Is an 8 1/4", 2.45:1 diff housing exclusive?

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I just spent a bunch of time reading the 8.25 axle thread linked in post #4 and I had to say there (and will add here) that I see no evidence to support two different housings.

Dr. Diff was quoted in the thread as saying he only knows of one pinion offset machined into the housings, the pictures of housings in the thread showing the "difference" look no different to me outside of camera angle, 1970-Dart specifically pointed out in the thread that he swapped 3.55 gears into his housing that came with 2.45 hears by using the correct carrier.

There is no argument with there being a different carrier based on the gear ratio, but I think the argument that the housing is different is due to the wrong carrier being used for the ring gear.

Buy a 2.45 axle and try and swap 3.55's onto the original carrier and the gears won't mesh. Buy and use the correct carrier for the 3.55's and I doubt there will be any problems.
 
DionR said:
I just spent a bunch of time reading the 8.25 axle thread linked in post #4 and I had to say there (and will add here) that I see no evidence to support two different housings.

Dr. Diff was quoted in the thread as saying he only knows of one pinion offset machined into the housings, the pictures of housings in the thread showing the "difference" look no different to me outside of camera angle, 1970-Dart specifically pointed out in the thread that he swapped 3.55 gears into his housing that came with 2.45 hears by using the correct carrier.

There is no argument with there being a different carrier based on the gear ratio, but I think the argument that the housing is different is due to the wrong carrier being used for the ring gear.

Buy a 2.45 axle and try and swap 3.55's onto the original carrier and the gears won't mesh. Buy and use the correct carrier for the 3.55's and I doubt there will be any problems.
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I just finished reading all fifteen pages and referenced links.

This was my brain at the beginning of page 1;
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And my brain at the end of page 15;
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Someone on here must have replaced a 2.45 carrier and pinion with a 2.75 or lower rear ratio carrier and pinion. If this is true and I'm knocking around in a wanna be daily driver /6, I could pick up a one wheel drive, ring and pinion in the gear of my choice for comparatively little cash.

There is a ton of talent on this forum. Someone has to have done this. :popcorn:
 
I’m fixing to try it. Picking up a 2.25 open A body 8 1/4. I will see if a lower gear and SG will fit in it.
 
The Mopar bible of the 70s/80s says the same thing about the 8.25, namely that it is the ring-gear carrier that is different.......... in the 70s and 80s. In an earlier post I called the ring-gear carrier, a case. To me they are the same...... but I guess I was wrong. So from no on I will use carrier.
The carrier is different because of the thickness of the ring gear. The 2.45s (and according to RRR, so are 2.21s, and that sounds about right) are on a different carrier, from all others. Back in the day, I recall an aftermarket spacer being available, to compensate for that, but I've never messed with 8.25s, because I have always had several 8.75 systems on the go.
 
I run a 2.45 housing that was converted to a 3.21 SG using the pinion, ring and carrier from my 84 D150. I had the work done at a transmission shop that knew their way around 8.25 rears. After 3 weeks it was ready and the mechanic was not amused - it was tougher than he figured. Been driving it for over 7 years.
 
I wonder if an early Dakota R&P and carrier could be used?

Reasonably easy to find those in 3.55, some even SG.
 
Also wonder if a using a late Dakota carrier would be worth having correctly splined axles made for.
 
AJ/FormS said:
In an earlier post I called the ring-gear carrier, a case. To me they are the same...... but I guess I was wrong. So from no on I will use carrier.
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Hope you didn't take my highlighting carrier and housing as busting your chops. It wasn't pointed at anyone, I was just trying to make sure what I was saying was clear. Saw plenty of posts in the other thread where it seemed like people read through it and then commented and seemed like they got lost on which was which.

I could have use the term case as well for the carrier, just seemed like "carrier" was a little more clear and I was working hard to make sure I was as clear as I could be.
 
YY1 said:
Also wonder if a using a late Dakota carrier would be worth having correctly splined axles made for.
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Seems like a grey area where it would certainly make the 8.25 better, but is it worth it over just stepping up to an 8.75"?
 
I see about a dozen or more Dakota's every time I go junk yarding.

I even see M and sometimes F bodies as well.
(Saw one last month and got the power trunk release)

I haven't seen anything with an 8 3/4 in over 10 years and that was a 68 C body.

It would be nice to know if you could build a 3.55 SG 8 1/4 from relatively cheap junk yard parts.
 
YY1 said:
I see about a dozen or more Dakota's every time I go junk yarding.

I even see M and sometimes F bodies as well.
(Saw one last month and got the power trunk release)

I haven't seen anything with an 8 3/4 in over 10 years and that was a 68 C body.

It would be nice to know if you could build a 3.55 SG 8 1/4 from relatively cheap junk yard parts.
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If you run across a early 27 spline 8.25 3.55 in a Dakota in your travels, I’d pay you to get it. I’m picking up a 8.25 2.25 this Saturday that I want to build.
 
DionR said:
Hope you didn't take my highlighting carrier and housing as busting your chops. It wasn't pointed at anyone, I was just trying to make sure what I was saying was clear. Saw plenty of posts in the other thread where it seemed like people read through it and then commented and seemed like they got lost on which was which.

I could have use the term case as well for the carrier, just seemed like "carrier" was a little more clear and I was working hard to make sure I was as clear as I could be.
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After the first half dozen pages of detailed conversation, and trying to visualize all the moving parts down to the nitty - gritty for the first time, it did become apparent that people had different terms for the same part. And being a newb to differentials, I got to guess what part they were talking about. It looks sorted out though and I'll patiently wait to see if an open 3.23 carrier set comes up from someone converting to a SG 3.55 or something. In the mean time, there is plenty other items to work on! :rolleyes:
 
YY1 said:
It would be nice to know if you could build a 3.55 SG 8 1/4 from relatively cheap junk yard parts.
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I would guess that yes, it could be relatively cheap.

One scenario I could see is someone picks up a cheap A-Body 8.25 with a bad wheel bearing and really tall gears. Since the bearing rides on the axle, probably best to buy a new axle, so why not replace both and upgrade to 29 splines at the same time? If so, grab an axle from a '96+ Dakota, toss the housing and swap the gears and carrier into the A-Body housing and add the new axles. Still might cost $5-600, but could be less if you are frugal.

Just not sure of the strength comparison with an 8.75" axle. It's probably close, but maybe not as strong. So where do you draw the line?

And to be clear, I am running an F-Body 8.25" in my Duster because I tripped over one in the junk yard with 3.21 gears and didn't want to spend the money to buy a B-Body 8.75" to run later model 17" wheels.

I might add, that I did go looking for 29 spline axles on Dr. Diff's site and could find any. So, no idea where to buy them, nor how much they would cost. Best guess would be $300 for a pair??
 
What I'm talking about is using an M (or F) body housing (again, I still see several of these every year), and a 1996 or earlier Dakota carrier and 3.55 gear set (I still see several of these yearly as well, but have not verified gears), retaining the 27 spline M body axle shafts.
 
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@SGBARRACUDA

80% of the yards I frequent are actually closer to you-

Tampa, Clearwater/Largo, and St Pete LKQ, and what used to be Big 3.
 
I use to frequent some of them. My back prevents me from doing much walking and lifting now days.
 
YY1 said:
What I'm talking about is using an M (or F) body housing (again, I still see several of these every year), and a 1996 or earlier Dakota carrier and 3.55 gear set (I still see several of there yearly as well, but have not verified gears), retaining the 27 spline M body axle shafts.
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In a lot of ways, that's what I did. Just didn't have to swap the gears, but I did put in a different carrier with a sure grip.

I just realized I am kind of approaching the question from the wrong angle. I have been thinking about ultimate strength/cost and ignoring the question of application.

In light of that, I think an 8.25" axle is a great solution. For someone not planning on run slicks and trying to lift the front tires, it's hard to beat. And even for a drag car, it is probably fine to a point. But I think someone that is looking at building a drag car has a different application and changes the question to more along the line I was thinking initially.

Honestly, I have never had an overly powerful A-Body, but all I have ever run is 8.25" axles and the only one I ever broke was the one I set up and then did a burn out with after putting a mile on it. Could have been I jacked up the pinion bearing when I was setting it up, or that I didn't break it in, but all it needed was a new inner pinion bearing to be good again. I wouldn't even hesitate to run one with a BB assuming it was a mild one.

Just my opinions.
 
8 1/4 came from the factory behind 400-2 barrel Cordobas.

If you've ever tried to move one, the 8.25 weighs a LOT less than the 8.75.

In a street car with a moderate engine, that's less weight to pull around.

I wonder how an 8.25 stacks up against a 10 bolt gm axle?
 
YY1 said:
I wonder how an 8.25 stacks up against a 10 bolt gm axle?
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Which one? Good grief, thought I would look and there are a bunch of "10 bolt" axles for GM's.

Looks like the 7.5" and 8.2" ring gear 10 Bolt use a smaller pinion diameter of 1.4375".

The 8.5" and 8.6" ring gear 10 bolts use a 1.625" pinion, same as the 8.25 Mopar and the GM 12 bolt.

Looks like the 10 bolt axles have more splines at 28 or 30 versus 27 or 29 for the Mopar.

No idea on the tube wall thickness for the Mopar but one article mentioned that the GM 10 Bolt uses .3125 axle tube wall thickness and that it could be an issue.

Overall, I would guess the Mopar 8.25" axle stacks up pretty good to the 8.5" 10 Bolt. But just a guess.
 
Interesting, found one article that said that the 8.25" with 29 spline axles is comparable to a Dana 44. No idea where that puts it in the hierarchy though.
 
DionR said:
Interesting, found one article that said that the 8.25" with 29 spline axles is comparable to a Dana 44. No idea where that puts it in the hierarchy though.
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And the Dana 44 has the same axle spline count and the clutch type Dana 44uses he same internals as the 8 3/4” Dana clutch type. Minus the thrust button holes in the spider gear cross shafts. But you can drill them. Done it a few times.
 
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