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PostPosted: Mon May 11, 2020 8:16 am 
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Joined: Sat Apr 09, 2016 6:18 am
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Need some input here. Attempting to install a new 3J Limited Slip Differential in an MG Midget SCCA rearend. Took it to an trusted, experienced auto machinist. After measuring for set-up, he said that he would need to turn 0.020" off the backside of the ring gear flange cover to get the pinion to align properly in the carrier. Talked to the folks at 3J America and they claim tolerances on old British stuff are all over the place and machinist is probably right. Has anyone else had issues like this? Thanks in advance. Paul


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PostPosted: Tue May 12, 2020 11:57 am 
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Joined: Wed Jul 06, 2011 3:48 am
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Location: Florida
Never heard of "ring gear flange cover" and .020" isn't a huge amount but I'd measure the new piece and the old piece and see who's off the .020". I wouldn't be cutting up anything until I found out why your new unit doesn't fit, especially if it's 40 or 50 years old or so.

Bob

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PostPosted: Tue May 12, 2020 12:42 pm 
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Hi Bob,
Trying to refer to the cover on the limited slip unit. The side opposite the ring gear, next to the carrier bearing. PL


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PostPosted: Tue May 12, 2020 1:36 pm 
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Location: Memphis, TN
I had a similar issue when i bought a LS already in the pumpkin. Don't remember the exact problem but it sounds familiar. i THINK it developed when i tried to install it in the axle housing. i remember talking to someone and they thought the problem i had may have been because i had early (Bugeye) rear axle housing. Then again it was years ago.

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PostPosted: Tue May 12, 2020 2:02 pm 
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Gotcha! I'd still go back to the manufacturer and ask what guidelines they used to design their unit. .020" isn't much but I'd sure check with them to find out why and how you have to modify their piece. Been working with the Quaife and Tranex units and have had them in both the late and early rear ends with no problems.

Now that I know which side you are working on I'd say he is saying he needs to move the entire carrier over with shims on the bearings. If that unit fits properly into the housing I'd leave the bearings alone and put .020 shim material between the gear and the carrier. This works if the bearings fit properly in the housing without shims. Still have to set the pinion properly on the gear but down the road adjusting for minimal wear is much easier using the shims behind the big gear. If he's modified the bearing area then you are out of options. Good luck.

Bob

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PostPosted: Wed May 13, 2020 5:45 am 
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Thanks Bob, Modifying the bearing area is what we are talking about. Did a rough measure this morning and it looks like I have plenty of bearing shoulder to safely cut without interference. Just surprised that it wasn't manufactured on the small size to begin with. Thanks all.


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PostPosted: Wed May 13, 2020 8:54 am 
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If you insist on modifying the bearing area on the case you are going to have to come up with some .020" 360 degree shims for both bearings to keep them in place. Lot easier to make one shim for the carrier/gear.

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