to change anyway once the box is out.
More likely (1) you have a damaged clutch, the Spigot bush at the end of the crank is damaged or (3) The flywheel is out of balance (I once saw an Imp engine shake itself to bits because the crankshaft had been changed).
Andy
From: Gary Henderson
Date: Fri, 18 Dec 1998 09:57:39 +1300
Subject: [imps] Re: Gearbox
Hi Dave
Are you sure it's not just excess run-out of the thrust-pad on the pressure-plate assembly? That sets the release-bearing going like a bucket of bolts in the works...
One advantage of the conversion to a release-lever pressure plate is that you can adjust the runout to zero. (No good for the 60 BHP-plus brigade though.) The other advantage was that I could get one when I needed it - it's the same one as Morrie Thou etc used.
Good luck
GaryH
Date: Thu, 17 Dec 1998 23:06:48 +0100
From: Carsten Bußmann
Subject: [imps] Re: Gearbox
Hi,
I just recognized my Imp gearbox is losing oil, along the driveshafts.
Haynes' book tells me to fit new driveshaft fittings- but where to take them from ?
any idea (Maybe from a Volvo :-)).
Bye,
Carsten
From: Gary Henderson
Date: Fri, 18 Dec 1998 11:34:05 +1300
Subject: [imps] Re: Gearbox
Hi Carsten
If they are the older style, with the flange held onto the shaft by a big stake-nut, undo the nut, take the flange off, and fit a 19 mm O-ring as commonly found in domestic water-tap bodies, placed just at the inboard end of the splines. Replace & restake the nut. This was a factory service modification and has worked on mine for over 10 years so far.
Becuase of the robust side-bearings, the shaft-seals seem to last 34 years and still counting...I can look up the generic typenumber of the side-seals if you need to know it.
Cheers
GaryH
Date: Fri, 18 Dec 1998 09:05:56 +0000
From: am018 Andy MacFadyen
Subject: [imps] Re: Gearbox
Why not go back to using solid wheels as well, diaphram clutches were a major advance.
Andy
From: Gary and Carol Henderson
Date: Fri, 18 Dec 1998 22:53:17 +-1300
Subject: [imps] Re: Gearbox
Hi Andy
They give a lower hold-down pedal force for a given torque capability, but there is no free lunch...
I could buy a 6.25" lever jobbie at the time off the shelf; I couldn't get a 6.25" dia & wasn't going to refit the bloody inadequate 5.5" again.
The bonus was I wasn't stuck with however many thou of thrust-pad runout the supplier's accountant figured I could tolerate. (Remember the thread about cracked release bearings a while back?)
A 6.25" lever-type hoses all over a 5.5" diaphragm!
I have no quarrel with the fact that the same size diaphragm would handle more torque and/or give lighter pedal. For a standard 875, dwelling at the top of what in much of UK would qualify as a mountain, the lever-type has proven a practical, civilised and (most important) available solution.
Cheers
GaryH
Date: Fri, 18 Dec 1998 02:57:23 -0700
From: Dave Edge
Subject: [imps] Re: Gearbox
Could someone describe this term 'run out'. I think that this fault is extremely unlikely to be with the clutch on my car because I have experienced it in the two brand new borg and beck clutches that I have had recently.
The fault is as follows: when the engine is revving beyond about 1500rpm and the clutch is pressed, when the gear lever is moved to any gear a vibrating sound is heard (underneath I can see the driveshafts snatching) which I can only assume to mean that the clutch is grabbing. bearing in mind that the flywheel is definitely not moving (although it is still chattering on a web on the B1 block). My conclusion is that the driveshaft is bent, possibly at the very end, and its location in the end of the crankshaft is non concentric; when fully engaged the shaft is held concentric but when unsupported with the clutch disengaged it is running out of true.
Any ideas(it's driving me mad)
Dave
From: Gary and Carol Henderson
Date: Sat, 19 Dec 1998 02:00:01 +-1300
Subject: [imps] Re: Gearbox
Hi Dave
In this context, runout means an axial wobble, whether the parts are concentric or not. (Like a buckled wheel for example.) It doesn't sound like your beast - it's worst with clutch engaged (pedal fully released) the free-travel allowing the release bearing to rattle like crazy.
There's a problem with your diagnosis too - the spigot-bush in the centre of the flywheel should maintain the gearbox primary-shaft well & truly centred at all times! Is there any possibility that it's missing? Or at best completely stuffed? (Such as by a new one having been fitted without the required overnight soak in oil first.) Easy to change once you're in there - no need for special tool RG-XYZ. Just a close-fitting drift, a teaspoonfull of grease in the bush first, and a hammer. The drift goes in and the grease displaces the bush by hydraulic pressure.
You mention the flywheel chattering on a web of the block. This suggests axial run-out there too - has it by any chance hung up on a burr on the dowel, preventing it seating 100% properly?
IF the primary-shaft extension is indeed bent, however unlikely, it will show as lopsided wear marks on the spigot-end of the shaft. If the shaft itself is bent enough to matter, you will pick it up by turning it with a ruler clamped to the bellhousing face with an end touching the shaft. All things are possible, including bending an Avenger half-shaft without apparent damage to the aloy wheel!
Good hunting
GaryH
Date: Fri, 18 Dec 1998 06:16:30 -0700
From: Dave Edge
Subject: [imps] Re: Gearbox
Hi Gary,
What is a spigot bush?
I think that maybe we have the problem. Could you describe a spigot bush to me, I am absolutely convinced that there isn't one there because it would cause the described syptoms.
When I bought the new engine, I didn't use my old crank but Roger & John gave me one from their old engine which I had reground, it is possible that the bush is either duff or not present. Sadly I have thrown my old crank in the bin so I don't have anything to compare it with.
This is also borne out by the oil that is currently leaking from the gearbox oil seal, presumably because it is being shaken as the shaft moves around.
Oh and who sells spigot bushes.
Dave
---
Bristol
From: Mark Chater
Date: Thu, 17 Dec 1998 18:37:34 -0000
Subject: [imps] Re: Gearbox
Dave
Couldn't you just replace the input shaft? Malcolm Anderson gave me said item when I bought a new clutch to use as an aligning tool just after I bought my first Imp.
The only gearbox I have not fitted to a car at present is has overall ratios of 6.55 and 5.3 (about 11.7mph/1000 revs) in 3rd and top, giving a theoretical maximum of about 106mph at 9000 revs on standard wheels/tyres.
It is already allocated to a vehicle however.
Mark
Date: Fri, 18 Dec 1998 16:02:18 +0000
From: am018 Andy MacFadyen
Subject: [imps] Re: Gearbox
The little bush in the end of the crank that supports the end of the gearbox input shaft, they often come out and get lost durring rebuilds. On most Imps it is an 'Oilite' bronze bush on very late cars it may be a needle roller. Both types are interchangeable --- the bronze bush is preferable as the needle roller is more easily damaged. Andy
From: TMo5018257@aol.com
Date: Fri, 18 Dec 1998 11:24:37 EST
Subject: [imps] Re: Gearbox
Hi Dave, Andy et al,
Yes, it sounds to me like this is the most likely cause of your problems -
To reiterate what Andy says, there should be a bronze (or needle roller) bush with an interferance fit in the back end of the crank that the input shaft to the gearbox locates in. If it is missing the input shaft can wobble about, and can smash the centre of your clutch out (you may or may not remember the poor sod at National Weekend 1996 who found it missing on a rebuilt engine en route to the event - no clutch- and set about replacing it in the middle of a field - with a bit of help from his friends, ie most of Dorset Area Centre & Derby Area Centre - and all this on a fresh engine costing well over £650!!!!!).
As already said, this bearing is phospher bronze and needs to be soaked in oild for about 24 hours before fitment - in fact, it is best boiled in oil but this stinks the kitchen out rotten (when we did this in the field, we did this using a bean can over a primus stove - nice and safe). Fitting is just carefully knocking it home with a suitable drift. If there is the remains of an old bearing, this can be removed using Gary's method, or if that doesn't work dig it out with a selection of bent screwdrivers, hacksaw blades etc.
Careful not to leave any burs though...
Speedy Spares used to do them, but on my list they say they have no stock - may be worth a call anyway. If not try Impetus, Malcolm Anderson etc...
Best of luck,
Tim
From: Gary and Carol Henderson
Date: Sat, 19 Dec 1998 09:54:20 +-1300
Subject: [imps] Re: Gearbox
Hi Dave
The spigot bush in question is a small 'Oilite' sintered-bronze bush, in the end of the crankshaft. It locates the 'spigot'- a smooth-ground protrusion of the gearbox primary shaft or, in this case, the shaft-extension - which otherwise would be very poorly controlled.
I don't know where you could best get one over there, but one salvaged from a dead crankshaft would be infinitely better than none at all! I guess a range of Oilite bushes can be had from engineering-supply firms. Otherwise, you could try for something from the SKF 'Glycodur' range. (By the way, neither of these types can be reamed to size.) If desperate, a plain bronze one could be turned up but this is likely to chew the spigot eventually. In that case, a felt pad impregnated with high melting-point grease placed down the hole might be a good idea.
You could convert to a modern needle-roller type, but I suspect that's not easy, because the 930 users seem to fit 875 crankshafts just to avoid the incompatible needle-roller problem! Anyone over there able to help?
Good luck
GaryH
From: Nickcleak@aol.com
Date: Sat, 19 Dec 1998 05:01:18 EST
Subject: [imps] Re: Gearbox
> All things are possible, including bending an Avenger half-shaft
> without apparent damage to the aloy wheel!
Exactly .. !
I had this on a Volvo 940 !
the half shaft is about 1½ inches thick
Nick ..
From: Nickcleak@aol.com
Date: Sat, 19 Dec 1998 05:01:16 EST
Subject: [imps] Re: Gearbox
> he fault is as follows: when the engine is revving beyond about 1500rpm and
> the clutch is pressed, when the gear lever is moved to any gear a vibrating
> sound is heard
Try looking at the 'cake frill' gearchange rod support bushes , one at the front and one at the rear ..
Nick ..
From: Mark Chater
Date: Sat, 19 Dec 1998 16:49:16 -0000
Subject: [imps] Re: Gearbox
>The fault is as follows: when the engine is revving beyond about 1500rpm
>and the clutch is pressed, when the gear lever is
>moved to any gear a vibrating sound is heard
I had a similar-ish problem - when the clutch was depressed with the engine in gear a truly awful grinding noise would start from the bellhousing area.
It was also difficult to select any gear from standstill. This started in the middle of a trial so I had the sump guard fitted which reflects all the sound back into the passenger compartment.
It turned out on removing the engine that the spigot bush had disintegrated and shards of phosphor bronze had become wedged between tthe clutch plate and the flywheel with the result that when the clutch was disengaged with the engine in gear (so the first motion shaft is spinning at a different speed to the engine) the bits of spigot bush were being dragged around the flywheel. I had soaked the bush before fitting, but not boiled it, which is what I did with the next one. If you think that smells bad, try using the oven to heat up the cylinder head to replace valve guides - the house will be filled with oily smoke.
This also resulted in a knackered oil seal, which I am yet to replace as it appears from the haynes manual that I have to take the whole gearbox apart to do it, that is before I read the 'don't even think about it' message in the 'Supplement for later models'. Is it really that difficult?
Mark