8 1/4 Rear end

[mag440]

I was wondering if anybody can tell me if a 8 1/4 rear would be strong enough for a 440 I have heard that they can hold up good. mine is a sure grip and was rebuild by the original owner right before i purchest it.

[dave571]

I think the only right answer is "maybe"

I beat the 8 1/4 in my van pretty hard. It never failed completely, for that matter I broke my 727 first. But the Side gears did fail. I swapped in a spare 8 1/3 housing I had as a temporary measure.

Keep in mind that my van wieghs in at 5000 lbs, with me and a tank of gas. Up to 5500 with a tool box, and the wife and kids. The 400 was making around 330 crank horsepower at that time

Although your magnum is lighter than the van, a 440 will most likely make more torque than my engine does(depends on mods of course).

Cuda66273 has run 12's with one, around 400 hp Don??. But it had a spool in it, and his cuda is alot lighter than your magnum is.

Again, I vote "maybe"

[PRO]

I think it depends on the 440,a 300-400hp one probably if you put aftermarket studs in for the caps,a suregrip for sure because an open carrier will grenade the spider gears in 50 miles,I know because Ive done it,ditch the c clips and get c clip eliminators,youll have to if you Go to a strip to race it and go faster than 12.99 but after all that why? why not just run an 8.75? or maybe if you cant find one run a 9.25,its stronger and will cost the same.............PRO.........

[6 packin]

Depends on how hard you drive the car. Depends on the physical condition of the rearend. Take it easy, ad will last you a few years. Take off with your foot in the carb, well better start looking for a bigger stronger rear end. A suggest a 8 3/4.
I dont think the gears its self is the weak poiny int the 8 1/4 rear, its the side (spider) gears in the diferential it self. I would not WASTE MONEY on buying c-clip eliminators for a rear end that probably wont last. I cant justify dumping money on strong studs, and other things just to see it fail. Just drive it tell it blows and let us know, I am curious o how long it does last.

[Canuck Dart]

Although tougher than say a GM 10 bolt, the 81/4 was not designed with any performance applications in mind.

I'm nervous about the one behind my 340 / 4sp. in a '73 Abody, so.....out she comes in favour of an 8 3/4.

RB torque + 8 1/4 rearend??? I would say don't be hammering on it too hard.

[NC PUTZER]

TO:>>>>>>>70net440

ALSO:

TO:>>>>>>>Dart65

Could you tell me how I identify the 8 3/4. I looked at several rear ends without gear tags.

Dart65>>>>>>>>>>How many bolts does the 8 3/4 have???
Is that 10 or 11.

NC PUTZER

[rumblefish360]

From looking under the car at the rear bummper, the rear has NO bolts. It is a soild cover welded on. The gears are housed in the 3rd member (Look in a MoPar catolog or on line. (It looks alot like the Ford 9 inch) The gears are removed from the front.
Any tags on a rear should ID the gear ratio.

[mag440]

The 8 1/4 rear had about 800 dollars parts and labor put into it and it is fairly new only bout 1000 miles on it. my other magnum has a 8 3/4 under it and that was a factory instal. from what i hear it is very rare.

And for the question about the 8 3/4 it will have no bolt on the back of it the have a removable 3 rd member. very tricky if you ned to change a gaskets trust me I had to do it. it was a pain in the A@#.

[dwc43]

You wont have any problems with that 8 1/4 sure grip rear. What everyone does not understand is the the 8 1/4 is equal to the 8 3/4. It replaced the 3/4 to save Chrysler production cost. They are very equal, but they have diferent advantanges.
3/4 gives to quick gear changes if you have the centers all ready set up. That's why I use them on our oval cars as well as the aluminum center from Randy's Ring to save weight. The 3/4 has a bad flex problem by it's design. That makes bearing wear higher on performance cars as well as possible gear breakage. There are weld on braces to elliminate this problem though. The 1/4 by design does not have this problem.
The 1/4 is equal in every way except slower gear changes and c clips. Which you can use the eliminators or simple tack weld them like the chebby guys at the race track do.
I have a 360 Duster 4 spd with a 8 1/4 sure grip in it now and it has never failed yet, but many a crapmaro has ......

[dwc43]

Originally posted by Canuck Dart
Although tougher than say a GM 10 bolt, the 81/4 was not designed with any performance applications in mind.

I'm nervous about the one behind my 340 / 4sp. in a '73 Abody, so.....out she comes in favour of an 8 3/4.

RB torque + 8 1/4 rearend??? I would say don't be hammering on it too hard.

You are incorrect. The 8 1/4 is a direct replacement for the 8 3/4 due to a cost savings for mopar. It is equal to the 3/4 in performance. As you see mag 440 came with a sure grip so how can you say it's not a performance rear. It also came out behind 340 and 360 Dusters. I have a 360 4 spd factory Duster with the 8 1/4 sure grip. It is very much a performance car. You will also find them in bb Chargers, Challengers too. I believe they are performance cars too. They hold up just as well as the 3/4 but get a bad rep for some reason.

[NC PUTZER]

TO:>>>>>>>>>RUMBLEFISH 360

THANKS FOR YOUR REPLY ON IDENTY OF THE FRONT DROP OUT GEARS IN A REAR END.

TO:>>>>>>>>>>ANYONE


I DO HAVE BOLTS IN THE FRONT, BUT HOW IS THE 8 1/4 TO BE IDENTIFIED AS DIFFERENT FROM THE 8 3/4 FROM JUST LOOKING AT IT????

I FOUND CASTING NUMBERS "2070742" ON THE PUNKIN (DRIVERS SIDE). IT HAS 10 BOLTS AND IT IS SITTING UNDER A 1965 DODGE POLARA. WHAT WOULD THIS BE?????????????

NEED YOUR HELP

JOE DENEEN ( NC PUTZER )

[dwc43]

Putzer if the bolts to remove the center section is on the front side where the drive shaft bolts on it's an 8 3/4 rear axle. This is a banjo type axle.

The 8 1/4 has the bolts holding a service cover in the rear of the axle housing opposite side of the drive shaft mount. The gears and carrier are removed from the rear of this axle.

[NC PUTZER]

TO:>>>>>>>>>RUMBLEFISH 360

THANKS FOR YOUR REPLY ON IDENTY OF THE FRONT DROP OUT GEARS IN A REAR END.

TO:>>>>>>>>>>ANYONE


I DO HAVE BOLTS IN THE FRONT, BUT HOW IS THE 8 1/4 TO BE IDENTIFIED AS DIFFERENT FROM THE 8 3/4 FROM JUST LOOKING AT IT????

I FOUND CASTING NUMBERS "2070742" ON THE PUNKIN (DRIVERS SIDE). IT HAS 10 BOLTS AND IT IS SITTING UNDER A 1965 DODGE POLARA. WHAT WOULD THIS BE?????????????

NEED YOUR HELP

JOE DENEEN ( NC PUTZER )

[ehostler]

As in the prior post... bolts in the fron 8¾, bolts in the rear 8

[NC PUTZER]

TO:>>>>>>>>>dwc43

THANKS FOR YOUR POST ON 8 3/4 I.D. INFO.

I THINK I HIT THE JACKPOT ON FINDING SOME 8 3/4 FOR THE '47 CHRYSLER NEW YORKER.

TN. IS CLOSE TO N.C. WILL YOU BE IN ROCKINGHAM IN APRIL FOR " MOPARS AT THE ROCK " SURE WOULD ENJOY MEETING YOU. THE NASCAR TRACK WILL NOT HAVE A RACE, BUT THE DRAG STRIP WILL HAVE ANOTHER GREAT RACE, SHOW & SWAP MEET.


E-MAIL FOR INFO. jcdeneen@peedeeworld.net

NC PUTZER

[ehostler]

I dis-agree about the 8¼ being equal to the 8¾.

First off the 8¼ has the poor C-clip design. Snap the little clip and the axle leaves the car.

Second, the 8¼ was the replacement for the 8¾, however the HP and torque numbers were way down, when that happened. So for the lower HP/torque number is waqs a good replacement. That does NOT mean that it is a good replacement behind a stout B/RB en

[NC PUTZER]

TO:>>>>>>ED HOSTLER

THANKS FOR REAFIRMING THE BOLT LOCATION ON THE 8 3/4 (FRONT SIDE ) COMPARED TO THE 8 1/4 (BOLTS ON BACK)

JOE DENEEN ( NC PUTZER )

[Mr.Mopar]

I run an 8.25 in my Dart with a 125 HP shot of nitrous and MT slicks and pinion snubber. 1.60 60ft. and a best of 12.35. Doesn't seem to hurt it a bit. Thats close to 500 - 600 ft.lbs torque right off the starting line. Ya, it may break some day but it hasn't yet! I wouldn't be afraid to use it in your magnum.

[dave571]

I think a big factor is vehicle weight. There comes a point when it's easier to break the diff than move the vehicle. I think this point is seen sooner in heavy vehicles.

This may also be helped in lighter cars, because the tires can break loose a little easier, than in heavy ones.

I do have to agree with ED. I don't think the 8 1/4 is as good as the 8 3/4.

Equally I DO think the 8 1/4 is a good diff for most applications, including street rods. Light weight ones anyway. I never had any problems with the one in my 73 340 duster. It had a hard life, and kept coming for more.

NC putzer could you PLEASE not type your posts in all capital letters. In Internet chat/mail it is considered to be SHOUTING. Some find it offensive to read.

Hope you like all the info

[mag440]

Thank you everyone for your input. I think I am going to run the
8 1/4 and if it blows up I will just put in a 8 3/4. Another Question: Does anybody know of a dirrect replace ment 8 3/4 rear out of another car without any modification for my 8 1/4 just incase?

[dwc43]

You can use a B body '68- '69 if you use the shock plates too. F,M,J bodies are all the same and I use a '69 Charger rear under an F body dirt track car. Fit right in place with no probs.

[ehostler]

Also, if you look towards the top, you will find a sticky title 'Axle dimensions'. As the name suggests, it is a listing of axle dimensions. It will give you a real good idea as to what will fit.

[NC PUTZER]

TO:>>>>>>dave 571

Thanks for the input. Maybe you can help those with spelling problems also.

Joe Deneen ( NC PUTZER )

[dave571]

No, my spelling is terrible.

Just thought you might like to know(the shouting thing) because in some chart rooms/ discussion boards they would be all over you for that.

This board is pretty friendly, so there's not a lot of flaming here.