8 3/4 Questions

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phish1270

phish1270

phish1270
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Iron Station, NC
I have found an A-body 8 3/4 with 3.55 gears, everything drum to drum for $250. It seems almost too good of a price considering what I have been reading on FABO. I am going to go check it out this weekend. I have asked what casting # is on it & if it is a sure grip; awaiting a reply. Is it inappropriate to take the housing apart to look inside before I buy it? What tools will I need without taking my whole box? Does it damage anything to open it up? Things are tight right now, as they are for most of us, & I am doing some convincing of the wife that this is a good deal; I can't buy a bad rear end. Is it worth it if it is a 741 &/or not a sure grip? My '65 Barracuda has the stock 7 1/4 right now or I can get a stock 8 1/4 out of a '7? Dart for $200.
 
First off, make sure it is an A-Body 8.75. The distance from center of perch to center of perch should be 43" and the bolt pattern will be 5x4". It will also have the 10x1.75" drums. The 741 case was all that was offered in the A-Body 8.75 rears and if it is a SG it will most likely be the cone style type. You will not hurt anything by taking it apart. You need a 9/16" socket, 6" extension and rachet to take out the axles and center section. Also take a hard rubber mallet with you to knock the drums loose and pop the axles out of the housing. The can be tight. Pull the axles out first and then remove the center.

The early B-Body rears will fit an A-Body and they measure 44" center to center and have a 5x4.5" bolt pattern. They also have 10x2" drums.

What are you running in the Barracuda? The 8.25 rear will most likey have the 5x4.5" bolt pattern and the bigger drums. IF you are running a stock /6, 273 or mild sb the 8.25 will work just fine and $200.00 is a good price.

Joe
 
Gear sets are a little more difficult to come by for the 741, the 742 and 489 rears have a much better ratio selection at shops like Yukon. But for the price hell ya buy it, everything inside is rebuildable considering that prices of A body 8 3/4's are going for 3 times that price or more. To pull the pumpkin you first have to pull both drive axles out then the pumpkin comes out of the rear housing.

Terry
 
Sounds like a real good price even if it is a 741 case but even a 741 case is a very good rearend and way under rated over the yrs. Like the others said just make sure it is in fact an A-body rearend.

Here's a link to a page on Moparts tech archive that you can read up on to educate yourself about the 8-3/4

http://www.moparts.org/Tech/Archive/axle.html
 
Thanks for all the info guys! The seller seems to know what he has, he told me that all a-body 8 3/4s have small bolt pattern. I don't mind the small bolt pattern. That is what I have now & I have the rally rims on it which I wanted. I am also looking at the scarebird disc brake conversion for the front so I could keep small bolt pattern all around. I am currently running what appears to be a stock '67-74 318 (not original) but plan on building a 273 or 360 to drop in. No more than 300-350 hp so anything other than the current 7 1/4 should be fine.
The guy with the 8 1/4 says it is also small bolt pattern. He also has b-body 8 3/4s for $200 but they would be the big bolt pattern & I would be looking for rims.
I am waiting to hear back about the casting # & sure grip or not on the a-body 8 3/4 so we will see how it pans out. All I need is a 9/16 socket, extension & ratchet to remove the axles & center unit? Is it obvious, I have never done it? Is it time consuming? Is the price too low, maybe something is wrong with it?

Thanks again guys, let me know if anyone ever needs any help.
 
I think you're gonna find that if it does indeed have a 3:55 gear in it, it will be in a 489 case, which would indicate that it is a 69 or later rearend. I would also be surprised if it did not have a suregrip with a 3:55, but of course that could have been removed. On the matter of the 8 1/4" rear, I believe that all 8 1/4" rearends have the large bolt pattern, as they were not introduced until 1973 when the 8 3/4" was removed from service in the A body lineup. As a matter of reference, if it does indeed have a 3:55 in any other than a 489 case, they will be aftermarket gears, as the 741 would not have come with that ratio. If I'm not mistaken, when the 489 was introduced in 69, the 741 and 742 cases were also eliminated from service. I know it replaced the 742 case, but I'm not sure about the 741. For your reference, there is an A body 8 3/4" in a junkyard by my house with a 489 case 3:55 suregrip that was removed from a 71 340 Duster, and I have offered $500.00 for it and was met with a no answer. I am with the others in that if it is $250.00, and has all of the brake components and a center section with 3:55's even without a suregrip it is well worth the money. I would pay the $$$ and take it home without opening it up and check it when you get it home. Everything inside is rebuildable, and unless the gears are just rusted or broken, opening it up on site will not yield you much info. The housing and brakes are worth the 250 alone!!! Good luck getting it and bringing it home!!! Geof
 
I disagree with the point that 741 cases did not come with 3:55's from the factory. I recently sold a 741 case with the cone style suregrip and it had factory 3:55 gears. They were definitely not aftermarket. The 741 was used until 72 and was retired. The 742 was retired in late 69 and the 489 replaced it. The 741 was used from 64-72.

Joe
 
I too have seen 3.55s in 741 cases. It would be a 741 case depending on the year. 742s I have found in 1966 cars. If it is older than '69 and has a posi, it would be the good Dana Power Lok unless someone changed it at some time. It happens. You had better buy that damned thing before somebody else does.
Pat
 
Sold before I got down there. Never got the casting # but it was an open unit. I shall continue my search. May have to call the other guy with b-body 8 3/4s for $200. Thanks for the help guys!
 
72Swinger360 said:
I disagree with the point that 741 cases did not come with 3:55's from the factory. I recently sold a 741 case with the cone style suregrip and it had factory 3:55 gears. They were definitely not aftermarket. The 741 was used until 72 and was retired. The 742 was retired in late 69 and the 489 replaced it. The 741 was used from 64-72.

Joe
Click to expand...

Joe, I'm taking your word on the 741 issue here. I am not positive on the post 70 stuff, as all my cars are pre 68, but I know up until 69 the 741 gear ratio was limited to the 3:23 and optional 3:91 in performance minded applications. Of course, we're talking Mopar here, so you are liable to find just about anything when you open it up. I bought a 68 Road Runner 4 speed parts car from the junkyard I mentioned, and when I tore into it, it had all HD underpinnings, an 18 spline trans, and an open 741 3:23 center. Go Figure!!! Thanks for settin' me straight, I"ll watch my facts more closely!! Geof
 
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