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axle upgrade qustion

Old 02-15-2014, 10:15 PM
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Default axle upgrade qustion

ok im posting this cuz im stumped. i have a 2000 gmc jimmy 4x4 with the 7.6 rear end and 3.43 gears. i recently purchased a zr2 np233c transfer case to uprage my factory weak transfer case. i also wanna upgrade my axles and gear ratio. i been doing research on things between the ford 8.8 rear end and the bolt in zr2 8.5 rear end. i know the ford requires a lot of modification. and finding a zr2 blazer or s10 rear end is next to near impossible in my area. so i am wondering will the 10 bolt 8.5 rear end from a checy truck work in my jimmy. also will the front diff bolt in as it looks the same as my factory one. im upgrading to either 3.73 gear ratio or 4.10. if the axle don't bolt in what other vehicles come with the 10 bolt 8.5 rear end so i can grab the right one
Old 02-15-2014, 11:23 PM
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Out of curiosity, why are you upgrading parts? The only common transfer cases for the Jimmys was the NP23x series, and they're all pretty much the same strength.
Old 02-16-2014, 12:19 AM
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I didnt think the 236 could be swapped easy to a 233, most people swap to the 231 because it is the strongest that bolts right up and you can get rid of the electronics by just putting a tcase lever in the interior.

The 7.2 GM IFS front differential from s10s bravadas and I believe some astro safari vans will bolt right up which finding one the right gear and putting it in yourself is probably cheaper than having one regeared. The front diff that came in the full sizes GMs is a 8.25 with fabrication/welding and custom cvs it could be made to work, but if your gonna put that much money into it you mine as well do a straight axle swap, I believe there a couple semi partial/more like universal kits out there that you could weld on.

Some regular s10s and blazers came with the 10 bolt 8.5/8.6 3.73 gears stock not just zr2s I think the RPO codes can tell you. Alot of GM vehicles came with the 10 bolt, its just whether or not the width will work, although if you really wanna do it I'm sure you could narrow a diff by cutting but your better off just finding the right one. You might have to cut the spring brackets off of the donor 10 bolt, or whether they have drum brakes. I know some trailblazers/envoys came with the 10 bolt 8.5/8.6.
Old 02-16-2014, 09:02 AM
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I wish the full size ten bolt would work, but I'm pretty sure it's too wide. Some guys say they've put them under blazers, but I think it would make the tires stick out way to far.
Old 02-16-2014, 11:35 AM
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A zr2 rear axle would be a bolt in strength upgrade and will give you 3.73 gears. If you can find a whole truck pull the front diff too to match ratios. The zr2 8.5" 10 bolt is a little wider then a standard 4x4 axle, but not as wide as a fullsize truck axle (way too wide). I'd say that's a no go unless you plan on SASing on full width front to match.

BTW, the np233c that comes in a zr2 is no stronger then any other np23x of a similar year. It will only be an upgrade if its an older model HD case with 1.25" chain and 6 planet pinion. Even then its kind of a moot point as the case normally lets go and cracks before the chain/pinion. The 1.25 cases don't have as many chain stretch problems from what Ive seen though

Last edited by KM346; 02-16-2014 at 11:42 AM.
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