Pinion depth is one and backlash is another....if the pinion isn't bothered, then all that needs to be done is backlash.
I guess I worded that wrong . But to get the backlash correct you have to have the ring gears at the proper depth on piniin teeth .
I've done a lot of rear ends.....most of them had an easy life and being 50 doesn't mean much. Once it's open, you can tell if it had a hard life and never had an oil change. The ring gear will tell a story if things are about to go south imo. If it was quiet before opening things up, I'll run it until it cries uncle. Rear ends are probably the toughest unit on a car.....and changing the pinion seal doesn't disturb the pinion depth and if the pinion bearings spin smoothly, I won't change them either.
On Roadkill ( at the Farm) Friedburger put one on his 8 3/4.
Lunch Box Lockers is what Friberger called them. I installed one in a buddy's car several years ago and so far so good....
I wasn't really referring to the age or durability of the rearend itself. Just the fact that new parts for a not-very-popular rear (outside of Mopar lovers, obviously) that hasn't been in production for 50 years are not likely to be at the top of production order.
Last time I checked, there's still lots of parts available for the 8 3/4 including shims and bearings....also crush sleeve eliminators which I recommend. Hate to brag but I was one of the first to order a solid spacer (crush sleeve eliminator) from the only supplier at the time but it was about .030 too long. Being that I have an engine lathe, I was able to make it work with shims but notified the problem with the supplier and they took care of the problem. After that, they were fine. Screw those dang crush sleeves! Never did like them.
And then again, I might be in the dark ages since I haven't built an 8 3/4 in several years now.....
I had a friend who ran a rearend shop (since passed away) who managed to get me a great deal on some 3.91s and a genuine Detroit locker for my 8 3/4., and set them up for me for cost of parts. Haven't touched it or worried about it for about 15 years now. Scary how much a REAL locker costs now.
Funny....9's actually draw a bit more power to operate...not much but still. To build a strong 9 requires all aftermarket parts as a stock 9 doesn't cut it and the 8 3/4 stock is barely.....and I mean barely weaker than a stock 9. The Ford 8" is a major weakling and the 9 is just a better version of the 8. In most cases, the 8 3/4 is fine for up to 500 hp depending on the weight of the car and if it isn't behind a stick and launching at 6k. Been there done that with a buddy of mine. We killed 3 8 3/4 chunks before finally installing a stock D60 with stock axles and continued to run mid/high 10's with a stick launching at 6k lol. Thing is, the aftermarket decided to coddle the Ford 9 for some reason....looks to me like there were $$$$ signs in the sky for that. I built one 9" for a guy and decided not to do another after that one years ago. Don't like them and never will.
I would agree 100% with all of that. I went with a 9" for Vixen, but purely out of a cost perspective. The entire rear end was GIVEN to me. All I have in it so far is about 300 or so bucks. That includes having it narrowed to the stock A body width and having 8 3/4 ends welded on. It has 4.11 gears on an open diff unit, but I have a reman Track Lock for it. I still have to get my custom axles and that will put the total somewhere above 800.
Parts availability and thousand dollar plus price tags on 8 3/4s make the 9" pretty attractive.
I would go along with that were it not for one thing. Ford never made a two spider gear Track Lock. They were all 4 pinion. All the Mopar 8 3/4 cone type sure grips are two pinion. .......and NO ONE sells replacement spider gears. You can almost get a 9" spider gear set at WalMart. lol
Another reason why everyone wants a clutch type posi! (Just kidding!).
That's just nutz!
