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How important is differential bearing preload?
Last Post 11-18-2009 08:59 AM by M-P. 6 Replies.
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M-PUser is Offline
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M-P

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11-10-2009 05:35 AM  

I have my NSX transmission apart right now to replace the outer housing and countershaft snap ring. I did all the necessary measuring for the new mainshaft thrust shims and ordered them yesterday. I also took the lsd down to a transmission shop and had them remove one of the bearings and press on the new one. After I got home I removed the old bearing race and shim from the old outer housing and took the old shim and new bearing race in pressed them into the new housing.

After putting the outer housing back on the inner housing and torquing it down to check the preload on the diff I realized I had no way of measuring the actual torque required to spin the diff without a special tool. I put the intermediate shaft in the differential and tested it by hand...it spun freely with just a bit of resistance, but no way of knowing if it was within the 16-28 in.lb. spec. that the shop manual calls for.

So my question, am I alright with this or do I really need to find a way to accurately measure this torque value? Not that it really matters, but this is not a track car, just a daily driven street car. I doubt it will ever see track time. 

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11-10-2009 03:04 PM  
I only know what I know about ford 9" diffs. Getting the proper preload can make or break things. Too tight and you destroy the bearing. Too loose and you can destroy the bearing and have premature ring-and-pinion failure. You can't even know if you have the proper shims in place if you're not properly setting the preload before you check gear engagement.

Not knowing your diff set-up, there should be some interface that attaches to the pinion shaft that you can get a bolt or nut onto to check the rotational torque.
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Mike Kojima

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11-10-2009 07:22 PM  
It is very important, don't mess around, do it right!
M-PUser is Offline
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M-P

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11-10-2009 08:02 PM  

I figured that was going to be the response and is what I was planning on doing. I was just hoping that it wasn't a huge deal and I could finish this thing up this weekend. Oh well, now I just need to find a tool to measure this with.

Does anyone know if any other Honda uses the same size splines for the axles? If they do I can get a old axle from a junk yard, cut it and weld on a 1/4" drive socket.

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M-P

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11-13-2009 06:14 PM  
Good news. I measured the torque with the existing shim and got a consistent measurement of 25 in-lbs (so that is within range of 17-26 in-lbs.). Get to put the transmission back together tomorrow morning, then hopefully have the car running Sunday.
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11-14-2009 04:38 AM  
fwiw, since you're messing with the shims, have you rechecked the ring gear tooth engagement? If it is off very far from where it was before dis-assembly, you can expect that you'll hear some whining/howling noise afterwards. Here is some reference material: http://www.differentials.com/install.html Ideally, when re-installing old gears, you want to try to match the existing wear pattern as opposed to setting it up like you have new gears.

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M-P

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11-18-2009 08:59 AM  

Thanks for the info. I got everything together and have been driving it the past few day (~360 miles). I have no whining, no leaking, and the damn thing shifts like butter.

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