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Dana 30 - Differential Side Bearing Preload

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I am currently Rebuilding a Dana 30 from a 79 CJ7 and am looking for advice on the Preload amount for the Differential Side Bearings. I am not asking about the Pinion Preload!

The Dana Spicer Service Manual states that it wants 0.015” of shims greater than what is required to achieve Zero End Play for the correct preload. My current setup requires 0.058" of shims to achieve zero endplay, so that would suggest I need to use 0.073" in Shims to create the required preload.

ISSUE
I just finished rebuilding my AMC 20 rear axle and the preload on the differential bearings was 0.008” in shims greater than what is needed for Zero End Play to create the correct amount of preload for the two side Differential Bearings. Disregarding that these two axles are from different manufactures. They both use roughly 3" Tapered bearings as Side Bearings and you would think the optimal preload would be somewhat similar.

I also follow a gentleman that has many years of experience and noticed he stated that he typically uses 0.005" of Preload on his Dana 30s.

QUESTIONS
1. Do I have the wrong information, or is there a reasonable explanation?
2. Is it really just a crap shoot, i.e. put some in and your good?
2. What thickness of Preload Shims should be used on a Dana 30? This is the additional Shim thickness above what it took to achieve zero endplay.
3. Looking for some technical feedback, because I am very interested in this entire process.

Thank you for your time and response. Mike
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Dana is right that you need an additional 0.015" shims when you achieve "0" end play. Bearings WILL seat once things are moving and lubricated.
I had shims left over when I rebuilt the Dana transfer case, AMC20 axle and the Dana 30 front axle thinking it was tight enough when we achieved "0" end play. But went back in and added the shims as per manual. It was a tight fit and felt like the bearings or something would break. But after an initial break-in period of a few thousand miles, all the bearings seated as they should and never needed to open up and redo again.
 

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Discussion Starter · #4 ·
I appreciate your reply. I just again read that some people are only adding 2-3 thousandths to both sides (that is spec for the AMC20 but the Dana asks to put them on one side). Looking for a few more confirmations before I button it all up. Thanks
 

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I appreciate your reply. I just again read that some people are only adding 2-3 thousandths to both sides (that is spec for the AMC20
One side only for the AMC20 as well. And if I remember correctly, the shims were on the drivers side only.

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Discussion Starter · #6 · (Edited)
I just finished my AMC 20 and the service manual specifically calls to 0.004 to be added to both sides. That is where I became alarmed when Dana Spicer calls for 0.015.
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I am now trying to get the Dana 30 in the background completed.
 

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I just finished my AMC 20 and the service manual specifically calls to 0.004 to be added to both sides. That is where I became alarmed when Dana Spicer calls for 0.015.
I don't know what year your CJ is but for the late model AMC20 axles, at least for the 1982-86 wide tracks, the service manuals only states to put shims on the left side. With a Dana 30, shims on both sides due to the open knuckles on the ends. But your AMC20 axle is not a factory unit anymore with disc brake conversion and possibly with one piece axles.

Excerpt out of the 1984-86 FSM...
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am looking for advice on the Preload amount for the Differential Side Bearings.
You are asking about the carrier bearing preload?
If so, start with shims on both sides since you have to move the carrier to set the picture depth.
2. Is it really just a crap shoot, i.e. put some in and your good?
Yes. Sorta. Not too loose so the carrier moves and the races spin, not too tight so the oil is squeezed out and the bearing runs hot. There is some leeway between these two criteria.
What thickness of Preload Shims should be used on a Dana 30? This is the additional Shim thickness above what it took to achieve zero endplay.
You can use as thick or thin (stack) of shim(s) as you need to get the preload you want. Traditionally, you will have a couple of thin shims on both sides to start with and shift them from side to side to set the picture. Once you have the R&P set, you can adjust the preload if needed (I usually set up my carrier with the preload already adjusted), then double check the picture. The adjustment always goes on the coast side of the carrier as adding to the load side can move the ring gear closer to the pinion.
 

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Discussion Starter · #9 ·
I don't know what year your CJ is but for the late model AMC20 axles, at least for the 1982-86 wide tracks, the service manuals only states to put shims on the left side. With a Dana 30, shims on both sides due to the open knuckles on the ends. But your AMC20 axle is not a factory unit anymore with disc brake conversion and possibly with one piece axles.
Not to get too far off topic, but I did want to clarify with you Keith that for my AMC 20 (79 Narrow Trac), I did not use an FSM, but a Service Guide that was written by a group of guys that included a pretty impressive list of qualifications. It appears to me that there are many approaches to get to the same solution of a set Backlash and Preload.

Just became alarmed when the AMC20 calls for .008 and the Dana30 calls for .015. For similar tapered bearing, I would have expected these to be similar as well.

Thank you for your response!
 

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Discussion Starter · #10 ·
Yes. Sorta. Not too loose so the carrier moves and the races spin, not too tight so the oil is squeezed out and the bearing runs hot. There is some leeway between these two criteria.

You can use as thick or thin (stack) of shim(s) as you need to get the preload you want.
@jeepdaddy2000 Yes this is the Differential Side Bearings OR Carrier Bearings. I do understand the process and since posting this, found more references of others using a wide range of Preload Shim thicknesses.

Thank you for your input! Mike
 
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