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Discussion Starter · #1 ·
Ever since I swapped in my sm420 - previous owner said was in good condition - hence no new bearing kit installed - I have either a gear mesh noise or bearing noise that increases with speed, not rpm's. I called Rube - since I used his adapter and he said it was possible that the bull gear had a different pitch to it than his adapter was machined for. He thought it would go away with time. Well...it hasn't. I drove it from SoCal to the Con and back - and the noise gets louder as the tranny warms up - i.e. tranny oil thins out more. Is this a bearing - or something else? Any input appreciated. TIA.
 

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Gears whine, while bearings tend to make a rumbling or whirring noise. If it increases with speed and is independent of the gear selected, it may be the transfer case and not the transmission.
 

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Discussion Starter · #3 ·
Well - that is why Rube thought of the bull gear - it doesn't matter on gear selection - just speed. The t/c is the same as before - no problems prior to the swap. Clutch in/out - only the speed determines noise. Once above 50 mph - it tends to go away.
 

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All my Sm420's made noise. A couple had worn out syncro's, others did not.

I talked to a guy that had fully rebuilt one... and it made the *exact* same noises it did before. :p
 

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Discussion Starter · #5 ·
I know it is not a quiet tranny - but two of my friends have them as well and this noise is not present with theirs. It is definitely gear or bearing related - just thought maybe someone else had the same problem and could either trace it to Rube - or the bearings. Rube said he would send a bull gear to me that would be guaranteed the right one for free - maybe I'll do that.
 

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If you are going to have it apart again, you might as well put new bearings and syncros in it for peace of mind. I got a kit for $130 at:
Stick Only Transmission Parts
9900 Glenoaks Blvd. Suite 2
Sun Valley, CA 91352
(818) 768-4747
(800) 225-8824
 
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