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8 3/4 or Dana

mmissile said:
If you want bullet-proof....your above combo seems to be working for lots of the faster guys. mopar engine, turbo400, 9-inch Ford.
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I'm obviously no purist but I am a Mopar guy through and through. I think I can live with myself with a GM trans and Ford rear as long as it's Chrysler powered.
 
mmissile said:
If you want bullet-proof....your above combo seems to be working for lots of the faster guys. mopar engine, turbo400, 9-inch Ford.
Click to expand...
Never !!! No Chevy or Ford Parts, mopar Engine Mopar 727 Mopar 8 3/4
 
YellowDodge67 said:
It is turbo'd. That's a pretty good lifespan for a fairly basic rear combo you have
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We also run the junkyard gears (3.54) that came with the Dana out of an F250. We narrowed it, added axles and a spool. It's in my sons SB turbo car. 9.55@142, 3775lbs, w/trans brake. So far , so good.
Doug
 
dvw said:
We also run the junkyard gears (3.54) that came with the Dana out of an F250. We narrowed it, added axles and a spool. It's in my sons SB turbo car. 9.55@142, 3775lbs, w/trans brake. So far , so good.
Doug
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Thats reassuring to hear. Any idea what boost or power levels he's running?
 
dvw said:
155 mph in the 1/4? at what weight and power plant? Unless it's turboed you will need at the least a 4.10. The 8 3/4 should not be used in this application. I've run Junkyard Dana's narrowed with a spool, 35 spline axles, and street gears. In my car the first ring and pinion lasted 450 passes. I can tell you at 3350 lbs it takes every bit of 900+HP to go just under 150 mph.
Doug
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How about at 2500lbs.?
 
YellowDodge67 said:
Thats reassuring to hear. Any idea what boost or power levels he's running?
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That pass was at 21psi. Best guess about 850hp. 360, stock block and crank, 75mm turbo, blow thru 750, no intercooler, Eddy heads .550 hyd cam, on E85.
Doug
 
YellowDodge67 said:
So I may have blown up my stock rear in my car last night. I'm going to take it apart to see exactly what broke but I'm thinking of upgrading anyway. (741 open diff with 2.94 gears) I was thinking about using a 489 case in an A-body width 8 3/4 housing as a "poor mans" narrowed rear to make more tire clearance. I didn't think they were much narrower but a local guy with a 67 Coronet said that's what he's running and fits a 315/60-15 with a mini tub and relocated springs.

My other option is possibly a Dana for strength. The problem is trying to find one that is already set up for a b-body , or getting one out of a truck then cutting it down and building it anyway or buying an S60 from Strange which are all expensive options. I do like the removable third member of the 8 3/4 and I don't think you can get a smaller gear than a 3.54 for a Dana. I want to stay between 2.94 and 3.23 ideally.

Or... for now I can just fix whatever is broken in my rear and maybe put a 489 case and posi unit in lol.

Basically is an 8 3/4 worth putting money into to hold up to high horsepower and torque levels (700-1000rwhp) or is a Dana required?
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although the 8-3/4 is a good rear axle for street cars you are limited to a --- very small gear ratio selection and case strength beyond 550 hp is marginal , it will break ,,, when is the question , and at the power level you are talking sooner than later .

the Dana 60 strong differential but gear changes are a pain and again limited in choice.

despite what the purists say go with a Ford 9 inch rear axle -- gear ratios 2.50 - 7.50 in increments of 10 --- drop out center section so gear changes are easier or have different center sections to swap in , parts are readily available everywhere ,

it will not be cheap but you want to do this once especially at the power level you mentioned.

helped a fellow with a 1965 440 dart measure up a Ford 9 inch for his car after breaking his 8-3/4 --
this is what i had him order from Moser Engineering
---- heavy 9 inch housing exact width/mounts for his car , with 8-3/4 housing ends so he could use his brakes ,, 35 spline axles ,, Moser center section with spool and i believe 4.11 gear --- 1350 yoke ---- the 35 spline axles were used for strength and if he ever wants to put the car on the street 35 spline Detroit lockers are available for street use .
 
john-9 said:
although the 8-3/4 is a good rear axle for street cars you are limited to a --- very small gear ratio selection and case strength beyond 550 hp is marginal , it will break ,,, when is the question , and at the power level you are talking sooner than later .

the Dana 60 strong differential but gear changes are a pain and again limited in choice.

despite what the purists say go with a Ford 9 inch rear axle -- gear ratios 2.50 - 7.50 in increments of 10 --- drop out center section so gear changes are easier or have different center sections to swap in , parts are readily available everywhere ,

it will not be cheap but you want to do this once especially at the power level you mentioned.

helped a fellow with a 1965 440 dart measure up a Ford 9 inch for his car after breaking his 8-3/4 --
this is what i had him order from Moser Engineering
---- heavy 9 inch housing exact width/mounts for his car , with 8-3/4 housing ends so he could use his brakes ,, 35 spline axles ,, Moser center section with spool and i believe 4.11 gear --- 1350 yoke ---- the 35 spline axles were used for strength and if he ever wants to put the car on the street 35 spline Detroit lockers are available for street use .
Click to expand...

MO875_MusclePak.jpg

Would this be any stronger or is the case still the weak link? It seems when it comes to the Moser stuff they are all around the same price?
 
A stock 60 is already really strong. All the others have to be built up to be strong including the ever so popular 9". As for gear changes....all gears have to be set up at least one time and if you plan on changing gears, just keep the shims from the setup from the 60 together and the next time you want to use them, all you have to do is plug it in. It's just as fast as doing an 8 3/4. Draw back on the Dana is that you can borrow someone's 9" chunk at the track if you break or fry one but usually when you break a rear end, there's going to be other damage further up the drive line. As for beefing up the 8 3/4....how strong does the housing need to be vs how strong can you make the 3rd member? You can make the housing stiff as can be but it's not going to stop gear deflection and broken teeth. You will actually help more by making the car light weight.
 
Cranky said:
A stock 60 is already really strong. All the others have to be built up to be strong including the ever so popular 9". As for gear changes....all gears have to be set up at least one time and if you plan on changing gears, just keep the shims from the setup from the 60 together and the next time you want to use them, all you have to do is plug it in. It's just as fast as doing an 8 3/4. Draw back on the Dana is that you can borrow someone's 9" chunk at the track if you break or fry one but usually when you break a rear end, there's going to be other damage further up the drive line. As for beefing up the 8 3/4....how strong does the housing need to be vs how strong can you make the 3rd member? You can make the housing stiff as can be but it's not going to stop gear deflection and broken teeth. You will actually help more by making the car light weight.
Click to expand...

True, the fabricated housing may be strong but if its the same old third member its the same old problems. I can definitely see the Dana having less deflection and being stronger with housing and case being one unit. My only snag on the Dana compared to the 9in is limited (or non-existant) gear options under 3.54.
 
YellowDodge67 said:
True, the fabricated housing may be strong but if its the same old third member its the same old problems. I can definitely see the Dana having less deflection and being stronger with housing and case being one unit. My only snag on the Dana compared to the 9in is limited (or non-existant) gear options under 3.54.
Click to expand...
Didn't you mention going with an OD trans? Heck, my 95 Yard Cart Dakota has a 3.55 (wish it had a 4.30!) and even my 2000 Durango has a 3.90 in it. OD's are great and with a stick, you can pick and choose your gear box. My nephew came over with his new Mudstain 350 with a 6 speed stick and let me drive it and said to go for it. After a few minutes to get used to the feel, I went for it but still short shifted it and wasn't all the way on the floor. Just not that comfortable abusing other peoples cars. Not to brag but I still have it.....power shifting that is. Anyways, top gear was way out there and the rpm was very low @ 60 to the point the car didn't have much pep after flooring it. IIRC, he said it had a 3.73 in it. Wouldn't mind having that transmission behind a potent 400 Mopar.
 
Cranky said:
Didn't you mention going with an OD trans? Heck, my 95 Yard Cart Dakota has a 3.55 (wish it had a 4.30!) and even my 2000 Durango has a 3.90 in it. OD's are great and with a stick, you can pick and choose your gear box. My nephew came over with his new Mudstain 350 with a 6 speed stick and let me drive it and said to go for it. After a few minutes to get used to the feel, I went for it but still short shifted it and wasn't all the way on the floor. Just not that comfortable abusing other peoples cars. Not to brag but I still have it.....power shifting that is. Anyways, top gear was way out there and the rpm was very low @ 60 to the point the car didn't have much pep after flooring it. IIRC, he said it had a 3.73 in it. Wouldn't mind having that transmission behind a potent 400 Mopar.
Click to expand...

The overdrive trans is a maybe, more than likely its gonna be the mildly built 727 thats in it then a th400 whenever the 727 has had enough. I'm trying to gear it to about 150-155mph at the top of 3 third (not going to use lock up or overdrive at the track even with a 4l80e) and with a 3.54 its pushing the rpm's a little more than I want to go even with a 30in tire. In the mean time until the car makes that level of power the 3.54's would be ok, I just don't want to have to completely redo the rear again.
 
Have you thought about using a GV unit? They are tough and there's many racers that are using then in their street legal race cars....some of them using the OD on the track too?
 
While a GV has s a good idea, there expense keeps me away. Not a fan of the added bulk ether.
 
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