8 3/4 not what it seems

[BeepBeepRR]

OP's name sounds like a robust waitresses name.

Kiss his grits..

 

[skicker]

I have a 741 in my 70 Satellite also...

3.23 with a sure grip...383-727...The car is such a slug I'll never be able to hurt it...

 

[R413]

Just LOOK at it a Minute before typing. Look at how much ring gear is showing out past the carrier flange. Look at how many ring gear bolt there are/aren’t and the odd casting shape between those bolts.

Yes I’d like to know the housing number also.

 

[33 IMP]

I am running a 741 in my Dart. Mild 440 with an automatic. I have a couple of units with different ratios.
Most of the time they are a cheaper choice.

Everyone says that they are weak. I have never broken a pinion shaft. But I have broken teeth on several through the years no matter what housing number it had on it.

Plus a 741 will have a clutch type Sure Grip in it. So don't pass on looking at one.
They can have almost any gear ratio in it. 3.23, 3.55 and 3.91 can be found.

AGREE! I will take all the 741 case 8 3/4s i can get cheap. If you look at Dr Diffs site, he shows the fracture point of the three pinion sizes, and the weak point on all three is exactly the same! The only drawback of the 741 is a very limited selection of new gear ratios.

 

[khryslerkid]

The ring gears between my 741 and 742 measure the same. Bolt patteren is 6 -5/8". The most outer diameter of the ring is just under 8 -3/4"

 

[Jerry Hall]

I guess you do learn something new everyday!

If anyone tells me they know everything about Mopars, I run like hell. You do learn everyday. Nothing is carved in stone.

 

[threewood]

Tell me about it! I tried to give a '68 741 away at a Mopar meet....no takers.

This saddens me. I have a 741 in both my cars and have had no issues. Never seen one fail either. I'd take an extra for the cost of shipping

 

[BigFlo]

He is correct in what he is saying.

Early Mopars used a 741 (possibly few other casting numbers depending on year) that used an 8 3/4 rear axle center section that used a ring gear with an 8 1/4 inch bolt circle.
Any center section that had a sure grip used a 8 3/4 ring gear. So no sure grip for that gear.
Best bet will be to have Cass build you one or find a used unit ready to bolt in.

Also if you have tapered axles you will have another problem. The axles will be too long and will have to be machined on the spline end to get them to the right length.
The center block in the carrier is a different length from the open carrier to a Sure Grip.

Thanks - I'll need to check those.

 

[BigFlo]

@BigFlo tell us what the last three numbers are.

View attachment 1020998

741

 

[BigFlo]

This saddens me. I have a 741 in both my cars and have had no issues. Never seen one fail either. I'd take an extra for the cost of shipping

I'd take one with an 8 3/4 ring gear!

 

[YY1]

Can the OP "just" replace the part that the ring gear mounts to?

The carrier?

 

[BigFlo]

OP's name sounds like a robust waitresses name.

BigFlo was my Grandmothers nickname - she was about 5'4" and maybe 110 lbs, lol. This is her car I am restoring.

 

[Nate S]

I had to go download a ‘65 Plymouth service manual and parts manual to see for myself. Very interesting. Looks like they put a 8.25 pig into the same housing as a 8.75 for just this application. Shows different numbers for the carrier so I’d be super interested to know that casting number. Maybe they machined the ‘741 casting differently? Came in 2.93 and 3.31 ratios only.

 

[Nate S]

 

[beanhead]

BigFlo was my Grandmothers nickname - she was about 5'4" and maybe 110 lbs, lol. This is her car I am restoring.

That's awesome.

 

[matthon]

I have a 62 Dart with a 318 poly, auto, 8 3/4 housing, 741 case, no Sure-Grip.

Would the V8 mean it has an 8 3/4 gear in it?

I have a spare 741 that I was going to put a Sure-Grip in and run, but I might just get everything from the Dr, including axles and all as it has tapered axles.

 

[Nate S]

I have a 62 Dart with a 318 poly, auto, 8 3/4 housing, 741 case, no Sure-Grip.

Would the V8 mean it has an 8 3/4 gear in it?

I have a spare 741 that I was going to put a Sure-Grip in and run, but I might just get everything from the Dr, including axles and all as it has tapered axles.

Before '65 I see no trace of the 8-1/4 version. There's nothing wrong with the tapered axles either. Just need a relatively inexpensive puller or swap the drums so they aren't swedged on any more. I'd just find a sure grip pumpkin in the ratio you want and drop it in. Dr Diff will do right by you of course but you'll pay for that. My 3.23 sure grip pumpkin cost me $325 on facebook, seems unlikely you'll get out of it that cheap if you get new stuff.

 

[khryslerkid]

I have a spare 741 that I was going to put a Sure-Grip in and run, but I might just get everything from the Dr, including axles and all as it has tapered axles.

That's what I did. The '62 has the narrowest housing of all the "B" bodies and I didn't want to swap in a newer/wider one. It's all in my build thread. Cass is the best when it comes to these rears.

 

[matthon]

Before '65 I see no trace of the 8-1/4 version. There's nothing wrong with the tapered axles either.

Good news for me, must be a 65 only thing.
Agree on the tapered axles, my 64 has the original Sure-Grip tapered axles and I did the 65 drum swap.

That's what I did. The '62 has the narrowest housing of all the "B" bodies and I didn't want to swap in a newer/wider one. It's all in my build thread. Cass is the best when it comes to these rears.

Saw it, read it, great info, agree 100%.
I already contacted Cass weeks ago, just need a few more pennies and some warmer weather.