7 replies to this topic

[Bell-nose]

Hi,

 

can anyone tell me how to fit the primary gear back on the crank please - it goes so far up then gets stuck. Does it need grease or oil?

 

Thanks

[Gremlin]

Is the crank clean?

[Cooperman]

Have new primary gear bushes been fitted?

If they have you need to measure t5he crankshaft diameter very accurately, then take the primary gear to a precision engineer and have the bore of the new bushes machine to the crank diameter +0.0025" +/- 0.005".

Do not grease the bushes as they run 'dry' on the crank.

[Bell-nose]

The crank is clean and no new bushes fitted. I have to be honest taking the primary gear off was a hard process as it seems tight on getting it back on is looking equally tough.

 

Should it simply slip on or should their be an element of force or firm pushing?

Edited by Bell-nose, 17 March 2014 - 09:56 PM.

[Cooperman]

It should simply slide on easily. The running clearance should be sufficient to prevent the gear from seizing on the crank due to the bushes getting hot & expanding. The latest Manganese-bronze bushes seem to need a bit more clearance than the older phos-bronze bushes.

[myredmini]

is it getting caught on the groove where the "C" tab goes to lock the primary gear in place? i have seen cranks where the edges of the grove have a small raised bit and it damaged the bushes.

[Cooperman]

Linish the edges of the C-washer groove so that the gear will easily slide over it.

Make sure that you measure and check the end float of the fitted gear and fit a thicker inner thrust washer if necessary.

[tiger99]

Cooperman's advice is very appropriate, and I had to do that at least twice, because the C washer had raised a burr exactly as myredmini suggests. I think it is fairly common, because the C washer is hard, probably made from "gauge plate", while the crankshaft is just a plain casting. A small triangular or flat needle file is a useful tool, you probably only need to remove a tiny amount of metal from the edge of the groove.

 

The only thing I would add is that you should check the bore of the primary gear very carefully for signs of scoring. Often a spiral groove develops when people twist the gear to "unscrew" it from the crankshaft, or a straight scrape if they forcibly pull it off without turning. Either may cause an oil leak, because the sealing relies only on the close fit of the bushes on the crankshaft, plus the radial grooves on the inner thrust washer, and drillings in the primary gear, designed to centrifuge oil that tries to get into the bush area back into the transfer case.

 

Check also your crankshaft surface. There is often some very light circumferential scoring, which is usually ok, as there is only movement when the clutch is disengaged. Any roughness or very light corrosion should be carefully polished away, ideally by setting the crankshaft in a lathe and spinning it slowly while applying some fine abrasive paper by hand. Last one I did had very minor rust only, and I just went round it by hand with Scotchbrite and a bit of oil.

 

I have never had to do this, but think that it is possible to have the crankshaft skimmed and a sleeve fitted if the surface turns out to be unacceptable. Or, it could be metal sprayed, or new, thicker bushes could be made.

 

But I think that the edge of the groove is likely to be your main problem, as you would have seen wear and corrosion.