I picked up a 85 442 and i know they come with the 8.5 10 bolt rear and 3.73 gears but mine happens to be the open diff and I would like to go to a posi that came in these things at the time which I was told are etons ? So im wondering since this is a 8.5 10 bolt can i just go to the yard and find the 8.5 carrier in posi in lets say a truck or something or am I stuck waiting for a part out of a gbody? thank you all in advance !

 

So long as the spline count for the axle shafts is the same, yes. Be wary of the truck GovLoc differentials, however. Those use a weight that is flung out by centrifugal force before the diff locks up. That means that one wheel needs to be spinning at a certain RPM before the diff locks up with a clunk. Not recommended for a performance car.

 

thanks so ill try and go yard hunting today.

 

Why rebuild a 30 year old differential with a 30 year old posi carrier?


Just put a new Eaton carrier in the differential with the gears of your choice. Do it once & do it right.

 

Yep, just ensure the axle spline count is the same as Joe said. Take a look at this application info on the Richmond Gear web site for which vehicles used the 8.5" 10 bolt rear:

http://www.richmondgear.com/pdf/Rich...n1.pdf#page=31

 

Car posi unit is not a EATON
It is a trac Lock
'S' spring unit
28 spline
You need a 410408 casting

I have a bunch on the shelf we can recondition one for you for 289.00

IF you find a 2 series 410409 you can use a spacer kit and still use it.

Both those castings are for C-clip axled rears.

 

ok thank you guys also ill keep that in mind @monzaz

 

Are you saying that Eaton does not make an 8.5" posi carrier for this differential or that it is no good? I don't understand your objection to my comment about installing a new Eaton unit in this differential.


This is the unit I am referring to


http://www.summitracing.com/int/part...-010/overview/


I certainly have no objection to installing a reconditioned factory unit; my point was not to install wore out 30 year parts.

 

I do not know what your quoting to me, I am posting to the questions and subject matter of easytobedead. This is not your thread. He thinks the 's' spring unit is an EATON posi. (first post Quoted from his first post ' I would like to go to a posi that came in these things at the time which I was told are etons' which was spelled wrong) He is junk yard hunting for this factory unit. The GM Factory Eatons for 8.5's are TRUCK unit gov locks. So the likely hood he will find a Car Unit aftermarket 19557-010 unit in a junk yard rear is slim to none...usually... I have found a few in the 1000's I have parted out but they were in trucks that guys probably replaced after the gov bomb blow sky high. So since in the junk yards he will be likely looking under cars, this maybe very unlikely to find a aftermarket performance unit. Hope that clears up the subject matter for that part.

Next, to answer your question towards the aftermarket unit you referred him in installing, yes it will fit into his diff just as a stock 's' spring trac lock unit would. Which might be the smart thing to do, BUT he may not want or can't afford a 500.00 unit in his diff -as he stated he wanted an original type unit for his car.
Finally, no where in my post did I object to him or you installing this aftermarket unit nor did I even refer to your posi post...? Remember, I would have quoted your post as you have quoted mine to answer or remark about your subject matter of some one other than the original thread posting.

Thanks,
Jim
J D

 

Jim


In post #6 you start with CAR POSI UNIT IS NOT AN EATON.

I realize now that this was not a quote but I took it as reference to my post when I responded. That is where the confusion came from.


My initial post still stands. Don't rebuild it with parts that are wore out. You offer reconditioned parts as well as new & encouraged the original poster to follow that path and not just pull a potentially wore out carrier from another donor.


No offense was intended to you. I am a past customer of yours' & have often recommended that others seek your services. Sorry about the confusion.

 

I know you were not attacking as I was not either just explaining your needed answers and how the posts work the way they read and work.
It was my first post so it would reference what the first poster listed. If not quoted off of someone else that has posted.


Take care, Jim