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SM465 nightmare, need advise

M

mpascino

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As mentioned earlier I swapped an sm465 into my diesel burb. All was well at first, but after the trans would warm up it would start making noise. The noise was only noted while the trans was in neutral with the clutch pedal not depressed. Press the clutch the noise stops. After a while I noticed with the tcase in neutral the trans would make the same noise in any gear. If the engine rpm was brought up to about 900 rpm the noise goes away. The best way I can describe it is a "deep rattle". With this info we had decided the input bearing or counter shaft bearings were on the way out.

Skip ahead a couple weeks later.... Tore the trans back out and went through a complete overhaul. New bearings, Bushings, tolerance checked, wear patterns inspected, syncros,.....the works. Turns out the input bearing was in good shape, but the output bearing was on the way out. There were no teeth chipped or damaged except for the leading egde of first and reverse, which is to be expected in a non-syncro setup. As far as I was concerned, the trans was in good shape and thought it would deliver at least 100K without concern.

Got the truck back together last night. Drove it to work this morning. It shifts very smoothly and "Feels" right. I come to a stop light and put it into neutral to hear THE SAME DAMN NOISE. The characteristics are identical to before except the trans itself operates a lot smoother.

I've been told this noise is considered normal by a lot of sm465 owners, this is my first one. You can hear the rattle both inside and outside of the truck. I've been told it's normally louder with diesels. Lets put it this way, I wouldn't buy a truck I heard making this noise.....I'm pulling my hair out. What else could it possibly be? I do not think it is the clutch because noise does not start until the input shaft is up to speed. I thought it may be the reverse gear "Rattling" on it's shaft, but it would stop once in reverse, which it does not. Again, once above 900 rpm or so the noise is gone, I do not notice it while driving and do not feel it in the shifter. Sorry for the long post. Any past experiences or advise is greatly appricated.
Thanks,
Mike Pascino
 
Did you change your throwout bearing?

I wouldn't have even considered the transmission with those symptoms.
 
Yup, the throwout bearing, clutch, flywheel, pilot bushing are all new. I did drive the truck I got the trans from, but I didn't go far enough to warm the trans up apparently to get it to make the noise. The donor truck had no brakes which make the 2 mile test drive scary enough..... Everything is new.... Also to note, when the clutch is depressed, everything is quiet...Throwout bearing included...I can drive a good ten minutes before the noise starts.....
 
First, replicate the problem with someone in the cab and you underneath so you can better pinpoint where the sound comes from. If it is from the bellhousing area, check the TO bearing and pilot bushing and clutch.
 
Already been there... 90% positive it comes from the trans.... All the clutch components are new and were visually inspected throughly again with the second removal......Going to crawl under it again tommorrow to give it another listen.
Thanks,
Mike
 
Sure sounds like a TO bearing to me. My SM465 behind my 6.2 is quiet as a mouse. :dunno:

Rene
 
Correct me if I'm wrong, but the throw out bearing is doing nothing while the clutch is not being pressed. The TO bearing is only spinning while the clutch pedal is pressed, with the bearing being loaded against the clutch fingers. From past experience, every bad TO bearing I have seen makes noise when the clutch is pressed. I have driven the truck around to get it hot and then unbolted the slave cylinder to get the TO bearing away from the clutch. I still heard the same noise......... Thanks again, keep the suggestions coming.
Mike
 
mpascino said:
Correct me if I'm wrong, but the throw out bearing is doing nothing while the clutch is not being pressed. The TO bearing is only spinning while the clutch pedal is pressed, with the bearing being loaded against the clutch fingers. From past experience, every bad TO bearing I have seen makes noise when the clutch is pressed. I have driven the truck around to get it hot and then unbolted the slave cylinder to get the TO bearing away from the clutch. I still heard the same noise......... Thanks again, keep the suggestions coming.
Mike
Click to expand...

This is true, only if properly adjusted...
 
Is it possible that this whole problem is a clutch disc rattle? Is there any way I can find out? I used a heavy duty Sacks setup......
 
Clutch Fork??

I've heard the noise your describing,it might be a loose clutch fork ratting on its pivot ball--usually there is a clip like a horse shoe shaped spring on the cast iron bellhousings on older trucks,the aluminum bells have a fork with a spring steel clip similar to the one that holds the crankcase breather filter into the air cleaner--if the fork has no clip or is sloppy,or the linkage is loose it will rattle,and sound a lot like the mainshaft input bearing does when it has too much wear...its weird it takes time to appear after it warms up though..:confused:

Another thought is the shift forks touching the teeth on a gear slightly,but since its been overhauled that seems unlikely..maybe too much end play on one of the shafts???...:crazy:
 
Did you test fit the pilot bushing (I assume bronze) on the input shaft before installation in the crank?
 
Saw no signs of interferance problems on the shift forks. I have the aluminum bellhousing with the u shaped clip, which is in good shape. The slave cylinder does keep a little pressure on the clutch fork, very minimal. Here's the catch, I can slip the clutch in neutral, so that the fork and bearing is loaded and the input of the trans is almost up to speed, and I still hear the noise. I am not completely ruling it out, but I don't think it's clutch fork or TO bearing related.....I'm getting afraid to drive it, I've sank a lot of time and money into this thing....

Thanks.
 
Yup, test fitted the bushing(bronze) at install and at the trans rebuild. Tight as a bulls AS $ at flight time....
 
mpascino said:
Yup, test fitted the bushing(bronze) at install and at the trans rebuild. Tight as a bulls AS $ at flight time....
Click to expand...

If you drive the truck and push the clutch in (while coasting) does it still make noise?
 
I'm 80% sure it does not. I will try it tommorrow under different conditions to confirm...... Beginning to wonder... I will try putting the tcase in low and coasting around to drive to get the trans output shaft speed up and keep everythign else quiet..... Thanks.
 
I'm 80% sure it does not make the noise while coasting, I will put the tcase in low tommorrow to get the trans output shaft speed up while trying to keep everything else quiet. Thanks.
Mike
 
What clutch did you put in? Was it a new clutch? Was it a clutch designed for a diesel engine? Clutches discs for diesels have extra springs and thicker fingers in the disc, to compensate for the diesel backlash. Diesels have a very inconsistent rotation, especially at idle, it's not a smooth revolution, hence the special clutch to absorb those extra vibrations.
Clutch and Manual trans noises have a tendancy to throw thier voice, it's hard to really tell what's going on.
 
Hmmmmmm...

I was reading this post again,and I remember my K5 I had years ago had a defective pressure plate that I installed--it had a rattling noise shortly after I put it in(like a week or so later)--and about a month went by,and one of the three "levers" failed,and it would not release anymore--I had to drive it with the clutch stuck "engaged"for a few days until I could install another one(12 inch clutch with 3 levers)--the second pressure plate was defective too,it chattered horribly--so I replced it with an 11 inch diaphram type clutch setup-

My left leg was thankful for that,it was 100 percent easier to push the pedal down with the diaphram clutch,and I never had any trouble with it after that was installed-( no annoying rattles either!)-but yeah,the pressure plate could very well be the source of the noise your hearing--especially if its not a diaphram type pressure plate...The Borg-Warner rebuilts I used had a lot of problems back in the mid 80's when I did the clutch--nearly every one I sold at the parts store came back defective--we ended up switching to another brand...:crazy:
 
Was the rattle there when you depressed the clutch or when the pedal was up? The setup I have is new, and not the three fingered setup. I have had bad luck with those as well, same problem, one of the fingers broke. did you hear the rattle imediately after cold starting or did it need to warm up first?
Thanks for the info,
Mike Pascino
 
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