8 3/4 tough enough?

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evil66

evil66

evil66
Joined
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Hi Guys,

Looking to build a rear end for my 69 Barracuda and wondering if an 8 3/4 diff will be reliable enough if fitted with 30 spline axles and a tru trac centre / 3.9 gears.

I don't have an 8 3/4 housing to suit and would have to shorten a b or e body housing out here which are more common out here in Australia and would have to ship most of the parts over.

Car will have around 600 flywheek hp hopefully once I get the W5 heads ported and fit a bigger cam into my 408 stroker (currently w2 heads). Car has a CRT 727 fitted.

Car wont be drag only and will see a lot of street miles but it will cop a set of slicks occasionally and don't want to invest a lot of money into something that may break at the drags?

Any advice appreciated.

Thanks
 
I think I would go Dana 60.
 
If you are using a trans brake it would be hard on an 8 3/4 at that power level with more of a street strip friendly converter I would think you would be ok on the occasional trip to the track.
 
The weak points on the 8 3/4 are the poinion and the housing.

For the money adn at your power level the dana is nearly impossible to beat. I was die hard 8 3/4 untill I looked at the $$ signs and what each can do. I now have a Dana.

Brand new, dressed to the hilt you are looking at about 2,500$ more for an 8.75.
 
It all comes down to what kind of shock loads you are going to be putting on it. If you plan to run slicks and your chassis is working well, I would move to a 60.
 
If you have a REAL 600 hp at flywheel...get a dana 60....in the long run you will be money ahead....

I just ordered Dana 60 yesterday for our 71 Dart....twisted the housing....was going to replace housing with a Moser Fab 875 but went I removed the third member...had several teeth chipped on the ring gear....
 
I just went through this. By the time I figured having a housing narrowed, buying shortened axles and having a third member built it was within a few dollars of having a strange s 60 built to the specs I wanted with a Tru trac carrier. So I went with the S60. Should be here next week.

Got to figure if you invest in the 8 3/4 and it breaks you're basically going to be investing and doing the job twice.
 
Thanks for the replies guys.

Have been looking at the whole dana 60 vs 8 3/4" scenario and don't want to spend the money on a nice 8 3/4 only to break it and then have to build a dana 60.

Hoping to have 600hp at the flywheel when the w5 combo is complete, current combo only has around 460hp but is limited by a small cam and unported w2's but has run an 11.7 as is.
Won't be running a transbrake at this stage.

Does a dana 60 fit into an a body with the fuel tank etc in standard location and are the dana 60 out of some of the f truck fords a similar diff as some of them out here have dana 60s I believe.
 
evil66 said:
Does a dana 60 fit into an a body with the fuel tank etc in standard location and are the dana 60 out of some of the f truck fords a similar diff as some of them out here have dana 60s I believe.
Click to expand...

With the springs in the stock location the Dana fits without issue. If you move the rear back 1.5" as needed to fit 28+" tires you will find it doesn't. You'd have to cut the tank or relocate it or fuel cell etc.

I cut my tank to fit the Dana and the tail pipes.
 
roccodart440 said:
The weak points on the 8 3/4 are the poinion and the housing.
Click to expand...



The issue with the 8.75 are cap walk, the cap moves, the spanner is then shoved to the side, the gear runs off the heel and then strips the gear. That is always what happens to the 8.75

It is a issue that can be solved, i have them in SS cars that leave on trans brakes.

Never EVER EVER EVER have we broke a pinion.


All housings will bend depending where the spring or link locations are to the bearing flange.
All housings will see twist, that's something that everyone making large power has to address with there stuff, the 8.75, 9" and other banjo style are more susceptible to bending and twisting forces than carrier style housings

20140501_202952.jpg
 
Just relaying what Strange told me when I called to order my rear. As you know I was torn between the 8.75 and the dana. Cost was really the determining factor for me.
 
Has anyone tried these new 742 housings, with the improved caps? [ame="http://www.ebay.com/itm/Chrysler-Dodge-Mopar-8-75-8-3-4-742-Nodular-Iron-Dropout-Forged-Caps-Billet-Adj-/390512393796?pt=Motors_Car_Truck_Parts_Accessories&hash=item5aec5a3e44&vxp=mtr"]Chrysler Dodge Mopar 8 75 8 3 4 742 Nodular Iron Dropout Forged Caps Billet Adj | eBay[/ame]
 
I run a 8 3/4 rear end with a factory 3.91 489 case with a clutch type sure grip with strange s/s axels behind a 408 stroker running 10.70s no problem.
 
Yeah at 425hp im leaning to set up issues aren't right.

The ones we have pushing the spanner are in the 800 area and leaving in the 6000 rpm area off a TB, round after round SS classes
If you're not doing that im not worried about the use of a 8.75.

However for a drag only car making more than 650 at real world weights the simple fix is the AL case, for the car needing the factory case for rules or street use the fix is a little more involved to stop the problem.
 
Mine were set up by Chrysler.All used chunks and in B Bodies.Maybe a new one would last longer who knows.Mine were all street cars but I drive them hard sometimes.
 
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