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  #31 (permalink)  
Old 02-03-2014, 09:18 PM
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Quote:
Originally Posted by rumpfox View Post
that mekes it fun and perdictable thats why cup cars use lockers not posis.

cup cars, most times, are set up to drive the right rear 95% and left almost zero.. unless it's a road course car..


Alocker in a cup car would put cars in the wall

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  #32 (permalink)  
Old 02-03-2014, 09:20 PM
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Originally Posted by big gear head View Post
There are many things that break in the 7.5 rear ends. I've seen the ring and pinion break, differential gears and axles. It's just a light weight rear end that was not designed for high performance use. I would recommend saving some money for a Quick Performance 9 inch Ford housing and axle package and then get a good used chunk to go in it.
Have you seen the moser 12 bolt new housings? are they as good as they say in the catalog..
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Old 02-04-2014, 02:46 AM
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Hello all I went with the ford 8.8 it's as close to the nine inch and you can get them pretty cheep and you can find them with the 31 spline axles . And the best thing their is no gear cut off
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Old 02-04-2014, 02:49 AM
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Stay away from the strange rear I have a few buddies that has had them strange did not stand behind there product the gears are loud and problemmatic
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Old 02-04-2014, 07:41 AM
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NASCAR Cup cars use lockers at every track, even the superspeedways.

Used parts and assemblies are cheap and plentiful.




Used RYP-121-450 Ford 9 Inch Rear Carrier Locker Gear Assembly 4.50:1 Ratio
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  #36 (permalink)  
Old 02-04-2014, 08:54 AM
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What I understand about the 12 bolt GM rear diff is that the pinion angle to the ring gear is not ideal for high torque. It places too much stress on the pinion shaft bearings. Even a well built 12 bolt will tend to be noisy after some amount of hard launches. The 9", and I have heard that the 8.8 is similar, has a more ideal pinion angle that helps them better handle torque thrust loads. The 9" (and maybe some of the 8.8s but I don't know) have a pinion shaft support with a needle bearing that supports the inboard end of the pinion shaft for even greater strength. I am no expert though. This is only what I've picked up in my research. That's why I'm looking at either the 8.8 or 9" as my solution. I will be asking alot of questions when the time comes closer.

The 7.5 in my Camaro has withstood 16 years and 25K mi of abuse behind a 450HP 430ft lb small block and a hard shifting automatic. It only does this because I have never put even drag radials on it, let alone slicks. Friends who have run drag radials or slicks with their built motors have had their cars brought home on the flat bed with broken rear diffs. What generally breaks is the diff case itself along a line from the cross shaft bores. I have also seen the cross shaft shear like it was cut with a knife. The axles twist and can end up crooked but they don't seem to break commonly.

Mine's not built to be a drag car anyway, but with a few rear suspension upgrades, it does get decent traction. Whenever I don't have the sound system blaring, drowning out all noises, I can hear that rear diff whine. I am running Valvoline synthetic 70W-140 in it now with BG LSII limited slip additive. That's probably the best widely available gear lube there is. For a long time I ran an industrial grade severe gear lube(something crazy like 70-90-140-210) from Stern Chemtech that was like syrup. That's probably got alot to do with why it's still alive. When I had it open, swapping in the 02 Z28 rear brakes, I could see the slop in the cross shaft to the diff case and there was a decent amount of metal in the fluid. I see this in all of the small diff cases that use that design after any kind of high mileage. My cross shaft was actually not torn up like I generally see in harsh applications, again the premium gear lube. The slop was in the case bores. This is unavoidable and part of why these small rear diffs will never be good for any kind of high performance use. Just my 2 cents.
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  #37 (permalink)  
Old 02-04-2014, 10:42 AM
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Quote:
Originally Posted by lmsport View Post
NASCAR Cup cars use lockers at every track, even the superspeedways.

Used parts and assemblies are cheap and plentiful.




Used RYP-121-450 Ford 9 Inch Rear Carrier Locker Gear Assembly 4.50:1 Ratio
look real close at that locker
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  #38 (permalink)  
Old 02-04-2014, 12:35 PM
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Originally Posted by gearheadslife View Post
look real close at that locker
They look something like this.
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  #39 (permalink)  
Old 02-04-2014, 02:17 PM
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ASE doc, the 8.8 Ford is very similar to the Chevy 12 bolt. It does not have 3 pinion bearings, and the pinion height is very close to what the 12 bolt Chevy is. It even uses all of the same bearings as the 12 bolt. The 9 inch has 3 pinion bearings and a lower pinion.
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  #40 (permalink)  
Old 02-04-2014, 04:05 PM
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Thank you Big Gear Head. That's the kind of thing I need to know. While I don't plan on using slicks on my car, If I'm going to go to the expense and effort of building a rear axle for my car, I'd rather have the best option available. There aren't alot of the 9" units with posi, 31 spline axles, and the ratio I'm looking for. But they are out there. I found a chart on a website called Fordified. I found it by simply doing a google search for 9" ford rear diff. It lists all of the 9" and 8.8" units by model and model year, ratio, limited slip, locking, or non locking. It's a good reference for anyone seeking one of these units.
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  #41 (permalink)  
Old 02-04-2014, 07:07 PM
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Talk to the local stock car guys. OR you can get a currie and get the same thing for 10 times more $ I had 3 rearends in my 68 Camaro. A 7.5 4.11 posi, a BOP 8.5 2.56 and a 8.5 with moser axles. poi and 4.11. You can screw around like I did or just score a used 9". Plus on a 9" the gears are all in the center section so you can swap gears WAY easier than a chevy rear.

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  #42 (permalink)  
Old 02-07-2014, 11:45 AM
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Thanks RAYFIN. I have looked at the aftermarket preassembled units. They start at $2K plus for open diff. Someone could easily drop $3,500 on one with posi and decent brakes. I know I can do better building my own. The hardest part is setting up the axle housing to fit my 87 chassis. I just need to find a used axle and carefully remove the brackets to swap onto the 9" housing. I'll be able to set the length where I want it also since the factory axle was built too narrow. Then I can do whatever I want with the carrier and axle shafts. I've even thought about an aluminum unit to shave unsprung weight.
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  #43 (permalink)  
Old 02-07-2014, 01:15 PM
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I think Currie Enterprises sells the brackets, and Moser might also sell them.
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  #44 (permalink)  
Old 02-07-2014, 02:27 PM
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I would suggest you consider one of these.

QP GM 1978-1987 G Body 9 Inch Housing & Axle Package
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  #45 (permalink)  
Old 02-10-2014, 12:03 PM
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That's not a bad way to go. The set for my 87 F body runs about $1K but it comes ready to install. That just leaves the center section and brakes. I will use the late model(02 Z28) brakes I have now and modify the caliper brackets as needed. When you consider the amount of work involved in setting the housing up, along with the risk of getting any part of the setup wrong, $1K isn't a bad price.

I have thought about starting on the final engine build after I'm done re-engineering the transmission. But, it would be ill advised to put anymore power in front of this rear axle. The 450HP it runs behind already is twice enough to break it. The 600+HP I plan as an end goal for the motor would be stupid on the stock axle.
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