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Old 10-13-2008, 11:14 PM
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Eaton posi's

Hi, I was wundering what the difference is in the older GM 7.5's and the newer ones. For example The one in my 1982 cutlass supreme v.s. a 94 s-10 or what ever has them after 1990. I thought the only difference was that the older ones had 26 spline axel's and the newer ones have 28 spline. Is this the only difference or is there more. I've never really done much swapping on rearends, just a little welding for the derby, so I'm a little in the dark hear. Thanks Danny

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Old 10-14-2008, 09:40 AM
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88 and earlier :26 spline
89 and later :28 spline

As far as the gear set's,they are the same.
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Old 10-14-2008, 09:45 AM
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What are you trying to swap around?
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Old 10-14-2008, 09:20 PM
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posi

well I found a guy that has a new eaton posi for a later model 28 spline, and I was wundering if I could but it in my 82' cutlass if I get some 28 spline axeles. What else will I have to change? I know the 7.5 isn't the strongest by far, but I can't afford a whole new rear end right now. I also know my cam needs atleast a 411-456 gear (lunati bracket master II 300) 3300-3500 stall TH400. I know If I stay with the 7.5 I need to beef up the axels and get a posi at the least. I thought of running a mini spool, but I hear they are a pain on the street. The car won't be a daily driver but it will see SOME street time. My motor should be around 450-500 HP.
Dynosim puts her at 464 FTLB TQ MAX at 5000rpm, and 501 HP max at 6500. So I'm just tryin to find the best way to get it to the pavement and still have mediocre drivability on the street...
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Old 10-14-2008, 10:37 PM
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Quote:
Originally Posted by eatonde
well I found a guy that has a new eaton posi for a later model 28 spline, and I was wundering if I could but it in my 82' cutlass if I get some 28 spline axeles. What else will I have to change? I know the 7.5 isn't the strongest by far, but I can't afford a whole new rear end right now. I also know my cam needs atleast a 411-456 gear (lunati bracket master II 300) 3300-3500 stall TH400. I know If I stay with the 7.5 I need to beef up the axels and get a posi at the least. I thought of running a mini spool, but I hear they are a pain on the street. The car won't be a daily driver but it will see SOME street time. My motor should be around 450-500 HP.
Dynosim puts her at 464 FTLB TQ MAX at 5000rpm, and 501 HP max at 6500. So I'm just tryin to find the best way to get it to the pavement and still have mediocre drivability on the street...
Yes, If you had axles it would work,And your right about the 7.5 not being the strongest, with that motor,converter and ratio,Your gonna really be testing that baby,

A spool is not a bad way to go with a car like your building,cheaper,less moving parts to break,and not really a big deal to drive on street.
1, how much does your bud want for the posi?
2, have you seen this posi or at least a pic? If it's a guv lock,pass on it,you WILL tear it up.
3, do you already have the gears for a ratio change?
4,can you do the ratio change if needed or will you have to pay to get it done?
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Old 10-15-2008, 01:15 AM
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With that much power you need to get a 8.5" Posi rear from a Buick GN or Olds 442. If you plan on any strip/drag time. They're much stronger. There are a few for sale on the TurboBuick.com classifieds.
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Old 10-15-2008, 10:21 AM
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Be aware that the light truck (even S-10) may not have a "posi" in it, it could be an Eaton "No Spin" which is a governor type locking diff. It may make no difference for your application but you need to know the difference.
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Old 10-15-2008, 12:39 PM
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Quote:
Originally Posted by SSedan64
With that much power you need to get a 8.5" Posi rear from a Buick GN or Olds 442. If you plan on any strip/drag time. They're much stronger. There are a few for sale on the TurboBuick.com classifieds.
Kinda was I was starting to hint at also, If we can figure out how much money Danny would have in his 7.5 doing gear swap's,posi etc,he can compare it to getting ahold of a 8.5 and see if it's even close to the budget. The 71 to 77 cutlass had a 8.5 also, not sure if the housing is the correct configuration.
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Old 10-15-2008, 11:24 PM
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71-77 cutty

I looked at these also but If I remember right, Its not a bolt in. Aren't those a bods?? mine Is a G. I think the spring pads and some other stuff is in diff places. Seem's like all the ones i find from SS's and GN's and T Types are striped to just an empty case and tubes and guys still want a grand for them... ugh.. go figure.... I think I might just try a mini spool for now. they seem reasonably priced. and a budd of mine had one in a stock 373 s10 rear that held 430HP no prob. with ET streets. Not positive which way to go yet but something has gotta be done. either cam or gears. I really like my cam thoughIt would just be a lot better for the street with a manual tranny, but again you just cant find em w/ out givin an arm and a leg.

Question, How come some guys say a mini spool is terrible on the street but some say thier fine. The one I rode in was OK, even in rain....... you know anywhere that sells used manual tranny's that will hold some power.
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Old 10-16-2008, 01:02 PM
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Quote:
Originally Posted by RetroWill
Be aware that the light truck (even S-10) may not have a "posi" in it, it could be an Eaton "No Spin" which is a governor type locking diff. It may make no difference for your application but you need to know the difference.
Exactly! This is why tossing around the word "posi" bugs me. 73-up GM trucks almost exclusively used Eaton Gov-Locks as the optional (G80) diff. Do a search on here for Gov-Lock and you will see why they have been given the name Gov-Bomb...which is what that S10 diff. will be.

If you want an upgrade get an aftermarket 28-spline diff.

Last edited by Triaged; 10-16-2008 at 01:17 PM.
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Old 10-16-2008, 04:08 PM
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Quote:
Originally Posted by eatonde
I looked at these also but If I remember right, Its not a bolt in. Aren't those a bods?? mine Is a G. I think the spring pads and some other stuff is in diff places. Seem's like all the ones i find from SS's and GN's and T Types are striped to just an empty case and tubes and guys still want a grand for them... ugh.. go figure.... I think I might just try a mini spool for now. they seem reasonably priced. and a budd of mine had one in a stock 373 s10 rear that held 430HP no prob. with ET streets. Not positive which way to go yet but something has gotta be done. either cam or gears. I really like my cam thoughIt would just be a lot better for the street with a manual tranny, but again you just cant find em w/ out givin an arm and a leg.

Question, How come some guys say a mini spool is terrible on the street but some say thier fine. The one I rode in was OK, even in rain....... you know anywhere that sells used manual tranny's that will hold some power.
For what your doing a spool will be just fine,I hardly ever notice mine and my tires are BIG!.If you have to use that diff you have for now,honestly I would limit your spending on that diff, and save up and spend the big money and a tougher diff.
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Old 10-16-2008, 04:21 PM
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Quote:
Originally Posted by Triaged
Exactly! This is why tossing around the word "posi" bugs me. 73-up GM trucks almost exclusively used Eaton Gov-Locks as the optional (G80) diff. Do a search on here for Gov-Lock and you will see why they have been given the name Gov-Bomb...which is what that S10 diff. will be.

If you want an upgrade get an aftermarket 28-spline diff.
See above post,I dont think he has verified which unit he was looking at.It could already be a aftermarket unit, he never said it was factory.Dont look like a 28 spline upgrade is going to be a option, unless he has some axles made. the 26 spline axle should be 28 7/16 long and I'm not seeing any 28 spline that are the correct length.
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Old 10-16-2008, 06:38 PM
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mini spool

OK please bare with me. I've never done any rear end work so I am kinda blind in this field. My dad has done several, and he's gonna be helpin me, but my question is. If I decide to use a mini spool, which I think a am, What all is involved in the swap??

can I use the same 7.5" carrier and just change the ring and pinion to a 411??? Or do I gotta use a special carrier?? If I can use the same one, What to I remove to install the mini spool?? any special tools required??? like I said I'm blind right now. Is there anywhere that show's a step-by-step install of a mini that I could read to atleast get some idea of what I'm gettin myself into.
Thanks for your help guys
Danny
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Old 10-17-2008, 09:36 AM
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Quote:
Originally Posted by eatonde
OK please bare with me. I've never done any rear end work so I am kinda blind in this field. My dad has done several, and he's gonna be helpin me, but my question is. If I decide to use a mini spool, which I think a am, What all is involved in the swap??

can I use the same 7.5" carrier and just change the ring and pinion to a 411??? Or do I gotta use a special carrier?? If I can use the same one, What to I remove to install the mini spool?? any special tools required??? like I said I'm blind right now. Is there anywhere that show's a step-by-step install of a mini that I could read to atleast get some idea of what I'm gettin myself into.
Thanks for your help guys
Danny
What ratio is in the diff now? if its 323 or lower your fine with the standard 411 gear set,if you have 308's now,when you order the gear set,order a THICK ring gear set,this allows you to run the 411's on the 308 carrier.

As far as the mini spool,YES it will fit in a stock open carrier,as far as installing the mini,its pretty straight forward once you look at alll the pieces,no special tools needed,This will give you a idea.
http://www.markwilliams.com/servicebull/sb0034.pdf

Yukon makes a mini spool for your diff and sells for $117.00

Last edited by prostreet6t9; 10-17-2008 at 05:01 PM.
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Old 10-17-2008, 04:10 PM
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Quote:
Originally Posted by prostreet6t9
Kinda was I was starting to hint at also, If we can figure out how much money Danny would have in his 7.5 doing gear swap's,posi etc,he can compare it to getting ahold of a 8.5 and see if it's even close to the budget. The 71 to 77 cutlass had a 8.5 also, not sure if the housing is the correct configuration.
Those are wider, spring pearches may be different location also.
I've seen 2 or 3, Buick GN 8.5" rears on TurboBuick.com site. They have a clutch type Posi & 3.42 gears. For $800 & up. Those are a bolt in fit. I wouldn't put any money into a 7.5" if he's gonna drag it. MiniSpool is cheap tho' & worth a try.
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