Tranny question

[engineco713]

Hey all.....I have a 4 speed with granny trans and I'm not sure if the throw-out bearing or the slave cylinder is going bad. Question is, how hard are they to replace and is it easier to just get a "new" used tranny and just swap it? Thanks

[James McClure]

713. Exactly what are the symptoms? Just hard shift? Noise? Grinding? They don't call the sm465 a rock crusher for nothing. It's almost bullet proof as long as there is grease in it. Post the exact problem with when it started and how it presented itself. Also tell if there was any work done beforehand. jim

[RuralRoute C-30]

Originally Posted by engineco713

Hey all.....I have a 4 speed with granny trans and I'm not sure if the throw-out bearing or the slave cylinder is going bad. Question is, how hard are they to replace and is it easier to just get a "new" used tranny and just swap it? Thanks

Sounds like it could be time for a new clutch. As was mentioned, that transmission is darn near bullet proof. Sadly the clutch is not.

The good news: Having been there done that myself with replacing a clutch then it is my opinion (mine only, of course) anybody can do it if you take your time, ask questions when needed and can turn a wrench. At least this is what a friend who is a mechanic by profession told me when he loaned me his transmission jack and smiled. I think he knew I was going to learn something.

Just be very careful when that transmission comes out. Experience in that moment led me to discover it tends to weigh a "few pounds". It was one of those "memory makers" in my self-education on safely removing the SM465 transmission.


Meanwhile, use the search mechanism here on clutch's and throw-out bearings, ask questions as you are here, and everything you need to know can be found. A service manual helps too.

And maybe it is not the clutch at all and a simple solution instead.

Good Luck!
Mark

[engineco713]

Originally Posted by James McClure

713. Exactly what are the symptoms? Just hard shift? Noise? Grinding? They don't call the sm465 a rock crusher for nothing. It's almost bullet proof as long as there is grease in it. Post the exact problem with when it started and how it presented itself. Also tell if there was any work done beforehand. jim

It's an 86 C-20 with about 130,000 miles with a 350 engine and 4 speed with granny setup. I was not using it as a daily driver but my "new" truck was in the shop so I drove it to work. Upon stopping at 7-11 that morning I went to start the truck and it seemed like the clutch was engaging even though I had it to the floor. I had to shut off the truck to get it to shift into neutral. I was able to get it started and shift but when I pulled up to the first red light the engine was dying out like I had the clutch out. I can't get it into "L" at all, and 1st is a bear, 2nd and 3rd shift fine. So then last night as I'm nursing it home and I go to back into my driveway and I can't get it into reverse while its running. So I had to shut it off and back up as I was starting it to be able to move it. To me it seems like the clutch isn't releasing but someone said it could be a throw-out bearing. I just had the clutch master cylinder replaced about 10 months ago and have only driven it about 1000-1500 miles if that since the replacement. I also read it could be air in the master cylinder but I haven't had any problem before now. Any idea's?

[engineco713]

Bump

[RuralRoute C-30]

713:

Chances are there are others more experienced than I on this topic who will add to this but the symptoms you describe are, "to a tee", exactly the same ones that led me into replacing a clutch and more. If I started the truck in gear with the clutch pressed in, it was rolling. Shifting when running was not an option in or out of gear when I finally tore it apart. Earlier it was making an occasional growling noise at times when the clutch would disengage, but like all noises, it got worse and so did the problem.

But first, are you sure the slave cylinder is working? Air in these hydraulic clutches are a known pain when it occurs and bleeding the air that is known to settle in that slave can seem to take forever.

Another point to ponder would be how does the pedal feel? Lose/to the floor or like it should?

Since you mentioned the master cylinder was replaced not too many miles ago it may be worth checking to see if the slave is functioning before committing to a tear down for a clutch. If it isn't then it can't put enough pressure on that clutch fork to manage the throw-out bearing.

Here is a link that chronicles my learning curve last year on this topic. In the end, air was the nemesis at the end of the job, but I wound up with a needed new clutch and overall clean-up of that area of the truck as well.
http://67-72chevytrucks.com/vboard/s...d.php?t=410276

Either way, bleeding air in that system can take some patience. Somewhere here I read from a member where they would pump the clutch "up" until it felt "right", bleed, do it again, walk away with the clutch to the floor, (I used a 2x4 to keep it compressed), let it sit for half an hour, bleed again, repeat the process and eventually bled all the air out. Also with the cap off the master cylinder, while pushing on the clutch, look for air bubbles. For me, this process finally worked when nothing else did, and that was after a new clutch was installed!

Personally I'd just be sure it was not an air problem before dropping that transmission. But if bleeding doesn't work, just remember it is just nuts and bolts and turning a wrench with time to see a new clutch installed.

Curious to hear what you find to be the problem.

Good Luck either way,
Mark

[RuralRoute C-30]

713:

Chances are there are others more experienced than I on this topic who will add to this but the symptoms you describe are, "to a tee", exactly the same ones that led me into replacing a clutch and more. If I started the truck in gear with the clutch pressed in, it was rolling. Shifting when running was not an option in or out of gear when I finally tore it apart. Earlier it was making an occasional growling noise at times when the clutch would disengage, but like all noises, it got worse and so did the problem.

But first, are you sure the slave cylinder is working? Air in these hydraulic clutches are a known pain when it occurs and bleeding the air that is known to settle in that slave can seem to take forever.

Another point to ponder would be how does the pedal feel? Lose/to the floor or like it should?

Since you mentioned the master cylinder was replaced not too many miles ago it may be worth checking to see if the slave is functioning before committing to a tear down for a clutch. If it isn't then it can't put enough pressure on that clutch fork to manage the throw-out bearing.

Here is a link that chronicles my learning curve last year on this topic. In the end, air was the nemesis at the end of the job, but I wound up with a needed new clutch and overall clean-up of that area of the truck as well.
http://67-72chevytrucks.com/vboard/s...d.php?t=410276

Either way, bleeding air in that system can take some patience. Somewhere here I read from a member where they would pump the clutch "up" until it felt "right", bleed, do it again, walk away with the clutch to the floor, (I used a 2x4 to keep it compressed), let it sit for half an hour, bleed again, repeat the process and eventually bled all the air out. Also with the cap off the master cylinder, while pushing on the clutch, look for air bubbles. For me, this process finally worked when nothing else did, and that was after a new clutch was installed!

Personally I'd just be sure it was not an air problem before dropping that transmission. But if bleeding doesn't work, just remember it is just nuts and bolts and turning a wrench with time to see a new clutch installed.

Curious to hear what you find to be the problem.

Good Luck either way,
Mark

[PRattenbury]

If your clutch is hydraulically actuated, it seems like that is what I would check first. It sounds like you have air in the system somewhere. Sometimes pumping the clutch pedal a few times with a hydraulic system will let you get it into gear if itisn't too air-bound. And putting it into neutral as you come to a light or whatever will help. Of course if it is just mechanical rods that make the clutch work see if there is any more adjustment left in the linkage. If it is already adjusted all the way, you need a new clutch.

[engineco713]

When I first start it the clutch feels fine and I can start it in gear. But after a minute it starts engaging. Then if I pop it into neutral and pump the clutch it feels soft. I was thinking it had air in the system but I drove it a couple of months (every now and then) with out problem. Guess it's back to the garage when I get some time to start bleeding. Thanks for the help. I'll let everyone know how it goes. If anyone has a further insight feel free to post please.