Building a 7.5"

[patmckinneyracing]

So far from what I can see, summit has their brand on sale and theirs are the cheapest. Nothing wrong with summit's equipment either. I was offered a deal on my yukon gears from the guy who build my rear end for me. Summit's are all under a 150$ for whatever gear set you want, so if you want them I would suggest getting them now. As far as a posi trac carrier, that's gonna be a little harder to find cheap. I know where there is one down here in a caprice that has a 7.5 rear end. It's gotta a posi in it but I didn't bother counting the turns and figuring out what ring and pinion it has.

 

[Phoenyx]

Look at it this way. You will see people all over here arguing about the 7.5, some say it's good and others say it's junk. Lots of debates on that one. But how many threads are there people questioning the strength of the 8.5?...

There's a reason for that.

 

[RITTER]

Aftermarket parts for a 7.5" are just as strong as aftermarket parts for an 8.5" rear-end. The only difference is the ring size, so yeah the little bigger ring is a bit stronger because of size but that's it. The axles and posi units and bearings are all made the same way and with the same materials. With the percentage of people that actually run drag radials/slicks and launch their cars on a regular bases is pretty small. There is no need to upgrade a rear-end size for a 300-400 hp street car.

So my buddy has a used posi unit for a 7.5" with 28 spline axles and a set of old (unused) 3.42 Richmond ring/pinion, what would y'all say is a decent price for this?
Then I could go ahead and get the aftermarket 28 spline axles.

 

[patmckinneyracing]

So my buddy has a used posi unit for a 7.5" with 28 spline axles and a set of old (unused) 3.42 Richmond ring/pinion, what would y'all say is a decent price for this?
Then I could go ahead and get the aftermarket 28 spline axles.

For just a used unit and a good ring and pinion, I would say $150. The majority of that is going to be because the Richmond gears are unused.

Look at it this way. You will see people all over here arguing about the 7.5, some say it's good and others say it's junk. Lots of debates on that one. But how many threads are there people questioning the strength of the 8.5?...

There's a reason for that.

The reason for that is cause most of us can't afford the d*** things.

 

[jrm81bu]

Just on the malibu sites i'm on there are quite a few people running into the 9's on an 8.5 would any of you try that with a 7.5. Also it's not just the ring gear being larger. Everything is. The pinion shaft has a larger diameter, the spiders are bigger and you can also go bigger than just 28 splines on the axles. A built 7.5 is gonna leave off where a stock 8.5 begins. Just my opinion.
And yes I still run a 7.5, just because I haven't been able to buy anything else. You can bet that as soon as I can I will, and if it ends up being a GM rear it will(eventually) get c-clip eleminators. Four axles coming out is more than enough for me.

 

[art]

Has anyone considered a 8.8 swap from the fox mustang? The 8.8 is plentiful,strong,reasonable and only 2 inches wider (one inch per side) TRZ makes a swap kit that is a lil pricy and if you are making serious power (400 plus), that factory 2-1/2 dia driveshaft will need to be upgraded anyway, so that's kind of a moot point. Something to think about. For my BBO project I'm currently working on, it's a direction I'm considering.

 

[patmckinneyracing]

If I ever do a rear end swap, it'll probably be to a 12 bolt or probably just end up by a 9 inch. I'm still considering at some point taking out my sbc 350 and putting the spare 440 I've got into her. I've got a cousin who has a 74' Nova that runs low 10's with a 440 in his car.

 

[jrm81bu]

Has anyone considered a 8.8 swap from the fox mustang? The 8.8 is plentiful,strong,reasonable and only 2 inches wider (one inch per side) TRZ makes a swap kit that is a lil pricy and if you are making serious power (400 plus), that factory 2-1/2 dia driveshaft will need to be upgraded anyway, so that's kind of a moot point. Something to think about. For my BBO project I'm currently working on, it's a direction I'm considering.

As a ,atter of fact I have. One of the other issues with the 8.8 is the mounting points for the upper control arm is kinda low on the housing. That tends to mess up the instant center of the car, but baslinesuspensions.com has a fix for that too.

 

[RITTER]

Just on the malibu sites i'm on there are quite a few people running into the 9's on an 8.5 would any of you try that with a 7.5..

You kind of just gave proof that we don't need an 8.5" in our street cars. How many guys here have a 9 second car? I think if most of us had an unlimited budget we would just run a 12 bolt GM rear-end or a Ford 9", but that isn't the case. I don't know about most you, but when I am planning a project, I stock pile the parts I need over a period of time and once I have everything needed the project gets completed. To go out and purchase a complete bolt in rear-end is out of most peoples budget limits.

 

[jrm81bu]

Just on the malibu sites i'm on there are quite a few people running into the 9's on an 8.5 would any of you try that with a 7.5..

You kind of just gave proof that we don't need an 8.5" in our street cars. How many guys here have a 9 second car? I think if most of us had an unlimited budget we would just run a 12 bolt GM rear-end or a Ford 9", but that isn't the case. I don't know about most you, but when I am planning a project, I stock pile the parts I need over a period of time and once I have everything needed the project gets completed. To go out and purchase a complete bolt in rear-end is out of most peoples budget limits.

No, the only thing that comment proves is that the 8.5 is quite durable. If I had said they were running the 7.5 with those times then that would prove that it is durable, however it's not. I'm not trying to change anybody's mind about what rear they want to run. The arguements I'm seeing for not going to an 8.5 is because "the only thing better is a bigger ring gear". When it really is a LOT better rear than the 7.5. And the comments about how expensive an 8.5 is, well if it's capable of handling that kind of power than i'd say it justifies the cost. There is some people that would argue the 8.5 is better than a 9" or a 12 bolt, based on weight savings and less power being "wasted" to turn it, all the while being able to handle the power.
Also while we may not have 9 second cars(i know I don't), i've still managed to accomplish breaking plenty of 7.5's, without being on a dragstrip or running sticky tires. And yes there is people that say they have ran 10's pulling the front left off the ground with the 7.5. So it really seems to be hit or miss. I just don't like the odds, especially when it means hurting someone or your car.