identifying rearend, installing posi and gears
03-17-2017, 05:06 PM
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identifying rearend, installing posi and gears
OK, group. School me! Got an 85 IROC with a healthy motor and trans. Need a posi and gears. How do identify the carrier, which Posi is good for the dough, and where do I order a set of 3:73s?
03-17-2017, 06:38 PM
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Re: identifying rearend, installing posi and gears
First of all, do you have the GM 7.5 10 bolt or do you have the Borg Warner 9 bolt?
If you have the GM 10 bolt then you need to make several upgrades. You need to swap the 26 spline axles for 28 spline axles. Then you need to decide if you want a clutch type limited slip differential or a gear type LSD. We are going to need to know what you are going to do with the car before any accurate information can be given.
If you have e Borg Warner rear end then it should already have a LSD in it. It might be worn out, but it can usually be reconditioned once. Gears and parts are a little harder to find for this rear end, but they are available. This rear end already has 28 spline axles, so no need to upgrade.
If you have the GM 10 bolt then you need to make several upgrades. You need to swap the 26 spline axles for 28 spline axles. Then you need to decide if you want a clutch type limited slip differential or a gear type LSD. We are going to need to know what you are going to do with the car before any accurate information can be given.
If you have e Borg Warner rear end then it should already have a LSD in it. It might be worn out, but it can usually be reconditioned once. Gears and parts are a little harder to find for this rear end, but they are available. This rear end already has 28 spline axles, so no need to upgrade.
03-17-2017, 09:09 PM
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Re: identifying rearend, installing posi and gears
First of all, do you have the GM 7.5 10 bolt or do you have the Borg Warner 9 bolt?
If you have the GM 10 bolt then you need to make several upgrades. You need to swap the 26 spline axles for 28 spline axles. Then you need to decide if you want a clutch type limited slip differential or a gear type LSD. We are going to need to know what you are going to do with the car before any accurate information can be given.
If you have e Borg Warner rear end then it should already have a LSD in it. It might be worn out, but it can usually be reconditioned once. Gears and parts are a little harder to find for this rear end, but they are available. This rear end already has 28 spline axles, so no need to upgrade.
If you have the GM 10 bolt then you need to make several upgrades. You need to swap the 26 spline axles for 28 spline axles. Then you need to decide if you want a clutch type limited slip differential or a gear type LSD. We are going to need to know what you are going to do with the car before any accurate information can be given.
If you have e Borg Warner rear end then it should already have a LSD in it. It might be worn out, but it can usually be reconditioned once. Gears and parts are a little harder to find for this rear end, but they are available. This rear end already has 28 spline axles, so no need to upgrade.
So I guess, in addition to gears and posi, we need new axles.
03-17-2017, 09:13 PM
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Re: identifying rearend, installing posi and gears
I sure wouldn't trust 26 spline axles with a strong V8. You could start with a '90 to '92 rear end and you would have 28 spline axles. Just check them to be sure that they are still good before buying another rear end, only to find that you have to replace the axles anyway. C clip axles wear where the bearing runs on them. If they are worn then the only way to fix it correctly is to replace the axles and bearings.
03-18-2017, 10:38 AM
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Re: identifying rearend, installing posi and gears
03-18-2017, 10:49 AM
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Re: identifying rearend, installing posi and gears
NO!!!!!!
ABSOLUTELY NOT!!
That's the WORST POSSIBLE thing you could put in your car. That's the notorious Gov-Bomb aka Grenade Lock. The way it works is, you have NO POSI ACTION WHATSOEVER until the difference between the axle RPMs exceeds some threshold (around 150 RPM if memory serves), at which point it locks up with a bang. And I do mean A BANG literally: if the car has traction, it can actually EXPLODE and send shrapnel through the cover. In fact there's a picture running around where that happened to someone and it came apart with such force that the shrapnel went through the cover and into the gas tank.
That system comes stock in a lot of trucks; go hang out on some S or full-size truck boards, and look at what happens to those guys.
Keep looking.
ABSOLUTELY NOT!!
That's the WORST POSSIBLE thing you could put in your car. That's the notorious Gov-Bomb aka Grenade Lock. The way it works is, you have NO POSI ACTION WHATSOEVER until the difference between the axle RPMs exceeds some threshold (around 150 RPM if memory serves), at which point it locks up with a bang. And I do mean A BANG literally: if the car has traction, it can actually EXPLODE and send shrapnel through the cover. In fact there's a picture running around where that happened to someone and it came apart with such force that the shrapnel went through the cover and into the gas tank.
That system comes stock in a lot of trucks; go hang out on some S or full-size truck boards, and look at what happens to those guys.Keep looking.
03-18-2017, 02:17 PM
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Re: identifying rearend, installing posi and gears
I agree, that's a Eaton Governor Lock. You do not want that. What are you going to do with the car? If it's going to be street strip then get an Eaton Posi or a Yukon Dura Grip. If it's street auto cross then get the Eaton Truetrac. Do not get the Eaton Gov Lock or Auburn.
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03-25-2017, 09:15 PM
#8
Re: identifying rearend, installing posi and gears
Here's a Truetrac for a 26 spline 10 bolt:
http://www.ebay.com/itm/Eaton-Detroi...VXgCd4&vxp=mtr
They have 28 spline versions also.
Gear sets are available in any ratio you could want.
The 10 bolt is not very strong without some 28 spline axles. Even then it's not the best.
I upgraded my Borg Warner 9 bolt but gear ratios are more limited and had to get my Truetrac from Australia. Not that it was difficult or that much more expensive ($530 shipped). But people make a big deal out of not being able to get parts. I had no real problem with a little legwork. You can find 9 bolt rear axle assemblies pretty cheap from IROC and Trans Am models from 85 to 90 or so. They have a larger ring gear (7.75"), are more rigid and heavily constructed, 4 pinion carrier (doesn't matter if you go Truetrac), rear discs, semi-floating, 28 spline, etc. If you aren't planning to go nuts and need a Ford 8.8 or 9" then it's a worthwhile thing to find and upgrade. Straight bolt in for all third gens of course.
Rick
http://www.ebay.com/itm/Eaton-Detroi...VXgCd4&vxp=mtr
They have 28 spline versions also.
Gear sets are available in any ratio you could want.
The 10 bolt is not very strong without some 28 spline axles. Even then it's not the best.
I upgraded my Borg Warner 9 bolt but gear ratios are more limited and had to get my Truetrac from Australia. Not that it was difficult or that much more expensive ($530 shipped). But people make a big deal out of not being able to get parts. I had no real problem with a little legwork. You can find 9 bolt rear axle assemblies pretty cheap from IROC and Trans Am models from 85 to 90 or so. They have a larger ring gear (7.75"), are more rigid and heavily constructed, 4 pinion carrier (doesn't matter if you go Truetrac), rear discs, semi-floating, 28 spline, etc. If you aren't planning to go nuts and need a Ford 8.8 or 9" then it's a worthwhile thing to find and upgrade. Straight bolt in for all third gens of course.
Rick
Last edited by GeneralDisorder; 03-25-2017 at 09:18 PM.