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Nothing wrong with the 8" for a street car, it is a tough rearend. If you are just upgrading the third member for a locker and better gears it is a great way to go. For me though if you are upgrading the axles and spending more money trying to make the case stronger just start with the 9". I did a budget 9" in my Wifes Comet , started with a housing from a 69 cougar for $100 had it narrowed for $100 and found a set of moser axles on craigslist for $275 and a good 3.50 Detroit locker third member for $50.
How Loud is that locker?
 

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Nothing wrong with the 8" for a street car, it is a tough rearend. If you are just upgrading the third member for a locker and better gears it is a great way to go. For me though if you are upgrading the axles and spending more money trying to make the case stronger just start with the 9". I did a budget 9" in my Wifes Comet , started with a housing from a 69 cougar for $100 had it narrowed for $100 and found a set of moser axles on craigslist for $275 and a good 3.50 Detroit locker third member for $50.
true you can also build a 9" fairly cheaply, if you have an idea of what you are doing, and do some judicious shopping looking for deals. and i agree to a point that a 9" is better depending on what you want from the car. but since most of us are not going to be racing the cars we drive all the time, then the 8" does well for the street and occasional forays to the track.

that said my mustang will get a 9" since i have to build a read end for it anyways, but the 8" gets rebuilt for my falcon to replace the 7.25 rear end at the same time.

There are a lot of aspects not being discussed here...curb weight of the car makes a big difference in how long a rear end lasts under abuse...also, people are throwing around numbers like 300 and 400HP...but HP doesn't break rear ends...torque does. For instance, with the v6 in my car I could clutch dump at 5000 RPM all day long and never break an 8" if I were making 400HP, because the torque that engine would make(naturally aspirated) at 400HP would be something like 350 ft/lb. That is why people have such different experiences...the torque of the engines involved and the curb weight of the cars those engines are in...it will vary results fairly widely and it will be hard to nail down the limits without listing those specs.
actually i have seen people taht can break dana 70s with a stock V6, and others that never break saginaw five speed trans from a vega with 500hp in front of it. yes torque is also a factor, but unless you are running a diesel, most of the time when talking torque on modified engines, the peak torque is high enough that the hp numbers are just as important to deal with.
 

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How Loud is that locker?
Both my G force locker and Detroit locker are pretty loud. Not really noticeable while driving but in a parking lot at slow speeds t's pretty noisy. I got a good laugh at the gas station when the guy next to me asked if my car was ok. Of course just a light application of throttle and it goes from a knock knock knock noise to the tires chirping while turning.
 

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Would you go with the Locker again or use a trac loc,.....is it worth the noise?
 

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Would you go with the Locker again or use a trac loc,.....is it worth the noise?
If I could find the same type of deal on the used Nascar third member like I did I would do it again. The money I paid for what I got was a steal. billet yoke for 1350 u joint, N case with Daytona pinion support, ARP hardware, REM treated gears. It's like a work of art. lol. You get used to the noise but on a driver car it might get old. Does not bother me though but I still like loud exhaust.
 

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As we all know from forums, this great nation is littered with the remains of thousands of grenaded 8” rear axles who gave their life to provide their owners motivation to swap to a 9” when they accidentally put a 2 barrel on their 200 Inline 6 and overpowered the teeny axle. Everyone would love to have the brawny 9” under their car with gleaming 31 spline axles, but let’s face it. Is it truly needed? I’d like to discuss the merits of keeping the 8”. What are the real weak points of them and where and when do they fail? I bring this up as someone who use to slap M/T ET Streets on my daily driver ‘66 with a stroked small block and hammer on it at the track. My 8” never failed me and never showed signs of premature failure. I’m currently building my ‘66 coupe into a street/track car to toss around the track on weekends. I’m planning to push around 400 at the crank and run a Detroit true trac. I won’t be shocked if I have to pick my 8” up off the track at some point, but for now I’m on the verge of ordering a new nodular center section and heavy duty pinion support to try and beef up the 8” under the car currently. What are your thoughts and experiences? If you’ve had an 8” give up the ghost, what were the circumstances and what actually failed?
Well, BoulevardofRustedDreams hasn't replied back but-
All that wit and only 6 posts.....
I'll avoid the temptation to direct you to the VMF search function, but we've discussed this topic numerous times.
As others have mentioned, there is a certain wisdom of the "automatic" upgrade at a certain horsepower level. That's the way Ford thought too.
I personally like the approach of the more combined stress.... the more need for a 9" upgrade. (HP & sticky tires & drag racing & etc.)

I got my 9" in the '66 courtesy of a shortened Lincoln disc rear end upgrade. There wasn't an identified NEED for a stouter pumpkin.
I've never broken an 8' rear. I broke leaf springs before the center section ever got close to exploding. (built 289, shift kit C4 and lots of abuse)

In the past I think the 9" upgrade was cheaper to pull off and that's why a lot of them were done.
 

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Whatever your preference I will make the point that it is not always CHEAP to upgrade to a 9 inch. I just had one built after I grenaded my 8 inch with street tires at the drags and all told I was close to $2000 with new gears, a new Detroit locker, 31 spline axles, an upgraded nodular center section and a drain plug added. This was after I ruined a nice detroit locker and gears for the 8 inch. Spend your money once or twice, roll the dice. If I was doing an 8 inch again I would do like some have said and get a later center section and invest in good hardware.
 

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?
 

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Whatever your preference I will make the point that it is not always CHEAP to upgrade to a 9 inch. I just had one built after I grenaded my 8 inch with street tires at the drags and all told I was close to $2000 with new gears, a new Detroit locker, 31 spline axles, an upgraded nodular center section and a drain plug added. This was after I ruined a nice detroit locker and gears for the 8 inch. Spend your money once or twice, roll the dice. If I was doing an 8 inch again I would do like some have said and get a later center section and invest in good hardware.
It’s not cheap, I paid $2700 drum to drum everything brand new, billet ends, big bearing, Nodular, 31 spline , TrueTrac etc and I justified it based on how much I would spend rebuilding , replacing etc. No doubt you can get deals out there and do a great job with that but I don’t have the time to wait and search and I’ve seen more than a few people get taken (outside of this website and other forums as the people are like family and are pretty tight and truthful) and didn’t want to deal with it if it was junk. Just my .02 cents. :)

Chris
 
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