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 Post subject: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Sat Nov 18, 2017 10:52 am 
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I just replaced the standard diff centre in my 1300 with a 323 3.9 long nose centre. My car currently runs the standard 4-speed. Obviously the standard tailshaft didn't fit but we found an RX3 shaft (to suit standard long nose 12A/1600 diff and rotary 4-speed) was the correct length which has helped to get the car moving under its own power again. The 5-speed is 20mm longer so we need a tailshaft about 1100mm long from the diff flange to the yoke approx. 20mm from the bottom end of the yoke to allow for some movement. Any thoughts on a standard Mazda shaft that may suit? Will need to have the 60x45mm flange pattern and the deep recess on the flange to clear the big nut on the pinion flange.

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Sat Nov 18, 2017 2:17 pm 
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What 5 speed did you use? I put one from as 323 in a 1300 years ago and I don't recall having any tailshaft issues, the stock 4 speed is same as 323 overall length and 4 and 5 speeds are the same I thought.

I also put a 12A and RX-5 5 speed in my 1300 now with R100 diff and I reckon I've got early RX-7 tailshaft in that.

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Sat Nov 18, 2017 11:34 pm 
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Yes I used a 323 5-speed. The box is definitely longer then the 4-speed, by about 20mm. It is possible that if I still had the standard diff centre there may have been just enough extra unused length on the yoke to accommodate this but it would surely have been near the bottom which wouldn't allow for much movement during suspension travel.

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Sun Nov 19, 2017 2:04 am 
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chop 10mm? not as brutal as it sounds. i ran that way for a long time

i suspect your option that is a shorter single than rx3 is s1-2 rx7 . i think a little long is better than a little short

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Mon Nov 20, 2017 7:06 pm 
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Custom is probably the easiest option. It's amazing that the RX3 tailshaft is so close to the correct length.

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Mon Nov 20, 2017 7:38 pm 
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I honestly cant remember whether I had long or short centre, but it was definitely a standard 1300 tailshaft I used.

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Tue Nov 21, 2017 2:43 pm 
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There are apparently 2 diff versions of the 323 5 speed. Someone else said they swapped one in to a 1300 (one of the adelaide guys- maybe REV100?) and didn't use a shortened tailshaft, but I think he was wrong and probably went from an auto car to a 5spd.

An auto 1300 tailshaft will apparently bolt straight in to a 1300 with the stock diff centre and 5spd.

When I put a 5spd into my 1300 FA, I had to shorten the tailshaft by 1.5 inches.


Good to know about the 3.9 diff. I want to use the same thing with my STB.

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Tue Nov 21, 2017 6:03 pm 
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Ah very interesting well I think it would be pretty unlikely there is two different boxes but who knows. Auto 1300 tailshaft will be hard to find and even identify for that matter but good to know. I think I jumped into this too blindly as I already had a spare tailshaft that was the 'correct' length but it turned out to have a different pinion flange on it! :roll:

Yep the 3.9 diff bolts in but as I said it's actually a longer carrier like the 12A RX3 item.

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Wed Nov 22, 2017 10:18 am 
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There's also a shitload of mis information out there.

I had people swear that a 121/626 5spd is the same externally (dimensions) as a 929 4spd, when clearly they are not. Again I got caught out late on a sunday afternoon when I needed the car to go to work the next day. :evil:

It never ever "bolts straight in" !!

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Wed Nov 22, 2017 7:26 pm 
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Amazing! I was caught out too but didn't need the car to get to work... just to get home after working on the damn thing all day! Frustrating. Nearing the end with it all though. I took the car on the highway today and I think the 3.9's have made a noticeable difference. Bring on 5th gear!

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Thu Nov 23, 2017 3:50 pm 
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I imagine it would because there were loads of 323's out there with 4spds, while the 5 speed wasn't as common.

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Fri Dec 15, 2017 7:49 pm 
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Gearbox is now in the car. The installation itself was ok and the new shortened tail shaft is spot. I feel the ratios are not as nice as the 4-speed though but I think I just need more time.

Mounting it was quite difficult and I would love to know what other people did. We thought an adaptor plate to reach back to the factory crossmember would work but the it simply fouled on the gearbox case itself let alone any bolt heads that would have protruded. On that note the gearbox also sat on the crossmember. We ended up sectioning the top section of a spare crossmember and then I had to keep offering it up and cutting away more material to clear various curves and bolt heads etc. We then welded in a piece of RHS to extend back to the mount. I feel it's still not quite right and possibly the gearbox is too high.

I might have to start another thread or ask around elsewhere but can anyone show me a picture of what blocks or rubber insulators go above over the mounting studs; above the crossmember and against the floor?

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Sun Dec 17, 2017 2:26 pm 
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Something is sus with these 323 boxes, because mine was pretty straight forward, as I said before, I;m sure I used a standard tailshaft, unless possibly I used a long centre 4 speed shaft onto a short diff centre as I would have had the parts, I can't recall having issues, but I may have had the shaft just sitting there.

As for mount, I remember for sure, I sectioned the front half of the top, cut straight through the mounting holes on top about 100mm or so wide, and horizontally from the front level with the double thickness, flipped the cut out bit over and welded it back in place to try and keep some strength, then three lengths of 20 or 25mm RHS side by side and welded on top of the lip at the back. Holes drilled for the mounting bolts on top and large holes to get a socket in.

Sectioned the front just for some clearance on the fifth gear housing, and moved the mounting points back about 75mm.

I also never noticed any real difference in ratios through the first four gears

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Sun Dec 17, 2017 7:05 pm 
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I used a flat piece of mild steel to extend the 'reach' of the gearbox, which was another thing that people neglected to warn people about on here. Oh I needed to trim the trans tunnel hole as well too I think from memory.

Yes, also had the same problem with bolts fouling on the gearbox. Didn't even make it 20m up the road before I was heading back to the workshop to grind bolt heads down.

5spd gearbox wasn't really worth the effort IMHO. Woudln't bother these days, I'd just throw an SR20 and matching 5spd and fab my own gearbox mount.

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 Post subject: Re: 1300 diff centre/5-speed swap - tailshaft?
PostPosted: Mon Dec 18, 2017 6:29 pm 
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Even if I stayed with the 'short nose' 1300 style diff centre the tailshaft still needed to be shortened as the gearbox is some 20mm longer. I didn't have time to seek out Mazda shafts that may have been the right length.

I guess I ended up doing something similar with sectioning the top skin of the crossmember however I did it around a piece of 75x25 RHS which really didnt allow for a wide enough section to totally clear the gearbox. If it was a 100mm wide cut probably yes. I'm not really happy with it so I think I will build something entirely fabricated from RHS and add some bushes between the rail and crossmember.

The flat plate extension/adaptor to the mount just doesn't work in my opinion. I think this well known write up shows that as you can see how the gearbox mount is twisted backwards under the strain and I can only assume the bolt heads and/or plate would be touching the gearbox.

http://www.andrewlawton.com.au/1300%20G ... index.html

I went to the trouble of getting a plate bend to maintain the same mounting plain but there is no way it would have worked. For me I wanted to do the 5 speed as I already have a built D5 1500 in the car and want to do some more long distance cruises in the car.

P.S. - I should add that the shifter came up in the exact same position and no trimming of the tunnel was required.

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