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I will be building a 1998 chevy extended cab soon as I buy it off my friend. I have a 1977 1500 truck with a 12 bolt rear in it. I really want to keep it all chevy so I am thinking about using the 77 rear in my 98. Is the 77 narrower than the 98 and does anybody know what to expect when I open up the 77 rear to rebuild it as to what gears are in it or is there a posi in it too. Where should I look for someone to rebuild this 77 diff for my newer truck. I am hoping it is narrower so I can put on bigger meats on the back. Wider and its just not going to happen. Can anyone help with some info !!!Thanks--I dont happen to have the 77 here yet to measure !!! or the 98 !!!

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Really-----Does anybody have one of these models and years so they can let me know what I need !!!!!

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I believe the 90s ten bolts are about a half inch per side wider than 80s ten bolts. The 12 bolts I'm unsure. As for whether you have a posi or not you will have to open it to find out
Randy's ring and pinion does work though
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Thats Great but I have a seventies rearend to work on not an eighties !!!!Thanks for the help with the company though !!!

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I'm sure the 70s and 80s 10 and 12 are the same length. I will measure tomorrow on my 77 and my 86.

I swapped axles in my 86 ten bolt with a 90s 5 lug and they were half inch wider per side.

If your going for strength the 12 bolt isn't a good place to look. The ten bolts are still stronger. Almost as much as the car 12 bolts. Reason is the truck 12 bolt has a spindly small pinion shaft that brakes. If you aren't using slicks though and racing then you won't know the diff between the two.
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Like INSIDIOUS said the rears are the same width from 73-87


-Sam

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Really; I thought I could build a 12 bolt that was almost as good as a 9 inch !!! I wont be racing at a track but probably using it a little I hope. Will be using a 355 or a 383 with it !!! I just wanted to stay true to Chevy !!! I also thought the 12 was a couple of inches narrower on each side too !!! Hopefully the measurement will tell !!! Thanks Guys---I guess I am still up in the air about using the 12 bolt still !!!

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i was going to swap a 12 bolt into my '82 as well, but after much research decided to go with the GM 9.5" 14 bolt. worth looking into if you are looking for strength and staying GM.

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Thanks kSStamp0182----I will check that out 2. Don't know anything about them --Thats for sure !!!

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Notice that your from Tyler,Texas---I might be coming down there this winter looking for another 98 to build(extended) . Hows the pickins down there. Did you save me any trucks to buy and build !!! LOL

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there are older chevys EVERYWHERE around here. everyone drives a truck, the only big issues we have with rust are if its sat with water in the bed, & beware of mud or "hunting" trucks. other than that its quite easy to find great trucks at decent prices.