03 Civic M/T UOA 4900 mi - bad input shaft bearing

Dec 23, 2020
2003 Honda Civic EX manual, 170k miles

I have had a bad input shaft bearing (ISB) in my M/T for at least 35,000 miles / 7.5 years. It was first diagnosed at the dealer as something that I can continue to drive, but will eventually need the tranny rebuilt (the ISB can only be gotten to by disassembling the entire transmission). The noise that defines it as the ISB only happens in Neutral, when the clutch is released while idling. It goes away when you press the clutch in. See here for reference:

Up until about a year ago, the noise pattern was consistent and unchanging. In the past year, the noises have started to change/get worse. I have been changing the M/T fluid more frequently (it's easy to do) and sampling to see if I can document anything from the UOAs. Perhaps my biggest mistake was neglecting to change the fluid for too long (115k miles). Whether this caused the bearing failure or not, I can only guess. I'm the original owner of this car and changed the M/T fluid at 23k and 45k, then I became a father and maintenance took a backseat. :( I went 115k (from 45k to 160k) until I bothered to change the fluid again.

Here is the latest UOA. From a PPM/1000 mi perspective, it actually improved from the last sample. Aluminum and Iron have gone down (they are both still above Universal Averages) and everything else is at or below Universal Averages. I've actually got a guy lined up to rebuild the tranny in the next couple of months, so I will be addressing it. I have a feeling, though, that I could probably keep driving this car as-is for several more years. It seems bullet-proof. The sounds get worse but it keeps working completely normally. LOL. BTW, the "SHORT" note in the Flashpoint section is due to me accidentally spilling the sample after taking it. There was only about 1/3 of the sample bottle left, which was not enough for them to measure the Flashpoint.

03 Civic MT 112722.jpg
Here is some data breakdown. Far left (green) is a virgin analysis of Honda MTF. Blue section are Universal Averages for this transmission (which include other MT fluid brands besides Honda, hence the differences in additives). The Universal Average results are based on an average 15,800 mi. I also break down the Universal Average to PPM per 1000 miles for easier comparison to my own results. Next three sections moving right are my last three MTF analyses -- the 115k run, followed by two 5k runs. The clutch was replaced just prior to the 5k run on 1/9/22. To me it looks like the iron (and possibly the aluminum) on the most recent two is washout from the new clutch. Everything else, on a PPM per 1000 mile basis, seems to line up pretty well with Universal Averages. Which is honestly a little surprising for me. I expected there to be a more visible affect from the bad ISB on wear metals.

010623 MT Breakdown.jpg