I have been searching but nothing yet sooo..

I have an 8 1/4 rear end with 2.45 gears...would like to change it a little lower before I install...
will these parts swap with 8 3/4?
any tips on what parts needed, would be great I have never dug into one of these
what would be the best way to go used or new..cost vs. quality..
where is a good spot to find them
I have a very modest built /6 duel carb...
3speed OD manual

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Its so nice out side, I think I'll go lay under my car..

2.45...you'll be ditching your carrier...the 8 1/4" is a rear loader with axle cover...the 8 3/4" does not interchange and is a front loader will the whole thing....

Since you need a 2.76+ center section now is the time to make a $$$ decision... The carrier and some gears can be gotten out of junkyards if you have a buddy or a mechanic that can set the used gears up... the possibility exists for two scenarios:

1) you can use the 8 1/4" gears found under any truck/van/diplomat with the round 10 bolt cover ...the "carrier' you will be bolting the ring gear to will have to be any 2.76-4.56 ratio truck/van FMJ body (Trucks with towing packages may have a sure grip...), must be pre-1997 as the axle spline count changed (Anybody know if Strange is making a set of A-body 29 spline axle shafts so we can use the new carriers or the Eaton TrueTrac?)

2) you can buy a new 8 1/4" sure-grip carrier, and either use junkyard gears (may growl/clunk), or buy new gears... price for the whole set up installed is about the price of an 8 3/4" rear axle with carrier and whatever gears it came with....


Good luck on your decision, I'll be doing the same for one of my 8 1/4" soon, ditching the 3.21 open for a 4.11 sure-grip...

-D.Idiot

so as long as I find a carrier..2.76+ I can choose the ring gear I want?
or does any thing else need to be replaced too..

....just to say..if I wanted 3.55 and found a used 2.76 carrier can I just change the ring gear...or do I need other parts to make that happen?

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Its so nice out side, I think I'll go lay under my car..

any one?? I have a used one lined up but need more info..thanks

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Its so nice out side, I think I'll go lay under my car..

Forgive me if you already know some of this, but to clarify, you can only use parts from an 8 1/4", nothing will interchange with the 8 3/4", nothing, not ring gear, not carrier, it's a totally different rear end.

The 2.45 carrier in the 8 1/4" rear is a lone ranger carrier casting because of the thickness of the ring gear (or maybe it's the size of the pinion gear) so I'm pretty sure you can only run 2.45 on that carrier. Therefore, you need to find another carrier that is cast for the 2.76 and numerically higher ratios. You can buy a new one (sure grip) or find a junkyard rear to pull the guts out of (you can take just the carrier or both the carrier and the ring/pinion if it's the ratio you want).

Once you have the 2.76+ carrier, you can then run any ring and pinion you want, within 2.76-4.56. You must have a matched ring and pinion, they are only cut to work with each other (you cannot just change the ring gear only, you need to change both). Then you will need the gears installed and set up correctly by a gear shop. They will usually charge labor plus parts, which consist of new bearings, shims, crush sleeve, etc, known as an "install kit". You can do gear installations yourself but it's best to have someone reputable who has experience setting up gears.

Also note: ALOT of 8 1/4 axles made during the 80's were actually 7 1/4 axles contained inside an 8 1/4 housing!! Try to find a carrier from a pickup (78-90 eg.) to avoid the "fake" 8 1/4's.
Note that the "real" 8 1/4 has axles that have 3 shallow round holes on the end of the axleshaft {in the register area}. One larger one in the middle and two smaller ones on each side of the large hole at 180* apart.
The 7 1/4 rear in the 8 1/4 housing has kind of a rectangular depression that is roundish on the ends, in the register area.
Like i said, alot of the Diplomats/gran fury's/ fifth ave's actually had
7 1/4 ring and pinions that were installed in the 8 1/4 housing.
In general, all 8 1/4 equipped A-bodies had actual 8 1/4 rears.

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1979 W150 Shortbox
225, NP435, 9 1/4, Dana 44

The Good Life.

A diplomat, Fifth Avenue, Gran Fury, etc., that has a 7 & 1/4 rear will have axle tubes that get narrower as they connect to the center section.
An actual 8 & 1/4 differential in an M-body will have axle tubes that are the same diameter from end to end.
An F-body station wagon, or any M-body cop car is your best bet, in my opinion.

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"Ja, Ich fahre ein altes auto."
'78 Volare 225
'67 Charger 318

what about the vans? will they work you think

go to say sorry about all the no brainer questions but this is something I have never done and not only that finding info..or a book that help is far and few
just so I get this straight..
as long as I can find a 2.76 carrier I can put in most ring and pinion and it will work..ie...(i dont have to find a 3.55 carrier to get 3.55..the 2.76 carrier will work and ring and pinnion can be changed to achieve 3.55...)

I think I hane found two rears both in vans..will those swap too..thanks

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Its so nice out side, I think I'll go lay under my car..

Correct

...Regarding the vans, if the rear looks like yours and has 10 bolts on the rear cover you should be good... just check the van and make sure it's not a 2.45 gear in it (remember that carrier lives alone), there should be a tag on the housing that has the ratio stamped... or better yet just pull the cover and count the teeth on the gears then divide the ring by the pinion to find out exactly what it has. Use a piece of chalk to mark the teeth for counting.

You might find some good info on this page, it also has exploded views of the rears internals.

http://www.dippy.org/svcman/sm03a.html

Wow, that is a loooong site.
Hey you are right about the tapered axle tubes, I never noticed that before. I was looking at a rear axle in a jeep. Looks like a 8 1/4 axle and it too has the "slimmed down" axle tubes. Jeep was a 4 cyl. [cant imagine why they would put a 7 1/4 axle in a jeep but that's what it looks like]
Any body got the low down on the Jeep/Mopar axles?

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1979 W150 Shortbox
225, NP435, 9 1/4, Dana 44

The Good Life.

Jeeps had 7 1/4 s and 8 1/4s also a selection od danas. AS for the 7 1/4 parts in the 8 1/4. Sorry but thats not true at all. they simply dont fit. THere was 2 diferent axle spline counts the splits in 92-93. You can take a 92 ABS sure grip and put it in a 73 housing and it all fits. But sorry 7 1/4 bit just isnt true. Trust me

I had read in certain mopar mag that the ring gear was installed into the 8 1/4 axle with a modified gear carrier. cant remember exactly what years but applied to 1980's M bodies. Are these 8 1/4 actually modified 8 1/4's into 7 1/4 or was this incorrect too. Trying to get the actual story.

So the jeeps were 8 1/4's, just some of them had smaller spline axles

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1979 W150 Shortbox
225, NP435, 9 1/4, Dana 44

The Good Life.

The split is 1996-97... 8 1/4" axle shafts are 27 spline from late-60's to 1996, then 29 spline 1997+...

Try to watchout on Jeeps, my buddy at work has a 1991 Cherokee with the 10 bolt "round" cover it's a Dana not an 8 1/4". Try to stick to Dodge/Plymouth and you should be in good shape.

-D.Idiot