My 69 has a 12 bolt posi with 3.73 gears. It is a stock rear end as far as I know. I am trying to determine whether or not it should be rebuilt. Here is my situation and any advice is much appreciated:

1. It has been drained of rear end fluid for almost three years. I was going to change the lug studs since I was converting to rear discs and then Uncle Sam gave me a different plan and I had to put a stop my project until now so I never refilled the rear diff with fluid. Is being dry for this long mean the clutches are done for? What should I check for, the car is without an eng/transmission so doing a test drive is out of the question.

2. Since I was going to have to pull the axles to install the studs I am thinking of replacing the axles because I don't know the history of them. Supposedly the car only has 46,000 miles on it but...you know how that goes. Is this cheap insurance or am I engaging in overkill? How would I check to see if the axles have any twist in them and what is unacceptable?

3. If a rebuild is in order can I use stock components or should I upgrade and to what (there appears to be a plethora of options but I don't have enough knowledge to make an informed decision other than Eaton is probably the best way to go)? I plan on installing a 400-500 horsepower small block or LS motor with a TKO 600 transmission. I do not plan on running slicks on this car or much strip time. The intent of this car is to be a hot street car that can handle not a drag strip warrior.


Thanks for your time,

Lee

If the cover was left on... what I mean is the insides were not exposed... then I suspect it's ok. I bet those posi clutches still have a film of lube on 'em. I'm all for pulling the axles and inspect 'em. Replace the axle bearings (Timken) and seals while you're at it. If you are replacing the lug bolts with standard length ones, you shouldn't have to pull the axles just for that reason. When I converted to rear disc brakes, I installed longer lug bolts which required pulling the axles, but I had the rear apart and rebuilt anyway because of a bad pinion bearing. If the carrier bearings, pinion bearings, posi clutches, and gears are all still good, I would not worry about rebuilding it.

The clutches are steel, so unless they rusted, they will not be hurt by draining the fluid.

If the axles are bad where the bearings run on them then you should replace them. If they are not bad then I don't see a big reason to replace them, unless you are going to do some drag racing with slicks. Tom's Differentials has some of the best off-the-shelf axles.

The Eaton that you have now can be rebuilt in most cases. If the rear end was good when you drained it then it is probably still good. Rust is about the only thing that could have damaged it.

Thanks for the advice, I didn't know the clutch plates were metal, thought they had some type of friction material on them like the plates an automatic trans has. I need to pull the axles to put longer studs on them for a rear disc brake setup so I will check them out before re-installing.

The cover was kept on the rear diff and the car has been in covered storage the whole time but not climate controlled. I guess I will take a good look at the innards prior to re-installing the cover for good. Sounds like things should be ok.

Thanks again.