8.25 upgrade

[1STMP]

Yes disc brake is going to help keep it in place. Still not as good as retaining the axle outside of the bearing.
In a drag racing application 11.0 is the fastest allowed for clips in NHRA, IHRA. They don't care what brakes... if you aren't a racer.. it don't matter.
I think the carrier is likely the weak spot on a 8 1/4. I would think running a light weight car(or '40 truck) should help.

Original plans were to race
the truck strictly track use.
The axle has the C clip
eliminator kit, and has been
shortened 3 inches per side.
Under a stress analysis CAD
program shortening the axle
greatly reduced the forces
applied to both the carrier
and the outer bearings due
less of a moment arm along
the axle. We also added a
girdle and bearing cap
reinforcement bolts. The
4-link bushings are a high
durometer rubber vs heim
joints to lessen the shock.
Ain't sayin' this was the best
way to approach this. It
certainly isn't going match
the strength of a Dana 60.
If anything, it's an
experiment. All in all,
changes made were cheaper
than the initial cost of an
8-3/4, with the benifit of
some weight savings. If
it blows up, I'll humbly
accept the failure.

 

[mrhemi]

The 8 1/4" axle changed in 1996 so I don't think much interchanges between 1996 and newer and the 1995 and older versions.

I was not aware of that. I am more up to speed with 8 3/4's and Dana 60's.

 

[Sparky Anderson]

Alright all, I'm about to give up hunting for a 71-74 b body 8 3/4 to bolt into my 73 satellite. I can't find anything local in Oregon.

So, i'm toying with refreshing and regearing and adding a suregrip to my 8.25 that is in there now. Problem is, the more research I do, the more confused I am.

Here are my problems. Chrysler used 2 different carriers depending on the gear ratio? I know there should be a tag with the ratio attached to the cover, but it looks like it's gone missing over the years and I have no idea what gears are in there. Looking at the housing, looks like it is offset and not centered. The only marking on the housing is "2 11P9". Can't find any info on that.

I'd like to put in 3.55 or 3.73 gears with a suregrip. Is this even possible on my current rear end? I guess i want to know what my options are. I appreciate any advice in advance. I know nothing about the 8.25. BTW, I have 30" tires in the rear.

DrDiff obviously has 8.25 gearing but says it requires a carrier intended for at least 2.71 gears.


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I have the same exact car n year, yes you can upgrade to a limited slip and upgrade to a 3.55. I have done it, but stepped up to a 4.30 gear set with limited slip. I run a 400 hp 340 and use it for drag racing and have not ever had a failure. In addition I did all the work myself, only thing is I had to get the pin in the limited slip machined so the axles will fit in and c clips reinstalled. I also made my own adjuster to set backlash with an large nut welded to a socket.
I did this upgrade 25 years ago before YouTube and be a heck of a easier in this day and age. My only question is the cost now versus the going to an 8 3/4 rear-end. Also you could use an 8 3/4 out of a late 60's C body, should be not that hard to find, example 69 dodge Monaco. Good luck and have fun with the upgrade.

 

[justanotherguy]

I have the same exact car n year, yes you can upgrade to a limited slip and upgrade to a 3.55. I have done it, but stepped up to a 4.30 gear set with limited slip. I run a 400 hp 340 and use it for drag racing and have not ever had a failure. In addition I did all the work myself, only thing is I had to get the pin in the limited slip machined so the axles will fit in and c clips reinstalled. I also made my own adjuster to set backlash with an large nut welded to a socket.
I did this upgrade 25 years ago before YouTube and be a heck of a easier in this day and age. My only question is the cost now versus the going to an 8 3/4 rear-end. Also you could use an 8 3/4 out of a late 60's C body, should be not that hard to find, example 69 dodge Monaco. Good luck and have fun with the upgrade.

Thank you!

 

[Sparky Anderson]

Thank you!

Your welcome.

 

[Sparky Anderson]

On a final note, make sure your ring gear is the same thickness as the original or u will have to get the center pin machined so axles will fit with c clips. In addition if u buy new should have a diagram showing how much to machine off, very important for machine shop. If it's a thicker ring gear. If you get stuck don't be afraid to ask more questions, willing to point u in the right direction.

 

[justanotherguy]

Well, as an update to this, I bolted in the 8.75 and everything lined up well! It ended up being a direct swap, brakes bolted on from the 8.25, and no drive shaft mod was requited (at least it fit up just fine). My old 3rd member and the 489 I got had the same yoke so it mated perfectly.

Did some sick burnouts....and now my transmission is acting up. Hooks in when I manually put it in 1st and 2nd, but not in drive. Hoping it's just low on fluid.

 

[1STMP]

Yes disc brake is going to help keep it in place. Still not as good as retaining the axle outside of the bearing.
In a drag racing application 11.0 is the fastest allowed for clips in NHRA, IHRA. They don't care what brakes... if you aren't a racer.. it don't matter.
I think the carrier is likely the weak spot on a 8 1/4. I would think running a light weight car(or '40 truck) should help.

It does as the truck weighs
less than 3000 lbs empty.
So far, after a few hard
launches, the 8-1/4 seems
to be holding up. May sound
crazy, but I'm keeping a log
as to the abuse applied.
We've programmed this
diff"s changes using a
finite analysis program,
and compared it to a OEM
8-3/4.
Testing is ongoing.