Transmission Front Input Bearings

I went through a lot of trouble finding an input bearing for my J20's T-18. there are two thicknesses of bearings for the T-18, the thin one and the thick one, 20 mm (0.7874") thick and 23 mm (0.9055") in thickness. My troubles are shown here - T-18 in the driveway - Page 2 - Full Size Jeep Network - if you are interested in the original story.

AFAIK all our Jeep T-18s use the thin 20 mm bearing. This is the same input bearing as a T-15, Jeep PN 448 8141. The T-14 is a different bearing, PN 941648.



After receiving two identical 23 mm bearings from RockAuto, correctly boxed but incorrectly identified as a 20 mm bearing, I bought a bearing through Part Mike which I presume is the import bearing sold by Crown.

Seeing a thread about broken gears in the T-14, I looked at this again. If you look up the T-14 part number, you find two name-brand bearings, a Timken and an SKF for ca $40 and $50 resp.

I was surprised to find a National bearing for the T-15 for ca $50, and it claims to be the proper thickness of 20 mm. This is a different bearing maker from the one that would not work in my T-18. Certainly I would have gone with this bearing if it were available when I needed it - assuming it is described correctly.

JMO - If I went into one of these transmissions to replace a broken gear, I would be tempted to inspect everything and only replace the damaged parts (broken gear), the 2nd gear blocking ring (which sees the most wear), and the front main bearing. Maybe the 1st gear blocking ring too.

I recall another broken T-14 that resulted from speed shifting (aka power shifting) behind a 225. This is a shift that is executed without lifting the throttle. It'll work, but don't miss the shift! (I would not attempt it, but I'm old and of a calm and deliberate nature). Just FYI anyone who is reading or interested.

 

it's a jeep, not a porsche. it's meant to be driven slower and calmer.

 

I bring up the speed shifting because I suspect that is how the 2nd gear was broken in the transmission I referred to. That transmission looked really clean, and putting it back together as I suggested could be justified.

Not suggesting that anyone speed-shift their Jeeps. The shift tops are not made for fast shifting, and 2nd gear is likely what you'll blow up if you try it and miss.

 

Here is a set of photos of the Jeep p/n 4488141 (Crown 35 years ago or equivalent) T18 transmission front or input bearing.
Federal Mogul box/BCA Bearing # 308-L1 as shown.
The thickness is shown on my Chinese measuring device at 20mm or so.
This bearing includes the snap ring installed.
According to my Jeep parts manuals, this would be used in the Jeep factory mid to late 70's version of T18 4 speed and T15 3 speed transmissions.
If you are recreating a T18 from other parts, unknown if this would work for you; I'm not that smart.
Posted for informational purposes.