Howdy all,

Could I ask you to fill in the attached poll please?

As you may well be aware, the standard pressed steel diff cover plate on all manual 300 series models is of questionable quality. They're pretty prone to rusting through, basically, and once bent (at all) they're very difficult to get flat. In a word, they're a pain in the arse. Some time ago, Mac expertly made a prototype, which we've given to a foundry to get an idea of costs.

We should be getting indicative costings back from Chris' foundry contact tomorrow. If we want to do it, we either have to hit the "GO" button on Tuesday (yes, one day later...), or wait for months. Long story...

The new cover plate will be cast aluminium, milled flat, and generally full of booyah! It will be a quality piece, and Mac's prototype looks amazing. Unfortunately, I don't seem to be able to find a pic just now. I'm considering advising 300 series owners on the direction of Mac's house, so they can bow in his direction several times a day. His contribution to the 300 series scene is pretty huge.

A quick decision will have to be made...so when the figures come back, we need to be able to work out if it'll be viable. We won't be ripping anyone off by selling them for more than we have to...but we need to be able to cover the costs. If it's going to cost £100, but people will only pay £25, we will have to abandon the plan.

So here's the deal: how much would you be willing to pay - if necessary - for a diff cover plate?

I'm willing to front the money, as long as a) I'm actually going to get it back in a reasonable timescale, and b) I can make a little bit of beer money for my trouble. We're talking about a substantial amount of money here, so forgive me if I'm a little mercenary about this. I appriciate it's a community project, with input from various parties, so I don't want to take the piss...but I still need to make this work for myself, financially, if I'm going to do it. I think it's also going to be a lot easier to administer this way. Getting help from the VOC in a hurry just isn't going to happen. I will try to give George Mitchell (Friends of the Volvo 300) a call tomorrow to see how he's going, but I think he would want to quiz his membership first. I hope you appriciate what I mean by all that. I'm not trying to rip (or piss) anyone off...but this is essentially going to be done on a commercial basis, so I need to put a commercial hat on.

Anyway...vote away, and we'll see if this is going to be viable.

cheers

James

I also can't find any pictures currently... lame.

Right, to give all a heads up. Mac made a prototype cover plate when he was setting up his super diff gasket scheme. It's a really well thought out piece, and a lot stronger than the original. It would be cast in ali, a material that is more brittle than the pressed tin, however Mac has added strengthening ribs around, and the plate is thicker than standard so the only problem I can see here is with white roading (white as I think I'm the only one stupid enough to do this shouldn't be an issue) It certainly won't warp like the original did.

If this goes ahead, both me and the foundry want to make sure that these work properly and therefore, in true barley pickers style, want a "proper job". As cast ali shrinks by roughly 1.5% on cooldown if we used Macs original the bolt holes would be roughly 2/3mm out on pitch radially which isnt good enough... the whole point here is to stop leaks. So, Mac's plate will go to the pattern makers who also will be sent technical drawings (again provided by Mac in the main part) so that the flange is perfect. This will give us enough for the raw castings, which on completion will have the flange milled flat, and depending on the technique used bolt holes milled too.

I'm doing everything I can to reduce workload at the pattern makers and foundry to reduce setup costs here, and we need to know if this is going to work out. I wrote to George last week, but Foggy ringing him tonight is a great idea.

Please guys, opinions at this point are essential

Pix, Pix, Pix.






My head is now so large I can no longer get through my workshop door. Thanks guys!

Chris is absolutely right - my prototype was never intended as a casting buck but rather as a full size "what it would look like". It was made to exactly fit my gasket jig - which itself is made from a diff casing. The thickness of the cover was designed to take M8x20mm setscrews rather than the std M8x12 (naturally I would supply the correct option in my gasket kits) Before producing anything the prototype must be remade to account for shrinkage in the mould. I would suggest that no holes are cast but rather the bolt holes and filler plug hole be jig drilled afterwards. Also worth considering is a thread insert for the filler plug rather than direct tapping in the alloy. The breather passage could be cast in and cleaned up afterwards - the breather port was designed to accept a piece of resized 15mm copper tube (split and soldered) to (from memory) 13mm which would then accept the original breather box.

A large headed old fart.

Im trying to in-vision where this bit is? is it located on the back of the diff? Is the original really that weak? as my 5 speed is sitting in its arse in the shed and im woried it will of been bent outta shape now

Cheers Dan

p.s the prototype looks so much better then the original, great work Mac, and great work Chris and James for getting this thing rolling.

Now that's engineering! I think I'd pay 'whatever' for one of those, but might not be able to afford 3 any more, I have to buy a clio engine every month these days you know.

Postage to here is probably quite a lot, so can't choose option which I would choose if I would live in there, so it is in lowest category for me, sorry

That "new design" plate is just wonderful, far much better than the genuine one...

It's also looking quite cost prohibitive I'm afraid to say guys. We have decided that after waiting 5 years without having a new diff cover, we'd be silly to rush this. Luckily, there are several backup plans (which are running as we speak) so will keep you informed!

only 8 years gone by

Does it add any mechanical strength to the diff? I assume not since its a soft gasket.

You could 3D print it these days. For plastic it would need a thicker section for the bolt areas + longer bolts but I don't think it would need machined.. or worse case metal sintered. Would just be a case of getting oil compatible material.

Is there a 3D model available?

Once you have the stl its very easy to chose material and a cloup print service with a few clicks. Gives you the price straight away.

Id've thought not either - it's only very thin plate... nowadays 3D Printing one of these is probably the best way forward!

Sorry to dredge up an old thread, just wondering if anything further happened on this ?
Very interesting about the casting proposal, and I see there were 'backup' plans mentioned.
Even if a small run was made, with a higher price, I am sure they would sell to those who want to make genuine improvements to their car i.e like myself

Unfortunately I don't think the project progressed past prototype stages, though it is possible to still find decent diff cover plates if yours has been damaged/corroded. Worth checking, sometimes people carelessly jack the car up on the diff and crush the lip of the coverplate. In some circumstances they've been known to rust through too.

Thanks Steve.
Looked to have the makings of a great upgrade/replacement project.
My cover is weeping a little, the plan was to source a good spare to refurbish/rustproof ready to fit with a new gasket kit when I came to do the job. I would then refurb my original cover as a good spare.
I ordered a 'used' cover along with a new gasket kit from a well known parts site, but the cover that turned up is only fit for the scrap bin.... Still waiting on a response from the vendor and still looking for a good spare cover....!

I was wondering does yours leak from the edge or is it rusted through? If the latter then I agree that it's only fit for scrap. Instead if its a bit bent at the edges it's probably as good as any replacements you will find now.