SM465 eternal rattle (spark knock) on highway

[JoeliusZ28]

I agree that it seems to be in front of the trans. Previous owner had been using either 40 or 50 weight motor oil, but yes i fully drained and refilled with brand new 85-90 GL-4 fluid 2800 miles ago.

When the clutch is in its resting position (engaged), should the the TO bearing be firmly against the pressure plate? Or not even touching it?

 

[diesel4me]

The throwout bearing only touches the pressure plate when you push the clutch pedal in--otherwise it should have about 3/4" of pedal free play with the pedal "up",and not touch the pressure plate-...if it has been in contact with the pressure plate this long it is a good bet its about worn out..

I had two SM465's and both had their share of unusual noises at times--one in a '72 K5 with the 10 spline output shaft had worn splines and ate 2 of the splined couplers connecting the transfer case to the transmission--second one rattled constantly and drove me nuts,I tried filling the splines with red locktite and it did kill the noise for a month or so,and when it returned it was not as loud or annoying--went from a rattly grinding noise during take offs and coasting to a buzzy kind of sound..

 

[chulisohombre]

With the springs on it being the Older style it will probably rest itself on the pressure plate. I'd have to look at mine to see. But with the spring it would have constant pressure equal to the spring pulling force against the pressure plate thinking in my head.

 

[JoeliusZ28]

So I'm probably not going to get a chance to take this apart until the spring (truck will be in storage soon), but I found a possible culprit today. I stumbled upon a website that says the throwout bearing is supposed to be greased:

1. Coat this groove and fork tangs with a thin layer of grease
2. Pack this recess with grease

Being that I installed the trans, i know specifically that I did not do this. I've never worked on a trans that required such a thing, so its not something I would have even bothered to think about. Is it possible that the bearing is eating up the bearing retainer? The way the trans works perfectly, I'm thinking that come spring time I might just replace everything ahead of the trans.... clutch, TO bearing, pilot bearing, fork, and bearing retainer. Obviously before I go ordering a bunch of parts im going to see if i can see any obvious issues through the inspection plate, and check the gear oil as well.

 

[diesel4me]

Some old style throwout bearings actually had grease fittings !..
They deleted them I think ,because too many put too much grease in the bearings and it ended up on the disc's lining..

Though there is a recess for grease where the bearing collar slides on the input shaft bearing retainer,I rather doubt you'd notice any difference after greasing it unless the retainer was rusty ,all it would do is help it slide freely,not so much take up any slop and reduce a rattle..
-Usually normal oil seepage from the input shaft or the engine's rear main seal keeps that area pretty well lubed even without grease,in my experience..pretty rare to see it bone dry in that area..

 

[JoeliusZ28]

Its hard to discern whether or not my noise is a squeak or a rattle, I actually think its a little of both. My truck could actually be one of the few cases where it is bone dry in there, i fixed every leak I could while I had it apart... new valve cover gaskets, oil pan, and also a new input seal on the trans. Truck hasn't left a drop of anything on the ground all year. I didn't touch the rear main but it appeared dry. (is that even possible to do without a teardown?). If theres any lubrication on the TO bearing it would have been grease from from the previous install, but i don't remember it having any. Normally I'd replace a TO bearing while I'm that far into something, but this one was fine and only had 2k miles on it so i reused it.

Maybe I can get lucky and get away with applying grease to the bearing retainer with the inspection cover off!

 

[diesel4me]

The throwout bearing only could make noise for two reasons--either with the pedal depressed,when the bearing is pushing in on the pressure plate,that is when you'd hear a scoring type noise if the thrust bearings were rusted or "dry"--or a squeak when you depress the pedal ,when it slides on the bearing retainer...
Other than that its sitting still doing nothing..


Perhaps the fork could rattle on the bearing with the clutch engaged,if the retaining clip is broken or the ball & socket is sloppy enough that it pivots on..I have had "rattly"3 finger pressure plates,they eventually failed,wouldn't let the clutch fully release..
Some diaphram pressure plates had a wire ring retainer (and maybe some balancing weights) on the "vanes" also,that could loosen up and rattle when the clutch is fully engaged..

 

[JoeliusZ28]

I'm confident the bearing itself is fine, there's no noise when depressing the pedal. Noise is dependent on engine load/rpm though, so its either something thats spinning, or is hitting a resonate frequency of vibration from the engine. I need to get the inspection cover off and take a look, i might get a chance tomorrow night.

No ring retainer on the pressure plate that I see:

 

[JoeliusZ28]

Small update - I drained the fluid this weekend and it came out as clean as the day I filled it. Ran a magnet through it for good measure and nothing stuck to it. Maybe I'll get "lucky" and the culprit will be the throwout bearing/retainer. The teardown begins in about a month when i finish school.

 

[JoeliusZ28]

See both those springs on the clutch fork...both top and bottom? See if both of those are attached. That is the easiest thing to look at first. I am guessing your 84 has a mechanical linkage. Who's Ferrari is that?

Just looked back through this thread and it looks like this might be setup wrong on my truck. One of the springs is missing / different. However the clutch pedal actuates fine and rests at the very top of its travel.

Sorry these pictures aren't the best, but is there any chance this is my problem?

 

[1-ton]

You do have the springs on there...I guess you could say. The clutch fork should have a small hole in it to hook the spring that holds the adjustment rod up against the well in the clutch fork. The return spring is not normally hooked up to the frame. It has been a long time since I worked with an SM465, and I cannot remember where that is supposed to be hooked up to.

 

[JoeliusZ28]

Yep I noticed connection on the fork doesn't have a spring connected to it right now. Maybe theres a diagram in a chilton / haynes manual I can reference. I know this was the one detail I wasn't 100% sure of when I put it back together. I took some pictures before I took it apart but I'm also not the only one that's had the clutch apart on this truck.

 

[chulisohombre]

My return spring hooks up direct to the clutch fork and I believe in a hole on the frame. It's a double spring in case one breaks. That keeps a little pressure on the throwout bearing. Maybe that is your rattle.

 

[JoeliusZ28]

My return spring hooks up direct to the clutch fork and I believe in a hole on the frame. It's a double spring in case one breaks. That keeps a little pressure on the throwout bearing. Maybe that is your rattle.

Interesting are you saying the clutch pedal isn't intended to rest at the top of its travel? I thought the purpose of the springs was to hold the pedal up, but I haven't stood under the vehicle and watched how it works when the pedal is pressed.

I would definitely like to get the springs configured the way they should be, but that said I'm relatively confident this isn't the source of my problem as putting pressure on the pedal at cruise speed doesn't stop the noise (until the clutch disengages).

 

[chulisohombre]

Mine sits at the top of its travel. The spring is just on the clutch fork where it's supposed to be. So the bearing is always preloaded against the pressure plate. Don't know if the way yours is is putting enough pressure on the fork itself the keep the throwout up against the pressure plate good enough. Try switching it and see if anything changes. Your one spring looks broken on the right side and looks more like a brake return spring than what I have on mine.

 

[JoeliusZ28]

Well update on this story. Pulled the trans out this weekend, and I found obvious issues with the throwout bearing. It seemed to be partially binding, and it had worn a fairly significant groove into the top of the bearing retainer which wasnt there the last time I had it apart 3-4k miles ago. There was also a groove worn into the TO bearing where it hits the pressure plate. Seeing all that, I figured I'd found the source of the noise. I installed a new bearing retainer and gasket, and then installed a brand new LUK 11 3/4" clutch kit, this time with a composite throwout bearing that doesnt require lubrication. I left the old pilot bushing in the crank since this one came with a bearing and I'm not crazy about those. Got it all back together, everything felt great at first... clutch pedal is actually noticeably easier than the old 11" oreilys clutch it had which is nice!

However, 8 miles down the highway i started hearing the same dreaded rattling . After seeing all the apparent issues with the throwout bearing I admit i thought I had solved the mystery, and didn't give the input bearing a close inspection. Guess I get to pull this trans a third time. She's gonna have to miss the 400 mile road trip I had planned for her this weekend, but I WILL get this figured out.

Trying to decide what my next plan of attack should be. I want it fixed within the month. Thinking about pulling the trans back out but leaving the clutch. Then replace the pilot bushing (in case there are any alignment issues with the input shaft) and take the trans to a shop to deal with the input bearing or whatever is causing the problem. Fluid in the trans is *clean*, i ran it through a paper filter and there were no metal shavings to be found.

 

[chulisohombre]

Sounds like time to rebuilt it. Only way to find out and make sure all is good is to get it apart. Sucks you found that much damage and it ended up not being the problem.

 

[diesel4me]

Getting the pilot bushing out with the clutch disc & pressure plate still bolted up is....well...."impossible" !......

You may find a gear is loose on a splined shaft inside the trans,or maybe the input shaft bearing is "rough" or loose..

 

[JoeliusZ28]

Getting the pilot bushing out with the clutch disc & pressure plate still bolted up is....well...."impossible" !......

The method I was thinking of using is the wet paper towel trick...hydraulically force it out. But now that I am thinking about it, that might wind up with paper towel crap in the clutch... so youre right, probably safer to just pull it again.

You may find a gear is loose on a splined shaft inside the trans,or maybe the input shaft bearing is "rough" or loose..

It has to be something simple like this. The trans drives flawlessly other than this noise. Shifts well, doesn't pop out of gear, etc. And the problem hasnt gotten any worse over the last 8 months of driving it around town.

The other question I had is why the bearing retainer was only worn on the top. Makes me wonder if there is a miss-alignment of the trans/engine somehow. But not sure how that would be possible.

 

[diesel4me]

Its possible...the bell housing might be "tweaked" or made out of spec,or perhaps there was some strain on the transmission from a mount that was over tightened (or loose ) ,that would put things in a bind situation..

You may be able to pull the pilot bushing out with a slide hammer puller,but it'll be harder to drive in the new one, with the clutch fingers so close...be easier with it out of your way..

Seeing the noise wasn't there for 8 miles,then started again,kind of points to it being a loose gear ,the gear lube is thick at first starting off "cold"--once it heats up and thins out it'll let things rattle,rather than tend to silence them..

I used to put STP or Motor-Medic in my SM465's,but it did make them a bear to shift in frigid weather after a cold start..it did reduce a lot of noise in warmer months..the one I had in a '72 K5 I swapped in rattled from day one,the output shaft splines were hogged out,and it eventually ate the coupler between the trans and NP-205,and stripped it out...one day I let the clutch out on a hill,and "Blagghhhht"-"eek:-it refused to move..putting it in low range worked long enough to get it off the busy road,but not home!..

After I replaced it,it was blissfull silence,and I had tried using a lot of RTV in the coupler splines in hopes it would prevent the worn splines from chowing the new coupler up in short order,but the buzzing & rattling returned after a few weeks...it never stripped again ,but I never quite trusted it either...