Steel caps for 8.75" Mopars???

[bill dedman]

I have a bracket car that has a Vortech-blown 360 Magnum, and I am wanting to build a third member for its 8.75" rear end that will have a reasonable life-span.

I have no transbrake, nor high stall converter (it stalls about 2,500 rpm) and the ring and pinon are 4.10:1 ratio.

The tires will be 9"-wide M-T bias-ply slicks (no d.o.t. tires or drag radials) and will be 28"-tall.

I plan on leaving at about 2,000 rpm, if the brakes will hold it still. (Less, if they won't/can't.)

The engine was tested on a chassis dyno @ 477 ft. pounds of rear wheel torque (445 rear wheel hp) at 10 pounds of boost. Abundant low-end torque....

It will hopefully, be capable of some low 1.70 60-foot times, maybe better, but not counting on it.

I have a NEWLY BUILT 489-case center-section (with a crush sleeve eliminator kit installed) that has a cone-type limited-slip unit (this is a street/strip car), with the larger, (7290) u-joint yoke.

I am wondering if I might need to install a steel carrier-bearing back support (CAP) in place of the cast iron one that it comes with (OEM.)

I don't want to have to do this if it's overkill. The car weighs 3,600 pounds and should run mid-11's if it hooks (118 mph.)

I'd appreciate some advice on this from people who have experience with the 8.75" in a moderately powerful 3,600-pound car like mine. {That's 3,600 pounds with me in it, ready-to-race weight.)

Like I said, this is not something I want to do unless it's actually necessary. Do these 8.75" units break that bearing cap in the kind of useage I described? I will only race it occasionally.

Thanks for any information... it will be much appreciated.


Bill

[Jeff Lee]

Mark Williams sells the caps you want. I would think they are only neccessary if you have a t-brake or stick. I've known guys that run an 8 3/4 with these caps with both a stick and t-brake and they hold up very well. For your application it's probably overkill. If you get one or both caps you will need to align hone the case. At the very least I would get the billet spanners. They move less and maintain the side-play clearance.

[Greg Barsamian]

Originally Posted by bill dedman

I have a bracket car that has a Vortech-blown 360 Magnum, and I am wanting to build a third member for its 8.75" rear end that will have a reasonable life-span.

I have no transbrake, nor high stall converter (it stalls about 2,500 rpm) and the ring and pinon are 4.10:1 ratio.

The tires will be 9"-wide M-T bias-ply slicks (no d.o.t. tires or drag radials) and will be 28"-tall.

I plan on leaving at about 2,000 rpm, if the brakes will hold it still. (Less, if they won't/can't.)

The engine was tested on a chassis dyno @ 477 ft. pounds of rear wheel torque (445 rear wheel hp) at 10 pounds of boost. Abundant low-end torque....

It will hopefully, be capable of some low 1.70 60-foot times, maybe better, but not counting on it.

I have a NEWLY BUILT 489-case center-section (with a crush sleeve eliminator kit installed) that has a cone-type limited-slip unit (this is a street/strip car), with the larger, (7290) u-joint yoke.

I am wondering if I might need to install a steel carrier-bearing back support (CAP) in place of the cast iron one that it comes with (OEM.)

I don't want to have to do this if it's overkill. The car weighs 3,600 pounds and should run mid-11's if it hooks (118 mph.)

I'd appreciate some advice on this from people who have experience with the 8.75" in a moderately powerful 3,600-pound car like mine. {That's 3,600 pounds with me in it, ready-to-race weight.)

Like I said, this is not something I want to do unless it's actually necessary. Do these 8.75" units break that bearing cap in the kind of useage I described? I will only race it occasionally.

Thanks for any information... it will be much appreciated.


Bill

Get in touch with Jim Bailey, his suggestions will $ave you time & $$$$$

[bill dedman]

Thatks for the good advice!!! Both of you.

Bill

[Everett Vassar]

I have a 8.75 in my Duster 3200lbs with me in it Braced housing 35 spline spool and Moser axles Everything else stock stuff.Its a 440 runs 7.0,s 1/8 @93 MPH So about 475HP ? Foot brake sometimes t/brake I have broke a couple of stock axles before I went to the Mosers and 1 R&P but thats it.
I think the housing brace is very important to keep everything in line.

[gmonde]

my car weighs 3665 we me in it,i have two center sections 4:86 & 4:57 with 35 spline axles the 4:57 is a yukon 489 case with the stock caps i have 80 or so passes on it and and no troubles,pulled it and swaped to the 4:86 witch has the mark willams caps,this 60's around 1.60 but we had 1.589's this weekend ,like mentiomed the most important thing is to get rid of the stock spanners,the threads are to loose and somtimes will give way from the side load,the billet ones have more threads and are by far a tighter fit,also check your bolt lenght you might want to put in longer allen head bolts to get all of the threads , gmonde

[bill dedman]

Well, it looks like speed costs money, but I'm afraid I'm already going about as fast as I can afford to,,,... LOL!

All that expensive stuff is wonderful to have, and surely works to provide a trouble-free drivetrain (which, of course, I'd LOVE to have), but I think this business with housing braces and billet spanners just might be overkill for my junk. I dunno; my car weighs 3,600 pounds with me in it and runs 93+ in the eighth-mile, but doesn't run anywhere CLOSE to 7-flat. More like 7.50's....

With bite like that, perhaps I won't break anything, after all.

I will take everything you guys have suggested under advisement and as funds become available (and, hopefully, they will), I'll add what I can, when I can.

Thanks a bunch for all the great information!!! I appreciate it a lot!

Bill

[Tom keedle]

Originally Posted by bill dedman

Well, it looks like speed costs money, but I'm afraid I'm already going about as fast as I can afford to,,,... LOL!

All that expensive stuff is wonderful to have, and surely works to provide a trouble-free drivetrain (which, of course, I'd LOVE to have), but I think this business with housing braces and billet spanners just might be overkill for my junk. I dunno; my car weighs 3,600 pounds with me in it and runs 93+ in the eighth-mile, but doesn't run anywhere CLOSE to 7-flat. More like 7.50's....

With bite like that, perhaps I won't break anything, after all.

I will take everything you guys have suggested under advisement and as funds become available (and, hopefully, they will), I'll add what I can, when I can.

Thanks a bunch for all the great information!!! I appreciate it a lot!

Bill

i've seen braces on ebay for less than 100, spanners for around 25....
the caps will be the most expensive cuz of some maching work....

try finding an "A" body housing.....$$$....
i'm gonna narrow one...

[Dwight Southerland]

Bill -

Race it till you break it. Then fix it. Analysis paralysis. Guys have abused those 8 3/4 MoPar rears for years and the percentage of breakage is low.

[Sean Haning]

Originally Posted by Dwight Southerland

Bill -

Race it till you break it. Then fix it. Analysis paralysis. Guys have abused those 8 3/4 MoPar rears for years and the percentage of breakage is low.

My 66 Belvedere with a 3500 converter, 440, slicks and 4.30 gears running low 7's never broke the 8 3/4. Who knows how old the center section was. I bought it used and was on stock axles for 3 years. So if its not your daily driver and you can't afford to beef up, just enjoy it until it needs it.