I am wondering if a set of Mark Williams billet caps and spanners would be overkill or not.
I am going to be going through a 8 3/4 rear to put in my 69 Bee. I am going from a 4.56 behind my low 13 second at altitude 383 4 spd car, to a 3.91 and a 500 stroker by spring. I have everthing to do it ( new Detroit Tru Track, bearings, ordering a Dr. Diff yoke) and was wondering if these caps and spanners might be in my best interest while its apart ? I don't have the money to go Dana and would like this to hold up. In all honesty it will see may ten to fifteen passes a year.

Wouldn't it be close to the same money as a Dana after you buy all that stuff and have the case machined. If that big B-body hooks with a 500" something will break and believe me you really need to build a stroked B-body from the rear forward
Gus

I would be in this less than $1000 with the caps and machine work included. I would love a Dana and I am not ruling one out, just can't swing it now. Sounds like anything would help.

these old cars FROM THE FACTORY had D-60 rears with the performance big block/4spd combos. If that doesn't make you rethink..... good luck. Going from a 4.56/383 to a 3.9 gear 500 cid.... increasing the torque AND making it more work to move the weight. Save your money boy!

Jump on Craigslist and find a Dana 60 out of a pickup [I paid 80 dollars for one complete] You should be able to put one together for around 1200.00 dollars.

Heck NO!!

I wouldn't spend any money on a 8 3/4, save it for a Dana or even better a 9".

Mark Williams would shake there head(and laugh) and take your money if you asked them to do that. Real bad investment IMO.

If you hook it good at the track with slicks, it will break someday but it will take a while.
The ring gear (or pinion, or both) will develop cracks and eventually break. If you don't hook it hard, and mostly street drive it then it's not as bad....after saying all that I agree the Dana 60 is the best and really should be what you use. I use one in my duster and I would not use anything else personally.
Brian

I run a BB MT stroker in a handling application with 8.75. In perfect conditions it will "hook" in 2'nd gear with 200 TW road track tires. Full power 1'st gear would blow off the tires and I have never even tried it. Launch means feather the clutch and throttle in 1'st and if the track is warm maybe full power in 2'nd. I believe the 8.75 will live with full power in 2'nd and higher gears.

If I got to the point I thought it might hook in 1'st the 8.75 would be gone. D60 or well beefed 9". Major parts breakage is expensive. The 8.75 worked on high speed circle track behind hot Hemis... not so much for drag race.

I think this issue has been well covered , but there are differences of opinion.
The cap is a band aid.
If you brace the housing and add the cap , there isn't much more to do.

Making sure it is well set up and using quality parts goes without saying.
With a stick and a lot of weight ( 3000 or more ) I don't like their odds.
With an auto , a light car and foot braking , it may last forever.
I believe that weight is a big issue for them , but a stick and the shock they impose on the driveline just compounds that.
If it hooks hard , I really don't like their odds.
I am in the 9" camp , but the Dana is also a decent choice.

Speaking from experience, I broke multiple 8 3/4 rearends with a mild 440 and a 4 speed in my old '68 Charger R/T. Axles, yoke, a pinion in half, etc. If you launch it hard at all, you're going to break parts. Sell what you have and use part of the proceeds to finance a Dana or 9".

The only other option is to never put drag radials or slicks on it, and slip the clutch on launches.

the problem with the stock 9" is that it breaks the cap too. you have to buy a Strange nodular housing or similar. i modded my 8 3/4 years ago before Mark Williams had their fix for the problem. stuck behind a 650hp bb with a brake this held up well.

My 8 3/4 broke the teeth off the ring and pinion gear, the cap was fine. I put a new r&p in it and sold the whole rear end and put the money on a new Strange S-60.

I'm a guy that generally believes 8-3/4's can live if you prep them right, but @ 500 cubes with a 4-speed and B-Body weight, my sense is that you're way past the limit of an 8-3/4. I'm running MW steel maincaps in my 742 8-3/4; along with a Detroit Locker differential, Dr. Diff axles, and a Moser Backbrace. A couple of years in, it seems fine and has held up to my abuse, but that's in an automatic car with 452 cubes, and my 67 probably weighs a bit less than a 69 Dodge. Frankly, I'm surprised Cass sold you the TruTrac (Assuming you talked with him and he knew where it was going??). I would think your only chances for survival involve a Spool, a hefty backbrace, and the steel caps. At that point, the gearset itself becomes the weak link.

Now, all of this is assuming the car hooks at the racetrack, and you're stepping fully into it. on the street with the hardware you've described, you'll likely never see enough traction to break it. If you're going to the track, my advice is: Have a trailer ready for the ride home.

Waste of time IMO. I've seen way to many 8 3/4's break. Save your money do it right once with a Dana 60.

Trust me, the 8 3/4 will fail.

Let see, 500 C.I. stroker with a 4 speed with a 8 3/4 in a 1969 B body, what is wrong with this picture Don't do that

There is an alternative to going with a Dana. About as strong. A lot less $. Bone yards are full of them.

I'd sell your 8.75 and build a Dana 60 starting w/ a junkyard truck rear. My dad did exactly that w/ his 440-6 4 speed '69 road runner. After selling his 3.55 suregrip 8.75, he was only a couple hundred bucks short of breaking even on a 35 spline, 3.54 gear Powerlock diff. Dana 60.

I'm soon to be in the same boat.
Just curious, what's the best donor vehicle to get a 60 housing from?
Looked at Moser's website & a complete 60 starts at about $2200.
I've got more time than money so building one myself may be the way to go.

Mine came from mid '70s dodge and ford trucks I believe. They came in lots of different vehicles over a wide range of year models. Got lucky w/ the one from the dodge truck...it had 3.54 gears and the stronger powerlock differential. Install new bearings, cut the housing and weld on the pass. car ends, new 35 spline axles and 35 spline side gears from Dr. Diff, and put it in the car.

The new rears have definitely gotten more expensive. Back in 2003 or 2004, I paid $1750 for the Moser 60 that's in my cuda. No brakes, 35 spline spool and axles w/ long studs, 4.10 street gear, billet 1350 yoke, chrome cover. Been beating the snout out of it ever since and only took the cover off one time to change the fluid after 10 years.

I was wondering what differential is best for a street/strip car.
A complete 60 with a Truetrac or Detroit Loocker will cost me $2890 from Moser ... i think i could do one myself for less.