Need help on 8.75 rear end.

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68DartProject

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Okay this is what I have.
An "A body" 8 3/4" 741 open rear end with 2.94 gear ratio.
I know that the 742 and 489 casing will bolt in, I got that.

I know some say just buy a 742 or 489 easier said; than done. They weigh a ton so the cost of shipping is outrageous.

My question is, lol bare with me.
Can you buy, say all the stuff needed as in ring gear, seals, bearings, pinion and ect. and build the 741 casing as a 742?

Will all the deferential gears work along with the 742 new bought components. being you can just drop all the different types units in? I'm thinking yes,"chime in on this one".

I'm looking to go with a 3.91 ratio with full spool. All I am finding is 3.73's. All new product that is.

And who has the most selection of building components available for reasonable prices?

Thanks,
Michael
 
Short answer is no. The difference with a 742 case is the pinion size, brg size, and no crush sleeve. The 741 and 489 case use a crush sleeve. Your best bet would be to get a complete case with the gears you want, or get a rebuild kit for your 741 and gears of your choice.
 
What's the problem with a 741 case? It's plenty strong.
 
twofosho said:
Pinion size as explained above.
Click to expand...

It's BS, it's not the weak point of a 8.75 rear. Another one of those things that someone wrote, weakness, that isn't a real world issue.

741's don't use a crush sleeve, at least none that I've ever had or set up.
 
My bad on the 741's using a crush sleeve.
 
build the 741, any decent parts store can get u all the bearings and seals........doctor diff or randy's ring and pinion has gears 4 ya...........kim.......
 
I like my 489 with its solid sleeve and no crush sleeve!
 
Just got off the phone with Dr Diff and Randy's Ring & Pinion and Drive Train Specialist, just like i mentioned I'm wanting to go to the 3.91 gear ratio. They do not make new stock 3.91, it stops at 3.73 unless you can get NOS from a Chrysler dealership parts counter or find a van or old truck that may have the unit still in it from where Chrysler put them in OEM . Please go back to my post and you will see that I mentioned that all I am finding for the 741 is 3.73
They are not a weak link and I never had a problem with them. And never mention that they were a weak link. There weak link is that they don't offer any lower gears than 3.73 new. That is why I asked the question. If I had all the 742 minus a case would it go into the 741 case. Simple yes / no and why. or what would i have to do as far as machining it.
 
3.91-4.30 gears pop up for 741 cases, or the cases themself. I may have some 3.91 gears out of a 741.

Gear selection for new parts is an issue for the 741.
 
68DartProject said:
Just got off the phone with Dr Diff and Randy's Ring & Pinion and Drive Train Specialist, just like i mentioned I'm wanting to go to the 3.91 gear ratio. They do not make new stock 3.91, it stops at 3.73 unless you can get NOS from a Chrysler dealership parts counter or find a van or old truck that may have the unit still in it from where Chrysler put them in OEM . Please go back to my post and you will see that I mentioned that all I am finding for the 741 is 3.73
They are not a weak link and I never had a problem with them. And never mention that they were a weak link. There weak link is that they don't offer any lower gears than 3.73 new. That is why I asked the question. If I had all the 742 minus a case would it go into the 741 case. Simple yes / no and why. or what would i have to do as far as machining it.
Click to expand...


rrdd01.jpg

489 741 742

742 stuff will not fit in a 741 case. I picked up a 742 case at mopars in the park last year for 35 bucks. clutch type sure grip for 200 (68 single spline side gear unit with 742 3.23 gear set) I would just go to swap meets and keep your eyes pealed.
 
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