Is a Strange S-60 more efficient than an 8.75", as in enough to help offset (some of?) the weight difference?

I'm trying to calc some target ET & MPH #s for my new combination. I know the Strange S-60 conversion has added some weight (not sure exactly now much; estimating 50#s) compared to my old 8.75". Neither old or new diff use spools; 8.75" had Power-Lok and S-60 and Strange has S-Track.

However, I've read here that a Dana 60 is more efficient than an 8.75" and the ETs are usually very close, despite the weight increase. True?

The weight is a push at best. When you get the 8.75 braced, used a NI case and all that, what weight you gain with the S60 is almost nothing.

Also, the weight is low and far enough back to almost not matter.

Also, the S60 is only more efficient when the gear ratios are lower (numerically higher) than ~3.90 otherwise that's a push.

If I'm wrong, Dr. Diff can come along and fix it, but I think I'm correct.

I specifically remember an old magazine article that showed a Dana 60 to be more efficient than an 8 3/4 mainly because of the ring & pinion orientation. Dana 60 is more centered. It also pointed out that a Ford 9" is the least efficient not only because of the R&P, but also because of the extra bearings. A GM 12 bolt was the most efficient of the "common" rears tested and I would guess that a 10 bolt would have been a bit better. In fact, I believe some rear end manufacturer had/has a 12 bolt gear drop-out made for Ford 9" rears with improved efficiency.

Granted, these differences were pretty small, but it apparently was worth the effort by several class racers who noted that they didn't see any loss of ET, especially after their cars had the weight adjusted back after the swap. Also worth noting, there would be less difference in weight if both were using a spool as opposed to a Sure-Grip or other such part. Added bonus is the durability.

I believed in it enough to replace the 8 3/4" in my Stock class Aspen Wagon with a Dana 60. I believe the weight difference was between 35-40 lbs,.Both had spools and star-flanged axles with the 8 3/4 being braced. The Dana had a thick, aluminum girdle cover. But I was mainly interested in durability as I doubt I'll ever have any breakage problems in a high-11 to mid-12 second car, despite it's 3,927 lb weight in K/SA. Unfortunately, with the problems I had, I was never able to establish a baseline to compare from and am currently trying to get an engine for it again.

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FWIW, 4.10s in both and the 8.75" had a back brace (I don't recall the weight increase for that alone).

Jacking around w/ the latest dyno #s, old dyno #s, old track results, and the other stuff that's changed... I THINK the MoPig "should" be capable of squeaking into the 10.1s at 129+ MPH. But reality has a funny way of changing hopeful expectations...

Now that I've put it out there publically, the laughter may begin.

No laughter here, just waiting with GREAT anticipation for you getting the car running & at the track

I agree with Myron (Locomotion); the efficiency is in the centering of the pinion to the ring gear.
An old SS/FC racer buddy who's basically a genius at mechanical principles, also pointed all that out to me years ago.
And he runs a 12-bolt conversion diff in his 9-inch housing in a 12-second stick Chevy "toy" that he races.
Years back, some SS/AH cars were playing with the 12-bolt diffs, not sure what's in them currently.

I'm going to say yes based on pushing cars in neutral with a 8 3/4 compared to similar cars with Dana 60

We ran back to back weekends with 8 3/4 and then with Dana 60. With 3.55 and 3.54 gears, the car ran identical to the hundredth. 11.41's as I recall.

Our 71 Dart 360 ran best of 10.35 with the 8 3/4....after twisting axle housing. A Strange D60 was installed with same gear ratio and spool.....35 spline axles compared to the 83/4 30 spline...the Dart ran 10.31...with pretty much the same mph...

The lighter axle is easier for the shock to control: unsprung weight.

a friend of mine has a roadrunner and has changed back and forth a few times and his car loses a tenth every time with the dana

S60 is way more efficient in keeping money in my wallet over my past 8.75 experiences....

Thanks for everyone's replies, even if there isn't a consistent result seen. It'll be another IIWII deal, but I had to at least ask.

This!

Under pressure, pushin' down on me...

Ran an 8.75 forever( well sorted car) broke it. By the following race weekend a Dana was installed. Despite being heavier, i saw absolutely zero difference in time slips. As if i never made the swap regards, incrementals, MPH, ET, you name it.
So it must be more effecient to weigh 60-70 pounds more and have zero impact on my slips
This was running 10.40’s at the time

There are things besides the pinion to ring gear centerline aspect that effect how much power a rear end assembly absorbs. Tooth design, gear treatments, weight of internal components, bearings used (ceramics), how it is assembled (turning torque/preload), oil viscosity and amount in the housing, housing fabrication (nice true centerline from axle bearing to axle bearing), etc...

Instead of sweating the efficiency enjoy the comfort of being able to drive home after ripping some new best ETs because your Dana didn't even realize it was at work. I like the "set it and forget it" feeling the Dana swap gave me.

One other thing about the Strange D60 is it uses spanner adjuster to remove the carrier....no shims....make changing the ring and pinion easier...

I definitely made the switch out of concern the fuse was lit on my 8.75". My question was more out of curiosity as to how much I should factor in the weight gain on the performance.

Changed from a 8.75 with 3.91 gears to a S60 with 3.73. No difference at all. Just more relaxed as it is under a Fuselage.