Auto to manual

[Sicma]

hi all, I have an 87 GN Sigma. It is currently a 2.6 auto and I am wanting to convert it to 5 speed. Is there any specific do's and dont's. Do I need to use a certain gearbox? Any help is greatly appreciated.

[Superscan811]

A few Questions need answering before you start.

Is it a Wagon or Sedan?
Are you wanting to use the current engine?
What diff do you have (BW or MMC)?



Cheers.

[Sigmaproject]

If it is all factory GN then you will need a KM132 narrow gearbox/clutch/Flywheel/Pedal box/gearbox mount/clutch cable from a 2 litre manual Sigma. The 2 litre manual has the same bellhousing bolt spacings as your 2.6 litre auto block.
The 2 litre gearboxes show up on this site occasionally..also on eBay. Not sure on the rear spline for the tailshaft..I think the manuals and auto's have a different spline count (but I could be wrong)

[Sicma]

It's all standard was a 1 owner car and am planning on putting a 5 speed manual in. Gonna keep original engine and rebuild it for boost and efi and aftermarket computer. Mainly Coz it's an astron 2. Where as my gj was a cammed and Webber fed 5 speed. Was hoping to use that box and pedal box.

[Sigmaproject]

If your previous Sigma was also a 2.6 .. then your 2.6 manual gearbox will not bolt up to The GN 2.6 auto block..sad but true.

This is a bellhousing from an earlier BW box..but it will show you your issue. The problem is the spacing indicated in this shot. On a 2.6 manual block it is 330mm. But on a block from a 2.6 auto..it is 310mm.

[Sigmaproject]

There may be a one in a million chance that you previous Sigma was converted from auto to manual by a previous owner. So do the measurement to make sure.

[Sicma]

Is there much advantage of the later gn engine over the earlier gj engine. I already have a gn head on the astron 1 and got the magna manifold reversed with xf throttle body. Will the pedal box be usable if I keep the astron 1 engine and 5 speed combo and put it in the gn.

[Sigmaproject]

The block castings are different..but the main change was the pistons and head and upgraded electronic Ignition . So if you have a reasonable GJ motor and box you have just saved yourself a lot of hassle.

[Sicma]

Will give the motor a freshen up anyways. New rings, bearings etc.I think it's a TN magna head which is on the gj motor atm. Reconditioned and never run. Not sure on cam to run though.