Jss240z Posted June 11, 2017 Share Posted June 11, 2017 So I decided to remove my rear diff which is a 3.7 and install a 3.9 I had laying around. When I romoved the back cover on the one I removed from the car I noticed a little piece in the centre (first pic) that the 3.9 I planned on installing did not have(second pic). Does anyone know what it is? Some kind of locker? Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 11, 2017 Share Posted June 11, 2017 (edited) Not positive but I think that the piece is part of a a four pinion diff. Your 3.9 is a two pinion. They're both open diffs, but the 4 pinion is stronger, I believe, or at least, more durable. Edit - #7 here shows a good comparison picture. http://www.gmh-torana.com.au/forums/topic/66959-mystery-diff-conversion/ Edited June 11, 2017 by NewZed Quote Link to comment Share on other sites More sharing options...
Jss240z Posted June 11, 2017 Author Share Posted June 11, 2017 Great info. Went outside to check again and it looks like there is only one rod going through the centre like my 3.9, but with that rectangular piece around it. If it's only one is that still considered a four pinion? Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 11, 2017 Share Posted June 11, 2017 That would still be a two then. Don't know what that thing is. Spin the wheels and see what it does. Interesting puzzle. I've seen similar parts in images but haven't dug in to the various varieties out there. Quote Link to comment Share on other sites More sharing options...
Jss240z Posted June 11, 2017 Author Share Posted June 11, 2017 Well when I spun the wheels when it was in, one went forward and the other back. So it must be an open diff right? What I'm really trying to get at is do I need to swap it into the 3.9. Plus knowing what is is would be helpful. Quote Link to comment Share on other sites More sharing options...
softopz Posted June 13, 2017 Share Posted June 13, 2017 Yes open diff Quote Link to comment Share on other sites More sharing options...
Jss240z Posted June 13, 2017 Author Share Posted June 13, 2017 Ok, I realize that's what it is but the rectangular piece in the centre? Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 13, 2017 Share Posted June 13, 2017 It might just be a different style of shaft, instead of a length of machined rod. Could be that the center piece locates and retains the shaft ends in the center of the diff. The sides of the piece also support the spider gear, and act as another bearing surface, probably reducing wear. It looks like just a more robust two pinion diff. Probably little benefit to swapping, unless the other diff is worn. Spend some time measuring wear on the other diff. Quote Link to comment Share on other sites More sharing options...
Jss240z Posted June 14, 2017 Author Share Posted June 14, 2017 I showed the picture to mike at whitehead performance here in Ontario and he said it looks like some kind of cheap locking device but not completely sure and that he is used to seeing them open like the pic on the right (3.9). Still going to put the 3.9 in and yes for sure i will check for wear before swapping. Thanks for the suggestions guys. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.