Differentials

Differential, Installation procedure

"No shims necessary!? Unlikely."

Procedure for installing standard diff:

• Install differential assembly skewed over to clutch side before putting on the casing
• Tighten casing nuts ligthly (2-4lb/ft) to allow assembly some freedom to move
• Put on end cover and gasket on clutch side
• Tighten end cover bolts to 16lb/ft. This will push the diff assembly over to the radiator side
• Put on the rad side cover without gasket, and tighten bolts finger tight (too hard will distort cover) and evenly
• Measure with feeler gauges the gap between end cover and diff casing (where the gasket will sit) at several places - this is your measurement "A" as used below
• If not same measurement, loosen and retighten bolts more evenly
• If you could not get any feeler gauge in, something is probably wrong. You should recheck the diff and bearings

Now on to finding the correct shim:

And some examples:

In the third example, you probably have done something wrong, like not pushing over enough in the first step above, or there is a mismatch of components.

Now if you're picky, you may install the shims and then measure again. Then you should come up with 0.008" to 0.009". I would go for 0.009" to get max specified preload. As the bearings are run in, they will loose some preload. I prefer high preload, as no preload makes sounds, wears down bearings and make it more prone to piss oil.

What may have happened to you is:

• Not pushing it over, thus having some slack on the clutch side mucking up your measurements
• Being too "finger tight" here, thus not pushing up the left end cover enough

If you assemble the whole shebang and torque down the casing nuts before the end covers, the casing will pinch the bearings. Then as you torque down the end covers, they will push the diff and bearings over to the side away from the cover that has no slack against the bearing. The other cover will have air between it and the bearing, but there will be preload. Until the differential assembly gets a sideways force that overcome the pinching force of the cover that is. Such forces may be a result of the helical pinion, or your hammer blow.

OK. All that aside. It is *not* this setting that make your inner flange wobble!

That is the play of the cylinder shaped part of the flange in the bushes of the end cover. Did you check this? What Haynes says is to "fit a new cover". (Thank you Mr. Haynes! Got any stock in the spare parts dept.?) The play in the differential gear shafts in the diff cage bushes also affect the sloppiness of the shafts, although they seldom are very worn down.

What you should do is not reinstall parts that does not have a good fit when you put the flange into the cover. Alternatively to grind down the flange until all wear is taken out, then fit and ream new bushes to the end cover. Oilways must also be carved into these bushes. To my knowledge you cannot buy the needed oversize bushes, and need to make them yourself.

If the fit is sloppy, then your inner CV's will also slop. And the seals will be left with an impossible task, so they will let oil out onto your driveway.

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Differential shim preload

"I now understand the 0.002" bearing preload which previously I could only visualize as a 0.002" space. DOH. Well at least I finally get it now.

Regarding preload, I wasn't sure how much to shim as my measurements were ambiguous. While a 0.012" feeler gauge would fit between the end cover and the diff. cover, only a 0.006" would fit between the end cover and the gearbox casing. This was with two 0.020" and one 0.012" shim in place and no gasket.

I figured this was going to be the best compromise I could reach. However, I feared that on the 0.012" side I was over-shimmed. However, my father's opinion was that since the output shaft can be finger-turned with the end cover torqued into place, it's probably not excessively preloaded."

Differential drive ratios - what's yours?

(See also Final Drive)

Differential unit swap

Some say this can be done with the engine in the car, but this will require:

• bolts on the diff cover, not studs
• the ability to get into the radiator end of the gearbox via the speedo drive housing aperture.

Assuming engine out...

It is a major job (engine out, box off, box in pieces) but something the DIYer can do. If you take your time and do it properly and carefully then there is no reason why it shouldn't all work ok afterwards. Gearboxes look terrifying at first but once you know how it works and how to dismantle and re-assemble one they are easy.

The good news is you don't need to remove and dismantle the mainshaft (the nasty bit).

You will need to:

• remove and swap the pinion (you *DO* have the pinion for this new diff don't you???)
• You will need to lock the box into 2 gears at once ...read haynes on this....
• rotate the selector rod fully anticlockwise <?> so that it moves past the selector levers
• move both synchro hubs across (either direction will do, I think I locked mine in 2nd and 3rd)...
• DO NOT be tempted to jam a screwdriver into the gears to jam them!!!
• Remove the speedo drive housing from the radiator end
• The big nut on the end of the mainshaft is 1.5" (deep 1.5" hub nut socket) and it is (or should be) VERY tight...150lbft I think
• Turn the box over, stand on it and using a long bar on you wrench, swing on it. Getting this b*stard undone can be some fun!
• Once that nut is off, pull off the pinion.

Assembly is the reverse of removal!