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Discussion Starter #1
Hi All,

I have spent some time researching rear end options on the forum. I have a few specific questions before moving forward with sourcing a replacement.

My truck is a 1st gen with a mild 350 swap and will see mainly street use. Currently has the 7.5" 10 bolt s10 rear which is leaking from the pinion.


While I have the tools and ability I would like to stay away from a Ford swap. Mainly because I don't want to run different wheel spacing front to back. It seems the only way to keep everything as "factory" as possible is to run the s10/blazer rear end. I understand the 4X4ZR2 comes in at 63", 4" longer than standard 4X4.

I don't know the standard length of the 7.5" rear so I am unaware if the regular 4X4 rear is a direct swap? Or if the 63" ZR2 can be shortened ln a similar way as many people do with the Ford 9"?

Basically I am looking for the best option to beef up the rear, nothing crazy, without having to worry about drilling rotors or ordering custom wheels.


Any help or opinion is appreciated,
Thanks.
 

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A mild 350 on the street will not break the 7.5.

I have an 8.6 out of a blazer, same exact width as my stock 7.5/7.625 in my '99, with disc brakes.
Not planning on swapping it any time soon.
I used to have a '87 with a 355 that ran 12 flat in the 1/4 mile. Did an 8.8 swap on that. Thinking back it didn't need it in my opinion.

Unless your dead hooking from a stop and pulling the wheels off the ground. Not common with a mild 350.
 

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End-all answer to S10 axle widths?
Thank you What?

2wd 54.5"
4wd 59"
ZR2 63"
This is WMS to WMS

All 3 widths were manufactured in the 8.5" 10 bolt. Some are harder to find than others. Usually came behind 4.3 5 speed. 98 up 4wd are disc brakes. There is a guy locally that wants $1K for an 8.5 2wd. He'll have it awhile.

As far as narrowing a ZR2, that's a lot more time and money than drilling rotors. The same abuse that will blow a 7.5 will blow an 8.5 a week later.
 

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Discussion Starter #4
A mild 350 on the street will not break the 7.5.

I have an 8.6 out of a blazer, same exact width as my stock 7.5/7.625 in my '99, with disc brakes.
Not planning on swapping it any time soon.
I used to have a '87 with a 355 that ran 12 flat in the 1/4 mile. Did an 8.8 swap on that. Thinking back it didn't need it in my opinion.

Unless your dead hooking from a stop and pulling the wheels off the ground. Not common with a mild 350.

Yes I do plan do drive and occasionally tax the rear end but it's not going to be a drag truck by any means. So another reason to avoid the Ford.
 

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Discussion Starter #5
End-all answer to S10 axle widths?
Thank you What?

2wd 54.5"
4wd 59"
ZR2 63"
This is WMS to WMS

All 3 widths were manufactured in the 8.5" 10 bolt. Some are harder to find than others. Usually came behind 4.3 5 speed. 98 up 4wd are disc brakes. There is a guy locally that wants $1K for an 8.5 2wd. He'll have it awhile.

As far as narrowing a ZR2, that's a lot more time and money than drilling rotors. The same abuse that will blow a 7.5 will blow an 8.5 a week later.
Thanks for the advice. With your opinion on the 7.5 vs 8.5 the only reason I would look for a new rear end would be if I wanted to upgrade to disc brakes?

Which leads me into my next question. You guys who are sourcing salvage yard rear ends. What sort of maintenance or upgrades are you performing if any before putting it under your truck?
 

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Thanks for the advice. With your opinion on the 7.5 vs 8.5 the only reason I would look for a new rear end would be if I wanted to upgrade to disc brakes?

Which leads me into my next question. You guys who are sourcing salvage yard rear ends. What sort of maintenance or upgrades are you performing if any before putting it under your truck?
Get rid of the gov loc. The one I have has a stripped governor gear, even if it wasn't I'd put in some other diff before using it. It also has 3.42's. My truck has 3.73's so I'd probably put 3.73's in with a new differential.

The gov loc works fine in my two other trucks, like getting stuck in wet grass. Heavy street use will break the gov loc in some way.

For what it's worth I paid $150 for my 8.6.
I saw a blazer that had an 8.6 missing at a junkyard that gets $130 for any rear.
I see an ad on craigslist, the guy wants $800+ and has several.
 

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I see an ad on craigslist, the guy wants $800+ and has several.
And probably will have them for a long time. Before I'd spend $800 to a 1000 on a 8.5/6 I'd look real hard at a custom 9" Ford. Not that there would be an original Ford part in it.
 

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Discussion Starter #8
And probably will have them for a long time. Before I'd spend $800 to a 1000 on a 8.5/6 I'd look real hard at a custom 9" Ford. Not that there would be an original Ford part in it.
The Ford avoidance isn't because I'm crazy and don't want any non GM part on the truck. I'm just trying to keep a 'factory' type setup where I can have 4 wheels that all fit properly at any location on the truck.

Using car-part to search it seems there is only one 2wd 8.5 in my area from a 2000 blazer. 121,000 miles list price of $295

Now I need to determining if it is worth the money to upgrade from my 7.5 or just rebuild what I have..
 

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Ignore the custom 9" suggestion, Older doesn't know what they cost... he needs to "look real hard".

Your 350 won't break the 7.625.

The 8.5 is a marginal upgrade.

The Ford Explorer 8.8 is a better upgrade but more work involved to shorten one side and get 2 new axles with correct BP from Moser (though in my book the 8.8 is the best budget rear end out there... but I am biased, I run a built 8.8).

Weld your existing tubes at the pumpkin, put a trutrac in it and go have fun. F' the rest of it... until you get a real motor :surprise:
 

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Discussion Starter #10
Ignore the custom 9" suggestion, Older doesn't know what they cost... he needs to "look real hard".

Your 350 won't break the 7.625.

The 8.5 is a marginal upgrade.

The Ford Explorer 8.8 is a better upgrade but more work involved to shorten one side and get 2 new axles with correct BP from Moser (though in my book the 8.8 is the best budget rear end out there... but I am biased, I run a built 8.8).

Weld your existing tubes at the pumpkin, put a trutrac in it and go have fun. F' the rest of it... until you get a real motor :surprise:
Interesting. Keeping the 7.5/7.625 (I'm not sure how to identify between the two) I would need about $400 for the new carrier. About another $400 if I wanted to change the ring and pinion.
Or build the Ford, I had never considered the backspacing issue could be fixed with new axles instead of just running two short side axles and dealing with it. Estimate for salvaged rear $150-$250. Estimate for new axles about $300. How are the factory Ford carriers?
 

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Interesting. Keeping the 7.5/7.625 (I'm not sure how to identify between the two) I would need about $400 for the new carrier. About another $400 if I wanted to change the ring and pinion. Or build the Ford, I had never considered the backspacing issue could be fixed with new axles instead of just running two short side axles and dealing with it. Estimate for salvaged rear $150-$250. Estimate for new axles about $300. How are the factory Ford carriers?
7.5 uses 26 spline axles, 7.625 uses 28 spline. They changed around 86/87 from the 7.5 to 7.625. The carrier internals are different. You mentioned it has a 7.5" so I assumed it probably does. Strength difference between the two isn't much though, not enough to swap a 7.5 to a 7.625 for anyway. Though there is more carrier selection for the later 10 bolts.

Backspacing isn't fixed with new axles, only bolt pattern is (well unless you're running some custom axle flange offset to accomodate a specific brake setup). Otherwise axle flange offset is constant. You'd still need to narrow one side. My point was more the bolt pattern is likely wrong for you...

As for the posi generally more durable than the Gov bombs, but they will still break with slicks. Generally, though a JY 8.8 3.73 with factory posi will work just fine, especially behind a mild 350. A used 10 bolt can be hit or miss and finding good posi 8.5's in 3.73 is getting harder as the years go by. There are none around my area now, haven't been for a few years. Still lots of 8.8's around though. You Americans have it so much better for parts... you don't even know lol.

I suppose the biggest question- if you haven't broken your read end already, why are you worried about it right this moment? As a hypothetical type upgrade to empty some cash burning a hole in your wallet- yeah 8.8 is a safe bet in stock form. It may be cheaper just to buy 4.50 BP deeper backspace wheels and run it as it is. I run vette wheels so I actually wanted the 59.5" WMS to WMS.
 

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Agreed.
Wait till you break it, if that ever happens. Use the money now for engine upgrades to expedite the process.
I built a stock 454 swapped 85 S10 with a 7.5 and even with severe wheel hop didn't break the rearend.
The weakest link on a 7.5" 10 bolt axle is the big nut on the steering wheel.
 
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Discussion Starter #13
7.5 uses 26 spline axles, 7.625 uses 28 spline. They changed around 86/87 from the 7.5 to 7.625. The carrier internals are different. You mentioned it has a 7.5" so I assumed it probably does. Strength difference between the two isn't much though, not enough to swap a 7.5 to a 7.625 for anyway. Though there is more carrier selection for the later 10 bolts.

Backspacing isn't fixed with new axles, only bolt pattern is (well unless you're running some custom axle flange offset to accomodate a specific brake setup). Otherwise axle flange offset is constant. You'd still need to narrow one side. My point was more the bolt pattern is likely wrong for you...

As for the posi generally more durable than the Gov bombs, but they will still break with slicks. Generally, though a JY 8.8 3.73 with factory posi will work just fine, especially behind a mild 350. A used 10 bolt can be hit or miss and finding good posi 8.5's in 3.73 is getting harder as the years go by. There are none around my area now, haven't been for a few years. Still lots of 8.8's around though. You Americans have it so much better for parts... you don't even know lol.

I suppose the biggest question- if you haven't broken your read end already, why are you worried about it right this moment? As a hypothetical type upgrade to empty some cash burning a hole in your wallet- yeah 8.8 is a safe bet in stock form. It may be cheaper just to buy 4.50 BP deeper backspace wheels and run it as it is. I run vette wheels so I actually wanted the 59.5" WMS to WMS.

The reason i'm looking into this when it hasn't broken yet is because the truck is not on the road yet. I am planning to be road ready by spring. With having to address the leaking pinion seal I figured now would be the time to explore alternative rear end options. This is/would be my first experience diving into a rear end so I'm admittedly a little green on the subject. Given the fact that I haven't driven this truck in any significant fashion is why I am looking here for advice from others who have. If it was 100% necessary to beef up the rear I would rather do it now when I have the time then have it blow up the first week I start yo drive it.
 

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The reason i'm looking into this when it hasn't broken yet is because the truck is not on the road yet. I am planning to be road ready by spring. With having to address the leaking pinion seal I figured now would be the time to explore alternative rear end options. This is/would be my first experience diving into a rear end so I'm admittedly a little green on the subject. Given the fact that I haven't driven this truck in any significant fashion is why I am looking here for advice from others who have. If it was 100% necessary to beef up the rear I would rather do it now when I have the time then have it blow up the first week I start yo drive it.
Your options:

Replace the bearings and seals in the existing rear.

Fabricobble an 8.8, you narrow it on one side and don't get it right it'll eat wheel bearings and the axle. Can you properly narrow a rear? I'm guessing no since you said you never worked on a rear. Narrowing one isn't the place to start.

Swap in a stock wirth 8.8 and get wheels with deep back space.


Buy a custom 9"

How much money do you want to spend?

Is it the seal or bearings too? I'd take the carrier out and look at the bearings on it. Before you do that you have to pull the axles out then you can see if the bearing surface is torn up. If it is you need new axles. I know how to just change the pinion seal without doing an entire tear down, some people don't.

You don't need any tools that I would consider special to fix the existing rear if you did decide to do a tear down and full rebuild. You keep the original pinion shim and keep the carrier bearing spacers on the proper side and it won't need special set up. Just verify the tooth contact pattern when you're done.

On the other hand I've seen people screw up a simple rebuild and swear it broke because they put too much power to it.

What would I do. rebuild the existing rear. OR there is a 79,000 mile rear sitting in my local junkyard right now. $150. If it had the right gear I'd probably look into that.

EDIT**** I forgot were talking about a rear with a gov loc. Factor changing that into the cost.
 

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Hello,

If the rear you have is in good condition other than the leak, has the ratio you want, etc. then there's not a lot of argument against just fixing it and driving the truck while you decide what you want next (disc brakes, different gearing, nothing at all?). There is a lot of value in having the truck move under its own power :)

Depending on local costs, it may not be that much more to narrow a junkyard 8.8 than to rebuild your 7.5 if you're replacing the Gov-Loc, and if you get a 1995-1999 Explorer rear, it will have disc brakes. I'd price out both before sinking a lot of cash into your 7.5, especially if discs are something you want as well. You can add rear discs to your 7.5 (I've done it, twice), but it's going to cost several hundred dollars on the low end, depending on what route you decide to go for a kit or donor vehicle. 7.5 + new limited slip + disc brake swap may not be cheaper than an 8.8 + narrowed + axles.

For those that are curious, Moser will sell you a fully assembled 9" rear, disc brakes, limited slip, powdercoated assembly, the works -- for a bit more than $4000 depending on how you option it.

I'm in a similar situation. I've got a 5.3 L33 + cam / intake manifold / headers / manual transmission that I'm swapping in right now. I have to either re-gear the existing rear (mine's 3.08 right now), or swap it for something else, so for me an 8.8 swap is almost certainly the cost-effective option.
 

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Discussion Starter #16
I haven't worked on a rear before but I know given the proper information I could successfully complete any of these options, including shortening an 8.8. I have had my hand in just about every other component of this truck and had I avoided projects I had never done before it would still be a bucket of bolts.

I think for now I will just replace the seals and run as is.

In the meantime I will work on sourcing a disc brake 8.8 and start the build process. The 8.8 seems to be the way to go for a couple reasons. Not only does it appear to be the most cost effective way to upgrade to disc brakes, but also will add strength at a fraction of the cost of building a 7.5/8.5. Estimating costs it would be about the same price to upgrade the carrier on my 7.5 than to build the 8.8, but the 8.8 would also include the disc brake upgrade.

Correct me if I'm wrong but this would be the plan of attack for the 8.8

- 1996-1998 Explorer Rear
- Conversion u-joint
- Shorten tube
- Corrected bolt pattern axles
- Rotors (will GM fit?)
 

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I haven't worked on a rear before but I know given the proper information I could successfully complete any of these options, including shortening an 8.8. I have had my hand in just about every other component of this truck and had I avoided projects I had never done before it would still be a bucket of bolts.

I think for now I will just replace the seals and run as is.

In the meantime I will work on sourcing a disc brake 8.8 and start the build process. The 8.8 seems to be the way to go for a couple reasons. Not only does it appear to be the most cost effective way to upgrade to disc brakes, but also will add strength at a fraction of the cost of building a 7.5/8.5. Estimating costs it would be about the same price to upgrade the carrier on my 7.5 than to build the 8.8, but the 8.8 would also include the disc brake upgrade.

Correct me if I'm wrong but this would be the plan of attack for the 8.8

- 1996-1998 Explorer Rear
- Conversion u-joint
- Shorten tube
- Corrected bolt pattern axles
- Rotors (will GM fit?)
A lot of 8.8 equipped vehicles use a companion flange. There are three different sizes that I know of. One fits the stock s series driveshaft.

Heres how you find out. Go to advanceautoparts.com and look up u-joints for your vehicle. Then look up u-joints for 1995 ranger, 1995 explorer, etc. one matches. Get the companion flange (the part that goes on the driveshaft) when you get the rear.
 

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Not a big fan of rear discs on a pickup. The very first rear ABS systems were fitted to late 80's S-10 pickups because they had a bad habit of the rear end coming around when braking hard. Particularly in rain or snow. Making the rear brakes more powerful is counter productive on the average pickup since they have a very front biased weight distribution. If you have a 1 ton with a service box on the back I could understand the need, but your average empty pickup box weighs nothing and preventing rear lockup is more important. Yes rear discs look cool, but if you do a 180 in the rain on the freeway the results won't look at all cool. Not to mention setting yourself up for some possible lawsuits not covered by insurance since you modified the brakes.
 

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....unless you do the big brake mod up front. My rears used to lock up on occasion with factory size tires. When the 285-45-17's were out back it was better. Since the front upgrade there have been zero issues other than needing seatbelts for my cupholders. Had I done then prop valve mod prior to the big brakes, I think the lockup issue would have gone away. Since the mod there have been no issues. Keep In mind that the '97+ trucks abs will take care of any prop valve problems.
 

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I have done the big brake front swap along with the rear disc axle assembly to 3 of my S10s.
No mods to the P valve or anything else. Simple straight bolt in for everything. No touchy anything else at all.


I've also added drilled/slotted/plated rotors with ceramic pads to all of them. Flushed the brake fluid and of I went.


Do they stop?
Noooooooo not at all. :yikes:


It is an amazingly HUGE difference compared to the original brakes.
Doesn't take much to do a face plant on the w shield....


Sorry, didn't mean to jack here, but I don't think there is a single production truck that doesn't run 4x disc brakes anymore - unless you're in Russia....
 
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