Digger 5
Well-Known Member
I didn't read every post of the 5 pages but the first couple of pages had some very questionable info provided.
While the M186 (D30) in the JL uses a unique diff cover, the gears are the same as a JK. Check any Spicer guide and you'll see the part numbers for JK and JL are the same. The stock 3.45 gear is unique in that it is a thin gear. The usual carrier break on a D30 is 3.54 down, 3.73 up. This 3.45 ring gear is factory fitted to a 3.73 up carrier so no new carrier is needed to go to lower (like 4.88) gears. 35" tires have usually been the limit for the D30 ring gear. The weight of these trucks can be very heavy and that must be considered when trying to determine what will survive. Drive style, tire design and weight also matter. As usual, your experience may vary. Some guys can make a weak assembly last forever while some guys can break a steel ball in a rubber room. Due to gear tooth contact area, a 3.45 gear will be much stronger than a low gear such as a 4.88 or 5.13.
The rear M200 is called a 35 but really isn't the same. The gear is different, it is not a c-clip design and has 29 spline shafts. It's certainly stronger than the old POS D35 but not as strong and as JK 44.
JL Sport M220 rear axles are pretty readily available so they would be your best option to build instead of the M200.
FWIW, the new JT has 2 different axle track widths, MAX Tow/Rubicon and standard (?). All JT trucks are supplied with the M210 (D44) front axle regardless of package. I would consider looking for a standard width JT M210 front axle for replacement on any sport JL with the M186 front.
While the M186 (D30) in the JL uses a unique diff cover, the gears are the same as a JK. Check any Spicer guide and you'll see the part numbers for JK and JL are the same. The stock 3.45 gear is unique in that it is a thin gear. The usual carrier break on a D30 is 3.54 down, 3.73 up. This 3.45 ring gear is factory fitted to a 3.73 up carrier so no new carrier is needed to go to lower (like 4.88) gears. 35" tires have usually been the limit for the D30 ring gear. The weight of these trucks can be very heavy and that must be considered when trying to determine what will survive. Drive style, tire design and weight also matter. As usual, your experience may vary. Some guys can make a weak assembly last forever while some guys can break a steel ball in a rubber room. Due to gear tooth contact area, a 3.45 gear will be much stronger than a low gear such as a 4.88 or 5.13.
The rear M200 is called a 35 but really isn't the same. The gear is different, it is not a c-clip design and has 29 spline shafts. It's certainly stronger than the old POS D35 but not as strong and as JK 44.
JL Sport M220 rear axles are pretty readily available so they would be your best option to build instead of the M200.
FWIW, the new JT has 2 different axle track widths, MAX Tow/Rubicon and standard (?). All JT trucks are supplied with the M210 (D44) front axle regardless of package. I would consider looking for a standard width JT M210 front axle for replacement on any sport JL with the M186 front.
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