Powdercoat on mating faces?

[B reg 90]

As the prop bolts are not 'fitted', ie reamed out holes with bolts with machined shanks, the torque is transmitted between the prop flange and diff flange via friction between the metal faces. The clamping force of the prop bolts holds the flange faces together tightly enough such that enough friction is created to transfer the design torque level.

So.... Introduce powder coating:

1/. You have altered the coefficient of friction - my guesstimate says that is lower. So the flange faces will twist against each other when you load the joint in reverse and forwards direction.

2/. The powder coating will crush (it's softer than steel) as the flange fave move.

So the joint will become slack as the powder coat disintegrates, the friction levels will be inadequate to transmit the torque. The bolts will then end up driving the diff. These will elongate the prop and diff flange holes and give u drive train slack.

To summarise - don't powder coat the flange faces!

Adrian

[Lewis]

Breg90 - the OP is referring to the axle casing end flanges where the stub axles mount to, not propshaft flanges

Ross, without giving anything away, the best coating for the underside of a vehicle I ever saw was spray on bed liner. The coating was 7 years old and had some scars but was seriously tough - some of it had been over sprayed onto some fixings we needed to remove - we ended up cutting the fixings off as we couldn't clean the heads up enough to use tools. The vehicles it was used on were driving through Caribbean Sea water on a weekly basis, in an environment that was truly destroying vehicles - we saw year old hilux's and amaroks with rust holes in the doors. The only issue with that coating for our use would be the textured surface retaining dirt

The place applying the coating thoroughly washed down the underside of the vehicles, then sprayed them with an aggressive solvent cleaner, before applying the bed liner

It's worth noting that bed liner type coatings available in the uk may not be the same/as resilient as the ones I refer to above. The country where the above vehicles were located has significantly more lax coshh and H&S legislation that Western Europe (as an example when buying shutz I was offered "with asbestos" or "regular")

[Tanuki]

I really don't like powder-coating: some years ago we had a number of trailer-mounted telescopic antenna-towers made up and the various bits of metalwork were part galvanised, part powder-coated, part Cadmium-plated and part acid-etched-then-two-part-Acrylic-painted.

After acceptance-trials in the UK they went out to VP8-land as deck-cargo and by the time they arrived the powder-coating was showing signs of lifting, with rust creeping under it. After three years in the open we were replacing powder-coated parts as they failed safety-inspections because of rust. The non-coated parts are probably still down there and working just fine.