66 Fury III rear end upgrade advice?


"Get off my lawn!"
Sep 8, 2021
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LIttleton NC
FWIW, I think a 741 case is fine for a street car. Have a quality shop upgrade your 741 to 3.55 gears and go have some fun.

(Be sure to adjust the axle tapered bearings to a tiny amount of right side axle play after reinstall of the pumpkin.)
Tiny amount of right side play.....just curious as to why?



Active Member
May 27, 2019
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Mystical Land of OZ
O.K. (Another Long & Boring Rant)
A Couple of Comments,
A Professional Friend of Mine Who used to Build Speedway (Dirt Track) Engines had a Favourite Saying.
"More Engines Have Died on a Dyno Than on a Race Track."
Not necessarily True, BUT I Have been the "Driver" on a Couple of Occasions When Engines Came Close to Seizing on the Dyno.
Race Car Drivers Can Afford to Replace an Engine.
The Average Working Joe Not So Easy.
Now "741" Centres are Stronger than Most 9" Ford Diffs BUT Remember Most "741s" are Now Around 50 Years Old.
I Remember having 15 or More 8.75 Centres in Stock, But Never Being Able to Keep a 9" on the Shelf.
About the Only Thing I Sold off an 8.75" was the Passenger Side (U.S.) Axle Because Some Know it All Mechanic Smashed
the Adjuster When He Tried to Press the Bearing Off.
New Bearings Etc. Will Help an "741" a Lot But Don't Drive STUPID.
If You Want to Do Burnouts Then Look for a "742" or "489"
But Under Most Circumstances a "741" will Suffice.
I was in the Wrecking Industry for Many Years and One of the First Things I Learned was:
Give a Older Fella a Worn Out Part & He Will Still be Nursing It 3 Years Later.
Give Some Young Fellas a Fully Reconditioned Item & He Will manage to Break it in 3 Weeks.
It Depends So Much on Taking a Little Care & NOT Being an Idiot.
Having Said That I have to Admit Having Worn That Hat on a Number of Occasions.
(What the heck, We All Like a Little Fun!)
Anyway a Quick Story.
An Old Friend of Mine Reconditioned His Entire Car When He retired.
Engine / G/Box / Steering / Brakes Etc.
The Only Item He Didn't Reco was His "741" Centre.
He Decided Some Time Later to Complete the List & Reco the Diff.
We Had a "741" Centre Done & Then delivered the Car to the Diff Specialist.
Some Hours Later He Rang & Asked What was Supposed to Be Wrong With the Original Diff.
After Exchanging the Centres He had Examined the Old Unit & Could Not Find Anything Wrong.
( Bearings, Gears Etc. Were All in Good Condition)
He was Concerned That the Owner Had Mistaken an Axle Bearing Noise.
We Explained That This Was Only Completing the List.
Now the Car Had 329,000 Miles on the Clock.
Diff Had never Been Touched.
So, How Good are "741" Centres ?
The Only Thing Against Them to My Way of Thinking is AGE.
And being a Geriatric Myself I Find That Very Hard to Hold Against Them LOL.
Kind Regards Tony.M

As far as the Mount Strap Goes
A Short length of Chain to Restrict the Amount of Stretch in the Mount is Usually Effective.
I Bought My Car From a Gentleman 84 Years of Age.
When I had My mechanic Go Over the Car He Asked the Former Owners Age
When I Asked Why, He Replied, He Must Have Been a Rev Head
You Could Anchor the Queen Mary with the Bit of Chain on the Engine Mount LOL.
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Senior Member
Aug 8, 2014
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Richmond, VA
Tiny amount of right side play.....just curious as to why?

The adjuster is on the right side shaft. 8.75 axle shafts have tapered bearings that need a little play in order to survive.
Factory is to adjust to zero end play and then back off to .008-.018 inch end play.
On 1970, it's adjusted by turning that toothed adjuster behind the axle wheel flange. A clip goes under the bottom nut to hold the toothed adjuster in place. A tiny amount of play mimics .008-.018".
12 a2 RS Adj installed.jpg



Old Man with a Hat
Jul 31, 2013
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Germantown, MD
Tiny amount of right side play.....just curious as to why?


You need the end play because when the gears and bearings all heat up, the clearance, Clarence, will tighten. Just re-installed axles with new tapered bearings on my '66 300 convertible. FSM called for .013 to .023 end play. Set mine at .018 with a dial indicator.

ACR Nick

New Member
Apr 10, 2022
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Houston, TX
4 link, bags and dump the leaf springs i just finished bags all around on a full resto on a 70 fury 3.


New Member
Aug 1, 2022
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Queens, NY
I suspect you need to head over to the Nick's Garage YouTube videos and watch their dyno runs. Lots of interesting information, generally, plus some neat camera angles during the runs.

Consider that how the engine acts on a "full-load" dyno might not fully reflect how it will act in the "partial-load" vehicle. No dyno issues with part-throttle acceleration or off-idle driveability when cold. SO . . . as close as you might get with the carb cfm, you will STILL NEED to massage and tweak the carb for best general results. That means main jetting, accel pump tuning, when the secondaries open, PLUS making sure the ignition system is all it needs to be. No real "plug 'n play" items here, as a general rule. They might all work decently well together as it, but would not really be the best they might be, by observation.

So, once you get everything in the car and driveable, seek out a speed shop that has a chassis dyno where you can do "road load testing" for the carb mixture and such. Do not worry about horsepower, you are just seeking to make sure the air/fuel ratio is where it needs to be and NOT too rich at normal cruise rpms on the highway.

As to the "duty level" info you came up with, consider that those who made those designations might have some definite torque capacity levels THEY are thinking about. Which might not mesh what what "enthusiasts" are thinking about. The issue of "high traction" can be in the mix, too.

Probably need to make a motor mount torque strap for the lh side, too!

Learn how to "drive" the car, too!

Enjoy responsibly,
Thanks, everyone, for your input...keep on truckin'!