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Rear end differential mystery

How do I go about buying a posi diff.

Rear end differential mystery

Postby Killain [OP] » Feb 22 2013, 9:58pm

I'm trying to buy and install a posi-trac differential in my 1990 Chevy 1500 Silverado, it's got a 305 ci. V8 and a 700R4 and the gears back there are 3:42. Can anyone tell me how to go about figuring out if I have a 28 or a 30 spline rear end ? I called a couple of dealers, but they all say the truck is too old to look up any information on. Any ideas are more than welcome. I can buy a brand new Eaton posi-trac for about $450.00 but I need to know what number of splines it has. Thank you !
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Re: Rear end differential mystery

Postby steved » Feb 22 2013, 10:11pm

Call Randy's Ring and Pinion, they should be able to tell you...
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Re: Rear end differential mystery

Postby Killain [OP] » Feb 25 2013, 10:25pm

How do I contact them ? Thank you !
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Re: Rear end differential mystery

Postby 19trax95 » Feb 25 2013, 10:32pm

Off topic but....

Thats a pretty clean looking obs you got there.
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Re: Rear end differential mystery

Postby Killain [OP] » Feb 25 2013, 10:58pm

Whats an OBS ?
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Re: Rear end differential mystery

Postby 19trax95 » Feb 25 2013, 11:09pm

Obs is just an acronym for old body style. Which encompasses model year 1988-1998. Then there is oobs (old old body style) which is 72-87. Nbs is 99-07.5 and nnbs is 07.5-2013
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Re: Rear end differential mystery

Postby Daly » Feb 25 2013, 11:18pm

In 1990 they were 30 spline. And +1 on the truck, it is a beautiful looking truck.

I do hate the acronyms for trucks. People should get use to calling them by there GM names, at least from 88 on.
88-98 GMT400
99-07 GMT800
07.5-13 GMT900
What are they going to call the 2014's, NNNBS (new new new body style) It's stupid IMO.
2014 Silverado LT…
Daly's 2014 Silverado
2012 Silverado LS - gone
Daly's 2012 Silverado
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Re: Rear end differential mystery

Postby Killain [OP] » Feb 26 2013, 1:11am

Well then, Thank you very much. I've wanted to install a Posi-trac differential and I have found a few, prices are all about the same $425.00 New, but I didn't know what splines I needed. Thank you. And yes, It is a great looking truck, which took a lot of sweat equity to get to where it is. Thank you for your help !
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Re: Rear end differential mystery

Postby steved » Feb 26 2013, 3:28am

Randy's Ring and Pinion should have a website. There is also 4xHeaven, which is a little mom and pop type store, but they always treated me well and gave good prices.
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Re: Rear end differential mystery

Postby Killain [OP] » Feb 26 2013, 10:48am

Thank you !
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