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Thread: Spicer 23-2 differential backlash question

  1. #1
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    Spicer 23-2 differential backlash question

    I'm in the process of tearing down a 23-2 differential. My concern is the backlash. Before pulling it apart the backlash measured .024. this appears to be excessive. This is my first differential rebuild and I want it back together correctly for obvious reasons. I haven't pulled the bearings yet so not sure what shim dims are yet. Question, when putting it back together should I attempt to adjust the shims to tighten the backlash to the correct spec or start with the original configuration? Spec is .002 -.009. Thanks in advance for any information.

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    Super Moderator bmorgil's Avatar
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    Pabutler1, that is a great question. I would think that if that much backlash is present, there are one or more bad bearings, or the ring and pinion are worn, or both. The best way to do this in the field is first to do a good visual. The ring and pinion should show no signs of wear. There can be a real good polish where the mesh is occurring, but no indentations that you can feel with your finger tip or thinning of the teeth. Next you have to set it up. You measure the lash before you take it apart to try to get it as close to the way it was as possible WITHIN SPECIFICATION. It still needs to be assembled within specification. The assumption is made that when you check it before removal, it is within specification. If the axle has any kind of damage or bad bearings, this is seldom the case.

    So if it is .024" either a bearing is badly worn and/or the ring and pinion is. If it looks good in visual and passes a good inspection for wear, go ahead and set it back up. If it is a bad gear set you will not get a good pattern. All this said, what is the intention for the vehicle? Parades or hard use? Send some close ups of the ring and pinion and the carrier bearing races.
    Last edited by bmorgil; 11-29-2019 at 10:00 AM.

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    Bmorgil, thank you for your response. My first impression is the rear end has been rebuilt in a previous life. The jeep had been used as off-road only as it had been unregistered for decades. The gears appear to be in good condition. I will do as you recommend and feel for wear patterns, etc. Prior to removal the pinion turned freely with no resistance at all and was leaking badly. The bearings feel loose so that may be contributing to the condition. My intention is to use as a road only vehicle, nothing off-road, mated up to a GM smallblock and warn overdrive. I'm out of town for the holiday but will post pics of the gears in a couple of days. Thanks

  4. #4
    Super Moderator bmorgil's Avatar
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    If the pinion turns freely, there is a good chance the pinion position is not holding. The backlash will be affected if the pinion is or has moved. If there was no preload on the ring gear carrier bearings and/or the pinion bearings, the pre-disassembly backlash reading becomes something that is nice to know and no longer that important.

    OK good info you have given here. If it is going on highway with an overdrive, the application has radically changed. There are a few things about a sustained higher RPM drive line in a jeep that you definitely should follow. The axles need to be set up correctly. The input RPM will be significantly higher than originally intended. You need to watch your set ups. Set the preloads the way we have discussed. The backlash needs to be in spec or corrected. A good pattern on the gear set will need to be obtained or it may howl, scream and may even puke.

    You caused me pause at the "it may have been rebuilt before". Since you are running this rig in "high performance mode", you should go ahead and set it up with correct preloads. Then you are going to need to read the pattern. There is a trick or two to that but I think you will find it doable. Let me know.

    The pinion preload should be easy to obtain. I am a bit concerned about the carrier and pinion position. If the rebuild was "haphazard". The preload and position could be lost. When you reassemble, go slowly on the carrier install into the housing. The best way to explain what I am saying is to explain the correct way.

    The carrierer is inserted without the ring gear or pinion suspended in "precision dummy bearings". The carrier is slid side to side to determine the total amount of shims it would take to make an exact fit. .015" is added to that number to provide pre-load. That is the total shim pack. Now with the pinion installed in the correct position, the carrier is inserted with the ring gear and dummy bearings installed. Now the carrier is forced into mesh. The distance to the mesh point at 0 backlash is the shim pack for the ring gear side. It is subtracted from the total. The rest of the shim pack is placed on the pinion side. The extra .015" provides the preload and pushes the ring gear over enough to provide backlash. If it is not correct shims are moved from side to side until it is. This is a bitch with bearings on. You must have the proper bearing pullers to remove and reinstall the bearings without damage. There are a lot of special tools to do this.

    The pattern tells the story. If it is bad the adjustment begins. Remember that as pinion depth changes, it changes backlash. Lets hope it just has worn out bearings, and the positions with the original shims is still good. If not I am confident you will get through it correctly. It isn't as difficult as it seems. I think it will help to understand why you are checking and adjusting it. There are many who just bang them together. These are tough axles and they will live through a lot.There is definitely a right way and a reason to do it the right way. The tools required to do this professionally are costly and rare. You can get through it without them if you practice a little caution. Keep us posted and I think we will get er' done!

    This is a lot to get in a single post. Ask away we will "kill as we go". We should discuss your drive shaft angles for the higher speed.
    Last edited by bmorgil; 11-29-2019 at 07:47 AM.

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    Thanks for the valuable information. I understand the procedure you detailed on the carrier install. I have watched YouTube videos and the procedure multiple times. At this point my confidence level is increasing. My intention is to ensure the setup is done correctly so I can have assurance on the road. This is a slow total restore on the entire jeep. It's a 41 MB and I want as much to remain original as possible. The engine, trans and transfer that was in it came out of a 53 cj. The engine was shot but the trans and transfer were salvageable. Those are the only non-original pieces on the MB. I will post pics of the ring gears soon and thank you so much for your time and help.
    Last edited by Pabutler1; 11-30-2019 at 01:49 PM.

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    Pulled the bearings. Pinion shims = .056. Carrier- bolt side = .051. Carrier gear side = .024. the pinion wear can be felt when running my finger on it, thinking it may need to be replaced. Ring gear feels smooth. pics added.
    Attached Images Attached Images
    Last edited by Pabutler1; 11-30-2019 at 06:57 PM.

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    More pics including ring gear.
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    Super Moderator bmorgil's Avatar
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    The concern is on the drive side of the gears. That is the convex side on the ring gear. That side should be the one that tells the story. The drive side of the pinion is a little blurry in the photo. It looks pretty good. If you can feel a dent at all however, its no good. The color of the lube looks very rusty or dirty. Abrasive in a Hypiod gear set is deadly. It will hone the gear set teeth right down.
    Last edited by bmorgil; 12-04-2019 at 08:45 AM.

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    The drive side is where the roughness is at. Looks like a new pinion/ring gear is on the list. The case has crud in it. I'll be sure to thoroughly clean it before reassembly. Thank you again for your time and expertise. I hope this thread helps others as much as it has me. By the way there were no shims for the pinion preload.
    Last edited by Pabutler1; 12-03-2019 at 04:19 PM.

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