The 8 1/4 thread

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Just to jump in here.

I believe there were two different case sizes for the 8.25. If you want gears that are 3.21 or numerically bigger, you would have to find a rear end that already has a 3.21 gear in it. Not that its hard to find, but adds another thing you have too keep in mind when looking for a 8.25

but I am with what the others have said, keep the 8.75 and get new axles.
 
Been through this thread, read all the posts now. I think it needs to be pointed out that so far I see no evidence to support two different housings.

Dr. Diff was quoted as saying he only knows of one pinion offset machined into the housings, the pictures of housings showing the "difference" look no different to me outside of camera angle, 1970-Dart specifically pointed out 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.

If there is in fact truth to the supposition that there is a 2.45 housing versus a 2.56/2.71/2.92/3.21/etc. housing, then there needs to be more detailed info presented. At least measurements or something more than just pictures saying "these are different" when they look the same to me.

Not trying to bust anyone's chops or call anyone out, but if this is supposed to be the definitive thread on 8.25's, then it should be correct. So far I don't see supporting info to call it that.

Carrier bearings, axle splines, Dana 35 vs. 8.25, etc. are all different issues and unrelated to this.
 
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DionR said:
Been through this thread, read all the posts now. I think it needs to be pointed out that so far I see no evidence to support two different housings.

Dr. Diff was quotes as saying he only knows of one pinion offset machined into the housings, the pictures of housings showing the "difference" look no different to me outside of camera angle, 1970-Dart specifically pointed out 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 mess. Buy and use the correct carrier for the 3.55's and I doubt there will be any problems.

If there is in fact truth to the supposition that there is a 2.45 housing versus a 2.56/2.71/2.92/3.21/etc. housing, then there needs to be more detailed info presented. At least measurements or something more than just pictures saying "these are different" when they look the same to me.

Not trying to bust anyone's chops or call anyone out, but if this is supposed to be the definitive thread on 8.25's, then it should be correct. So far I don't see supporting info to call it that.

Carrier bearings, axle splines, Dana 35 vs. 8.25, etc. are all different issues. and unrelated to this.
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Well sometime soon I will be trying this. I’m picking up a 8 1/4 with a 2.25 open. I’ll be attempting to install a SG and a 3.21 or 3.55 in. I’ve questioned the two housing theory and never bought into the different housings.
 
DionR said:
Been through this thread, read all the posts now. I think it needs to be pointed out that so far I see no evidence to support two different housings.

Dr. Diff was quotes as saying he only knows of one pinion offset machined into the housings, the pictures of housings showing the "difference" look no different to me outside of camera angle, 1970-Dart specifically pointed out 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.

If there is in fact truth to the supposition that there is a 2.45 housing versus a 2.56/2.71/2.92/3.21/etc. housing, then there needs to be more detailed info presented. At least measurements or something more than just pictures saying "these are different" when they look the same to me.

Not trying to bust anyone's chops or call anyone out, but if this is supposed to be the definitive thread on 8.25's, then it should be correct. So far I don't see supporting info to call it that.

Carrier bearings, axle splines, Dana 35 vs. 8.25, etc. are all different issues. and unrelated to this.
Click to expand...


I think you're 100% right. I'll add though that there are MORE than two housings for the 8 1/4, but they vary based on body style and not carrier style. If that made sense.
 
DionR said:
True, I was kind of focused on the gear ratio issue.
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I kinda thought that's where you were. I've never in my life seen a housing that was specific to any range of ring and pinion gears......in ANY make, and lemmie tell you, I've worked on a BUNGLOAD of rear axles through the years.
 
I got tripped up, and learned a couple things.there is a 7.25 that looks like a 8.25. Dodge diplomats had them. Give away is the step in the axle tube. It necks down by the diff housing.
2.28 gears had a different carrier.
And the 8-3/8 used in mid 70’s pickups will run 8.25 gearsets.
 
Tooljunkie said:
I got tripped up, and learned a couple things.there is a 7.25 that looks like a 8.25. Dodge diplomats had them. Give away is the step in the axle tube. It necks down by the diff housing.
2.28 gears had a different carrier.
And the 8-3/8 used in mid 70’s pickups will run 8.25 gearsets.
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And all 3 share the same brake backing plates. Drums appear different but all fit.
 
I got excited when I first found this thread but after a quick check on part prices no longer interested lol I may get hated for this but it’s way cheaper to go 8.8
 
Notanova73 said:
I got excited when I first found this thread but after a quick check on part prices no longer interested lol I may get hated for this but it’s way cheaper to go 8.8
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no hate here. I planned to go that route till I stumbled upon an 8.25 rebuilt and ready to go for a good price. Wasn’t worth fooling with the 8.8 at that point for me. Good luck with the swap, seems guys are happy with them!
 
SGBARRACUDA said:
Well sometime soon I will be trying this. I’m picking up a 8 1/4 with a 2.25 open. I’ll be attempting to install a SG and a 3.21 or 3.55 in. I’ve questioned the two housing theory and never bought into the different housings.
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Let me know how that goes. I'm in the same situation, but will probably go with 3.23 gears. It has 2.2 gears now.

It is a later model 8.25, from a 1989 Fifth Avenue. I was told by numerous FMJ members that it HAD to be a 7.25, since "Chrysler never put 8.25s in Fifths." Bought it from the original owner who claimed the car was all original. To me, the housing looks just like every other 8.25 I've seen.
 
RustyRatRod said:
I think you're 100% right. I'll add though that there are MORE than two housings for the 8 1/4, but they vary based on body style and not carrier style. If that made sense.
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Only differences being flange to flange width, and spring perch locations. Correct? The center sections remain the same no matter the body style.
 
RussellSullivan said:
Only differences being flange to flange width, and spring perch locations. Correct? The center sections remain the same no matter the body style.
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I'm not 100 sure,but I believe that is correct.
 
RussellSullivan said:
Let me know how that goes. I'm in the same situation, but will probably go with 3.23 gears. It has 2.2 gears now.

It is a later model 8.25, from a 1989 Fifth Avenue. I was told by numerous FMJ members that it HAD to be a 7.25, since "Chrysler never put 8.25s in Fifths." Bought it from the original owner who claimed the car was all original. To me, the housing looks just like every other 8.25 I've seen.
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They do look like a 8 1/4” but they are 7 1/4”. I call them a Hybrid.
 
Not sure if this has been mentioned yet in this thread, but the way I understand it, the difference in carriers has to do with the thickness and/or location of the carrier mounting flange where the ring gear bolts up.

If you start with a 4.10 gear and work backwards, to 3.91, 3.55, etc., you will notice the pinion gear diameter growing to accommodate the increasing number of teeth, while the ring gear thickness decreases.

The reason a 4.10 gear has such a thick ring gear is so it can reach the small diameter pinion gear and mesh properly. Have a look at 2.2 and 2.45 ring gears and you will notice there is not a ton of material other than the gear teeth themselves.

You cannot use numerically higher than 2.45 gears in a 2.45 carrier, because the mounting surface of that carrier is moved too far away from the pinion centerline for the gears to mesh properly.

Conversely, you cannot use 2.45 or 2.2 gears with the same carrier your 2.76s and up came on, because the mesh will either be too tight or downright impossible to mesh at all. In this case, the carrier mounting flange is moved closer to the pinion centerline.

I hope I didn't muddle anything up. As I said, that is just the way I understand it. I welcome any corrections. Maybe this reply would do better with pictures.
 
RussellSullivan said:
Not sure if this has been mentioned yet in this thread, but the way I understand it, the difference in carriers has to do with the thickness and/or location of the carrier mounting flange where the ring gear bolts up.

If you start with a 4.10 gear and work backwards, to 3.91, 3.55, etc., you will notice the pinion gear diameter growing to accommodate the increasing number of teeth, while the ring gear thickness decreases.

The reason a 4.10 gear has such a thick ring gear is so it can reach the small diameter pinion gear and mesh properly. Have a look at 2.2 and 2.45 ring gears and you will notice there is not a ton of material other than the gear teeth themselves.

You cannot use numerically higher than 2.45 gears in a 2.45 carrier, because the mounting surface of that carrier is moved too far away from the pinion centerline for the gears to mesh properly.

Conversely, you cannot use 2.45 or 2.2 gears with the same carrier your 2.76s and up came on, because the mesh will either be too tight or downright impossible to mesh at all. In this case, the carrier mounting flange is moved closer to the pinion centerline.

I hope I didn't muddle anything up. As I said, that is just the way I understand it. I welcome any corrections. Maybe this reply would do better with pictures.
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Your absolutely right. I have both carriers. I’ll get a picture of them.
 
Here is a picture of the two. 2.20 carrier on the left. 3.55 on the right.

E1D815FA-69A0-4B1A-BA3A-8AF77C920FF9.jpeg


BF23FCC6-824B-4138-9719-C77ABDBEBC8C.jpeg
 
DionR said:
Been through this thread, read all the posts now. I think it needs to be pointed out that so far I see no evidence to support two different housings.

Dr. Diff was quoted as saying he only knows of one pinion offset machined into the housings, the pictures of housings showing the "difference" look no different to me outside of camera angle, 1970-Dart specifically pointed out 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.

If there is in fact truth to the supposition that there is a 2.45 housing versus a 2.56/2.71/2.92/3.21/etc. housing, then there needs to be more detailed info presented. At least measurements or something more than just pictures saying "these are different" when they look the same to me.

Not trying to bust anyone's chops or call anyone out, but if this is supposed to be the definitive thread on 8.25's, then it should be correct. So far I don't see supporting info to call it that.

Carrier bearings, axle splines, Dana 35 vs. 8.25, etc. are all different issues and unrelated to this.
Click to expand...

DionR sounds right - no one has presented any firm evidence that there are two different housings, and several people have posted things that make me think there is only one housing (though there are two carriers). It would be great if Halifaxhops could respond to DionR's post #353.

I'm not sure whether there are one or two housings, but unless someone can show the two housings side by side, or at least from the same angle, give some measurements, part numbers, or point to a Chrysler document that mentions two housings, I'm going to have to assume that there is only one. I've heard this two-housing theory on other pages, but there's a LOT of contradictory information out there on 8 1/4s.

This really needs to be settled if we can. I appreciate Halifaxhops and everyone posting about this, but if the original post is incorrect, the thread should probably be deleted. Most people aren't going to read 300+ posts to figure out what is correct, they'll just go with what's in post #1.
 
Actually 3 carriers
You have the low number carrier 27 spline.
You have the higher ratio number carrier 27 spline
And starting 97 up, they went to 29 spline.
 
volaredon said:
Actually 3 carriers
You have the low number carrier 27 spline.
You have the higher ratio number carrier 27 spline
And starting 97 up, they went to 29 spline.
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Higher number ratio ? Please give me an example of what ratios would work with this. Thanks for replying.
 
Higher number as in above 2.45
Not sure which carrier that is that you have. But that is the "break point". Any ratio from that point and numerical lower takes 1 carrier
Any ratio above that (2.71, 2.94, 3.21, 3.55 and higher yet) takes a different one. Luckily "most"take the same one, not as many 2.26 or 2.45 out there
 
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