8-1/4" rear end gear help

[Mstone68440RR]

Finally getting ready to start working on with my son on my first car that I have had since high school. Car is factory equipped with an 8-1/4" rear diff and 2.71 gears, non-posi

I would like to swap gears to at least a set of 3.23 or possibly 3.55 gears with posi. How difficult is it to rebuild the diff I have? I have read that it is capable for mild small blocks with light strip duty which is what this car will see. How abundant are gear sets for the 8-1/4", and do they also have sure-grip like the 8-3/4" diffs?

I have already come across a 741 case with 3.23 gears locally ( have to go back to find out if it is sure grip as I did not know what to look for the first time I saw it) and was wondering what the best route to take was?

 

[bbcharger71]

I had an 8 1/4 in my charger with 3.73 gears. I put an Auburn limited slip unit in it. It was great for a mild small block. The kicker is the limited slip unit was around $400. You also need to factor a couple hundred for some gears too. You might be better off get the 8 3/4 if it is a limited slip. Then you definately will not have to worry about breaking it.

 

[rumblefish360]

Parts are readily available for the 8-1/4. The differential is approx. under $400 and gears are Approx. $200 & change. They will take 400lbs. Of torque easy enough.

The 8-3/4 is a good bit stronger. My buddy ran high 9's with them for a long while in a all steel '69 Dart & a 500 incher Indy headed engine. It did fail after a while. Between monster torque and 3900lbs. It was a matter of time it would fail with high rpm launches and slicks. But that is also understandable.
It took about a year of abuse.

The draw back is expense to the 8-3/4. First is out right purchase.
Suregrips are pricey.

The case here with yourself is, do you need it? Or just want it? I hope this helps.

 

[Cranky]

The 8 3/4 is easier to build imo because you can bench build the 3rd member while the housing remains in the car. You can also do that with the 8 1/4 but you have to pull the entire housing out of the vehicle and have to have plenty of bench space but it's not too bad to do in the car if you can raise the back of the car high enough to at least sit cross legged under it and have the rear end at head level. Doing one on your back sucks. Imo, if I'm doing to put forth that much effort, I'm going for a heavier duty rear end like the 9 1/4 or a Dana 60 however, the 60 would be overkill in your case. If you've never done a gear change, it helps to have someone around that has some experience. Gear work isn't voodoo but it has to be done right.

 

[Supershafts]

It's voodoo and precise measurements