DIY GEM GEARBOX Refurb Procedure


Don’t know if this is the proper procedure but it’s the way I do it.

Remove from car and drain oil and clean exterior.

Secure upside down in a vise

Remove cover

Remove intermediate bearing caps (Freeze Plugs) by drilling a small hole in the center and forcing them out with a sheet metal screw.

Remove all snap rings.

Remove the input shaft assemble by pulling it out with a pair of visegrips applied LIGHTLY to the spline

Remove the input shaft housing bore O’ring

Remove the differential cover

Remove the axle shafts with a pair of visegrips applied LIGHTLY to the spline. These puppys sometimes stick. If they do you need to force them out with a long taper wood chisel and 5/16 nuts. plan on dropping a few in the case. Have 2 beers on hand to sooth your frustrations.

Mark the differential caps with a punch to make sure you replace them correctly.

Remove the carrier

Remove the intermediate gear assembly

If you are going to replace the axle shaft seals remove them. (I usually don’t replace the axle shaft bearings or seals as I have never run into bad ones)

If you are going with the seal type input assembly the O’ring doesn’t have to be replaced.

Change out bearings

Reassemble in reverse order

Straighten flange on cover and reinstall Use Permatex Blue for sealant. Only SNUG cover bolts at assembly. Tighten them up after 24 hours.


Grease input shaft seal inside and out, and push in using your 2 thumbs. Seal MUST be about a millimeter below the case bore surface when properly installed

I probably over kill but I put a bit of Blue on the intermediate shaft bores and press the caps in using my 2 thumbs

PM me if you have any questions


1 Like

I drained the oil and removed the cover or pan to get the residual oil and did not see much metal all the gears on the inside look good no unusual wear patterns I’m just going to put the pan back on.

It is a 12 to 1 ratio

The input shaft is a little rusty and the splines show some wear.

Where is a good place to purchase a new input shaft ?

21 tooth input shaft kit. $150 including shipping Have 2 left
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In a message dated 7/13/2018 12:28:14 PM US Eastern Standard Time, writes:

Thanks for the reply I assume that’s a new kit and 21 tooth is appropriate for the 12 to 1 ratio? How about the rubber bumper?

Do you have any experience in changing control arm bushing on a 2007 E4, mine are pretty cracked and the service manual seems to indicate they are not replaceable.
Also CV joint boots mine are not leaking but whether checked thanking to replace those as well.

Kit is new. I’m out of rubber bumpers. NEV’s parts has them. Bushings can be weather checked on surface but if not loose “it aint broke” dont fix it.

In a message dated 7/14/2018 12:09:05 PM US Eastern Standard Time, writes: