dbur Posted October 5, 2011 Share Posted October 5, 2011 I had to figure out what center diff viscous drive units were good and bad recently. It's not too hard. Mine was locked up, but you can't tell by looking, only by driving. But this test allows you to check a replacement before building it into your transmission. 1. You need a spare gear drive shaft. Don't remove your good one. Get a spare from a junkyard or somewhere. 2. A large screwdriver secures the case from turning. A large pipe wrench turns the gear drive shaft. 3. A paper towel on the gear can protect the gear if you want to keep it from damage. Also helps the grip since the pipe wrench can't grip on the hard gear metal very easily. The diff should turn at about 40 ft-lbs. (est -look it up if you want a better number). 4. Rotate through a full revolution. It should be smooth all the way around. View the viscous clutch inside the case turning through the hole shown by the red arrow. Link to comment Share on other sites More sharing options...
BAC5.2 Posted October 5, 2011 Share Posted October 5, 2011 That just tells you that it's not locked up. It doesn't assess the health of the diff. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
dbur Posted October 5, 2011 Author Share Posted October 5, 2011 Well it doesn't tell you the bearings and gears are all OK. You can open it up pretty easy to check that. Do you have some other test you would do to verify the viscous unit if this procedure doesn't do it? Thanks. Link to comment Share on other sites More sharing options...
BAC5.2 Posted October 5, 2011 Share Posted October 5, 2011 Yea, install it and drive it. Swapping center diffs is easy, if you have the ability to pull a transmission and own a torque wrench and caliper. The trans can stay in the car when you replace the diff. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
dbur Posted October 5, 2011 Author Share Posted October 5, 2011 I suppose that works, but for 5min effort I'll also check it my way as well before doing that. I just went through this and you are right, it's not a super challenging job to do. I shudder when I see some posts where they say they left the gasket out and used a liquid gasket, though. The gasket thickness is part of all the shim setups. Link to comment Share on other sites More sharing options...
BAC5.2 Posted October 5, 2011 Share Posted October 5, 2011 Nope, the gasket isn't required. It is perfectly acceptable to use a liquid type gasket during reassembly. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
dbur Posted October 6, 2011 Author Share Posted October 6, 2011 According to the factory service manuals it is. The creative mechanic could leave that gasket thickness out and adjust the shims accordingly though. Link to comment Share on other sites More sharing options...
BAC5.2 Posted October 6, 2011 Share Posted October 6, 2011 According to the FSM, there are a lot of things you should do but don't have to. I've had enough of these transmissions apart to know. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
dbur Posted October 7, 2011 Author Share Posted October 7, 2011 Well I'll certainly bow to one with more experience. Having only the service manual to go by and not getting answers to questions I posted in this forum (I even sent you a PM on someone else's recommendation) I had no option except to figure out and follow the manuals. Regards, David B Link to comment Share on other sites More sharing options...
BAC5.2 Posted October 7, 2011 Share Posted October 7, 2011 You sent me a PM? I'm usually pretty good at replying, but I get a bunch of PM's every day. I must have missed it, sorry! [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
dbur Posted October 9, 2011 Author Share Posted October 9, 2011 That's OK, I think I got it figured out finally. Though if you have any comment to this thread, I would still be interested in hearing it. http://legacygt.com/forums/showthread.php/92-center-diff-issues-parts-superceded-170343.html Link to comment Share on other sites More sharing options...
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