Rear-end break-in suggestions?

[Eric47Dodge]

Pulled the rear-end from my D24 and had new gears installed at a top-flight rear-end shop in Seattle area. This is a Chrysler 8.25 rear-end that I got at a junk yard a few years ago. Old ratio was 2.24; new is 3.21. I only run the car at the salt flats, and it is not street-legal. It will only run for about 7 minutes without overheating because it doesn't have a fan, and just a little aluminum radiator. When I picked up my rebuilt unit, the shop gave me a long list of "break-in" instructions, including running it under moderate loads for 500 miles. My dilemma is that this car won't run 500 miles for the rest of its life. It will only run 3 miles at a time under heavy load for a few times per year. My questions: is there anything I can do to "break in" the new gears that doesn't involve driving around (e.g., jack up one wheel and run the car in place for a few minutes)? and second, I usually use 90-weight in the rear-end. I know that you can get lubricant of at least 140-weight for use in high-demand situations. Under my circumstances, would it be better to use the lighter or heavier lubricant? Don Coatney, if you are reading this, I would be especially interested in your opinion. Thanks to all.

[Plymouthy Adams]

Read this..apply it as you deem fit..

http://www.metropartsmarket.com/rearend/warranty.html

[Don Coatney]

Eric;

Were it me I would not worry much with the break in procedures. You will only be driving 5 or so miles on each run. And as far as lubricant goes I would use 10 weight engine oil. Less resistance equals higher speed. Hope you set a record on the salt.

[Guest tagree01]

That is cool!! How fast are you guys running at the salt flats?

[greg g]

Is there any way to hook up a lube circulation pump and a cooler. I would think that 50 W might be a good compromise for lubrication and flow that could be pumped more easily and flw better through something like a tranny fluid cooler. Can you not make some break in runs on the slat flats prior to your timed runs??? didn't they used to do a 1 mile circular track out there??

Or borrow a tow dollie and pull it for 50 miles or so with the rear wheels on the ground (drive shaft disconnected)

[Eric47Dodge]

Don, I have some updated pictures of the car, but haven't been successful in posting them. Get a message that they are too big (data-wise). Just snap shots from my inexpensive digital camera really. Can you help? And thanks for your advice on the rear-end.

[BobT-47P15]

Eric.....instead of using the 'manage attachments' method, just click on the little yellow envelope above with the mountains on it and paste your photo url in the box provided. It will work with a larger picture.

[Don Coatney]

Don, I have some updated pictures of the car, but haven't been successful in posting them. Get a message that they are too big (data-wise). Just snap shots from my inexpensive digital camera really. Can you help? And thanks for your advice on the rear-end.

Eric;

E-mail the pictures to me and I will post them for you.

[Eric47Dodge]

I think I figured out how to reduce the density of my pictures. Here are a couple from last fall's USFRA meet at Bonneville, including the big flood that ended the meet. You can see the water covering the track -- it covered miles and miles. A most amazing sight.

[bob westphal]

Hey Eric,

Cool!!! What engine are you running? I've been working on cars since I was 12 and I never heard of breaking in a differential. Who says old dogs can't learn something?

[Eric47Dodge]

Motor in my D24 is the one that came from the factory. Only modifications have been 2 Holley 94 carbs; headers; and an ignition system from Tom at Stovebolt. This required a conversion to 12-volts, which is accomplished through a 1700 amp battery in the trunk, and no alternator/generator. Car will run long enough between charges, as it overheats after about 7 minutes because of its little radiator. It's run 80+ mph in second gear (stock 3-speed), but wouldn't pull to red-line with old gears, so I went a little taller to see what would happen.