If memory serves, then the 489 third member started in late 1969 or early 1970. It should have a finer spline pinion shaft. Bill Huff At 12/19/200704:02 PM, Richard Osborne wrote: >Dave, > >The numbers you have provided are the casting numbers. These have >nothing to do with gear ratios inside or wether or not it is an open >or sure grip rear. Any of these casings could have ratios ranging >from 2:76 to 3:91 (and maybe others from Chrysler) > >I assume these "pigs" are out of the rear end housing. If they are >still in the housing AND they have not been out before, there will >be a small stamped metal tag that goes onto one of the housing studs >that tells the gear ratio and will say "sure grip" if so equipped. >If it is not a sure grip, then only the ratio is stated. This is the >only exterior way to tell the ratio and status. > >The only way to tell if it is a sure grip if the pig is removed is >to look inside. There were 2 types of sure grips that Chrylser used >in 8 3/4 rears. A spring type (not serviceable) and a clutch type >(which is serviceable with new clutches). If you can see the spyder >gears easily, then it is probably an open rear. If these are not >readily visible, it may be a sure grip. > >I can't remember off the top of my head which casting number is >correct for which year if you are into the numbers matching thing. > >Hope this helps. > >Richard Osborne > > >>> david dumais > <<mailto:dvd_dumais%40yahoo.com>dvd_dumais@xxxxxxxxx> 12/19/07 11:13 am >>> >After checking the part # on my 3:23 unit, it is 2070742, with a >small 's' below the number. Is this a sure grip? I can see gears and >cross shafts. > >The other unit is 2881489, with a '9' on the opposite side. This >unit has springs visible, and the ratio is 3:55 to 1. This is a sure >grip unit of some kind. It has 21 bolts on the ring gear. > >I assume this is not the correct diff. for the K. If the 742 is a >conventional rear and not a sure grip, can the center drum from the >489 be intsalled in the 742, or should I seek a 742 >for real sure grip? Dave > >--------------------------------- >Be a better friend, newshound, and know- it- all with Yahoo! Mobile. >Try it now. > >[Non- text portions of this message have been removed] > > [Non-text portions of this message have been removed] To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Chrysler300/join (Yahoo! ID required) <*> To change settings via email: mailto:Chrysler300-digest@xxxxxxxxxxxxxxx mailto:Chrysler300-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/