How to fix a broken input bearing

For a while, I was driving my '88 Formula around with a broken input bearing. A few weeks ago I found out exactly what kind of damage that can do. I was stopped, waiting to go, with the car in gear and clutch pedal in, when all of a sudden the car started making a terrible noise and I couldn't use the clutch anymore. I had to get towed home.

When I got home, I had a pretty good idea of what the problem could be, so with my dads help, we swung down the cradle and removed the transmission. This is what we found:



What started out as just a broken input bearing had now become a bent fork as well.

I knew I had to do something, but with a new input bearing being at least a couple month away and not knowing where to get a new fork, I decided it would make the most sense to just swap the transmission for another.

A little bit of research later and I found out that 92-94 Sunbird/Cavaliers with the 3.1 V6 used the same Getrag 282 but with a nice upgrade: a hydraulic throwout bearing. Basically, that one part eliminates the need for a input bearing with the sleeve, and also does the job of the slave cylinder and clutch fork. The throwout bearing itself is a bit expensive, but when you're essentially replacing all those other parts in the process, it doesn't seem so bad.

I originally had intended to use the whole transmission out of a '93 Sunbird, but after discovering that the only one I could get would be out of a car with 400,000 km, I decided to look into using only the bellhousing, since my transmission still worked just fine apart from the now broken clutch fork and broken input bearing. If you want to be able to use the Fiero speedometer without any extra electrical work, you need to swap out a gear on the diff anyway, which requires opening up both the old and new transmissions.

I don't have many pictures of that process, but there is a nice post on doing that, here. It's the same with both of the transmissions.

When you open it up, the differential will be free to remove. At this point you can compare what the two speedometer gears look like.



Here you can see that I've set aside my old bellhousing and the other half of the transmission from the Sunbird.



Now we just had to put the two good halves together. The post I linked to above covers that, since doing it with with the different bellhousing doesn't change anything.





Here's what the new bellhousing looks like.



And notice, that instead of a slave cylinder, this is what you'll see.



Getting the Fiero hydraulics to connect to the slave was a bit of a challenge, but my dad handled that. I might see later if he'll comment on it (assuming anyone is interested).

Bleeding the clutch works pretty much the same as it did before. The new hydraulic throwout bearing has plastic clips that need to break once it's in the car, so you hear this once you've bled most of the air out. I noticed that the pedal feels lighter than it did before, I guess that's because you're directly actuating the throwout bearing instead of doing it through the fork. It feels good, though.

Since I've only had this in my car for about two weeks, I can't really comment on the long term reliability of this, but so far I'm really happy with how it all turned out. I'll should never have to worry about the input bearing or clutch fork again.

You da man Colby! Oh, and your dad as well.

That's excellent. Thanks for posting about this procedure. Very helpful info.

One question... Are there any reports of this internal slave being problematic, as in losing pressure due to leaking? (It would obviously be a real nuisance to service!)

 

karnak wrote: i do hope it can resolve this issue for a long time.

Yeah, I bet you do!  Great work, Gary.

Not to sidetrack this thread (too much), but how long before we see your car back together and back at the track?

I had that same explosion in an Isuzu.  I never thought to adapt a different bell housing and rebuild it.  Way to go you 2, congrats on the work.

       Just one word of caution, you are the first person I have spoken to, that has good things to say about the hyd throwout bearing.  The concept is great, like you said, it simplifies the entire shifting system, however makes slave cylinder changes 1000x more difficult and chances are it will wear out before the clutch does.

     If you prove me wrong and this works out great, I'll be the first in line to make the same conversion on my 88GT Getrag and the 4.9 Getrag.

D_sensitized wrote: What is the second pipe for? Is that the bleeder valve? if it is, it looks like a much better system then what I have on mine, where the bleeder is just T'd off the inlet.

Yep, that's a bleeder valve.

Capt Fiero wrote: Just one word of caution, you are the first person I have spoken to, that has good things to say about the hyd throwout bearing.  The concept is great, like you said, it simplifies the entire shifting system, however makes slave cylinder changes 1000x more difficult and chances are it will wear out before the clutch does.

Actually I said that I didn't know about the reliability of it yet, but yeah, it's a great concept so long as it doesn't leak. I'm hopeful that since the car it came out of had so many km that this particular design is OK. We'll see though.