how stong is a sigma 5spd?

[corty240]

How strong is a sigma 5spd, will be turboing my engine and putting in an r31 LSD but is the gearbox the next weakest link? How much power can you put through one before things start breaking? If not much what are some upgrade options?

[corty240]

The car is as it came out of the factory in 85, it has a 2.6 astron 2 so I am assuming it is a wide block but don't know if it is a jap box or a borg Warner.

[webby]

If reverse is next to first then you have a BW, if it's under 5th you have a Jap box.

[corty240]

Cheers webby, I have the jap box then, how much power will they take? And are they a reasonable box? Cheers ted

[webby]

I haven't got much experience with hot Mitsubishis, most of the performancey stuff I've played with have been Toyotas, but from what I've seen a Jap 'box in good condition looks to be on par with or a little bit stronger than a late model JDM AE86 T50. Means it should be good for up to around 150-160kw at the treads, provided you look after it.

I could be wrong though, like I said I haven't got much experience with these things.

[corty240]

Nice, I have quite a hot little ke70 with a t50 behind it, had it on the dyno puttin out 148kw @ the wheels and it seems to handle it, mind you I am not really hard on it as I am a bit worried that it won't take a thrashing, it has a 4 age with 7afe bottom end 20v head individual throttle bodies custom cam grind running a adaptronic computer, thing bloody flies for a 4 pot. Had a bloke dyno tune it in Sydney, got the papers somewhere with torque and who it was, sounds like I may have a nice little box then, I hope so :-D

[Billsy]

i had a narrow 2L jap box behind my turbo siggy pushing out over 200rwkw for about 10,000kms.

i had a very heavy but soft (full face organic plate) clutch which would have helped and also had std 185 tyres. so it wouldnt have had much load really.
but it did eventually break some teeth off 2nd.... so treat it nice and itll be happy. be rough and youll probably have issues

[corty240]

That is great to know, will be forgetting about the gearbox for a few months then, cheers guys

[A112H]

I will be running a RWD Triton gearbox behind my 4G63. They are narrow block and have virtualy the same internals as a Starion box (two different barings) so should be nice and strong.

[turbogj260]

my jap 5 speed after 5000 km on a fresh built motor running injection. as you can see 2nd gear didnt last 2 long...

and yes the box was sittig oustside for a while when the pic was taken

[corty240]

Maybe not as strong as I hoped then, honestly how hard were you on the box?

[A112H]

That doesn't look good but remember there are many factors to the strength of a gearbox, more than just the box itself. Remember these boxes are 25+ years old, some are on factory barings and gearsets and may have had a very hard life prior to you getting it.
The gearbox is no different to the engine, if you want a strong one then build it yourself.

Was the box rebuilt?
How was it treated before you got it?
Was there enough oil?
Was it the correct oil?
What sort of clutch was used?
How aggressivly was the clucth used?
What size tryes was the car running?
What sort of tyres?
Was it flat changed every time?

If you have a worked motor, H/D clutch, upgraded diff and are running sticky wide tyres the gearbox is going to be the weak link.

My hardtop was driven fairly hard for about 9 months and the gearbox is fine, infact it is going in the new hardtop, lol. But I never flat shifted it, never side stepped the clucth of the line and had cheap nasty tyres on the back so it was never shocked into action finding itself under strain.

[TUFSIG]

Im running a Starion Box with Hydrolic clutch conversion with 200rwkw and its fine and was also in my old turbo scorpion for about 9000ks as well, however i dont thrash the guys out of it, also running a cushion button clutch too

[corty240]

How hard is it to find a starion gearbox these days? They would have to be worth a pretty penny wouldn't they? I also need to change flywheels don't I?

[A112H]

Where abouts are you corty? I have one I probably won't need. I only bought it for spares but it is a good box.

[corty240]

I'm in nsw, about an hour north of Newcastle, a little town called nabiac

[turbogj260]

If you are wanting to give it shit then save your self the headache and time and put a w55 supra one in, Mines behind the 2.6 and cops a hideing and loves it. Running 225/50/15's on the back with a hilux diff with 4.11 detroit locker final ratio. Im just saying if ur wanting the power down spend the money once and once only.

[corty240]

I actually have a w55 in the shed, a spare for my cortina, i have that as an option down the track. At the moment will leave the stock the box in, in a couple of months going to put in the starion box, but if there is problems with the starion box will end up putting in the supra box. Thanks for the suggestion. Cheers ted

[webby]

I don't know how a 200kw turbo 2.6 compares to a 200kw 1GGTE or a 120kw 6MGE in terms of gearbox smashing ability, but if personal experience is anything to go by then they're a good, strong gearbox, but they aren't bulletproof. It'll take abuse better than any of the Mitsubishi 'boxes will but you can't expect a 30yo Celica 'box (Supras had a W58, much of a muchness really but they're a bit stronger and have different ratios) to cop a hiding day in day out and live forever. That said, if it's been rebuilt recently then give it hell, it'll take it, for a while at least. Best thing about the '55 is there's RT142 Coronas and SA63/RA65 Celicas everywhere so if you do break one replacement units are common and reasonably cheap, whereas Supra W58's tend to be a bit less available and can be pretty pricey.
That said, if you're just driving it on the street you should be fine. I drifted my cars, which is a hell of a lot harder on gearboxes than cruising about with the odd clutch dump off the line or pull to redline in 2nd or 3rd.


Of course, you could always just ignore me, or tell me I'm wrong, like some people around here are in the habit of doing. Up to you. Seems like you've got to be older than 30 or have some sort of formal trade qualification to have played around with cars before, anyone who isn't/doesn't has to be full of shit. Right?

[corty240]

Hey webby, I have found much the same and that's why I have it being saved for my cortina, 357 hp at the rears and a butt load of torque I know it will only be a matter of time until she goes pop. gunna stick with the starion box idea for a while if it doesn't handle it I will reasses the situation, I may just have a w58 that I can get for cheap but it is going to need a rebuild before I consider anything. And will probably go into my tc cortina, she is my pride and joy, the sigmas just some fun. I am only 26 and am only just starting my mechanical training as a truck mechanic but have had an obsession with cars motors and speed since 8, and been working on my own toys since 10. Thankyou for your input it is greatly appreciated. Cheers ted

[cheaterparts]

there are a couple of things to think about when trying to work out how strong your box needs to be

its not Kws that break teeth in gearboxs its torque - Kw or Hp is work done turbo apps increase torque witch in turn increases Hp
the lower the revs that you get high Hp or Kws the worse it is for the gear box

here some Math and sorry its old school but then so am I -- if you make 1 Hp @ 5252 rpm you have 1 ft lb torque
if you have 1 Hp @ 2626 rpm you have 2 ft lb torque and of cause if you have 1 Hp @ 10504 rpm you have 1/2 a ft lb torque

so the figures on a 100 Kw engine if that was doing it at say 2600 ( probably a turbo app )it would be putting 270 ft lb torque through the gear box
and a say Na engine putting out a 100 Kw @ 5200 the torque through the box is only 135 ft lb

both engines @ the same Hp/Kw but guess which one is nicer in the gear box

[corty240]

Thanks cheater, that has given me a Better understanding of the gearbox and the stresses that it is subjected too. I think it is almost time to invest in a dyno myself lol the amount i have spent on dyno runs in the last 2 years i should have bought one. When i get it running and i put it on the rolling road i will know a few figures to know what strength i will require for both the diff and gearbox, thanks mate, have a good one. Cheers ted