741 - crush sleeve and shims?

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70Hardtop

70Hardtop

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Hi all,

I need to get the pinion preload reset on my 741 (it is too tight from a previous rebuild many years ago) and want to buy a set of shims to give to the diff shop. (BTW , I'm in Australia so not much info around on these 8.75's, and differential shops usually are not familiar with old Chrysler stuff).

I am sure that only the 489 used a crush tube /crush sleeve with shims whereas the 741 used only shims. Is this correct? Because I am getting confused with places like Ratech and Dr Diff who are selling install kits for 741 and both have a crush sleeve in the kit (eg see this page: http://ratechmfg.com/chryslerstandard.htm)/ Ratech has listed for the 741 and 742 "CRUSH SLEEVE (shim pack)" Part # 1107. Which is the same as for the 489. Dr Diff has a Minimum Install Kit for 741 and shows a crush sleeve also.

So which is correct? Maybe they sell it in the kit but you just don't use it for 741 / 742?

ALSO, is there different shims I should get for either side of the pinion? Or just one type of shim style (varying thicknesses of course). As I seem to be seeing different styles of shims also -bit confusing!

Thanks for your help!!
 
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It may be a 'representative' photo?

Crush sleeve is 489 only.

If you order from Doc & tell him what you have, you WILL get what you need.
 
I do think the 489 is crush only as well. If you only need to back off the pinion preload any shim will do. Just removed the chunk and measure the turning torque. Add shims until you get it where you need it. I have got shims from tractor supply companies and a good hardware store before in a pinch.
 
I meant to say add or remove until you get what you need. :lol: Sorry
 
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Thanks guys, just as I thought. I know Dr Diff is pretty good usually, although on the two occasions where I emailed both these guys to confirm, with what I thought were emails worthy of a good reply, both were not at all helpful (no helpful explanation, just a link) so that's why I came here on this forum. I thought at least Cass would have been more helpful as I explained my situation and especially as I recently bought a new SG unit from him. Oh well.

Thanks Helllrats, that is exactly the plan of action I had in mind, even with my limited knowledge of these pumpkins. But can you tell me one thing not answered, is there only one type of shim in the 741? And does it only go in one position on the pinion? I suppose I should get off my A and look at the Dodge factory service manual, the info should be in there.

Thanks.
 
I'm not sure what additional information you were looking for, as I simply provided a link for the parts you said you couldn't find on my web-site.

This is the only question you asked me:

"Do you sell shims for these? I assume they use shims? I thought only the 489 uses a crush tube. I can't see a shim kit for these on your site."

This was my response:

Hi Steve,

See below (741 mini kit):

Mopar 8 3/4" (Mopar) Minimum Installation Kit

Thanks,

Cass
 
In addition, the link I provided shows actual images of the different shim kits (741, 742 and 489). In other words, if you scroll over the images of the shim kits, a pop up identifies the casting # associated with it.

Note, a crush sleeve is only available (and shown) for the 489 case.
 
DoctorDiff said:
In addition, the link I provided shows actual images of the different shim kits (741, 742 and 489). In other words, if you scroll over the images of the shim kits, a pop up identifies the casting # associated with it.

Note, a crush sleeve is only available (and shown) for the 489 case.
Click to expand...

I just tried the 741 link on your web page and it shows the 489 crush sleeve in the picture.
 
FYI the 741 has a sleeve that slides over the pinion in front of the rear bearing and then the front bearing rest against that and so you put shims in between that sleeve and the front bearing to get your pinion preload.
However there is a different size shim used behind the inner bearing so that you can set the depth of the pinion into the ring gear.
 
thanks for clarification Cass, yes I see now, sorry I did not notice that popup as they are very small and I am not usually looking for, or tuned in to looking for popups. What happened is that when I clicked on the 741 selection the left hand side picture came up with the crush tube picture. And also same picture for 742. That's what confused me. So I see now that it is for the 489. The next picture I looked at had different sized shims and as I didn't see the popup, I was wondering what they was for. I assume one set is pinion preload and other shims are for setting the side loads.

As I think I explained, my 741 was is all newly rebuilt (albeit 7-8 years ago). I had supplied the assembler with the full kit, I think I bought it from Mancini Racing at the time. So I was just needing shims only, to redo the pinion preload which is way too tight. So I don't need all the other things, just the shims to give to the diff shop, as they will have all the marking paint etc. I see there are shims, sets of 6 or 7 shims on ebay there for $10-15, so I will look at those.
 
Jadaharabi said:
FYI the 741 has a sleeve that slides over the pinion in front of the rear bearing and then the front bearing rest against that and so you put shims in between that sleeve and the front bearing to get your pinion preload.
However there is a different size shim used behind the inner bearing so that you can set the depth of the pinion into the ring gear.
Click to expand...
Thanks for that info Jadaharabi - that's exactly what I was looking for! Of course, I will only learn if I pull it apart myself but now I have a better idea of where things go. I was not sure about setting, if pinion depth and doing preload and backlash were the same, I thought these were the same process but seems as if they are different. Pinion preload I think, refers to the final amount of turning torque at the yoke and maybe is independent of the depth of the pinion which determines the teeth mesh pattern.
 
How are you measuring this preload as it being too tight?
With the carrier and ring gear removed?
With new bearings or used?


The correct way to do it is with the carrier and ring gear out and the front seal removed. You then use an inch pound torque wrench and pull the pinion around. Don't worry about the initial amount to get it started turning you just want the constant turning value.
 
yes the centre is out and as I said all newly rebuilt, so yes, new bearings. I have not as yet put a torque wrench onto it (have to hunt up a 1-1/8" socket) but I can know without any doubt that it is more than inch pounds. I can turn it with two hands and the diff guy who is twice my size and with ham fists can turn it with difficulty with one hand. I agree the front seal, esp being new, will affect it. But not that much. But I don't want to install it and hope it loosens up, might as well get it right the first time. And in any case I have to install the SG unit anyway, so it's getting halfway pulled apart on the bench. I am now wondering if the yoke will slip off or if that will need a puller? And maybe I should buy a pinion depth setting tool, as these guys charge $125 an hour (standard rate here where live) and he said it could take 2-3 hours to get it right by "trial and error".
 
70Hardtop said:
yes the centre is out and as I said all newly rebuilt, so yes, new bearings. I have not as yet put a torque wrench onto it (have to hunt up a 1-1/8" socket) but I can know without any doubt that it is more than inch pounds. I can turn it with two hands and the diff guy who is twice my size and with ham fists can turn it with difficulty with one hand. I agree the front seal, esp being new, will affect it. But not that much. But I don't want to install it and hope it loosens up, might as well get it right the first time. And in any case I have to install the SG unit anyway, so it's getting halfway pulled apart on the bench. I am now wondering if the yoke will slip off or if that will need a puller? And maybe I should buy a pinion depth setting tool, as these guys charge $125 an hour (standard rate here where live) and he said it could take 2-3 hours to get it right by "trial and error".
Click to expand...


The front seal doubled the inch-pounds on the 9 1/4 I just finished doing. With the crush collar eleminator and New bearings it was set at 20 inch pounds. I put the new seal in. tighten it all down checked it and it was at 40 so there is a reason that you check it without the pinion seal.
 
wow, that is a big difference with the seal. I will get into it, no way to learn without some hands on. Will order a correct socket for the nut tonight. Thanks for your help and sounds like you are pretty experienced.
 
My pinion depth gauge is a Vernier caliper and a push rod. And a bearing that's honed out so that you can slide it on and off of the pinion instead of having to pressure the good one on and take it off multiple times.
You bolt the pushrod across the center caps from one side to the other at an angle and then you can measure from the bottom of it to the backside of the pinion to get your depth.
 
Great advice, I do have a 6" Vernier and I also have a 440 pushrod, so I will look into that. The dummy bearing is a good idea but will have to see what I have in that department.
 
70Hardtop said:
Hi all,

I need to get the pinion preload reset on my 741 (it is too tight from a previous rebuild many years ago) and want to buy a set of shims to give to the diff shop. (BTW , I'm in Australia so not much info around on these 8.75's, and differential shops usually are not familiar with old Chrysler stuff).

I am sure that only the 489 used a crush tube /crush sleeve with shims whereas the 741 used only shims. Is this correct? Because I am getting confused with places like Ratech and Dr Diff who are selling install kits for 741 and both have a crush sleeve in the kit (eg see this page: http://ratechmfg.com/chryslerstandard.htm)/ Ratech has listed for the 741 and 742 "CRUSH SLEEVE (shim pack)" Part # 1107. Which is the same as for the 489. Dr Diff has a Minimum Install Kit for 741 and shows a crush sleeve also.

So which is correct? Maybe they sell it in the kit but you just don't use it for 741 / 742?

ALSO, is there different shims I should get for either side of the pinion? Or just one type of shim style (varying thicknesses of course). As I seem to be seeing different styles of shims also -bit confusing!

Thanks for your help!!
Click to expand...


just curious but what was the pinion preload at that you say was too tight ----.most people cannot believe how tight 20-25 in/lbs rotating will feel when turning just the pinion and the effort increases with the carrier installed.

Australia must have 9 inch Ford parts available ----if you need pinion shims to reset the preload get a solid spacer kit and shims for a 9 inch Ford -- the shims out of the 9 inch kit are the same as used in the 741 and 742 cases
 
Jadaharabi said:
The front seal doubled the inch-pounds on the 9 1/4 I just finished doing. With the crush collar eleminator and New bearings it was set at 20 inch pounds. I put the new seal in. tighten it all down checked it and it was at 40 so there is a reason that you check it without the pinion seal.
Click to expand...

the seal will maybe add 2-3 in/lbs to the rotating torque --- the reason for the doubling of the torque was when you set the initial preload before installing the seal you must torque the pinion nut to at least 150 ft/lbs to get an accurate reading of the preload -- then when you do the final assembly the torque will be the same except for the 2-3 in/lbs for the seal.
 
"just curious but what was the pinion preload that you say was too tight ----.most people cannot believe how tight 20-25 in/lbs rotating will feel when turning just the pinion and the effort increases with the carrier installed"

Well as I said, I have not checked that yet although I have two torque wrenches, as I don't have the correct 1- 1/8" socket. I will be buying one in the next few days. I might see if I have a metric one that goes close though as I am interested to see what it reads at. Although I am pretty sure I don't have anything between 25mm and 30 mm. 1" = 25.4mm

the diff guy who felt it and who has 25 years experience in diffs said it is on the high side and "may" loosen up with use but he said if it gets too hot then it would need to come out again.

"Australia must have 9 inch Ford parts available ----if you need pinion shims to reset the preload get a solid spacer kit and shims for a 9 inch Ford -- the shims out of the 9 inch kit are the same as used in the 741 and 742 cases"

Thanks for that great advice John, yes Aust has plenty of Ford 9's, many of our vehicles had them. So that's great news, it will be much easier to hunt up a shim set for a 9" and use them. You saved me some time and effort, I'll buy you a beer!
 
when you set the pinion bearing preload on a rebuilt differential with new bearings ( 20-25 in /lbs ) it will feel tight --- 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 .

before you send the differential out check the preload and if it is in range leave it alone . it will ease up as the miles go by and eventually go to zero.

your "diff guy" should have put a in/lb torque wrench on it and checked it that way while you were there and gave you the actual info not "on the high side "--- going by feel is not the way to do things unless you are stuck in the bush / outback and you have to get home.

if you are going to have a differential rebuilt ,,,the one question you should always ask a "diff guy" is what do you set the pinion bearing preload at -- if he says tight or can't give you an actual number --- find someone else who understand the importance of this procedure.
 
john-9 said:
the seal will maybe add 2-3 in/lbs to the rotating torque --- the reason for the doubling of the torque was when you set the initial preload before installing the seal you must torque the pinion nut to at least 150 ft/lbs to get an accurate reading of the preload -- then when you do the final assembly the torque will be the same except for the 2-3 in/lbs for the seal.
Click to expand...

That's a good theory on your part. I learned a long time ago you don't check your preload at a hundred and fifty pounds if your pinion nut is supposed to be at 200 to 250. Because you get a false reading and when you do your final setting of The pinion nut it will be off. I checked mine at 200-210 and it was a 20 inch pounds then I installed the seal retorqued it with red Loctite to 210 foot pounds and I was at 40 inch pound. So don't use a hundred fifty pounds to test because it's inaccurate.
 
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).
 
You may also be getting that tight reading because sitting on the shelf all these years the oil drained away from the bearings. So squirt some oil in to those rollers and see if that doesn't change your preload.
 
"You may also be getting that tight reading because sitting on the shelf all these years the oil drained away from the bearings. So squirt some oil in to those rollers and see if that doesn't change your preload."

thanks, Yeah, I did consider that as a big factor. I only have 'click' style torque wrenches too, never liked the ones with the gauge and the pointer, but they are needed really, for times like this. I will have to frigg around with the torque settings so I can estimate what it is by turning. I can't wait to check that torque. It has loosened slightly from when I first tried it, had to get a bar across the yoke and turn it that way - impossible by hand. But now can just turn it with two hands.
 
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