sm420 question
 

hey kids. I just pulled the SM420 outta my 64 chev K10, due to a blown throwout bering, and have something for y'all to look at ... not sure if it's a problem or not but heres a couple pics:

Re: sm420 question
 

it's that 'ring' near the end of the input shaft cover... is that normal? is it something I should be worried about? when you put the throwout bering on, it stops over that 'ring' and goes no further -- is that supposed to happen?

this is my first time dealing with this trans, and though I've got the 63+64 shop manuals, and several other resources, I see nothing (or understand otherwise) that actually tells me anything about that shaft cover, and where the throwout bearing is supposed to finally rest, and if that ring is supposed to be there or if it matters at all... any help is appreciated...

fyi - aside from the throwout bearing dying on this trans, I had no problems with the tranny whatsoever... as solid as any sm420 I've read about...

Re: sm420 question
 

I'm not sure about that ring. It don't look good. I looked in my '67 overhaul manual and the pictures do not show that ring. They made these for a lot of years though, so maybe older ones had it?

These guys are a good resource. Check their "Knowledge" section.

http://www.novak-adapt.com/

I haven't had the clutch out of my '67 yet, but here's what the inside looks like:

Re: sm420 question
 

There is a product Titanium Putty used for rebuilding shafts. Since the collar is used to simply allow the bearing to slide back and forth you could fill in the gap and sand it down. This way the throwout bearing should not catch on the edge. Did the bearing simply slide off or does it bind?

Re: sm420 question
 

This is the stuff I was referring too...

http://www.devcon.com/products/produ...m?familyid=124

Re: sm420 question
 

Picture from Ebay 1955 SM420 no ring.

http://www.hotrodauctions.net/ebay/TRM/9-8-09/072.jpg

Re: sm420 question
 

If it were mine, I'd weld the groove up and machine it smooth again with a grinder and flap wheel.

Re: sm420 question
 

I would just find a good replacement. It shouldn't be hard to find as there were lots of these transmissions made. If you weld that up, it will likely shrink that area which would be as bad as a worn one. A worn input shaft bearing retainer (what it's called) can cause premature throwout bearing failure. Ask me how I know.....

Re: sm420 question
 

haha, how do you know Cap'n?

anybody know how far the throwout bering is supposed to slide back?

the throwout bering definitely stops sliding onto the shaft, once it gets a little past the ring (you can sorta see that in one of the pics I posted) there was no binding, it wasn't jammed on there it came right off when I pulled the trans...

I will take the advice and try to find a replacement... I've been to the novak site and their billet unit definitely doesn't have that 'ring' and I've seen a pile of pics of those trans via google... mine is a 'late model' with the side ribs, and the pics of those on google are pretty crappy, and do not clearly show whether that ring is supposed to be there or not...

Re: sm420 question
 

well, so far novak has not responded to either of my emails... and I've had no luck finding a parts trans or retainer that isn't over priced...
:waah:

if anybody knows someone that'll sell & ship me a retainer, pm me or whatever, as I'm having some poor luck here!

Re: sm420 question
 

I would just clean and polish that frt brg retainer up(so that the t/o brg collar can ride back on it) and use it.. difficult to see whether or not that groove is machined or worn that way.. it does look like a difficult wear pattern for that area..
if you were in the area, i have a complete 420 sitting here on the ground
ron

Re: sm420 question
 

I've got an SM420 Same serial # only it has a 13 above GM instead of 16 ??
still attached to block so ?? clutch is good
Yours for the taking and 10 hours closer
Trent

Re: sm420 question
 

hey thanks for the offers... I may yet take them up... :chevy: I think that groove isn't supposed to be there.

and I think I know how it got there... For a couple of days before the throwout bearing failed, I was hearing a squealing noise. Soft at first, and quite loud near the end. I had thought it was the shifter linkage rubbing against my driver's exhaust pipe, because it seemed to go away when depressing the clutch pedal...

anyway, later after I began the teardown, I found a piece of the throwout bearing cage, wedged in between the throwout bearing and the retainer shaft. and later, once the trans was out, I cannot slide the throwout bearing past that groove. So the squealing noise I was hearing, was probably that groove being cut into the retainer.

my guess is the throwout bearing failed awhile ago, and until it was unable to slide back and forth on the retainer, it would have just continued to chew at the clutch fingers until they eventually failed...


On a good note, I did have some luck at Nat'l Trans here in Calgary. Brock knows his stuff there. We had a bit of a technical language barrier regarding the identification of my old trans, but he was able to locate a new retainer with the new style seal type (instead of the old style reverse thread/weep hole type) for my 'late model' SM420, and have it in by Tuesday... :metal:

That is a big relief. I was worried I'd either have to shell out the bucks to Novak for a fancy billet unit or get a used one... both of those cases were not good options as I'm on the clock. I need to get this truck rolling before my May 1 weekend camping trip! And I've got so many other issues to deal with... :waah:

anyway, I appreciate all the help folks! I'll post up after tuesday with a pic of the new retainer and seal kit, and let yall know how it pans out...

Re: sm420 question
 

quick update:

the retainer showed up last week... it was a good unit, and I installed it as soon as I got home.

I test fitted the new throwout bearing on the new retainer, and it slides back all the way without any problems. nice and smooth.

Once the weekend got here, I had my dad and brother over to help put the beast back in.

I made one guide pin out of a 4 inch long bolt of the same thread type as the 4 trans to bellhousing bolts. I cut the head off the top of the bolt, and cut a groove in so it could be removed with a flathead screwdriver once the trans was in place... (thanks to whomever originally came up with that idea!)
combined with the tranny jack adapter my brother welded up, it made the installation go very easily, with a minimum of frustration. In fact, the hardest part was getting the throwout bearing seated properly on the fork. We could not seem to get the trans shaft lined up with everything at once, including having the throwout bearing already installed on the fork...

So we left the bearing on the retainer shaft, and once we got the shaft in the bellhousing lined up with the clutch splines, we popped the clutch fork off, then backed off the fork ball to allow clearance to properly get the fork end in its proper place on the throwout bearing... Once that was done, it was just a matter of tossing the shifter back in the top to get trans in gear so we could move the splines around to mate with the clutch, and then some angle / height adjustments and a few wiggles to get the trans to slide all the way into the pilot bushing, and boom! four bolts, and the trans is back in done deal!.

I'll post a pic of the trans in it's proper place later.. :chevy:

Re: sm420 question
 

the squealing noise was the t/out bearing it self n it's way out(it must have squealed for a while but you ignored it hoping that it would go away). the reason for the groove was when the brg seized and spun on the shaft and you still ignored it until the brg finally disintegrated and you couldn't drive it anymore.. all that you had to do was clean up the retainer where there was a bur on the edge of the groove; new brg and good for another 100,000
ron

Re: sm420 question
 

I hope that you replaced the clutch assy at the same time as the fingers on the pressure plate should be pretty well beat up from that t/o brg and you more than likely needed a clutch disc anyway
ron

Re: sm420 question
 

The squealing was not ignored. I made adjustments, hoping to cure the noise, but nothing I did got rid of it. Never having heard this noise or experience with a throwout bearing dying, and right up to the point of failure, having ANY problems shifting whatsoever, I did what most do...drive it till it breaks.

As for reusing the retainer. Not a chance. At least I would not reuse it. I have spent too much time and effort on this truck. It is now part of the pile which will be welded together for this year's carnage trophy. The fingers on the clutch were worn down at the point of bearing contact, but I'm sure I could have cheaped out. Re-used em and driven it until they broke. The clutch disc and pressure plate surface were just fine, & could have been reused too... In fact I suspect the PO may have replaced the clutch & pressure plate without replacing the throwout bearing...

For me it boils down to effort. it's a pain in the butt removing and reinstalling large parts such as the engine/trans. So reusing parts, that are a pain to get to...Something I try to avoid.

Wherever I can, I put new/upgraded parts in, hoping that'll mean I don't have to fix it again for a long time.

So I had the flywheel turned, new flywheel bolts, new pilot bushing, new clutch & pressure plate & bolts, new fork, new fork ball, new fork accordian rubber, new throwout bearing, & new retainer. Hopefully it all works as advertised!

Re: sm420 question
 

The rule of thumb is anytime you see the throwout bearing and pilot bearing you should replace them. ;)

Re: sm420 question
 

True this is. :burnout:

Re: sm420 question
 

well, just to update this post, all has been working well all year. every dime spent on parts has been worth the effort, and a little fresh paint keeps the idea alive that it's worth the effort...

anyway, the whole story is posted here on my home forum, check it out if you like:
http://www.bomp-bomp.com/forum3/viewtopic.php?f=4&t=877