14 replies to this topic

[mickyh]

Advice needed please, at last I think I have found my problem after buying another primary gear ready to insert I found that the old one is fine and that the bolts houlding the clutch housing to the engine were loose, however I used the correct torque 18lb/ft I find that it is very hard to move the idler gear!! Even using the primary gear you have to give it some force, I would have thought it should spin quite freely?? Can anybody advise?

My main issues were a whinning clutch when released and difficulty changing gear, new gearbox and clutch!

Thanks

Edited by mickyh, 29 September 2009 - 07:26 PM.

[mickyh]

BUMP

[MRA]

I think that as is so often the best advice is for you to get a Haynes manual..... at a fraction of the cost of repairing your current handywork

This will then give you the confidence to work on your car and hopefully doing so in safety, both for you and other road, pavement, shopping centre users....

If you had been working on the brakes you may not have been able to ask your question above and that would not be good at all

So the answer you are looking for here is that the idler gear (transfer gear or drop gears) need to be correctly shimmed... the gap between the flat surface of the gear and the housing need a very small gap, not too big and not too small, now you have first hand experience of too small, too big will destroy the parts just as easily

This gap is often called the working tolerance and allows items to heat up but not to "drag" which will cause heat..... or to rattle which will cuse other failure modes.

The gap should be between 0.003" and 0.008" ("=inch) or in metric 0.076mm to 0.203mm

Hopefully this helps, but do heed the safety hints above it could be yous or someone elses lives on the line

[mickyh]

Yep, have haynes manual, but it doesn't help much here!

I take when you refer to shims your are relating to thrust washers which I haven't changed the only thing that has changed on the drop gear is the gasket and it has been torqued up accordingly as per manual. As we have not had the crank out and not changed any parts here I cant see why we would adjust end float etc. I just found it strange that the idler gear is very hard to turn after following instructions accordingly.

Many thanks

[bmcecosse]

The thickness of the gasket used is important - they come in different thicknesses for this very reason! It MUST rotate easily when fully bolted up.

[MRA]

Have you got the gearbox off the engine ? if so you can fit the transfer housing and measure the clearance.... The primary shouldn't matter as the end float is taken up within the crank and primary gear assembly.....

The idler clearance is defined by the transfer case and the gearcase and gasket ( the gasket can differ in thickness should be about 0.032" thick when new)

Another method uses a special tool made for Rover which you can use instead of the thrust washer or you could try a bit of blue tack or plasticene..... fit it all together and then remove and measure the thickness take away the 3 to 8 thou of an inch and this will give you a close "guess" at the correct thickness

If its an A series then check the length of the shaft out each side of the idler gear as they where different lengthes

Also I appoligise if my last post was a little rude it wasn't meant to be

[mickyh]

Ah, that makes sense, we bought the 'pack' from a reputable source; now I see they offer an exact one! why sell the pack then?

[mickyh]

Will also check the lengths of the idler shafts, largest towards gearbox?

Thanks

[MRA]

Ah, that makes sense, we bought the 'pack' from a reputable source; now I see they offer an exact one! why sell the pack then?

Not too sure what you mean by pack etc..... is it a gasket pack ?

we also sell a gasket pack and we sell individual gaskets, there should be only one type of transfer housing gasket..... however I have seen thicknesses vary by over 0.020" the correct gasket should be about 0.032" thick give or take a few thou.... 0.030" to 0.035"

I don't know who your reputable source is ? but personally I think that sometimes reputable is confused with well known

[mwalsh]

The gaskets come in different thicknesses based on source. These thinner gaksets aren't necessarily bad, just different. I think the only thing you might have been able to do to throw it all together and not worry about checking idler gear clearance is to buy the very same gasket (or thickness of gasket) as you took off. I suspect the new one you used is thinner, and made idler gear clearance that was perhaps less than optimal to begin with even more non-existent. Hence your problem now.

I still personally think you're going to have problems with a thicker gasket. They aren't THAT much thicker. So while you might get better idler clearance, I think you'll have to ask yourself if it's going to be in spec or not. I suspect it's either not going to be or will just barely be.

The point in having adequate idler gear clearance in the first place is to avoid having the gear either seize when hot or drive the thrust washer face into the flywheel casing. Both scenarios are bad - destruction of flywheel casing and drop gears will probably be the end result and no doubt stray metal will get sucked into other areas of the engine. My advice would be to sort the problem properly.

[mickyh]

A little confused on the positioning of the idler gear, Haynes quotes as follows:

32 Refit the idler gear to its bearings in the
transmission casing, turning it slightly to mesh
with the other two gears as it is installed.
Ensure that both the thrustwashers are in
position, one each side of the idler gear: if the
later type gear is being fitted, the longer boss
goes toward the transmission casing.

Does the larger shaft sit in the housing for the clutch/fly wheel or the gearbox? I think gearbox?

Thanks

[mwalsh]

Does the larger shaft sit in the housing for the clutch/fly wheel or the gearbox? I think gearbox?
Thanks

Gearbox is correct. That's what they mean by rather long-winded (and somewhat Americanized) term "transmission casing".

[mickyh]

thanks, playing it safe.

[MRA]

The gaskets come in different thicknesses based on source. These thinner gaksets aren't necessarily bad, just different. I think the only thing you might have been able to do to throw it all together and not worry about checking idler gear clearance is to buy the very same gasket (or thickness of gasket) as you took off. I suspect the new one you used is thinner, and made idler gear clearance that was perhaps less than optimal to begin with even more non-existent. Hence your problem now.

I still personally think you're going to have problems with a thicker gasket. They aren't THAT much thicker. So while you might get better idler clearance, I think you'll have to ask yourself if it's going to be in spec or not. I suspect it's either not going to be or will just barely be.

The point in having adequate idler gear clearance in the first place is to avoid having the gear either seize when hot or drive the thrust washer face into the flywheel casing. Both scenarios are bad - destruction of flywheel casing and drop gears will probably be the end result and no doubt stray metal will get sucked into other areas of the engine. My advice would be to sort the problem properly.

Some of the thinner gaskets (which are out of spec by the way just do not fit as the gap left between even the thinest thrust washers is too little....

The gaskets don't have to be "that much thicker" just enough to give you the correct tolerance..

Definately needs to be sorted correctly, if you have driven it like this then it's probably a new gear case and a new transfer case when I say new a good second hand unit would do.

[mwalsh]

Some of the thinner gaskets (which are out of spec by the way just do not fit as the gap left between even the thinest thrust washers is too little....

Well, if they are way too thin....clearly that would be a problem. The ones I'm thinking in terms of are the "green" Unipart and "pink" 22A2237B. Those are the only ones I've seen offered by reputable suppliers and personally purchased/used.