Tips on AMC20 Gear Change - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 03-28-2000, 09:41 AM
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Tips on AMC20 Gear Change

They say you learn by your mistakes...I guess that is why I'm so damned smart by now....That must be how CJDave and TeamRush got so smart....(just kidding guys)

Anyway, I replaced my R&P in my AMC20 'AGAIN' over the weekend. The first time I used the attitude of "that looks good enough"...well, it wasn't. The rear end whined and I had a vibration from it. I wish I could blame it on a bad gear set...but after looking at the pattern, nope...bad installer...ME! I had the Pinion depth wrong....way wrong.

This time around I followed the instructions a lot closer. I also download the advice from Randy's Ring and Pinion for reference. Here are some of the little details they don't mention....I guess because they take it for granted.

1. It is a 'bitch' getting the pinion gear out. In my case it was a BFH and heavy punch with lots of swings. Next time I'm going to buy a brass hammer.
2. Save that spacer that is between the inner pinion bearing race and diff case. You will need it for the new one.
3. If your R&P gear set comes with white marking grease...don't waist your time...too hard to read...get the yellow GM stuff.
4. Make sure you allow several hours for just the setup...try to avoid too many beers in the process...there seems to be a direct corralation between "thats close enough" and the number of beers consumed.
5. Make sure you save that front bearing that you took off the original pinion gear. Because your going to use your moto tool and grind out the center of it so that it will slid over the new pinion gear....unless you love spending 10 minutes beating the pinion gear out while trying to get the pinion gear depth right.
6. *** Important point here...PINION DEPTH IS IMPORTANT......changing the shim by as much as .004 made a big difference in contact patteren. Start with the original spacer (remember note 2?). Even if it looks perfect, try a some addition shim, say .010, and make sure it moves the contact pattern the direction you expect.
7. Once you think you have it perfect, put on the bearing caps and check it again.

Following the above along with the included instructions should give you a good setup. This morning I am a happy [img]/wwwthreads_images/icons/smile.gif[/img] diff is nice and quiet. Now I get to do the front diff this weekend [img]/wwwthreads_images/icons/smile.gif[/img]. the way, my u-bolt conversion came out great. I'll post some pics as soon as I download the images from my camera....and resize them so they will fit in the small space allocated to us....I guess I should get to work on that web site......wish I could find a way to do without sleep.....

John......southern CA
84CJ7, 3"lift, 32"BFG, 4.10's, ARB Locker, Solid Axle's, Durabak
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post #2 of (permalink) Old 03-28-2000, 02:19 PM
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Re: Tips on AMC20 Gear Change

Hey John,
I did my AMC 20 a couple of weekends ago. I must have gotten lucky because my diff is nice and quiet and I had a good pattern using the same pinion shim. It is hard to know if it is right when you have never done it before. I wish I had an expert to watch, or to tell me my pattern was correct. Once you have done it once and know it is right it makes you much more confident the next time. I still have to do my Dana 30. Right now I am not that excited about doing it. I will probably wait another week or so. Let me know how your install goes or e-mail me if you have any questions I will be around this weekend and I usually check my mail a couple of times a day.


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post #3 of (permalink) Old 03-29-2000, 04:40 AM
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Re: Tips on AMC20 Gear Change

Tip-- BFH and a BF Oak Block of wood will take that pinion right out of there[img]/wwwthreads_images/icons/smile.gif[/img]

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