63SplitWindow
Well-Known Member
If I change my 742 center section to a 489 center section, will I need a different length drive shaft?
8.75 rear change
- Thread starter 63SplitWindow
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63SplitWindow
Well-Known Member
Perfect.....thanks J
And there are combo joints available so you might not need to change anything other then the rear u joint.
No, but I fail to understand the swap. Going from a non crush sleeve differential to one with a crush sleeve. If I had the choice, I'd stay with the one without the crush sleeve.
I've been contemplating a swap to 489 from 741 due to limited gear availability
No crush sleeves in 741 Rob?
No crush sleeves in 741 Rob?
Yes sir, it uses a crush sleeve. It's splittin hairs really, Steve, but if I had a 742 already, I wouldn't swap. Under a LOT of power, the crush sleeve can actually crush further and cause the pinion depth to change. If it changes enough, it could be catastrophic. It takes a lot of power and a lot of bite to do it, though.
mopowers
Well-Known Member
Only the 489 uses a crush sleeve.
63SplitWindow
Well-Known Member
Yes....simply changing for the gear ratio. Looking to go from 4.56 to 4.10
Are you sure? I was almost 100% sure the 741 did also. Course yall all know how my memory is.
Yeah, you're right. Don't know what I was remembering. Sorry for the wrong info.
mopowers
Well-Known Member
All good. I'd use any of them. I've never understood why so many people piss on the 741s.
I agree 100%. Man, you have no idea how many rear axles I've done in my lifetime. It seems everywhere I've worked I've been the only one that knew how to do them correctly, so I got them all. They all just kinda run together. LOL
junkyardhero
Well-Known Member
it's the folklore, that's all. fools thinking that because the 489 pinion is whatever .000 percent bigger means it sooo much stronger. they put 741's in trucks ffs.
Yes, plus ALL of the early "oddball" 8 3/4 rears like from the early 60s on back were 741s as well, even though they sported different casting numbers. They were all the 1 3/8 pinion stem. Also, the Ford 8.8 pinion shaft "I believe" is smaller at 1.320". I could be wrong about that, but for some reason, that sticks out in my feeble mind.
junkyardhero
Well-Known Member
Dr.Diff sells a kit to replace the crush sleeve with a regular shim set up. Put my first one in 10-15 years ago and never looked back...
1.313 I THINK, but there's THREE pinion bearings. 2 front and 1 rear. Actually, I think the industry refers to the small one at the rear of the car inside the case as the front. It also depends on "which" 9" assembly it is, as there were several sizes used through the years. I don't even remember which one mine is and I set it up not too terribly long ago. I just don't care cause it'll never break.
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