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Path of Least Resistance - Gearbox and Diff/Shafts for 300-400bhp?


Miscbrah
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Evening all,

Have been browsing the projects on and off before joining fully today. Had a part in a Calibra Saab B204 engine swap, and the ambition one day is to restore a Manta, but stick the same Saab engine in there, looking around 300-400bhp.

I'd settle for the R25-R28 Omega box and convert to hydraulic clutch, but from the gearbox back (prop > diff > rear shatfs/assembly) I'm not sure what the best options would be. I've heard people use Volvo, Ford Atlas, even Scimitar driveshafts and/or diffs, but the amount of fabrication and lining up might be beyond me and the facilities I have here.

Question (finally! Lol) is, what would the least misery be? Short of sleeving the Omega > Manta prop, limping it to Quaife etc and going "make that all stronger please" do I have any bolt on or "pretty much" bolt on options? Ones that aren't hen's teeth rare or shockingly expensive?

Any and all suggestions very very welcome and thanks for reading this. :)

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Hehe! Yeah I'll write up this project (long into the future) when I get myself there. And when I'm armed with enough info to make an actual project rather than butcher a lovely Manta.

Okay, so the proper weak point does seem to be the torque tube, which seems to be the thing that holds the entirety of the Manta back end together.

Further question is then, is it possible/feasible/sensible (in any way) to convert to open driveshaft? Any way of, say, just shortening the Omega setup and sticking the whole rear subframe business on it?

Thanks again anyone reading (and happy Friday!) You might have got the impression that at this point I've no clue really, but attempting to get one nevertheless! :)

Edited by Miscbrah
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You could do that, buts it's a lot of work to make up all the new mounting brackets.

Scimitar 4HA axel can be modified to fit using all the original mounting points and will take a Jag LSD, lots of different ratios available.

If for a Manta B/C then you need a 6 Se axel if for an A series then you need a 5SE axel.

This is my 4HA set up I have on my A series.

tn_jpic(152).jpg.803608e8fe1b0741f8a34b8c47e3e9cd.jpg

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Manta ray, looks a good strong setup. Any idea on what jag lsd fitted your a series 5se axle. 

And what jag lsd will fit the 6se? 

Like the extra ribs for strength on the diff casing, did you fit the opel spring seats, and the a frame mounting point, top work, looks strong and up to the job,

Whats the brake setup? 

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Mantaray thanks hugely for that - gosh this might even be do-able! Yes I'd be going for a Manta C myself.

And, er, what evo03 asks above plus could you outline the mods necessary for the Scimitar/Jag diff setup? Will be mega grateful if so!

Again, cheers muchly everyone. :)

 

EDIT - though having had a little dig around, is it just a case of welding on the spring seats at the appropriate angle, then bolting up those double-u-bracket bits (whatever they're really called) wherever they need to be for the braces/bars? Then I'm guessing get a propshaft made open-diff style for R25-R28 box <-> Jag (or whichever) diff.

Apologies if this is painful btw! I'm fairly green.

Edited by Miscbrah
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8 hours ago, Miscbrah said:

EDIT - though having had a little dig around, is it just a case of welding on the spring seats at the appropriate angle, then bolting up those double-u-bracket bits (whatever they're really called) wherever they need to be for the braces/bars? Then I'm guessing get a propshaft made open-diff style for R25-R28 box <-> Jag (or whichever) diff.

Yes, that about it, double-u-bracket are also welded to axel and A frame is rose joints all around. Brakes are Astra callipers with solid discs. LSD is a power loc from an XJ jag, straight swop, just need to have some tophats machined which I have the drawing for.

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Thanks again for that Mantaray, immensely helpful. :)

Do the double-u brackets *need* to be welded or is it just better in this case? Also, which generation/size of Astra disc did you use, if you have that info? And if you have the tophat drawings available to post up that'd be amazing!

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  • 4 months later...
  • 1 month later...

Hi Chris, Paul Barrett has suggested I do the same, I have a beam, the spacers and the lsd.

Please can I ask how you have connected the prop to the axle/diff, also do you have any specs or pictures of it fitted or off the car?

Cheers, Matt

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