741 - crush sleeve and shims?

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When it was built 7-8 years ago, was it as hard to turn as it is now or do you not remember? The 741 uses a solid thick sleeve over the pinion and then a few thin shims to set preload. Does your pinion have the heavy thick sleeve? If all you need is the smaller preload shims and the larger pinion depth shims behind the large race, i can send you all you need for the cost of postage. I have the set up bearings for all cases but if you have a spare pinion bearing, you can hone the I.D. till it slides on and off. Thus making your own set up bearing.
 
Thanks for the offer Roy. I have not even pulled the main part (crown wheel bit) off yet. So I have not seen what spacers or shims are in it. We only just got to check out the turning torque of the carrier fully assembled. With the small click style torque wrench, we came up with approx value of between 48-58 in-pounds, turning, (not starting) torque. So this is considerably higher than what John-9 was talking about, however I am not sure if that value he said (20-25 in-lbs) was on the bench before tightening the main carrier and installing the seal , or when all assembled ready to install.

After it was rebuilt 8 years ago I did not even turn it. It was all heavily wrapped in shrink plastic and I just put it on the shelf and forgot about it! It has a little oil in it so it's not dry inside.

Tomorrow I will pull out the centre part and crown wheel and have a look for those shims and spacer. And also measure the turning torque of just the pinion. It may just be a case of adding one shim to get the correct preload value.

One other question, I see a lot of these kits have a set of new crown wheel bolts. Is this just for the racers and heavy footed drivers' peace of mind? How important is it to put in new crown wheel bolts?

Thanks
 
70Hardtop said:
I appreciate the advice John and have a question about your post after this... Yes true, well even though this guy is white South African, he still has the Aussie trademark attitude of that as I described. I don't think there would be many places in Aust that would run in and get a torque wrench. look up the correct value for that rear member and check it while you wait, it just wouldn't happen. That's why having 60s-70s American cars can be frustrating - things like this always pop up where you wish for more people who know them. Can you believe I went to a differential shop in my city (biggest city on the west coast of Australia), they had been in the same location for at least 35 years, and ALL they did was differentials. This was about 7 years ago. I took my Challenger there with a noise in the driveline. The old guy in there had never heard of the Chrysler 8 3/4 rear end !! I couldn't believe what I was hearing. So of course I didn't get any work done there.

Now, you said that, "you have to do a proper break in of the differential as new bearings build a lot of heat initially and you can ruin your new bearings and gear in minutes"

Do you mean a break-in on the bench or in the vehicle? I can't see how it could be done on the bench, even if I had a rattle gun (pneumatic socket drive) which I don't and no load on it anyway. Also, as Jadaharabi mentioned about checking the pinion turning torque without the seal, is that 20-25 in-lb you mentioned the value I should see before tightening the main chunk and before the seal or is that when the whole thing is ready to be installed in the car?

Now I can't wait to get the socket to see what the turning torque is. However, don't forget, as I mentioned previously, I still have to put in the clutch type SG I bought new from Dr Diff. This 741 was rebuilt as an open centre 7-8 years ago; now I have pulled it off the shelf and putting in the SG. So the tightness could possibly change after that, even if I didn't touch the pinion, although I can't see how (with my limited knowledge).
Click to expand...

you break in the diff once it is installed in the car --- pinion preload is checked with the--- pinion gear only --- installed into the case --- 20-25 is the pinion bearing preload you need without the seal -- your seal may add 2-3 in/lbs after it is installed and is nothing to worry about .
turning the complete rear diff -- ring and pinion gear installed -- you will get higher readings like 50-70 in/lbs.
 
70Hardtop said:
Thanks for the offer Roy. I have not even pulled the main part (crown wheel bit) off yet. So I have not seen what spacers or shims are in it. We only just got to check out the turning torque of the carrier fully assembled. With the small click style torque wrench, we came up with approx value of between 48-58 in-pounds, turning, (not starting) torque. So this is considerably higher than what John-9 was talking about, however I am not sure if that value he said (20-25 in-lbs) was on the bench before tightening the main carrier and installing the seal , or when all assembled ready to install.

After it was rebuilt 8 years ago I did not even turn it. It was all heavily wrapped in shrink plastic and I just put it on the shelf and forgot about it! It has a little oil in it so it's not dry inside.

Tomorrow I will pull out the centre part and crown wheel and have a look for those shims and spacer. And also measure the turning torque of just the pinion. It may just be a case of adding one shim to get the correct preload value.

One other question, I see a lot of these kits have a set of new crown wheel bolts. Is this just for the racers and heavy footed drivers' peace of mind? How important is it to put in new crown wheel bolts?

Thanks
Click to expand...
By crown bolts, I assume your talking about ring gear bolts? When they came in the bearing kit I would use them. Other wise I have reused used ring gear bolts many many times without an issue. There are only two different types to watch for , non shouldered and shouldered bolts. just use the right ones.
 
If you go back and read this whole thread you will find 90% of the information that you need to set up your pumpkin.

The only thing that has not really been discussed is the backlash of the ring gear to the pinion gear. After you do a lot of these you can feel almost exactly the backlash that is needed then you put the dial indicator on it and check for the final setting.

Then torque down your carrier bolts and you should be good to go.


If you are getting less than 70 inch pounds of pull over on that pinion with it fully assembled I don't think you have very much of a problem.
 
"By crown bolts, I assume your talking about ring gear bolts? When they came in the bearing kit I would use them. Other wise I have reused used ring gear bolts many many times without an issue. There are only two different types to watch for , non shouldered and shouldered bolts. just use the right ones."

Yes, Ring gear, (Crown wheel must be an English/Aust name for it), I will reuse mine, can't see a problem for driving the way I do (mild). thanks
 
Man, you sure are makin all this way more complicated than it is. All you have to do is call Cass, talk to him, order what he tells you and you're done. Simple as that.
 
Yes I was thinking about the backlash adjustment - I have a dial indicator and the factory service manual. I have less than 70 inch pounds full assembled (as I said, we got about 60 or less) so looks like this is ok then, should be even less when full of oil. BTW This forum is great, really appreciate the help and the info. I was a bit worried that the 741 might not be strong enough behind a 400HP+ 340 but reading through the posts over the years from people worried about this and all the information about the 741, I have no concerns at all about using it. Eg, some things I read from this forum:

The 741 which is supposedly the "weakest" of the three cases, has a larger pinion diameter than a 9" Ford!
The 741 even though has the smallest diameter pinion, it is straight, whereas the 742 and 489 pinions had steps or risers to give greater diameter and this is potentially a stress area, and one poster said that is the place where he has seen them fail
The 741 in the early and mid 60s was used behind Max Wedges and Hemis, as that's all they had, also used in the Dart 383 GTS and more...
And in heaps of racing applications with no problems by people

So I have much increased respect for this carrier now
 
I think ur good, cause the side bearings have pre load also, did u oil them? Also check the back lash b4 u take it apart. Then check the pinion rotating torque. Kim
 
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