Surley, if there was the slightest doubt in the weld, if someones got any common sense, they will get someone else to weld it. Im no welder - I will openly admit that. I employ 4 of them. I tack it/set it up, they weld it for me. There all coded and I trust them.

As for people questioning the Saturn build guide - ITS A GUIDE!!! Its not a foolproof way. Its a learning curve. That's why im building one. to 'play' and have something worthwile at the end (plus I need an excuse to leave the wife indoors with the 2 toddlers!!)

Im not wishing to call anyone down, and I feel kinda guilty for Phil getting a kicking on a thread I started.

Your all great engineers. You've all got guts to take a project on like this, and I admire the talent that there is. Ive got to admit, ive copied some of your ideas (not saying whos :) )and theres one or 2 builds that I aspire to challenge. Keep up the great work, ALL of you.

Hi everyone I wanted to mount the diff nose on rosé joints with poly inserts,this was the idea but when I mocked up a bracket like Phil's there doesn't seem to be enough room between sb4 to be able to do anything but a solid connection, the drive axles don't come out central between sb1 and d11 they are slightly forward is this correct, I have placed the plates cp26 as per Saturn alterations to the build show with the measurements as shown but I would like to move the diff back a bit to give me room to mount the nose as I wanted to do nothing is welded yet no suspension brackets or the cp26 plates, also my chassis was built as per the book for Sierra donar so top damper mount has to be moved forward so if I could move the diff back it would save me doing that, anyone got any suggestions?.
Regards Mick.

Why would you mount the diff on rod ends? I can't see any advantage to doing it...

Maybe I've not explained properly not rod ends more like the suspension mounts like Caterham mount theirs but just two not four
Regards Mick.

Yes, that's correct. Bear in mind that if you do bring the diff back you might need to make the wishbones longer (which wouldn't be a bad thing as the rear wheels are very close to the chassis on mine).

I went the route of solid mounting the nose combined with poly diff bushings. I don't know how common it is on your side of the pond, but state side its pretty common to either switch to poly bushings or go with a solid aluminum bushings for the diff carrier, with the only negative side effect being increase vibrations and noise. Also doing either of these is effectively solid mounting your diff. Prior to fabricating the nose bracket I had just the poly bushings installed and was only able to move the diff nose 1mm. So solid mounting the nose would have very little effect on things.

Hi StruveD thanks for that information, can I ask do you hang the diff underneath the diff cage like we do over here and what do you use under the bottom poly bush? I was thinking of using a large washer approx 3 and half inch.

I was looking at a forum Locostusa and on a build blog Johns he mounted his above the diff cage and made poly inserts at the front have you seen that build blog?.
Regards Mick.

So the bushing kit I purchased is from a company called "energy suspension". They have a kit specifically for the miata diff and its a 2 piece poly set with a crush tube/sleeve. The upper portion is pressed into the carrier, and the lower portion just slips over a portion of the crush tube. You then use the factory washers to press everything together and hold it in place. See the pictures below.

Cheers for that, when people use these bushes, are they getting breakages of the diff arms at all please ? I have ordered my gbs diff mounting kit which is coming in at a whopping £150, but with this bracket kit, you cut the arms off the diff completely. I don't know how this works exactly, because when I went on my tour of gbs, there was no diffs available to look at, which was a bit of a shame really. But, if your bushing at £35 pounds each ( if my conversion rate is right ? ) , will be a much better deal. I know you have to include shipping, but still would work out a lot cheaper. :D

Looking good Struve. 1 thing I will suggest, where your nuts are at the bottom of the diff nose, id put a plate approx 25x75x5mm (1inch x 3 inch x 4g) with 2 holes in to take the nuts. It will spread any load over more of the diff, reducing the chance of cracking at the hole.

They look good but I have already bought mine from Flow-Flex they are two pieces with crush tube like the top section of your ones ie flat that is why I was thinking of the large washer underneath because they don't dish in so I think that would be okay what do others think?.
Regards Mick.

That's what I was going to do with mine. Use the floflex bush and tube, and make a large 'washer' the same diameter as the bush, around 5mm thk. You could use a standard washer (as long as the washer is bigger than the crush tube) but I would like the look of a chunky one!

I couldnt find any information on anyone having a breakage that wasnt in a accident. The only negative information was with the use of aluminum bushings and the excessive noise. With the poly units being a nice compramise between the stock rubber and the aluminum set. As for cost, yes about £35 plus another $30 for the shipping. Can you get access to the US version of amazon.com, shipping might be less going through them.

Noise shouldn't be a problem in a roadster!! The noisier the better!!

Are these designed to be used with the mounts that come on the MX5? The ones that sit under the diff arms?

David

No the replace those with those 2 big poly pieces and just reuse the big washers.

75mm x 5mm disc on eBay 2 off for around £5 and drill hole in centre is what I have decided to do with mine

So are guys just using pressure to hold the bushing in then? Instead of something that extends beyond the bushing to catch the bottom side of the carrier.

I'm using a design alteration of the original ie by NTS/Saturn which has alterations to the diff cage.
Two plates 5mm thick one on each side bolt through from top diff mounted underneath then large 75mm x 5mm disc and nut, Flow-Flex bushings in diff carrier these are flat both top and bottom of diff carrier not dished like the ones you are using so yes the bushes are compressed between the top plate and the disc there is a crush tube through the centre of the bushes so they will only tighten up so far.
Regards Mick.

cant say im a great fan of the mx5 diff design and the way works in 7 kits.

i have looked at both the mx5 redesigns and if it was me i would be going down the talon/voudu one if i had to build one of the two.
i dont like the way the other one is designed

stress is under estamated in diff areas and even some of the pro's got it worng

How are they doing?

Has anybody bought a Talon mx5 diff cover ? Do they sleave the diff, or do they replace bits ?:confused:

All the cast ali cover does is hold the oil seals in place and act as an oil bath for the diff. The fabricated cover will need 2 new oil seals pushing in place and takes the standard drain/fill plugs with the vent. It also provides a 6mm thick plate with 4 M12 bolt holes that I doubt most people will be able to break in normal use.

Will it work on bolt on driveshafts?

1.6 or 1.8?

David

I would have thought the ends of the out put stubs would be the same as the 'push in' type,but you never know. I must confess I don't have the 'bolt on' type diff or drive stubs to look at.

When Mazda designed the Ali part of the diff with fins for cooling and size for lubrication will it not get to hot or not be lubricated enough with your design?.

weld on some fins then?

I was speaking to Westfield today and they have had no reports of broken differentials on their cars. Theirs appears to use the normal mounts with a solid nose mount.

David

Did Westfield have to redesign the back end of their car to accommodate the cast ali cover? The whole point of this cover is that it allows the use of the mx5 diff to be fitted to a standard book spec chassis with out a major redesign.
As for the cooling effect of the fins on the the mazda casting they are there due to the limited amount of oil that it contains, the oil used in the diff does get warm during normal use and should be changed every 30,000 miles or so. If you compare the amount of oil that the fabricated cover holds to the Mazda item I'm hoping that the extra capacity should keep the temp down. Those that have any concerns about diff oil cooling then you could always duct passing air towards the diff the same as a race car has brake cooling ducting.

But I thought the 1.6 diffs were not finned? or am I wrong?

If they are, I understand there smaller, and would generate less heat, but with the lightweight chassis of the roadster, they wont be under as much stress, so should in theory generate less heat.

There are 1.6 with and without fins. Mine has fins.

Phils box has a lot more oil in it though as the internals wont be formed around the diff gears the same way the OEM one is so theres more dead space. This will help a lot with cooling.

Cheers
Stot

is it more of an heating issue affecting the diff internals, or the heat degrading the oil? If its the latter, I cant personally see a problem.

Today after an hour and a half of trying to undo the bolts that hold the ali back bone to the diff nose I gave up and reached for the grinder, big Ammer and the drift. Long storey short the out put shafts bolt on type for LSD diffs are the same as the push in units so the fab'ed diff cover fits both.

Phil - Lefty loosy, Righty tighty :D

I had a spare Diff that I gave to Nathan when his broke. It was off a 1.6 and he was using the 1.8 running gear and it wouldn't fit in his car.

Erm minor edit.....just put the 1.6 LSD next to the open diff, erm so how many different sizes of diff are there?

The 1800 diff has a larger crownwheel and is physically bigger (might be a bit longer too). The 1600 and 1800 driveshafts are different, so if you fit a 1600 diff you will need 1600 driveshafts too. On MX5s, the prop must also match, but I don't know whether the prop length is the only difference and therefore not an issue on a Roadster.

Push in driveshafts will also fit bolt in diffs (at least for the 1800s, as I have this exact setup on my Torsen).

[silly ideas]
If you could machine down the bolting surfaces 6mm you could sandwich in the mounting plate to the standard diff.

Or maybe you could design a plate that can be bolted on externally using the existing bolts that hold the diff together. Need to cut it around the casting webbing.



Then cut the wings off.
[/silly ideas]

Cheers
Stot

I did consider that at one point I even offered the cover up to the mill, then I had a little think about gripping a brittle ali casting in a machine vice....

Just re read my gillham guide, and under the section differential, it actually has the nose braced. It says, an additional length on 19mm box can be fixed between BR12 & RS3, with a 5mm packer welded between RS3. The second engine mount rubber can be used to secure the front of the diff. I have revision 3 notes, so maybe it was not in the earlier build spec. Maybe we were all that keen, we missed it. 19mm box & 5mm plate it is ! ( picture in notes is - figure 41 : front lower diff mount position). Tidy on a Friday !:D

That was what spud and nathan used but it failed. Partly due to the mount and they also didn't use the large plates that go under the diff mounts. Nathan then modified the mount be removing the rubber engine mount and replaced it with a steel bracket. Nothing to stop the diff twisting though

David