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Discussion Starter #1 (Edited)
just had a few basic questions.. I'm currently installing a set of FR 4.10's along with a motive bearing kit, pinion, carrier et cetera. replacing stock 3.27's

I had a friend telling me that I don't have to change the side/carrier shims since I am using FR gears is this correct? just replace them with factory size shims.

Also am I shiming the new pinion to match the original pinion shim or what?

this is obviously my first gear job, it's just that I've read a bunch before hand but I keep getting conflicting info.

If anyone can post a link or something to a howto on replacing stock 8.8 gears with FR gears that would be even better. thanks in advance

oh and one other thing I mixed up my bearing caps.. I understand that the arrows on caps always point to outside if diff casing... I also see that each cap has a different number on it... is there a way to tell these apart?
 

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You can use the same shims that you took out. That should get you very close to where you need to be. Once you get it all back in, you can check your backlash and see where the pinion gear is riding on the ring gear with some marking compound. Once you've checked those two things, you'll know what (if anything) you need to do to fine tune things.
 

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You can use the original shims as a good starting point, just make sure to check your backlash and contact pattern afterwards and adjust accordingly. Here is a link you can check out 8.8 Axle Gear Install I have seen better write ups than this one before, but this is the best one I can find right now. I will keep looking though.
 

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You can use the same shims that you took out. That should get you very close to where you need to be. Once you get it all back in, you can check your backlash and see where the pinion gear is riding on the ring gear with some marking compound. Once you've checked those two things, you'll know what (if anything) you need to do to fine tune things.
+1 I guess I hit post just a couple of seconds after you lol
 

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Discussion Starter #5
thanks for the info everyone. Hopefully I can get it all back together Sat. anyone have any info/advice on the bearing caps?
 

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Discussion Starter #6
so I have most of what I deam "the hard stuff" done now I'm onto the techn ical parts.. anyways can anyone tell me what the default differential shim sizes are for each side? mixed mine up a bit, just looking for a starting point.

it had two shims. one is .267 and .281 in
 

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KCCO
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You might have to duplicate the thickness of one of the factory shims with the smaller ones, so that way if you have the move it over one way, you can just do it by a very small amount by taking one of the smallest shims (in the duplicated factory shim made from smaller provided shims) and adding it to the actual factory shim. That way, you will maintain the overall thickness of both factory shims combined, but you can adjust by small amounts. Hope that makes sense. I had to move it over a little bit.
 

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Discussion Starter #8
You might have to duplicate the thickness of one of the factory shims with the smaller ones, so that way if you have the move it over one way, you can just do it by a very small amount by taking one of the smallest shims (in the duplicated factory shim made from smaller provided shims) and adding it to the actual factory shim. That way, you will maintain the overall thickness of both factory shims combined, but you can adjust by small amounts. Hope that makes sense. I had to move it over a little bit.
that makes sense. would the thicker shims on the right side or left?
 

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KCCO
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With mine, I believe the thicker one was on the right. So the right side would have been the factory one plus a small shim... I am not 100% positive it was like that but Im pretty sure
 

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i'd just take it to the local dealership to have it done. i've swapped gears before and ruined them because the wear pattern was bad. several hundred dollars later, i took it to the dealership with new gears and had it done again. i've done a lot of work on cars over the years, i just really don't recommend doing something like this unless you have a trained professional to guide you.
 

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Discussion Starter #11
i'd just take it to the local dealership to have it done. i've swapped gears before and ruined them because the wear pattern was bad. several hundred dollars later, i took it to the dealership with new gears and had it done again. i've done a lot of work on cars over the years, i just really don't recommend doing something like this unless you have a trained professional to guide you.
well I do have help from someone experienced. however we just have conflicting schedules so its hard to have him here at the same time. and besides that I'm completely capable however I'm sort of reading technical manuals but at the same time trying to gather real world advice. my only real hangup is the baseline for the proper shiming.


for instance I'm getting 48.3 mm measuring old pinion + old pinion shim.

new pinion + old shim measure 48.7mm. I thought I was reading something about the frp pinion having a baseline of 30mm plus or minus 2 on the shim. did I miss something?
 

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Nice choice with the 4.10's. Your going to wish you had them in sooner. I'd like to add-on (prob know this already I hope) but make sure you recalibrate your speedo after the gear sway either by installing the device or else changing it with your handheld tuner (diablo or SCT).
 

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well I do have help from someone experienced. however we just have conflicting schedules so its hard to have him here at the same time. and besides that I'm completely capable however I'm sort of reading technical manuals but at the same time trying to gather real world advice. my only real hangup is the baseline for the proper shiming.


for instance I'm getting 48.3 mm measuring old pinion + old pinion shim.

new pinion + old shim measure 48.7mm. I thought I was reading something about the frp pinion having a baseline of 30mm plus or minus 2 on the shim. did I miss something?
If you've got this done then just ignore my post :)



From what I've heard most people get away with using a .030 shim. However, your bearing thickness will be the key in your case. I just installed a set of frpp 410 gears also and I had to use NO shim because the motive bearing was over .020 thicker than the old bearing so it took up the space a shim would normally have taken.

If your frpp gears are +/- .002 then they are fairly close. You need to make sure how thick the new bearing is vs. the old bearing and calculate that into your shim choice.

One tip...when changing shims make large adjustments to see how your wear pattern turns out. That will give you a good idea what thickness your going to need. If your new bearing is about the same I would start off using the same stock shim and go from there.
 
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