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Old 07-27-2010, 08:04 AM   #1 (permalink)
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Default Impact on fuel economy with bad ISB?

Just curious if anyone has a before and after fuel economy comparison. My ISB (Input Shaft Bearing) has been making noise for a while now. So has the Clutch Release Bearing. I guess with 403,000+ on the original clutch and trans, some noise is to be expected, right? Anyway, just curious if anyone has fixed their trans and documented the difference in fuel economy. I'd think there would be SOME difference due to reduced friction but it may not be very dramatic.

Anyway, ordered new flywheel, pilot bearing, ISB, ISB seal, axle seals, clutch disc, pressure plate, and release bearing from Honda yesterday. It will be here tomorrow morning. I have a backup trans that is ready to go. Planning on possibly pulling the trans this evening so it's all ready to put back together tomorrow evening. I have a 1000+ mile trip I leave for on Friday and would really like to have it done by then.

If I think about it and if I have enough time, I'll take pics of the whole process of removing and reinstalling the trans. I've looked high and low and could not find a tutorial on how to do it online...

Ryan
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Old 07-27-2010, 10:21 AM   #2 (permalink)
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I think that many of us will run into this problem eventually, it would be good to see how this is done. It would be greatly appreciated if we had the pics of the process. It would be cool if I can get 400k+ out of mine, but I've got about 10-15 years yet since mine is only at 115k now.
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Old 07-27-2010, 02:05 PM   #3 (permalink)
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This guide helped me when I was changing mine:
Reviving a 2000 Honda Insight "beater" - Page 12 - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com
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Old 07-27-2010, 03:44 PM   #4 (permalink)
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The fuel economy difference would be so slight that it would not be measurable.
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Old 07-29-2010, 07:52 AM   #5 (permalink)
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OK, trans is out. The noise I thought was an ISB was not. ISB is nice and tight. However, it sounds like just about every other bearing in the trans is toast. The diff bearings are loose and the trans is pretty loud when you turn it by hand. The replacement I have for it is much quieter and smoother. My release bearing feels OK but it was starting to make a bit of noise. Honestly, for the miles the car has on it, everything looks like it has about 100,000 on it (clutch/flywheel/pressure plate, etc).

Now, question is, how large of an impact is there on economy with bad diff bearings and others? Still fairly low? Not that I care, I just want a quiet car...

Should be putting everything back together tonight.
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Best tank 75.6, best round trip 81.3
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Old 07-29-2010, 08:07 AM   #6 (permalink)
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There might not be much of an impact until the bearings become the consistancy of sand and sound like complete garbage. ...and then suddenly your MPG becomes zero as the transmission no longer produces any motion. :O Good thing you have it apart to find that. If I recall correctly, I think retepsnikrep said that the diff bearings and ISB were bad with his thread on the spare trans he bought to fix up as a spare, he said it scored the casing of the transmission, which if left too long would have damaged it irreperably.
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Old 07-30-2010, 03:13 AM   #7 (permalink)
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Well, car is back together and the results are in. I drove a little over 30 miles in my hilly area and the improvement is HUGE. I typically got between 60 and 66 mpg depending on traffic. Here is what I have done to the car and, at the end, the new mileage.

1. New flywheel, pilot bearing, clutch disc, pressure plate, and TOB.
2. New front rotors (had some cheesy crossdrilled ones that the previous owner had put on. Now has OEM Honda rotors, OEM Honda pads and hardware.
3. Replace rear and driver side mounts (yes, I know, no mileage increase but it DID get rid of my "shudder" that many seem to complain about)
4. Trans I freshened up. New ISB and seal, replaced a couple synchro springs, replaced diff bearings just to be safe.

Now, with the above done, same driving style, I just got 81.3 mpg. So, I guess the trans was crunchy enough and the front rotors/pads were dragging enough to kill the MPG. I'm taking a longer trip tomorrow (around 350 miles) so I'll see how it does at interstate speeds.
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Best tank 75.6, best round trip 81.3
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Old 07-30-2010, 06:32 AM   #8 (permalink)
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Pic of before and after FCD. The old one was a little farther along the same route. However, the "little farther" was no hills so the fuel economy is not impacted in a bad way. Also, my previous best trip mileage was 70.0 and that was really trying hard. My after is just driving normally and doing hypermiling when I can. If traffic was around, I kept with it. If there was no one around, I'd just worry about keeping the instantaneous mileage on the FCD in my range I was shooting for.

Before:




After:
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2001 MCB Insight 5 speed
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LMPG since owning 65.5
Best tank 75.6, best round trip 81.3
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Old 08-01-2010, 09:07 PM   #9 (permalink)
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Another update. Took a small trip this weekend and drove about 650-700 miles total. I had about 1/3 of my drive in some pretty hard rains and I currently have about 550 miles on this tank of gas and tank average is 75.6 mpg. Same trip before I was lucky to get 59. Not sure how much of it was the trans and how much was the new front rotors (old ones were crossdrilled POS's) and pads. Either way, I'll take it. Next up is some new spark plugs and fuel filter then start saving for a MIMA...

Ryan
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2001 MCB Insight 5 speed
403,000 and counting.
LMPG since owning 65.5
Best tank 75.6, best round trip 81.3
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