8 1/4 axles

[Backrd.Junkyard]

If you're using a girdle with load bolts that contact the center of the cap, you'll be fine with the stock bolts. And as far as any significant advantage of an 8.8 over an 8-1/4 on a street only operated vehicle is nil. I've beaten on the stock C clip 8-1/4 axles in several trucks (doing truck stuff with tree cutting) and have broken more drive lines than I have 8-1/4 axles that the drive lines were connected to.

 

[JR_Charger]

I don't mind spending a little extra $ on the cap studs, but I do have LPW's girdle and axle tube brace coming.

 

[Backrd.Junkyard]

Since you’re going all out with it, you may want to give these guys a call and see if this stud kit will work on the 8-1/4 axle or if they have one that does.
https://www.justdifferentials.com/NP1816-p/np1816.htm

 

[JR_Charger]

Here's a thread on ForABodiesOnly that has a lot of info about building the 8 1/4 - Link

I'm rather pressed for time for the next couple weeks though. It may sound lazy but I need the quick shopping experience.

edit - Just so I don't forget, let me make a note here to research "C-clip eliminator kit" as well.

 

[Master Gunner]

Don't get to wrapped up in how much of a upgrade is needed for X amount of HP. Horsepower won't kill a rear end, but torque will. If the Charger came with a 8.25 rear, the odds are that it also has the 7260 U joints, which would also be a weak point.
The main point of this is that unless you're running at least 12 inch slicks, a loose torque converter on a dragstrip with 400+ ft/lbs of torque that hooks up right now, your current setup will work just fine until you need to upgrade.

Mark

 

[JR_Charger]

I spotted this in the A-body 8 1/4 thread -

TRW makes a greasable heavy duty U-joint (part # 20124) that takes a beating and is well advised if you're going to spell your name on the highway in twin streaks of rubber (spelling "Malcolm" used to take a while until I installed the 360). Back to the U-joint. The nipple is on the end of one of the caps not in the valley of the inner cross where you can't get a grease gun on. Note: NEAPCO (New England Axle Product Company) also has one with the zerk in one of the caps.

I've got to replace the U-joints so I could upgrade to these. I found a couple on eBay but one of the listings says it doesn't fit the 72 Charger w/318. I'm guessing that isn't right. Why would it fit an A-body and not a B-body?

About the c-clip eliminators, I've found a few people asking about them but it doesn't appear that anyone found a set for the 8 1/4. I haven't found them either.

 

[JR_Charger]

The Auburn Gear 546074 appears to be the differential I'm looking for, although I think I saw 97 and up somewhere. I haven't found anything that says how much power it's good for.

What determines the gear ratio? I thought it would be in the differential but apparently not.

 

[Backrd.Junkyard]

2.71 and higher (lower numerically) axles have a different pinion location and a different carrier spacing than lower ratios. As far as C clip elimination, the only way available at the present is to cut housing ends and install 8-3/4 / Dana housing ends and have a set of custom 8-3/4 axles cut for the differential spline count. It may be worth it in an A body, but I wouldn't dump that kind of $$$ into a B body axle with intent on upgrading to a larger axle later.

 

[33 IMP]

The Auburn Gear 546074 appears to be the differential I'm looking for, although I think I saw 97 and up somewhere. I haven't found anything that says how much power it's good for.

What determines the gear ratio? I thought it would be in the differential but apparently not.

If you are worried about how much power it will support.... I wouldn't put any money in a 8 1/4. Mild small block/auto, okay. Stick, or a big block, I'd look for something else....

 

[JR_Charger]

I've done more research and it turns out disc brakes work well enough at holding in a broken axle. I'm converting to discs, so no need for c-clip eliminators after all.

I've already got the 8 3/4 ends, the LPW girdle, and I've ordered the LPW bracing kit. I've looked into custom 8 3/4 axles, but haven't made any progress on that front yet. I found a comment on a Jeep forum that makes me think someone already makes a 29 spline 8 3/4 axle for the 8.25. I don't know if that would work for me or not, but it's interesting.

2.71 and higher (lower numerically) axles have a different pinion location and a different carrier spacing than lower ratios.

I've got 2.71 gears. What will it take to change to a more desirable gear?

 

[JR_Charger]

If you are worried about how much power it will support.... I wouldn't put any money in a 8 1/4. Mild small block/auto, okay. Stick, or a big block, I'd look for something else....

It's going to be a 318 auto car for a while, possibly forever. I may stroke the 318 but I doubt I'll take it over 500 hp.

 

[Backrd.Junkyard]

I've done more research and it turns out disc brakes work well enough at holding in a broken axle. I'm converting to discs, so no need for c-clip eliminators after all.

I've already got the 8 3/4 ends, the LPW girdle, and I've ordered the LPW bracing kit. I've looked into custom 8 3/4 axles, but haven't made any progress on that front yet. I found a comment on a Jeep forum that makes me think someone already makes a 29 spline 8 3/4 axle for the 8.25. I don't know if that would work for me or not, but it's interesting.



I've got 2.71 gears. What will it take to change to a more desirable gear?

2.71 is the carrier break, your carrier will let you go all the way to 4.88. There’s a 2:18 to 2.56 carrier in the offset pinion axle.
https://www.doctordiff.com/8-1-4-ring-and-pinion.html

 

[Backrd.Junkyard]

https://www.forabodiesonly.com/mopar/threads/8-25-8-1-4-rebuild-and-modification.383176/

 

[JR_Charger]

3.55 is the best street performance gear, isn't it? I'm not overly concerned with mileage in this car, but the truth is it will be cruising most of the time. I don't need a 1/4 mile gear, just a gear that's not going to hurt it too bad on the street.

 

[JR_Charger]

Still researching differentials. I've noticed that the Eaton True Trac is $300 more than the Auburn unit, does that reflect $300 more of actual goodness?

Will the 29 spline units work in the older 27 spline housing, if the axles are cut for 29 splines? I.E., are there other differences between the pre '97 and post '97 8 1/4 axles that would keep a 29 spline diff from working in a 72 8 1/4?

 

[Ceedawg]

Don’t know if mentioned but get an 8.8 Ford Exployer rear, bolts in and very strong. Maybe $400 at the junk yard. Holds up to those 1000 HP Stangs

 

[Backrd.Junkyard]

Just back on the thread with a minor update. I talked with LPW today to inquire about the ARP carrier cap studs and they told me to measure the bolts in the 8-1/4 and call them back. The rep said that one of their ARP stud kits for other axles would probably work. But if the bolt dimensions are too long or short, they will see what options they can find. I’ll try to post back Monday to update.

 

[Backrd.Junkyard]

I spoke with LPW again today. The Chrysler 8-1/4 bolt is a 1/2-13 thread with an under head legnth of 2-3/8 inches. Their 325-4 stud kit will work with them. I’m going to be able to confirm next week coming, as my cover and stud kit ships out tomorrow. I’ve been looking into axle upgrades, also. Dutchman has a good replacement upgrade C clip axle made from stronger material.

 

[JR_Charger]

Is the Dutchman axle 27 spline? What are you planning to do with the differential?

 

[Backrd.Junkyard]

Yes, Dutchman carries stock replacement 27 spline, but custom are available, too. It’s going in my ‘71 duster. 4.56 gears and factory sure grip with Dr. Diff offset hangers and shackles, L60-15 bias plies, and homemade traction bars based on assassin racing’s design. I’m on running stock axle shafts initially but may upgrade to Dutchman along the way.