741 to 742 or 489 8 3/4 rear axle conversion possible?

[lacrebob]

I have a 741 rear axle and would like to keep the original rear axle, but also have it be stronger than stock. I understand that the pinion is the main or only difference between the three rear axles is the pinion diameter.

Can a 741 case be machined to fit a 742 or 489 pinion?

I've searched the web, but I can't find anyone who's tried it, so I'm not sure it's possible.

 

[Cranky]

Are you running 9 second 1/4 mile ET's? If not, don't worry about it. How many 741 rears have you seen broken?? None? Also, it's not about machining anything to fit but more about bearing sizes if you want to swap a 42 pinion into a 41 case....

 

[67 B-body]

Are you running 9 second 1/4 mile ET's? If not, don't worry about it. How many 741 rears have you seen broken?? None? Also, it's not about machining anything to fit but more about bearing sizes if you want to swap a 42 pinion into a 41 case....

You said it Cranky....
The 741 is just fine

 

[lacrebob]

I don't expect to drag race. A 741 is fine with 500-600 horspower and a manual transmission?

 

[Schober Motorsports]

Only difference is the pinion size as you said, the 741 actually is bigger than the Ford 9 inch lol why is everyone so damn worried about these 741 cases!!!

sorry can't help ya with your question

 

[YY1]

I'll take any of those junky 741 case chunks anyone wants to send me.

 

[Cranky]

I don't expect to drag race. A 741 is fine with 500-600 horspower and a manual transmission?

Just about any rear end is suspect to breakage if you hook up 600 hp but on the street, hooking up even with the best tires possible is a feat in itself. My question is why are you worried about having the correct number case in the car when you are obviously not going to be correct with the rest of the car? Are you planning on making 600 hp with a stock appearing car? And you for sure ain't going to hook up 600 hp on stock looking leaf springs if that's what you are trying to do. In the early 80's, a buddy and I were running a 69 Road Runner in Super Street running a 4 speed. The car ran low 10.70's and we were starting to break 8 3/4's when the car was hitting low 11's and it didn't matter what case the car had in it. Once a Dana went in, all of that stopped. What broke on the 8 3/4's you asked? Ring gear teeth! We never broke a pinion shaft but we shaved plenty of teeth off.....and the weak point of a pinion is where the splines meet the first shoulder where the bearing fit is. It's not much different but it's still the smallest area and I've never seen one broke there. Heard of a couple but never seen it myself.

 

[Cranky]

I'll take any of those junky 741 case chunks anyone wants to send me.

I've been doing that for years lol. Sell the expensive ones and keep the cheapies for myself

 

[lacrebob]

Thanks. I think I have it figured out. I can swap the entire 742 or 489 center aka third members and that will work fine, but can't swap parts pinion and gears from 742 or 489 into a 741.

 

[67 B-body]

Thanks. I think I have it figured out. I can swap the entire 742 or 489 center aka third members and that will work fine, but can't swap parts pinion and gears from 742 or 489 into a 741.

You got it!

 

[racedodge]

i ran a 550hp 440 on 10.5 slicks with a 741 case 3.91 suregrip (not even rebuilt) from a 70 dodge truck for 3 seasons and it never broke.. hit some good 12 second times though!