Axles design limits???

[67charger383]

An update to my previous post. I went back in my old books and found some casting numbers. If you have 2070741 it identifies the smaller 1 3/8th-inch-diameter, 10-spline pinion shaft. Generally only found in "A" bodies. The 2881488 and 2881489 were used from 1969 through 1974. The pinion shaft diameter on these rear ends was 1 7/8 inches, and these pinion shafts were either 10- or 29-spline. After 73 all of the 8.75's were the 489's Casting number 2070742 was used from 1961-1969 and has a 1 3/4-inch-diameter 10-spline pinion shaft.

My 8-3/4 has a 742 sure grip and 4.11 gears

 

[Cranky]

An update to my previous post. I went back in my old books and found some casting numbers. If you have 2070741 it identifies the smaller 1 3/8th-inch-diameter, 10-spline pinion shaft. Generally only found in "A" bodies. The 2881488 and 2881489 were used from 1969 through 1974. The pinion shaft diameter on these rear ends was 1 7/8 inches, and these pinion shafts were either 10- or 29-spline. After 73 all of the 8.75's were the 489's Casting number 2070742 was used from 1961-1969 and has a 1 3/4-inch-diameter 10-spline pinion shaft.

If I'm not mistaken the 89 came out in 68 but not sure if the others were discontinued after that. Just never found a 41 or a 42 in cars after that. Also....this info has been published in many other places besides here. http://www.doctordiff.com/blog/tech-info/rearend-pinion-comparison/ There's another thread about the 8 3/4 too and my age old question is....how many 8 3/4 pinions have you seen broken from any of the casting numbers? I've seen one but it was at the front and not at the back. I did a lot of rear end work starting in the early 80's and the the damage I saw the most was shaved teeth but don't do much anymore because my back won't let me.

 

[33 IMP]

In my humble opinion, the only thing wrong with a 741, compared to 489 and 742 is the poor choice of gear ratio available. If you look at Dr Diffs piece that Cranky referenced, you will see what I mean . A battleship anchor chain with one weak link is no stronger that a little tow chain made with the same weak links. I would never not consider a 741 just because it's a 741!
741s were used in maxwedge cars.

 

[Cranky]

In my humble opinion, the only thing wrong with a 741, compared to 489 and 742 is the poor choice of gear ratio available. If you look at Dr Diffs piece that Cranky referenced, you will see what I mean . A battleship anchor chain with one weak link is no stronger that a little tow chain made with the same weak links. I would never not consider a 741 just because it's a 741!
741s were used in maxwedge cars.

Yup, poor choice of ratios for the 41 case. Used to keep the 41's for myself and sell the 89's and 42's at premium prices and also robbed the 41's of their SureGrips if they came with one.

 

[33 IMP]

@alfaitalia, I located the chart I saw before, I found it on Mark Williams website. I doesn't give actual numbers as far as what each axle is capable of but it does give a relative comparison.
Using a twelve bolt Chevy as a baseline (coincidentally, same spline count as an 8 3/4, 30 spline) it shows Ford 28 spline as 19.3% weaker, 31 spline Ford at 10.7% stronger, 35 spline (Ford racing or stock dana 60) at 61% stronger, and 40 spline at 143% stronger.
This is for axle size and spline count only, it does not factor in hypoid ratio, gear strength or housing strength, all of which also factor into a rearend's overall strength.

 

[RJRENTON]

@alfaitalia, I located the chart I saw before, I found it on Mark Williams website. I doesn't give actual numbers as far as what each axle is capable of but it does give a relative comparison.
Using a twelve bolt Chevy as a baseline (coincidentally, same spline count as an 8 3/4, 30 spline) it shows Ford 28 spline as 19.3% weaker, 31 spline Ford at 10.7% stronger, 35 spline (Ford racing or stock dana 60) at 61% stronger, and 40 spline at 143% stronger.
This is for axle size and spline count only, it does not factor in hypoid ratio, gear strength or housing strength, all of which also factor into a rearend's overall strength.

Figures are nice, but the percentage numbers relate to ???? Torque transmitted at ????? RPM at differential gear ratios
Beside the axle size and spline count considerations, perhaps the alloy that was used to produce the axle and the heat treatment used in its productoon and the final hardness of the unit as produced. The bending moment and torsional capabilities of the shafts are a function of the initial alloy and whatever heat treatment it was subjected to.

Beside the affore mentioned factors, while important are not the only factors involved. Overall length of the shaft and its support points, the carrier's alloy also enter in to the determination of what is "best".
This is why a professional axle manufacturer should be consulted for a specific application recommendation especially how much horsepower will be transmitted. Just my opinion of course.
BOB RENTON

 

[Cranky]

@alfaitalia, I located the chart I saw before, I found it on Mark Williams website. I doesn't give actual numbers as far as what each axle is capable of but it does give a relative comparison.
Using a twelve bolt Chevy as a baseline (coincidentally, same spline count as an 8 3/4, 30 spline) it shows Ford 28 spline as 19.3% weaker, 31 spline Ford at 10.7% stronger, 35 spline (Ford racing or stock dana 60) at 61% stronger, and 40 spline at 143% stronger.
This is for axle size and spline count only, it does not factor in hypoid ratio, gear strength or housing strength, all of which also factor into a rearend's overall strength.

I know for a fact that an 8 3/4 with a spool and stock axles are not the way to go lol....at least not running low 10's/high 9's.....

 

[yella71]

This is like the old thread on moparts .....How much HP can an 8 and 3/4 take?

 

[beanhead]

This is like the old thread on moparts .....How much HP can an 8 and 3/4 take?

...Moparts??

 

[Charger Dana]

Can anyone post a definitive link to a chart or table that has the actual design limits quoted by the factory on Charger axles. I have a 8 3/4 but ive been offered a Dana 60.

I don’t have a chart. I have a full weight 67 street charger, standard, I have raced it with big sticky tires and had an issue with a USED 4.10 8 3/4 (shredded). Also twisted the Moser axles. I am not certain if any damage was done before I got them, it was in a much heavier fast car before me. I also built a Dana 60 for the car, decided not to put it in. If I was racing at 500 hp plus, I’d look at a D60. Street car? Zero issues. D60 is heavy, can’t swap gears, generally 3.54 or 4.10 are your likely choice. I have never seen a D60 break. Full bbody original D60 is probably $2500 us. Most drag guys seem to move to after market Ford 9” (strange, Mark Williams etc.).

Here is my opinion: keep your 8 3/4.
Also, take Doug/DVW’s comments over mine.

 

[66Satellite47]

My earlier post should have also said that the 8 3/4 needs a careful consideration of the ring gear tooth size difference with gear ratio. The ring gear tooth size difference between a 4.56 and a 4.89 is really big in the 8 3/4.

 

[joemish]

Can anyone post a definitive link to a chart or table that has the actual design limits quoted by the factory on Charger axles. I have a 8 3/4 but ive been offered a Dana 60.....over here they are an outrageous price. I wont say how much or you would laugh. I basically want to know the horse power and torque limits of both those axles top see if the gain is worth the cost. This car will NEVER see a drag strip (or be fitted with slicks etc) and will just be an enthusiastically driven street car. How much power are you running through your 8 3/4 ? I guess Im trying to persuade myself I don't need to spend the money.....but I will for a big gain on power handling and reliability. Even getting an axle upgrades here is not easy....not many live axle specialist this side of the pond.

You won't gain any power. you can gain torque by using different gear ratios but with your 8 3/4 unless you are running a hemi or a 440 4 speed, the Dana will withstand the higher torque from the 4 speed with 440 or hemi. anything else the 8 3/4 is all you need. The Dana looks sharp but i wouldn't throw money at one. I have a 383 roadrunner came with a Dana someone put in it I also have a 383 4 speed 67 Satellite with 405 HP and the 8 3/4 rear. Both work fine. ps the dana is chromed but i got it that way.

 

[Splangj]

Let’s not forget Mike Daughtry in his ‘68 Suprbee Low deck stroker in MA years ago. MA states he broke into the high 9s recently, with his 3.23 8.75 with after market axles. The didn’t mention what type of LSD, or spool.

 

[joemish]

This is like the old thread on moparts .....How much HP can an 8 and 3/4 take?

https://www.hemmings.com/stories/article/dana-60-differentials-2

 

[Splangj]

Yes! I have a Dana 60 3.54. That article looks good, except for accusing the ‘60 of being 500 pounds