Rear end selection help and opinions

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LivewireBlanco

LivewireBlanco

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Ok, so I'm wanting to finally get rid of my 2.76, 7 1/4" rear in my '71 Dart. It currently has a 300 hp(ish) 318, 904 transmission, 3000 stall, and small bolt pattern 9 inch brakes all around. What I would like to do is upgrade my rear with 3.54 gears and keep my sbp. That limits my choices greatly but there's still 8 3/4" and after market Dana 60s to choose from. I'd also like to have a direct bolt on rear since I am no fabricator and my choices locally are limited. At some point the 318 is going to come out and and possibly stroked or upped in compression and hopefully be in the 400 hp neighborhood.

With all that being said would ya'll just go with a Dr. Diff Dana 60 setup or piece by piece put together an 8 3/4"? Also, what would be your thoughts on brakes? I'd like to stick with drums in the rear and eventually I'll upgrade the 9" drums in front to discs but it stops decent now and I don't want to buy new wheels and tires.

The car is mainly just for fun and occasionally makes trips down the drag strip but that's about an hour away so highway driving happens and that's why the 3.54 gears. Thanks in advance!
 
For 3-400 hp I imagine the 8 3/4 will be more than up to the task.

If you put out the feelers you can get an unmolested A-body 8 3/4 SBP complete (drum to drum)in the sub 1000 range, with a limited slip center section I would expect to pay a few hundred more.

Keep on mind I'm talking used, so some rebuilding might be needed.

Your target gear ratio is good compromise for hwy and strip (others have more info there)

Just my two cents
 
What's your rear tire diameter going to be? Probably going to happy with anything in the 3.21-3.55 range.
 
With that 25 inch tire, 3.55s will have you at 63 mph at 3000 rpm and 70 will make for 3300 rpm. 3.23 will give you 70 mph at 3000 rpm and 2600 rpm will give you 60. The best way to tell if you can stand 3.55 at 70 is to drive around in second gear for a short trip at 3300 rpm. This is equal to a 4:1 axle ratio, so you'll pull 60 at that rpm. It makes me crave 4.10 gears whenever I do it with my 2.76's.
 
Garrett Ellison said:
With that 25 inch tire, 3.55s will have you at 63 mph at 3000 rpm and 70 will make for 3300 rpm. 3.23 will give you 70 mph at 3000 rpm and 2600 rpm will give you 60. The best way to tell if you can stand 3.55 at 70 is to drive around in second gear for a short trip at 3300 rpm. This is equal to a 4:1 axle ratio, so you'll pull 60 at that rpm. It makes me crave 4.10 gears whenever I do it with my 2.76's.
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3,000 rpm cruising is no biggie for me but I may expand my search to 3.23 also.
 
The Dana is your only choice if you want a 3.54. The 8 3/4 does not have that ratio available.
 
Ok, so how does this sound...try to find me a drum to drum 8 3/4 with 3.23 gears and sbp. Then if things get a little more serious at the track or highway isn't an issue get another pumpkin with 3.91 or 4.10 posi.
 
LivewireBlanco said:
Ok, so how does this sound...try to find me a drum to drum 8 3/4 with 3.23 gears and sbp. Then if things get a little more serious at the track or highway isn't an issue get another pumpkin with 3.91 or 4.10 posi.
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If you want basically the same gear in the 8 3/4 it's the 3.55, not the 3.54. The 3.54 is a Dana only gear.
 
dano said:
Any reason why not to go BBP? It opens the 8-1/4 up for you even the Ford 8.8.
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Cost. I'd need new wheels and tires as well as changing out the front end. That's a lot when I can hopefully find a sbp used 8 3/4.
 
I would use 3.70 r&p with a 28" tire for cruising and a 26" tire for drags or spirited driving or 3.55 r&p with any tire around 26-27" tall . The bowtie boys call it :"350/350 with a 350 turbohydro with a 3.55 r&p with a 26" tire , lol . the system works for the granny broomstick crowd .
 
LivewireBlanco said:
Close enough for me!
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Well it was close enough for the factory to use 3.55 in the read and 3.54 in the front on the Dana 44 in 4x4 Dodge trucks. I just wanted to make sure you knew there was a difference so you would get the right gears for the right differential.
 
8 3/4 will be plenty stout for your application, Dana would be overkill, complete sbp housings come up for sale from time to time, should have 10 inch brakes, sbp front disc setups are also available, but can get a little costly. If I were to do it again, I'd make the switch to bbp, I realize it is a little costly, and a bit of work, but opens up so many more options, just my .02.
 
RustyRatRod said:
Well it was close enough for the factory to use 3.55 in the read and 3.54 in the front on the Dana 44 in 4x4 Dodge trucks. I just wanted to make sure you knew there was a difference so you would get the right gears for the right differential.
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That's common in 4x4 trucks so the front moves a tad faster that the rear. My F-150 is 4.11 and 4.10.
 
dano said:
That's common in 4x4 trucks so the front moves a tad faster that the rear. My F-150 is 4.11 and 4.10.
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Yup. Some of the mud runnin guys run like a 5.13 in front and 4.10 in the back. lol It works.
 
Wouldn't that be the other way around if you wanted the wheels in front turning faster than the rears for a given engine RPM? (4.10 in the back and 5.13 in the rear)?
 
RustyRatRod said:
The Dana is your only choice if you want a 3.54. The 8 3/4 does not have that ratio available.
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RustyRatRod said:
If you want basically the same gear in the 8 3/4 it's the 3.55, not the 3.54. The 3.54 is a Dana only gear.
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I have a set of 3.54 8.75 gears from a 1958 dodge truck. Kim

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if you find yourself at a drag strip with slicks and glued track, a 8 3/4 may not stand up too long. kind of like Russian roulette. then again a Dana 60 will cost $$$$ and your street ride will suffer cause of the weight. even a 9 1/4 is quite hefty. if never a set of slicks and limited drag strip use, an 8 1/4 or a Dana 44 out of a jeep grand Cherokee will give you good street ride. especially the 44 if you get an aluminum one. around here a good one out of the bone yard is $350.00 USD.
 
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