Mark Williams caps on a 83/4?

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Do you need to replace both caps? If not which one do you replace? I bought 2 caps. Now I have heard you only need to replace one of them. What should I do since I already have two replacements? Jim

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The left side(drivers side) is usually the one that breaks, we put two of the Summer Bros. steel caps on a 8 3/4 340 4 speed Duster years ago, it ended up exploding the early clutch style posi later in that year A piece of the posi case went through the back of the housing and puncture the gas tank, it looked like a hand grenade exploded inside the posi Luckily it was on the starting line and no fire occurred He put a Dana 60 in it with 5.57 gears, ladder bars, mini tubs and bigger tires after that, no more problems, ever I have put one M.W. steel cap on the drivers side on several third members I had in my Duster, they flat worked Your choice, put both on now or save one for later

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replace them both, I did. and you still have a time bomb.

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Not me! Car has to hook up before it can go boom.
Maybe next year I'll be posting Dana 60's instead of weight transfer.

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replace them both, I did. and you still have a time bomb.

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If you have enough traction and power you can mess up a 8 3/4, my Duster started off with a 1964 B body housing, had it narrowed and new ends installed, order special made Strange 35 spline axles, to work with the A body brakes and length for them, bought a 35 spline Starnge spool. I had a set of 1/4 Max ladder bars instaleed along with tubs to the subframes and sub frame connectirs, Strang Engr coil overs and a diagaonla link. I broke a tranny yoke in half, then twisted up a pinion yoke opening up the saddle enough to spit the interior retainers out, ruining the rear sprag in the tranny and The final straw was I twisted the non back braced housing up enough to peel the right side ladder bar brackets off that housing on the starting line The bad thing about the housing twisting was it was talking to me before it broke but I wasn't listening. The right side axle was real hard to install, I had to drive it in with a block of wood and BFG I had also cracked the outside edge of all the teeth onseveral ring gears I had treid 3:73,3:91, 4.10 and 4.30 gear ratio in the car I ended up having a Dana 60 out of 3/4 ton pick up( 3 1/8 axle tube diameter) cut down and made to fit my car, I reused the axles by cutting about a 1/2 inch off of one end and reused the brakes and brackets off of the 8 3/4 My car weighed 3450 lbs with me in it and a full tank of gas at the track, ran low tens and high 9 at 134.+ MPH corked up with the air cleaner on

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I'm doing this on my 8-3/4 also. I can get you the diameter on Tuesday when I get back to work.

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I put a pair on one of my 3rd members. I'm not sure why but I had issues finding a shop around here that could do the simple task of grinding the caps. (supposedly same procedure as rod caps) I ended up running away from one shop in Worcester when he said I can't bore them to fit.
I ended up sending mine to Campbell in VA to get it done.

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^^^This^^^any decent local shop should be able to handle this.




I'v been running my(4.56) 8 3/4 since the early 90's without any ring gear failure and that's been with a stock cap ,around the mid 2000's i switch to an MW cap(same gears)and ran those gears up into this year,then the rear end were trying to tell me that gears were tried and need changing glad i caught it just in time the pinion gear were chip so i replace them with a set of 4.10s which i think or the weak link(these 4.10s r the yukon brand as Richmond is out of the business)