Throwout bearing woes

adman02

Well-Known Member
Joined
May 15, 2009
Location
Durham, NC
Did a 4.0 swap to my 79 CJ7 and replaced the clutch and throwout bearing while the engine was out. After a few hundred miles, I had to replace the throwout bearing because it started to chatter and chirp. A few hundred miles later (today) I'm starting to hear the chatter/chirp again. Would a misaligned clutch cause the T/O bearing to fail prematurely? Would appreciate any help or insights as I damn sure don't want to drop the T18a any more.

4.0/CJ t18a/Dana 20/AMC 20 with a lockright locker
 
Probably misaligned clutch. Might be something that's not letting the throwout release all the way, so there's a small amount of constant load when there shouldn't be.

Also check the input bearing to the trans, and the pilot bearing. I'm assuming you changed the pilot when you replaced the clutch?

Did you use both the engine and trans that came out of the donor Jeep?
 
I did replace the pilot bushing and soaked it in oil overnight before installing. Had to buy it special from Novak.

I used the engine from the donor jeep, but kept the tranny that came with the CJ (T18a). I reused the 232/258 flywheel but had it machined. The 4.0 was mated to an automatic tranny in the donor, so I didn't think the flywheel/flexplate would have been compatible with my T18a.
 
adman02 said:
I used the engine from the donor jeep, but kept the tranny that came with the CJ (T18a). I reused the 232/258 flywheel but had it machined. The 4.0 was mated to an automatic tranny in the donor, so I didn't think the flywheel/flexplate would have been compatible with my T18a.
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Ah, ok. Yeah, you should really check the bellhousing alignment. I'm not completely sold on that as the culprit though, unless you're killing the throwout bearing before you're doing detectable damage to the pilot bearing and/or input shaft bearing.
Regardless, the alignment should be checked because of the large manufacturing year difference between the engine and the bellhousing.
 
This may be a stupid question, but how do I check the bell housing alignment? The engine/bell housing is aligned with two dowel pins and I used both of them when mating the two together. Do I just visually inspect the seam to ensure no bolts have backed out or loosened up?
 
adman02 said:
This may be a stupid question, but how do I check the bell housing alignment? The engine/bell housing is aligned with two dowel pins and I used both of them when mating the two together. Do I just visually inspect the seam to ensure no bolts have backed out or loosened up?
Click to expand...

Dial indicator with a mag base on the flywheel (or attach a bracket to a pressure plate mounting bolt on the flywheel) rotate the engine and measure run-out on the bellhousing bore. You'd have to look up the run-out spec because I don't know if what it is off the top of my head, but you can get offset dowel pins to correct it if it's off by too much.

Google something like "bellhousing alignment", you should find some good info.
 
Might not be the problem, but it is something that should always be done when mixing and matching engines and trans, and it's a good sanity check while troubleshooting an issue like this.
 
Ugh. This could explain some things. The pilot bushing came out in pieces when I removed the clutch. The bushing with numbers was the OEM for a 232. The other intact bushing is one I just ordered from Novak.

Several questions now:
1. Would failure to adjust bell housing runout cause the pilot pushing to explode?

2. Should I be concerned the that new bushing is significantly deeper than the previous one?

2. I test-fitted the bushing and there's slight play between input shaft and bushing and slight play between busing and inside the crank shaft. Is that a problem? I was under the impression that it should be a tight fit.

3. What else should I check now that I've got the tranny separated from the engine (e.g. transmission input shaft play)?

4. (this one could be a dumb question) When setting up a dial indicator, how do you ensure the magnetic holder is in the exact center of the crank shaft? I would imagine that if it's off even a little it could skew the reading, no? THANKS TIM C; WATCHED A VIDEO ONLINE AND THINK I FIGURED THIS ONE OUT.

Any and all ridicule and help is welcomed.
 

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A misaligned bellhousing can cause problems with the pilot bushing, and the input bearings in the trans if it's not caught in time.

If the new bushing is longer it won't hurt anything, as long as it is close to where the old one was as far as engagement with the input shaft.

The bushing should definitely be press fit in the crank shaft. If it wasn't this is likely the problem all along.

Make sure the disc slides smooth on the splines, if it was off the splines could get burred up. You can check endplay in and out on the input if you're worried, but note that the input will be able to be wiggled around in a circle some, the pilot bushing is actually a support bearing for the input.

You don't have to center the dial indicator on the crank. With it stuck to the crank or clutch surface of the flywheel, you let the needle touch the inside of the circle hole where the throw out bearing retainer goes into the bellhousing. As someone rotate the crank you watch the dial. The crank/flywheel will run true so the only thing causing the readings to change would be if the bellhousing is off center in relation to the crank centerline.

Sent from my XT1254 using Tapatalk
 
Thanks for the info, Tim C. I watched several videos online and think I figured out the dial indicator question. Any AMC folks out there have ideas on how to correct bellhousing runout? Apparently AMC did things differently - their dowel pins are hollow and you run a bolt through them. All the dowel pins I can find are solid.
 
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