Scorp Diff into Sigma
Posted: Mon Jun 14, 2010 2:16 pm
The old Borg-Warner diff in my GH Sigma is on it's last legs. It's leaking oil and has heaps of play in it. It needs to be replaced asap. If i'm going to do this i may as well go to a stronger diff and disc brakes. A Scorpion diff would be perfect, and lucky me i have a couple spare.
For a long time i have said that the Sigma and Scorp diffs are a straight swap, as long as you use the right diff. GE and GH sigmas need a GH Scorp diff (can use a GE Scorp diff but these are smaller), and GJ and later Sigmas need to use a GJ and later Scorp diff. However i'm now finding out there are a few small issues.
For my GH Sigma i've used a GH Scorp diff. The diff housing itself does indeed bolt straight in. Lower control arms are exactly the same. Upper control arms are different where they bolt to the diff. Use the Scorp upper control arms and there is no problem. Unfortunately this means no more sway bar unless you want to get the welder out. Springs are interchangeable, and for shocks you can use Scorp ones (mine were the same as the Sigma anyway). The Scorp lower shock mounts use a different thread size on the nut so make sure you get the nut, etc with the donor diff or you will have to try and find some.
The flexible brake hose from the body to the diff are slightly different lengths - the Sigma is a couple of centimeters longer. I used the Scorp hose as the difference seems to be where it attaches to the diff. Not sure how the master cylinder will handle disc brakes instead of drums long term, but seems reasonable after a quick drive - will update it the next couple of days. I do have a master cylinder from a disc brake sigma i could use though.
Hand brake cable is a straight swap, but you need to use the Scorp cable to suit the disc brakes. Attached fine and works better than the old one.
Biggest issue has been the tailshaft. The flange that bolts to the diff is different between the Borg-Warner and Jap diff. A Scorpion 1 piece tailshaft may work but i didn't have one handy to try. Managed to find an easy enough solution - use a flange from a Galant. I've got one here out of a GD Wagon. It uses a Jap diff, and the flange bolts straight onto the GH Scorp diff. It also uses the same universal joints as the Sigma tailshaft - RUJ1786. Just swap the rear flange on the tailshaft with a new universal joint and it should be good to go. Later Scorp diffs use larger diameter bolts, you may be able to drill the galant flange out to suit, get some bolts made up with a step in them, or swap the flange on the diff itself.
Got it all in and working with a weekends worth of work. It could be done in one day if you had all the tools, universal joints, etc ready so you didn't have to organise parts. Overall it's a lot better than the old diff - but a lot of that could be due to going from a worn out diff to a good one. No more funny noises, no more jerking on gear changes as it takes up the play in the diff, etc. The only part that wasn't 'bolt-in' was the tailshaft flange, it should be done with a press, but I managed to make do with a hammer and a couple of sockets.
For a long time i have said that the Sigma and Scorp diffs are a straight swap, as long as you use the right diff. GE and GH sigmas need a GH Scorp diff (can use a GE Scorp diff but these are smaller), and GJ and later Sigmas need to use a GJ and later Scorp diff. However i'm now finding out there are a few small issues.
For my GH Sigma i've used a GH Scorp diff. The diff housing itself does indeed bolt straight in. Lower control arms are exactly the same. Upper control arms are different where they bolt to the diff. Use the Scorp upper control arms and there is no problem. Unfortunately this means no more sway bar unless you want to get the welder out. Springs are interchangeable, and for shocks you can use Scorp ones (mine were the same as the Sigma anyway). The Scorp lower shock mounts use a different thread size on the nut so make sure you get the nut, etc with the donor diff or you will have to try and find some.
The flexible brake hose from the body to the diff are slightly different lengths - the Sigma is a couple of centimeters longer. I used the Scorp hose as the difference seems to be where it attaches to the diff. Not sure how the master cylinder will handle disc brakes instead of drums long term, but seems reasonable after a quick drive - will update it the next couple of days. I do have a master cylinder from a disc brake sigma i could use though.
Hand brake cable is a straight swap, but you need to use the Scorp cable to suit the disc brakes. Attached fine and works better than the old one.
Biggest issue has been the tailshaft. The flange that bolts to the diff is different between the Borg-Warner and Jap diff. A Scorpion 1 piece tailshaft may work but i didn't have one handy to try. Managed to find an easy enough solution - use a flange from a Galant. I've got one here out of a GD Wagon. It uses a Jap diff, and the flange bolts straight onto the GH Scorp diff. It also uses the same universal joints as the Sigma tailshaft - RUJ1786. Just swap the rear flange on the tailshaft with a new universal joint and it should be good to go. Later Scorp diffs use larger diameter bolts, you may be able to drill the galant flange out to suit, get some bolts made up with a step in them, or swap the flange on the diff itself.
Got it all in and working with a weekends worth of work. It could be done in one day if you had all the tools, universal joints, etc ready so you didn't have to organise parts. Overall it's a lot better than the old diff - but a lot of that could be due to going from a worn out diff to a good one. No more funny noises, no more jerking on gear changes as it takes up the play in the diff, etc. The only part that wasn't 'bolt-in' was the tailshaft flange, it should be done with a press, but I managed to make do with a hammer and a couple of sockets.