Need help with AMC 20 - JeepForum.com
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post #1 of 10 Old 05-26-2020, 05:53 PM Thread Starter
Ben W
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Need help with AMC 20

Hey guys, Iíve been rebuilding both axles on my Ď77 CJ7. I got through the Dana 30 no problem but have gotten hung up on the AMC 20. Gears were in good shape so I am replacing all bearings, seals, etc. I am at the point where I am trying to set the rotational torque on the pinion. I am using a crush sleeve, not the shim kit. The problem I am having is when I tighten down the yoke nut and rotate the yoke 360 degrees, it feels like it is dragging about 90 degrees of a full rotation. Iíve taken it apart and put it back together several times at this point and finally went ahead and torqued it down all the way to crush the sleeve. I went a little more than I probably should have because Iím at the upper end of spec at 25 in-lb through 270 degrees of the rotation but then that last 90 degrees is at like 80 in-lb.

A couple observations I have made through this process is the inner bearing race was really tough to get in. I had to beat the old one out with a punch and a sledge hammer. Putting the new one in wasnít any easier. I ended up beating the crap out of the race driver set I rented from the local auto parts store. I beat on that some more today and I canít tell if it made a difference or not. I was worried that if the race wasnít seated properly it could have the bearing at a slight angle which could be the cause.

Also, the dust shield that is part of the yoke appears to be slightly bent. I could see it when spinning the yoke, the gap between the shield and the case would open and close slightly as I spun the yoke. I put it on a steel plate and found the difference from one side to the next to be roughly .010Ē. I also measured from the plate to the top of the yoke arms on both sides and they were dead nuts. Iím not really sure of any other way to measure a yoke to tell if there is an issue with it. The dust shield doesnít appear to be dragging or touching anything, so this being slightly bent doesnít seem that it would be a cause, but maybe thereís another problem Iím not thinking of. I just donít want to go drop $80 on a new yoke to have the same issue.

Anyone have any ideas?

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post #2 of 10 Old 05-26-2020, 07:01 PM
oldschool74cj5
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hello

ok a few things. when you install a race into the housing hopefully put them in the freezer. it will shrink a very little but helps it go in. sounds like you have a bearing and or race thats not fully seated. to install the bearings on the pinion or even the differential you need a good press. then really take your time and make sure they are seated in. for installing a race in the housings i normally use a driver with a 1" fine all thread that goes between. then i can press in even and when it gets snug you put a good amount of pressure on it then just give it a good tap on the end of the threaded rod. the shock will make the race drop in a little more evenly. putting the race in the freezer for a few hours first though normally makes it so it will drop in easily but have to do pretty quickly. i normally would freeze the bearing race overnight.

oldschool
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post #3 of 10 Old 05-26-2020, 08:44 PM
stripperguy
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A bearing that is not square to the axis of rotation gives a 2 per revolution indication.
An out of round race and/or housing will show however many features that are present, whether a single "lump", or multiples.
Are you sure it's the bearing? Anything else that could cause the disparity? There's a slinger in there, right? Dust shield on the yoke...
Do you have any way to check the bearing fit in the housing? You should verify that the interference fit is correct and that the fit diameter is round.

BTW, I spent 40 years in R & D, most of that in Aerospace design and testing. I know a little bit about these sort of things.

1977 CJ5 is a CJ build ever really done?
2002 TJ gone
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post #4 of 10 Old 05-26-2020, 09:09 PM
oldschool74cj5
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Quote:
Originally Posted by stripperguy View Post
A bearing that is not square to the axis of rotation gives a 2 per revolution indication.
An out of round race and/or housing will show however many features that are present, whether a single "lump", or multiples.
Are you sure it's the bearing? Anything else that could cause the disparity? There's a slinger in there, right? Dust shield on the yoke...
Do you have any way to check the bearing fit in the housing? You should verify that the interference fit is correct and that the fit diameter is round.

BTW, I spent 40 years in R & D, most of that in Aerospace design and testing. I know a little bit about these sort of things.
hello
from what you are saying is that the surface of one of the races is not true to the axis. would cause what he is experiencing. now i see that you would get a 2 per revolution indication if it was not installed properly. if the bearings are chinese might be the problem. they never been known for quality. i would probably lean towards the bearing before a case that has worked for over 30 years.

oldschool
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post #5 of 10 Old 05-27-2020, 01:19 AM
80cj
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Sounds like your bearing race is not seating fully. As others have said, try sticking the bearing cup in the freezer for a while and see if it makes a difference. You could also try painting the bearing race with gear marking compound and see what kind of contact you're getting. Check and make sure the bearing cup is not brinneled from the excessive preload. If it is, replace the bearing.
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post #6 of 10 Old 05-27-2020, 01:17 PM Thread Starter
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Quote:
Originally Posted by oldschool74cj5 View Post
hello

ok a few things. when you install a race into the housing hopefully put them in the freezer. it will shrink a very little but helps it go in. sounds like you have a bearing and or race thats not fully seated. to install the bearings on the pinion or even the differential you need a good press. then really take your time and make sure they are seated in. for installing a race in the housings i normally use a driver with a 1" fine all thread that goes between. then i can press in even and when it gets snug you put a good amount of pressure on it then just give it a good tap on the end of the threaded rod. the shock will make the race drop in a little more evenly. putting the race in the freezer for a few hours first though normally makes it so it will drop in easily but have to do pretty quickly. i normally would freeze the bearing race overnight.

oldschool
Thanks for this info, good input for sure. I wish I had thought or done more research first about putting the race in the freezer but unfortunately I did not do that. I may try to see if I can seat it one more time and if that does not work I will completely dismantle and start from scratch. I believe I have enough shims left over to do it again and I would only need to get a new yoke seal. The kit I ordered came with an extra crush sleeve, so I should be good there. The bearings/races are Timken, not Chinese. Sounds like the race which is kind of what I expected, just wanted to get a second opinion from those who know more than me. Thank you for the help.
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post #7 of 10 Old 05-27-2020, 01:19 PM Thread Starter
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Quote:
Originally Posted by 80cj View Post
Check and make sure the bearing cup is not brinneled from the excessive preload.
Sorry if I sound like a dummy, but could you elaborate on this? Not sure I understand, am I basically looking to make sure the cup isn't bent from me pounding it in or torquing down the preload?
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post #8 of 10 Old 05-27-2020, 01:29 PM
80cj
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Quote:
Originally Posted by Ben W View Post
Thanks for this info, good input for sure. I wish I had thought or done more research first about putting the race in the freezer but unfortunately I did not do that. I may try to see if I can seat it one more time and if that does not work I will completely dismantle and start from scratch. I believe I have enough shims left over to do it again and I would only need to get a new yoke seal. The kit I ordered came with an extra crush sleeve, so I should be good there. The bearings/races are Timken, not Chinese. Sounds like the race which is kind of what I expected, just wanted to get a second opinion from those who know more than me. Thank you for the help.
Probably the thing to do is to see if the bearing seats properly and try preloading the bearing without the crush sleeve and the seal out. Just use your old pinion nut and tighten it down checking preload as you go. At this point I would install the carrier and ring gear and make sure the pattern is correct. If very thing looks OK, then remove the pinion, install the crush sleeve and seal and go ahead and do the final preload.
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post #9 of 10 Old 05-27-2020, 01:50 PM
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Quote:
Originally Posted by Ben W View Post
Sorry if I sound like a dummy, but could you elaborate on this? Not sure I understand, am I basically looking to make sure the cup isn't bent from me pounding it in or torquing down the preload?
Many times if you place excessive load on a bearing, it could mark or cause small indentations in the bearing.
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post #10 of 10 Old 05-29-2020, 11:15 AM
John Strenk
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Quote:
Originally Posted by Ben W View Post
Thanks for this info, good input for sure. I wish I had thought or done more research first about putting the race in the freezer but unfortunately I did not do that. I may try to see if I can seat it one more time and if that does not work I will completely dismantle and start from scratch. I believe I have enough shims left over to do it again and I would only need to get a new yoke seal. The kit I ordered came with an extra crush sleeve, so I should be good there. The bearings/races are Timken, not Chinese. Sounds like the race which is kind of what I expected, just wanted to get a second opinion from those who know more than me. Thank you for the help.
Here is some good info:

https://www.jeepforum.com/forum/f8/f...setup-1176780/

https://www.jeepforum.com/forum/f8/a...thread-579159/


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