UPDATE: Help with SM420 (1 Viewer)

pjohnson

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Well, regardless of how you perceived their input, your post calling them trolls was uncalled for.
 
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What do you call people who offer no advice or comments to the Post (or to any Post I have ever made) and HAVE NEVER OFFERED ADVICE, and out of nowhere issue derogatory Emoji’s to my comments to express their derision? Where I come from, they are called Trolls.
 
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I too would defend Pig, Onur, Steve and anyone else on here. Help, help diagnosing the MYSTERY noise ????? I will offer that my sm420 which has been used, rebuilt, used some more, behind 2 different engines, I've rebuilt it, & my tcase alot all by myself, not speaking down to you just offering that I have seen, felt, fixed the particular unit you have myself and if you are confident none of the roller bearings fell out then it is a mystery at this point. Given your descriptions it is odd but if it is running then time will tell. My 420 did this once in 20 years, after a long hard day in low range I pulled into the stage area at Rubicon to air up, put truck in Nuetral, got out to unlock hubs, heard same odd rattling sound, looked at my daughter, said " you bump the shifter ?" she says no, huh ?, as rattle gets louder I notice truck trying to move, shut it off. Never figured what caused it, never duplicated it. I honestly think there is just a wierd spot that if the shifter gets too it puts the collar between input & output shaft in a spot that it bounces off the dog teeth as they just barely rub , other than that I got nothin. The input and output bearings can wear and let the gap where that collar rides increase and there are some spring clips in the 420 little planetary thingy that goes under the collar that if not put in right will cause the collar to drag causing same noise. I forget what oil you said you were running , IMO put 90w in a 420. After hours long freeway runs you should smell the 90 wt and maybe see a little up out shift tower, and as I said before the shifter will rattle in 3rd never did it in neutral but if I recorded my shifter rattle and played it with your eyes closed I bet youd say, "Thats the noise I heard ".
 
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If the needle bearings in the input gear pilot got loose, they would end up inside the transmission and probably be stuck to the magnet. There is no way for them to get outside without a big hole in the tranny case. The 420 is reasonable easy to work on, but I wouldn’t assume it is responsible for the noise If there is no obvious loose metal inside
I agree this makes the most sense. Watching the vision the installation of the Clutch shaft and Needle bearings, they apparently would drop into the case, but it seems like the shaft would have to come out quite far for that to happen. In any case, there are no bearings in the case, so that is not the cause of the noise.

It was suggested that the adapter locking collar was loose and caused some play in the main shaft, but I’m not sure why that would be intermittent.

As someone said, keep driving until you hear it again. I think that is all I can do. I was using Valvoline 80-90 Non-Synchronized GL4 Glar Oil. That may not be a good oil for the SM-320 so I switched to the GL1 Mineral Oil. I don’t know if it could just have been rattling gears?

I guess time will tell. As you said, if it “ain’t broke, don’t fix it.” No point pulling anything until you know what the problem is.
 
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I too would defend Pig, Onur, Steve and anyone else on here. Help, help diagnosing the MYSTERY noise ????? I will offer that my sm420 which has been used, rebuilt, used some more, behind 2 different engines, I've rebuilt it, & my tcase alot all by myself, not speaking down to you just offering that I have seen, felt, fixed the particular unit you have myself and if you are confident none of the roller bearings fell out then it is a mystery at this point. Given your descriptions it is odd but if it is running then time will tell. My 420 did this once in 20 years, after a long hard day in low range I pulled into the stage area at Rubicon to air up, put truck in Nuetral, got out to unlock hubs, heard same odd rattling sound, looked at my daughter, said " you bump the shifter ?" she says no, huh ?, as rattle gets louder I notice truck trying to move, shut it off. Never figured what caused it, never duplicated it. I honestly think there is just a wierd spot that if the shifter gets too it puts the collar between input & output shaft in a spot that it bounces off the dog teeth as they just barely rub , other than that I got nothin. The input and output bearings can wear and let the gap where that collar rides increase and there are some spring clips in the 420 little planetary thingy that goes under the collar that if not put in right will cause the collar to drag causing same noise. I forget what oil you said you were running , IMO put 90w in a 420. After hours long freeway runs you should smell the 90 wt and maybe see a little up out shift tower, and as I said before the shifter will rattle in 3rd never did it in neutral but if I recorded my shifter rattle and played it with your eyes closed I bet youd say, "Thats the noise I heard ".
Good comments. I appreciate it. I can take the scolding and will try try to avoid writing anything offensive in the future. I didn’t mean to be hurtful., it’s just that we aren’t all at the same skill level. I do more than I should…. Sometimes it gets me in trouble. Sometimes it works out. Things like a transmission are not a trivial item to experiment with, especially at my age. It’s too much work and expense if you screw up!
 
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I will say that IMO anything thinner than 90wt youll hear "things" you wish you didn't, happens when they get low oil, even the 90 wt, they will clang and rattle and shift wierd, thats when its time for fresh 90 wt.
 
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You may be right about the gear shifter. I never thought about it. I heard the noise twice: once when I stopped to start a trail, at again back home in the garage. Both times the transmission was in neutral. However, the Shifter could have been left in a position where it was rattling against vibrating against a [?] and it sounded like loose gears. I couldn’t be in two places, so there was no way to play with it. Now, when I have tried to test it, it’s possible the shifter is no longer being put in that position l, this, no noise.

This is the best theory/explanation that I have heard. Its entirely plausible. I’ll drive it tomorrow and if I can’t reproduce it, I think I would l be willing to believe this was the cause. I may play either shifter to see if I can reproduce the noise too.

THANKS PEES!
 
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Safe to say I have spent a fair bit listening to a 420 in a cruiser , your welcome. I have been happy and amazed at the abuse a 420 will take.
 
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Tons of rust formed in the equivalent equipment in my H42. There are balls and springs that need to hold shifter stuff in place by freely moving thru drilled holes. I think that I might even have an issue with dragging into reverse gear when I'm reaching for second gear. BTW, I'm a total amateur here.

They sell 140 wt at O'Reilley. It is too much for syncros to work well in cold weather, so I'm using 90wt from NAPA.
 
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I drove the FJ this morning on the Freeway at 60-70mph for at least 15-20 miles plus another 5-10 miles on city streets at 40-45 mph. Needless to say, the transmission ran at full speed and though all gears and got plenty hot, BUT, no unusual noise. When I got home I played with the stick, but I couldn’t get it to make any noise.

I’m at a total loss for whatever the noise was. I had a fine mesh screen on the oil pan when I changed the oil…. nothing came out of that case. , and there was no metal on the drain magnet.

I was totally prepared to pull the transmission, that was how sure I was there was something seriously wrong. Now just have no idea. I’ll put the tunnel and shifter’s back and hope I never hear that again.
 
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Yeah. Sounds good when the oil is clear.

I'd make sure that propeller shaft has good u-joints.

I ran a clutch down to the rivets, once, and it would slip at highway speeds?
 

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