SM420 gear shift rattle (1 Viewer)

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SM420 gear shift vibration

Anyone have any ideas to eliminate my gear shifter vibrating in 4th gear. If I touch the shifter with my hand while driving it stops completely. I installed some Reflectix sound barrier under my carpeting and trans cover. She still howls but at least I wont have to wear ear plugs when driving... the reflectix helped greatly reduce the noise level of the SM420. Now just gotta take care of the gear shifter rattling.... any ideas?

Fman
 
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All I can tell you is hopefully your rattle isn't as violent as you describe, you shouldn't need earplugs on account of your 420. If I was to guess, I would say that the nedel bearings that support the main shaft have been misplaced and that shaft is now running on the female destroying each other in the process. I would say pull the pto cover and see if you have some needles rolling around in the bottom. The bad news is you may have to find yourself a new tranny. Don't drive it till you know that is not the problem. What will happen is that eventually it will pop out of third, then it will get stuck in 4th, and not come out, then your tranny is pretty much toast. :frown: not to mention the horrible noises associated.
 
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bustanutley said:
All I can tell you is hopefully your rattle isn't as violent as you describe, you shouldn't need earplugs on account of your 420. If I was to guess, I would say that the nedel bearings that support the main shaft have been misplaced and that shaft is now running on the female destroying each other in the process. I would say pull the pto cover and see if you have some needles rolling around in the bottom. The bad news is you may have to find yourself a new tranny. Don't drive it till you know that is not the problem. What will happen is that eventually it will pop out of third, then it will get stuck in 4th, and not come out, then your tranny is pretty much toast. :frown: not to mention the horrible noises associated.
What it sounds like ot me is the slop associated between the end of the shifter and the shift rails that controls the shift forks. Mine does the same thing (and I put in a NOS SM420). If it's the noise I think it is, it's not a problem.

IF you're using the stock SM420 shift lever, that one has a bunch of slop associated with it and that slop can make noise. You can modify a 4 Speed transmssion shifter (perhaps even a 3 speed shifter) by extending it about 3/4". The modified 4 speed shifter will fit and looks like it's meant to be there.
 
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If the tranny is bad, I would be surprised. I have yet to hear an SM420 that was not loud. It shifts with no problems through all gears, and downshifts just as well with no grinding. Rattles bother me, and this is an annoying vibrating rattle. Most people would not bother to fix it, unfortunately I am a perfectionist, and want it perfect.... there seems to be a little free play as described earlier. I did not install the tranny, so I am assuming it is the standard gear shifter that comes on an SM420.

Are you referring to modify a 4 speed shifter from a stock l/c tranny?
 
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Fman said:
If the tranny is bad, I would be surprised. I have yet to hear an SM420 that was not loud. It shifts with no problems through all gears, and downshifts just as well with no grinding. Rattles bother me, and this is an annoying vibrating rattle. Most people would not bother to fix it, unfortunately I am a perfectionist, and want it perfect.... there seems to be a little free play as described earlier. I did not install the tranny, so I am assuming it is the standard gear shifter that comes on an SM420.

Are you referring to modify a 4 speed shifter from a stock l/c tranny?
YEah, I am referring to modifying a 4 speed shifter from a stock LC tranny.

Here's a drawing.

The top of the pic is the stock style shifter.

It's one piece of steel from the ball to the end of the shifter.

The bottom of the pic is the stock SM420 shifter.
It's a piece of steel (black) that goes into another piece of steel (red) and is secured by roll pins. This piece of steel then has another piece of steel inserted into it (black again) and securied by a roll pin that interfaces the shift rails. If the roll pins get worn (which they generally do) the shifter will have ALOT of slop in it, and probably rattle because of the slop.
 
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Oh...Durka Durka Durka.
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I have been using a 3spd shift cane in my 420 since '93 without issue.


No modifications required.


:beer:
 
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Try putting a rubber washer between the shift lever ball and the retaining cap to tighten it up. Something like a piece of inner tube might do.

BTW, my 420 is quieter than my Toyota 4sp in 3rd gear; in other gears they both don't make much noise.
 

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