I didn't go to Naperville to pick up 8 3/4 rear ends, but I got more then my share of them back then. The last production year for the 8 3/4 was 1974, so they have been out of production nearly 40 years. It's no wonder they are hard to find in salvage yards. The ONLY advantages the now famous Ford 9" had over the Mopar 8 3/4 was the number of years it has been in production and the number of them made. The 8 3/4 was every bit as tough (and likely tougher, because of design) then production Ford 9", only giving up to the Dana 60 in strength because of shear size of the Dana 60. Probably the weakest component of the 8 3/4 was the light weight housing that could twist and bend beyond the capacity of the center sections limitations. I love it when these guys drag up old posts. Gene
i gave up on the 8 3/4 after i broke three in one season. i went with a dana after that and never looked back. the car was a 64 ply with a stick. 20 years ago they were around for 75-150 dollars now they are 500 or more for the center chunk. if you break two its about the same price as a dana 60. i think the aplication has alot to do with the failure point. a heavy car with a stick is differant from a automatic a-body. the dragsters had more power but little weight to them. they also used slipper clutches and were back braced. they left soft (shock) compared to a full sized b-body stick car. chrysler in 65 did a test to compare the strength of the 60 behind a new 66 ply. hemi car. the 60 went 500 launches with out failure and the 8/34 if i remember correctly went around 200. i think this test is how mopar decided on putting a dana behind stick cars.
The housing problems are from caused largely by guys using housings from 6 cylinder cars. They were of thinner metal. Who knows why the factory would make a different housing? It would seem that part standardization would have ruled.
Yup, there ya go. Where the perches or bars/links attach makes a huge difference in how much the tubes can twist. The length of the tubes is a major factor too. The shorter, the stouter. I remember guys running a long traction bar from a bushing at the trans crossmember to a bracket right above the pinion. (GM did a Firebird like this from the factory.) That takes all the bending away from the center, but it moves to the outboard ends of the tube.
I run a 742 in an injected nitro hemi dragster. Back braced housing, anti-rotation, spool and 35 spline floater axles, 900 horsepower. Working fine.
Dodge Dakotas. I have a friend who has one behind a Hemi in his 33 Plymouth, right width and everything.
"...The reason people love the Ford 9 is the HUGE support for them in gear selection, and other components..." IIRC, the fundamental reason for 9" popularity is the easily adjusted pinion depth. While a trick is to find the 9" housings with a big "N" for nodular cast iron cast in, which are stronger than the grey cast common housings, it's worth noting that all [or almost all, my books are gone] 8 3/4" Mopar housings are cast steel, making them far stronger. Ford, as well as Mopar had various strengths of steel housings for various OE builds. Saw one forestry 1/2 ton 4x4 Dodge that was showing a degree or so of negative camber on both sides of the 8 3/4 after the idiots loaded it down with about 2 tons of stuff then drove it over a 6 ft dropoff escaping a shifting fire. Truck was in the shop for something else. Much as I love the Ford 9", they do have more pinion offset [more drag] and weight so learn to love and understand pinion depth adjustment and free yourself from 9" servitude. Must say, though, the old, original Ford training slideshow/film/tape on setting up 8-9" ring and pinions is THE best. Nothing else is even close.
The Jalopy Journal
