For those always looking out for the 8 1/4" rear end for their A,FMJ body cars...Here are a few things to note while in the field:



If you find an OEM rear, it will have the part number and ratio stamped into the ring gear...just roll the carrier over to see if you got what you wanted...not the 2.45/2.26 slug... Note the one in the picture is a 70's A-body 3.21 open diff...



This is a Sure Grip rear end...they are heavier because of the added meat in the casing... in this one we have a set of Richmond Gears that the previous owner had swapped in (look at the "meat" on the gear vs. the stock 3.21 gears)... Aftermarket gears may not be marked with the ratio, so you will be forced to count the ring gear teeth, then count the pinion gear teeth, and divide by each other to see what you got...in this case this 8 1/4" rear out of a 1973 Duster 340, garnered a 41 tooth ring and a 9 tooth pinion...41/9=4.55/4.56.... Sounds like a drag rearend that needs to be coupled to an overdrive to me...



Note the shafts can be pulled easily from the casing, by use of a 5/16" 6 point wrench to pull the "pin" out on an open rear diff, and a 1/4" 12 pt wrench on the SG.... once the center pin that holds the spiders is moved, or on large ratios "spun" to the notch in the pin...you can push the shafts in and pull the C-Clips off the end of the shaft then just pull the shafts out of the axle being careful not to mess up the end seals and the carrier bearings... picture up top shows the "downfall" of the 8 1/4"...the clips can fail on heavy cornering...the 7 1/4",8 3/4" do not use this style of axle shaft retainer and would be better for those going for autocross, road and track, or just trying to show the fartboys how to sway....




As Joshua Skinner had mentioned in a previous post, the 10" plates are available on lots of vehicles (late 'A' 7 1/4", 8 1/4"...some 8 3/4"...FMJ cars...etc...). The plate on the left is the 10" brake backing plate for the 10x2.5" brakes... the plate on the right is an 11" drum backing plate that came on the 8.25" pictured above, that was pulled out of a 1973 Duster 340... the 11" brakes are also common on diplomats, and heavy duty vehicles... (I also suspect one may also find them on the mid-70's B and C bodies cars that were saddled with the 8 1/4" and the 2-barrel 400 big block- I have owned two versions equiped this way:1974 Fury, and a 1973 Newport...)

Hope the pics help those crawling under Dakotas and Cherokees, you will probably need some metric wrenches to grab the goods, but they work just the same as these guys from the good old days...

Good luck,

-D.Idiot

as far as Dakotas and Cherokees go, as long as youre dealing with an 8-1/4 rear, the metric crap can still be left home.
one thing you need to know on those though is that most had 9"X2-1/2" brakes, 10" were optional and not that common on these.
on Cherokees youre more likely to find the 10" brakes on a Dana 35. but they are only 2" wide shoes, at that.

CEEEEEEEEEJAAAAAAAY! FAQ TOPIC!

Many thanks D.I. and Don!

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72 dart acquired 12/08 /6,holley2b, mopar perf intake, mopar perf header, cam, built motor,904 finally re-installed, 8.75....still needs sorting out.
99 dakota 318 5 speed reg cab picked up 9/09; Trans finally fixed! woohoo!

Thanks! Just in time for me since I think the rear gears on my brother's 83 van are getting worn.

Do most of your rear-end tips apply to 9+1/4 rears in late trucks as well?

Reason I ask is that 2nd gen durangos, aka chrysler aspen, come with a 9+1/4 rear equipped with a factory watts link.

Watt's links are just dead sexy!

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72 dart acquired 12/08 /6,holley2b, mopar perf intake, mopar perf header, cam, built motor,904 finally re-installed, 8.75....still needs sorting out.

99 dakota 318 5 speed reg cab picked up 9/09; Trans finally fixed! woohoo!

The Watts Link you speak of has to be one of the ugliest I've ever seen. Most factory Watts Link suspensions are badly compromised. At least the 1st Gen RX-7 was.

The 9 1/4 is basically an overgrown 8 1/4. C-clips, straight roller axle bearings, etc.

My '01 Dakota has a 9 1/4 and it failed in normal freeway driving. No towing or anything.

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Joshua

Thanks Don and Josh for chiming in... I don't get to post these threads as often anymore, but since I was swapping backing plates for the HPak duster rear upgrade I decided to snap a couple of pics and see if we could get some more info together since 8 1/4" rear is a common topic...

-D.Idiot

yeah like everything else... the 70s and 80s 9-1/4s were actually pretty stout, and in much heavier vehicles with more engine. About the time they started the "big rig" styling they went to pot.

IDK why.. different bearing supplier?

Maybe not pretty, but not as much one-side offset induced bind as a 1g rx7 I would hope.

Just having the factory cover would save a lot of fabrication.

Are c-clip eliminators available for 8 or 9+1/4s?

_________________
72 dart acquired 12/08 /6,holley2b, mopar perf intake, mopar perf header, cam, built motor,904 finally re-installed, 8.75....still needs sorting out.

99 dakota 318 5 speed reg cab picked up 9/09; Trans finally fixed! woohoo!