Horsepower lost to friction wise,
does the Ford 8.8 have design features that make it lower loss than a Ford 9 inch diff?

from what i am told the ring gear/ pinion gear friction is less in the 8 3/4 than in the 8.8.

also the ford 9" is probably one of the worse rears made in pinion / ring gear friction. the biggest advantage and why so many people install it is the strength in both the gears and the large bearings in the axles and ease of changing gears like the 8 3/4.
availability of both parts and service techs to repair it and price of the parts is also a consideration of the ford 9".

I really really wish someone would test the 9" and give us an ACTUAL percentage loss against a few other rears. This "rumor" idea/statement about power loss has never been tested rear for rear, yet this idea just hangs around and around. The magazine that tested rears drove it via the engine and there is so much not scientific about that its hard to believe they actual took the time to do it.

Mark Williams had a display at Indy one year with a 9" setup tied to an electric motor. The purpose was to show how much power it took to accelerate the ring gear through a 1/4 mile run.

It was 1/3 hp.

The lower pinion position in relation to the ring gear means more contact but also more drag.
If you had a pinion that intersected the ring gear at the 9:00 position instead of well below centerline like all other axles, it would have the least drag, the smallest pinion, the weakest rating and the most noise.

I realize that, but does that mean 0.002 percent lose, or does it mean 10% loss? See, no one can tell you that, its just the same statement that its a power loss.

Some of the best race advice I got was "If everybody is doing it, its probably a pretty good idea". Well, when you go to the track and look at the cars that are going 5 seconds and faster in the 1/8, there is no dana's down there. None.

So, take a rear, put a load sensor on the input, and a dyno brake on the output and compare them subtracting the bearing preload while you are at it. Then, we'd all know. But, right now, everybody doesn't know (yeah, I said it that way on purpose).

Where is Roadkill garage or some other car show that would do that?

I know a facility that has the equipment to do that. Willingness?

The 8.8 out will long outlive an 8.75 when it comes to power. Lots and lots of guys running 8s in the 1/4 on mildly built 8.8s, some manual transmission cars even.

Silly me almost paid for a Quickchange differential to be installed in a 1995 Ram.

$1400 plus $1100 installation about the year 1999.

Quickchange and 9” Ford are cousins, if I remember correctly.

Like an itch ya just gotta scratch,
I wanted to know how engine rpm and throttle opening
affected vehicle MPG, engine Brake Specific Fuel consumption, and acceleration.

I probably would have done some quarter mile runs with different ratios and 0-60 mph runs at Rockingham.

I could have further amused myself by towing different loads up my favorite steady 4% grade hill.

This might all sound crazy
but there is an old SAE paper from a British group
that took a vehicle,
fitted two Laycock overdrive units in series
behind the 5 speed manual transmission,
and drove around collecting a huge amount of on road data
that they condensed into interesting graphs of
speed, engine rpm, manifold vacuum, fuel economy, etc.

The two added gears on the Quickchange diff do add their own increased friction.

by quick change, do you mean like a franklin or winters rear ?

Frieberger(?) did that test years ago, D60 vs 12 bolt vs 9". Not sure that article is online though. And Mark Williams claim of a 1/3hp is patently BS.

Seems like a pretty good idea of frictional loss could be calculated easily since transmission losses are pretty well known and Dyno tests of both flywheel and rear wheel have been done of the same exact cars several times.

Winter’s I think was first design,
“Quickchange” a second “improved” durability design.

https://www.circletracksupply.com/d...mag-center-tubes-imca-legal.html?cat=194

Personally, I find it hard to fork out $500 or more for an 8 3/4 SG center section that is used and my or may not need rebuilding. And (at least to me) forking over $1K or more for a new one is equally hard to swallow.
An 8.8 for about $150 or so with 3.73s or 4.10s and a posi is a reasonable alternative.
It's not like they were abused in those Exploders.


Tim

The fact that the 9" has more drag is due to the pinion shaft being far below the ring gear centerline. This is also what makes it strong, lots of tooth contact. Power drag isn't enough to worry about unless your trying to run for some type of class record. Dana's have their place. Cheap strong in factory form. Why is everything that is really quick a 9"? Aftermarket support. Tons of parts available. Including center sections designed for 12 bolt Chevy gears. Which have the least drag of nearly any rear axle. A 5 second flat car isn't cheap. So cost generally isn't an issue. But a good 9" isn't cheap. Me? I'm cheap. My car runs well into the 5's. It uses a home built Dana that cost me less than $900 to build. Now a days on the street or general track use? I'd seriously look into the 8.8 Ford for sure. Watch what cars are running them. Plenty of fast stuff. They're modern, plentiful, cheap, disc brakes, factory gear 3.73/4.10. I'd be going to the junkyard if I didn't have 8 3/4 or Dana stuff in the car to start with. Even if you have 8 3/4, the sure grip, gear, and labor exceeds the junkyard cost. of an 8.8. Obviously the spring pads and drive shaft need mods to use an 8.8. But if you didn't have an 8 3/4 you probably needed a better drive shaft anyway.
Doug

These 8.8 axles don't appear to have a pinion snubber so do people just go without?

on my 08 mustang i had a 3 link rear suspension. this design doesn't need a pinion snubber.

couldn't tell you where they do this. just thinking maybe you could just bolt the snubber to the floor instead of the axle.
the 9" they make a bracket that uses the bolts by the pinion seal to mount it.

A snubber is pretty application specific. Do you have the power and tires to need one? If so, you probably need something stronger than an 8.8 to begin with.

Oh for crying out loud, the 7 1/4 has a pinion snubber. Let's try to keep the outlandish rhetoric within reasonable bounds.

Doesn't mean it does anything. They're known to be marginal behind slant sixes.