489 Case information please.

[RemCharger]

Bump this so I remember to check the parts this weekend.
Over the last year I bought a Richmond 3.55:1 gear set from Summit, and a rebuild/Install kit with solid spacer from Dr. Diff.
I was planning to put it in my old 3.23:1 sure-grip 489 case.
The gears were on back order for several months, and I got a few extra $$$ in the meantime, So I decided to just build a new center section with a new 489 case which I think is a yukon? (I'll have to check), and the "sure-track II" differential from Dr. Diff.
When I looked over the "sure-track II" there are no markings on it anywhere of any kind to identify part number or manufacturer. I was trying to find the torque-bias rating, but I guess I would need to call Cass and ask him?

Do you mean break-away-torque?
You could measure it.

 

[451Mopar]

Do you mean break-away-torque?
You could measure it.

Note that the torsen and helical diffs are slightly different designs, but operate the same basic way.
My understanding is the Torque Bias Ratios can range from 3:1 (will unlock fairly easy) up to 5:1 (one tire would have to only have 1/5 the traction of the other tire before the diff unlocks.) The design works best with vehicles with ABS traction control where the brakes can apply some drag if one tire has zero traction.

Quited from https://torsen.com/ask-torsen-torque-bias-ratio-functional-questions/

The simplest way to conceptualize torque bias ratio (TBR) is to think of it as a traction ratio. This represents how much difference is allowed from one side to the other; if the TBR level is exceeded, the differential will “open” and allow spin or differentiation to occur. If the ratio of traction from one side to the other is less than the TBR, the differential will remain locked up. For example, if the TBR is 4:1, differentiation (or spin) will not happen unless your low-traction tire has less than a ¼ of the traction that the high-traction tire has.

 

[rumblefish360]

From Doctor Diff, I ordered a 8-3/4 w/3.55’s & an 7290 yoke for my 360/904 small block. I’m did come in a Yukon carrier. It’s been about 5 years with zero problems.

 

[451Mopar]

I have some pictures, but my phone won't connect to my computer, likely have a charging only USB cable.
I E-mailed myself some of the photos, but haven't got them yet. Guess I will have to get a good USB cable.
The photos have a 1971 "489" case next to the aftermarket "489" case. The aftermarket case is painted black, and uses cap screws to hold the caps on. I did not notice and manufacturer symbols, but I need to clean it up because it was packed with an oil coating everything.
So far the only item that looks to need some help is one side of the notch on the front pinion bearing bore was not cut, which would make removing the bearing race difficult if it needed to come out.
I plan to take some measurements between the two cases also.

 

[451Mopar]

got a working usb cable.